Accurate distance measurement using RF techniques
Claim Score by NHIP
Abstract
A system, apparatus, and method for determining the distance between two objects using an indirect propagation delay measurement is disclosed. A frequency hopping scheme (such as the Bluetooth(TM) technology) is used to measure the relative phase offset of the received signal between the various frequencies. For a given distance between the objects, the phase offset vs. frequency curve is a straight line with the slope dependent upon the measured distance. After the phase of the received signals is detected, the data is plotted on a curve and the slope is calculated.
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Projected expiry passed 26 October 2021, 4.9 years ago.
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105 claims: 13 independent, 92 dependent
- 1A wireless communication device, comprising:a first synthesizer for generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers;a transmitter for transmitting the first RF signal;a receiver for receiving a second RF signal from a remote wireless device phase locked with the first wireless device, the second RF signal including a sequence of carriers corresponding to the carriers of the first RF signal, wherein the frequencies of the corresponding sequence of carriers of the first RF signal are different from the frequencies of the sequence of carriers of the second RF signal;a second synthesizer for generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the first and second RF signals, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signals are the same as the frequencies of the sequence of carriers of the third RF signal;a phase detector for comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal and generating a sequence of phase offsets;and a processor for determining distance between the wireless communication device and the remote wireless device by calculating an estimated slope of the sequence of phase offsets relative to the frequencies of the sequence of carriers of the second RF signal.
- 11A wireless communication device, comprising:a first synthesizer for generating a first radio frequency (RF) signal, the first RF signal including a single carrier having a frequency f t0 ;a transmitter for transmitting the first RF signal;a receiver for receiving a second RF signal from a remote wireless device phase locked with the first wireless device, the second RF signal including a sequence of carriers, wherein the frequencies of the sequence of carriers of the second RF signal are different from f t0 ;a second synthesizer for generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the second RF signal, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the corresponding sequence of carriers of the second RF signal are the same as the frequencies of the corresponding sequence of carriers of the third RF signal;a phase detector for comparing the phase of each of the carriers of the second RF signal to the phase of each of the carriers of the third RF signal to generate a corresponding sequence of phase offsets;and a processor for determining distance between the wireless communication device and the remote wireless device by calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal.
- 21A half-duplex wireless communication device, comprising:a synthesizer for generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers f n , where n is a plurality of integers;a transmitter for transmitting the first RF signal during a first time slot An;a receiver for receiving a second RF signal, during a second time slot Bn, from a remote wireless device phase locked with the first wireless device, the second RF signal including a sequence of carriers f n corresponding to the carriers of the first RF signal, wherein the sequence of carriers of the first RF signal are the same as the sequence of carriers of the second RF signal, and wherein the first and second time slots altenatingly repeat as n changes;a phase detector for comparing the phase of each of the carriers of the second RF signal to the phase of each of the carriers of the first RF signal to generate a corresponding sequence of phase offsets;and a processor for determining distance between the wireless communication device and the remote wireless device by calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal.
- 31A computer readable medium containing program instructions for controlling a wireless communication device and for determining distance between the wireless communication device and a remote wireless device, comprising instructions for:generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers;transmitting the first RF signal;receiving a second RF signal from a remote wireless device phase locked with the wireless communication device, the second RF signal including a sequence of carriers corresponding to the carriers of the first RF signal, wherein the frequencies of the sequence of carriers of the first RF signal are different from the frequencies of the sequence of carriers of the second RF signal;generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the first and second RF signals, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signal are the same as the frequencies of the sequence of carriers of the third RF signal;comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal to generate a sequence of phase offsets;and calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device.
- 41A computer readable medium containing program instructions for controlling a wireless communication device and for determining distance between the wireless communication device and a remote wireless device, comprising instructions for:generating a first radio frequency (RF) signal, the first RF signal including a single carrier having a frequency f t0 ;transmitting the first RF signal;receiving a second RF signal from a remote wireless device phase locked with the remote wireless device, the second RF signal including a sequence of carriers, wherein the frequencies of the corresponding sequence of carriers of the second RF signal are different from f t0 ;generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the second RF signal, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the corresponding sequence of carriers of the second RF signal are the same as the corresponding sequence of carriers of the third RF signal;comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal to generate a sequence of phase offsets;and calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal. wherein the distance between the wireless communication device and the remote wireless device is proportional to the slope.
- 45Broadest claimClaim Score 83, broad(NHIP)The computer readable medium of clam 41 , further comprising instructions for:mixing the received second RF signal with the third RF signal to produce In-phase (I) and Quadrature (Q) signals, solving for phase angle Θ by applying the following relationship: Θ=Arctan(Q/I)/2, and generating the phase offsets based on the phase angle Θ.
- 51A computer readable medium containing program instructions for controlling a half-duplex wireless communication device and for determining distance between the wireless communication device and a remote wireless device, comprising instructions for:generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers f n , where n is a plurality of integers;transmitting the first RF signal during a first time slot An;receiving a second RF signal, during a second time slot Bn, from a remote wireless device phase locked with the first wireless device, the second RF signal including a sequence of carriers f n corresponding to the carriers of the first RF signal, wherein the frequencies of the sequence of carriers of the first RF signal are the same as the frequencies of the sequence of carriers of the second RF signal, and wherein the first and second time slots alternatingly repeat as n changes;comparing the phase of each of the carriers of the second RF signal to the phase of each of the carriers of the first RF signal to generate a corresponding sequence of phase offsets;and calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal to determine the distance between the wireless communication device and the remote wireless device.
- 61A method of determining distance between a wireless communication device and a remote wireless device, the method comprising the steps of:generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers;transmitting the first RF signal;receiving a second RF signal from a remote wireless device phase locked with the wireless communication device, the second RF signal including a sequence of carriers corresponding to the carriers of the first RF signal, wherein the frequencies of the sequence of carriers of the first RF signal are different from the frequencies of the sequence of carriers of the second RF signal;generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the first and second RF signals, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signal are the same as the frequencies of the sequence of carriers of the third RF signal;comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal to generate a sequence of phase offsets;and calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device.
- 71A method of determining distance between a wireless communication device and a remote wireless device, comprising the steps of:generating a first radio frequency (RF) signal, the first RF signal including a single carrier having a frequency f t0 ;transmitting the first RF signal;receiving a second RF signal from a remote wireless device phase locked with the remote wireless device, the second RF signal including a sequence of carriers, wherein the frequencies of the corresponding sequence of carriers of the second RF signal are different from f t0 ;generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the second RF signal, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the corresponding sequence of carriers of the second RF signal are the same as the corresponding sequence of carriers of the third RF signal;comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal to generate a sequence of phase offsets;and calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal. wherein the distance between the wireless communication device and the remote wireless device is proportional to the slope.
- 81A method of determining the distance between a wireless communication device and a remote wireless device using half-duplex communication, the method comprising the steps of:generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers f n , where n is a plurality of integers;transmitting the first RF signal during a first time slot An;receiving a second RF signal, during a second time slot Bn, from a remote wireless device phase locked with the first wireless device, the second RF signal including a sequence of carriers f n corresponding to the carriers of the first RF signal, wherein the frequencies of the sequence of carriers of the first RF signal are the same as the frequencies of the sequence of carriers of the second RF signal, and wherein the first and second time slots alternatingly repeat as n changes;comparing the phase of each of the carriers of the second RF signal to the phase of each of the carriers of the first RF signal to generate a corresponding sequence of phase offsets;and calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal to determine the distance between the wireless communication device and the remote wireless device.
- 91A method of determining distance between a wireless communication device and a remote wireless device, the method comprising the steps of:generating a first signal;transmitting the first signal;receiving a second signal from the remote wireless device, the second signal including multiple carriers at different frequencies, wherein each of the multiple carriers are phase coherent with the first signal;performing a phase comparison using phase information of the first signal and the received second signal to generate multiple phase offsets;and calculating an estimated slope of the phase offsets relative to the frequencies of the multiple carriers of the second signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device.
- 96A wireless communication device, comprising:a synthesizer for generating a first signal;a transmitter for transmitting the first signal;a receiver for receiving a second signal from a remote wireless device, the second signal including multiple carriers having different frequencies;a phase comparator for performing a phase comparison using phase information of the first signal and the received second signal to generate multiple phase offsets;and a processor for calculating an estimated slope of the phase offsets relative to the frequencies of the multiple carriers of the second signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device.
- 101A computer readable medium containing program instructions for controlling a wireless communication device and for determining distance between the wireless communication device and a remote wireless device, comprising instructions for:controlling a first synthesizer that generates a first signal;controlling a transmitter that transmits the first signal;controlling a receiver that receives a second signal from the remote wireless device, the second signal including multiple carriers at different frequencies, wherein each of the multiple carriers of the second signal are phase coherent with the first signal;controlling a phase comparator that performs a phase comparison using phase information of the first signal and the received second signal to generate multiple phase offsets;and calculating an estimated slope of the phase offsets relative to the frequencies of the multiple carriers of the second signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device.
Independent claims13
101 paragraphs in 4 sections, as filed
BACKGROUND OF THE INVENTION
P-0001[0001] 1. Field of Invention
P-0002[0002] The present invention relates to a system and method for measuring a distance between two objects. More specifically, the present invention relates to a system and method of measuring a distance between two objects using RF techniques.
P-0003[0003] 2. Description of the Related Art
P-0004[0004] Mobile telephones, pagers, and other wireless communication equipment are now commonplace. More recently, laptop computers, personal digital assistants (PDAs)—such as the Palm™ organizer—have been equipped with wireless communications capabilities. One of the primary benefits of wireless equipment is portability. We can carry our mobile phone with us wherever we go. These wireless devices are currently used for relatively limited purposes, such as making telephone calls, when they are capable of doing much more.
P-0005[0005] One potential use for wireless devices is in mobile commerce. Wireless devices can be used for buying or selling goods or services, making payments, gathering information, advertising and promotion, and the exchange of information for other commercial or non-commercial purposes. The success of mobile commerce and other wireless applications will depend on their acceptance by consumers at large. Accordingly, wireless applications must be easy to use and convenient. New platforms are being developed to enable mobile commerce and other applications for wireless devices. Bluetooth™ is such a technology. Bluetooth™ provides a wireless networking protocol for linking various wireless equipment, such as mobile computers, mobile phones, and PDAs. Bluetooth™ operates in the Industrial Scientific and Medical (ISM) 2.4 GHz region.
P-0006[0006] In addition to platforms such as Bluetooth™, wireless devices require additional enabling technologies to reach their full potential. One such technology involves distance measurement. The distance between two or more wireless devices may be needed in a variety of applications. In many cases, it may be undesirable to measure the distance between two wireless devices directly. Direct distance measurement may be impossible, impractical, intrusive, or simply inconvenient. Moreover, because one or more wireless devices may be moved, the distance between devices will not be fixed indefinitely and re-calculation may be needed.
P-0007[0007] In such situations, ‘wireless’ distance measurements are used. Some ‘wireless’ distance measurement systems require an infrastructure to be put in place such as GPS based systems, triangulation methods, and other positioning techniques. Other systems require line-of-sight conditions (e.g., infra red, laser, and optical methods). Radar as well as ultra sonic systems are bulky, complex, and consume significant amounts of power. New ultra wide band techniques are currently not approved by the authorities. Some less expensive systems offer solutions based on field strength measurements with the tradeoffs of reduced reliability and high environmental dependency.
SUMMARY OF THE INVENTION
P-0008[0008] The present invention has been made in view of the above circumstances and has an object to provide a system and method for accurately measuring distance using RF techniques.
P-0009[0009] In one aspect of the invention there is provided a wireless communication device, comprising a first synthesizer for generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers; a transmitter for transmitting the first RF signal; a receiver for receiving a second RF signal from a remote wireless device phase locked with the first wireless device, the second RF signal including a sequence of carriers corresponding to the carriers of the first RF signal, wherein the frequencies of the corresponding sequence of carriers of the first RF signal are different from the frequencies of the sequence of carriers of the second RF signal; a second synthesizer for generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the first and second RF signals, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signals are the same as the frequencies of the sequence of carriers of the third RF signal; a phase detector for comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal and generating a sequence of phase offsets; and a processor for determining distance between the wireless communication device and the remote wireless device by calculating an estimated slope of the sequence of phase offsets relative to the frequencies of the sequence of carriers of the second RF signal.
P-0010[0010] In another aspect of the invention, there is computer readable medium containing program instructions for controlling a wireless communication device and for determining distance between the wireless communication device and a remote wireless device, comprising instructions for generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers; transmitting the first RF signal; receiving a second RF signal from a remote wireless device phase locked with the wireless communication device, the second RF signal including a sequence of carriers corresponding to the carriers of the first RF signal, wherein the frequencies of the sequence of carriers of the first RF signal are different from the frequencies of the sequence of carriers of the second RF signal; generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the first and second RF signals, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signal are the same as the frequencies of the sequence of carriers of the third RF signal; comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal to generate a sequence of phase offsets; and calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device.
P-0011[0011] In another aspect of the invention, there is provided a method of determining distance between a wireless communication device and a remote wireless device, the method comprising the steps of generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers; transmitting the first RF signal; receiving a second RF signal from a remote wireless device phase locked with the wireless communication device, the second RF signal including a sequence of carriers corresponding to the carriers of the first RF signal, wherein the frequencies of the sequence of carriers of the first RF signal are different from the frequencies of the sequence of carriers of the second RF signal; generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the first and second RF signals, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signal are the same as the frequencies of the sequence of carriers of the third RF signal; comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal to generate a sequence of phase offsets; and calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device.
P-0012[0012] Additional objects and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized by means of the elements and combinations particularly pointed out in the appended claims.
P-0013[0013] It should be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. It will be apparent to those skilled in the art that various modifications and variation can be made without departing from the scope or spirit of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
P-0014[0014] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiment(s) of the invention and together with the description, serve to explain the principles of the invention.
P-0015[0015]FIG. 1 is a block diagram illustrating an example of multiple electronic devices in accordance with the present invention.
P-0016[0016]FIG. 2 is an illustrative block diagram of a base station and remote unit in accordance with an embodiment of the present invention.
P-0017[0017] FIGS. <b>3</b>A-<b>3</b>C are illustrative block diagrams of the base station according to FIG. 2 having an RF transceiver, processor, and user interface.
P-0018[0018] FIGS. <b>4</b>A-<b>4</b>B are illustrative block diagrams of the base station according to FIG. 2.
P-0019[0019]FIG. 5 is an illustrative functional block diagram of a base station and a remote unit in accordance with an embodiment of the present invention.
P-0020[0020]FIG. 6 is an illustrative functional block diagram of a phase detector in accordance with an embodiment of the present invention.
P-0021[0021]FIG. 7 is an illustrative functional block diagram of a base station and remote unit in accordance with an embodiment of the present invention.
P-0022[0022]FIG. 8 is an illustrative functional block diagram of a base station and remote unit in accordance with an embodiment of the present invention.
P-0023[0023]FIG. 9 is an exemplary timing diagram showing one possible timing sequence of the transmission between a base station and a remote station of FIG. 8.
P-0024[0024]FIG. 10 is an exemplary chart showing one possible set of data obtained in accordance with the operation of the present invention.
P-0025[0025]FIG. 11 is an exemplary chart of the data of FIG. 10 modified in accordance with a phase ambiguity algorithm of the present invention.
P-0026[0026]FIG. 12 is an illustrative flowchart of the steps for measuring the distance between two objects in accordance with an embodiment of the present invention.
P-0027[0027]FIG. 13 is an illustrative flowchart of the steps for measuring the distance between two objects in accordance with an embodiment of the present invention.
P-0028[0028]FIG. 14 is an illustrative flowchart of the steps for measuring the distance between two objects in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION
P-0029[0029]FIG. 1 provides a block diagram illustrating an embodiment of a system <b>10</b> in which the present invention may be used. As shown in FIG. 1, the system <b>10</b> includes a plurality of wireless devices <b>11</b>-<b>1</b> to <b>11</b>-N (collectively referred to as wireless devices <b>11</b>) within a particular region. The wireless devices <b>11</b> may be communications devices capable of transmitting and receiving information between devices. The information communicated may be data or voice information. At least one and possibly all of the wireless devices <b>11</b> are mobile communications devices. For example, the wireless devices <b>11</b> may be mobile phones or pagers, or PDAs, handheld computers, laptop computers, or other devices equipped with wireless communications capabilities, or a combination of any of the foregoing. Moreover, the set of wireless devices <b>11</b> in the region is not necessarily fixed. Additional wireless devices <b>11</b> may enter the region and existing wireless devices <b>11</b> may leave the region. It should be understood, however, that the present invention may be used with stationary wireless devices.
P-0030[0030] To facilitate communications, each wireless device <b>11</b> includes one or more antennas. In a preferred embodiment, the antennas are omnidirectional antennas so that a particular wireless device <b>11</b> can communicate with any of the other wireless devices <b>11</b> within its operable range without regard to where the other wireless devices <b>11</b> are located. Of course, other antenna designs may be used with any one or more of the wireless devices <b>11</b>.
P-0031[0031] Each of the wireless communications devices <b>11</b> may store unique identifying data that it can transmit to the other wireless communication devices <b>11</b> in the region. Accordingly, each wireless communication device <b>11</b> can identify itself to the other communication devices <b>11</b> and distinguish between other wireless communication devices using the identifying data. For example, a wireless device <b>11</b>-<b>1</b> can transmit RF signals containing communication data intended specifically for wireless device <b>11</b>-<b>3</b>. By including the identifying data in the RF transmission, wireless device <b>11</b>-<b>3</b> can receive and perform actions responsive to the communication data, while other wireless devices <b>11</b> ignore the data. The communication data may be, for example, commercial data exchanged in a commercial transaction between owners or users of wireless devices <b>11</b>-<b>1</b> and <b>11</b>-<b>3</b>. Alternatively, or in addition, the communication data may include advertising data, news, weather, or other useful information.
P-0032[0032] Communications between the wireless devices <b>11</b> can be carried out using a protocol employing a master-slave relationship. In this case, one of the wireless devices <b>11</b> in a particular region may be a master with one or more others of the wireless devices <b>11</b> in the region serving as a slave. The master device will control communications carried out with the slave devices. In one embodiment, the wireless devices <b>11</b> communicate using the Bluetooth™ protocol, but of course other protocols may be used. The Bluetooth™ protocol uses a half-duplex, frequency-hopping scheme operating in the 2.4 GHz band. Bluetooth™ devices hop through 1600 frequency channels per second, with 800 transmit and 800 receive channels. The channels span 79 MHz with a 1 MHz spacing between adjacent channels. Bluetooth™ allows various wireless equipment (mobile phones, mobile computers, etc.) to communicate over relatively short range of about 100 meters.
P-0033[0033] The present invention determines the distance between wireless devices using an indirect propagation delay measurement. For example, an RF signal, transmitted from wireless device A to wireless device B, will be received at a given phase angle. Fundamentally, for a given transmission distance, there is a linear relationship between the received phase angle offset of the RF signal and the frequency of the RF signal. Accordingly, for a given distance between the devices, the received phase offset angle vs. frequency curve is theoretically a straight line with the slope of the line dependent upon the measured distance. Specifically, the distance between objects is proportional to the slope of the phase/frequency curve. Therefore, by transmitting an RF signal at multiple frequencies, and observing the received phase offset-angles of the RF signal for each of those frequencies, the distance between wireless devices can be calculated. Further, this differential phase measurement resolves the ambiguity caused by the unknown number of cycles the signal has completed before the received signal arrives at the receiving antenna.
P-0034[0034] One difficulty in implementation is caused by “phase folding.” As the frequency of the received RF signal increases, the received phase also increases. Since the phase measurement is constrained to a value from −π to π;, the phase angle will “fold” over to −π each time it exceeds π. A unique algorithm (e.g., software implemented) detects phase “folding” every time the phase difference completes a whole cycle, and corrects by adding π; to the phase result each time a negative slope (π=>−π) is detected. In this way, a linear series of received phase angles can be obtained. After the phase angles of the received RF signals are detected and corrected for the phase folding effect, the slope of the phase angle data, relative to frequency, can be calculated.
P-0035[0035] It should be noted that a significant distortion of the measured phase angles may occur in practice as a result of the multipath phenomenon. One or more techniques to analyze, minimize, or eliminate multipath interference can be implemented, for example, as suggested in related patent application U.S. Application No. [Attorney Docket No. 52625-5003], filed concurrently herewith and expressly incorporated by reference herein.
P-0036[0036] As described above, the technique of the present invention requires transmission and reception at multiple frequencies to determine the distance between wireless devices. Consequently, a frequency hopping scheme (such as that employed by Bluetooth™ technology) serves as an appropriate platform on which to implement the invention. While the invention will be described with respect to Bluetooth™, this is just one of many possible implementations of the invention. Any number of methods employ transmission of multiple frequencies could be used to implement the invention.
P-0037[0037] The present invention may be used in a variety of applications including, but not limited to, mobile commerce, mobile banking, and information on demand. While the present invention can be used to measure the distance between two wireless devices without any additional infrastructure, e.g., a base station and a remote unit, it can also be used to determine distance between any number of wireless devices, e.g., a base station and multiple remote wireless devices, or between remote wireless devices.
P-0038[0038] Transactions between wireless devices may be directed based on the result of this distance measurement. For example, if the distance between the wireless devices is within a specified criteria, information (advertisements, news, weather, travel) may be pushed from one unit to the other, payment for goods, services or information may be effected, or banking transactions initiated (e.g., obtaining account statement information, transferring funds between accounts). Other applications will be known to those skilled in the art and are within the scope of the present invention.
P-0039[0039]FIG. 2 illustrates the operation of an embodiment of the present invention. For simplicity, the operation of the present invention will be described with reference to two wireless devices: a base station <b>100</b> and a remote unit <b>200</b>. As shown, the base station unit <b>100</b> is separated from the remote unit <b>200</b> by a distance D. As described above, the distance may be determined by measuring the differential phase between two or more frequencies of a signal transmitted between the base station <b>100</b> and the remote unit <b>200</b>. In one embodiment of the present invention, frequency hopping is used by the base station <b>100</b> and the remote unit <b>200</b> to generate the signals necessary to determine the distance measurement.
P-0040[0040] A signal S<b>1</b> using a sequence of carriers at frequencies f<sub>t1</sub>, f<sub>t2</sub>, . . . f<sub>tn </sub>is generated at base station <b>100</b> and transmitted to remote unit <b>200</b>. At remote unit <b>200</b>, the signal S<b>1</b> is received and demodulated. The demodulated signal is used as a reference to generate a second signal S<b>2</b>. Signal S<b>2</b> includes a sequence of carriers having frequencies f<sub>r1</sub>, f<sub>r2</sub>, . . . f<sub>tn</sub>. The remote unit transfers the phase information of signal S<b>1</b> to signal S<b>2</b>. The frequencies in each sequence of carriers may be in ascending order, in descending order, another pattern, or in random order, for example. Additionally, the spacing between adjacent carrier frequencies contained in a sequence (i.e., irrespective of their order in the sequence) may be constant, vary according to a pattern, skip some frequencies, or occur randomly within a range. Thus, base station <b>100</b> and remote unit <b>200</b> remain synchronized, or phase locked, with each other. Signal S<b>2</b> is transmitted from the remote unit <b>200</b> back to the base station <b>100</b> where it is frequency converted to the frequencies of signal S<b>1</b> and phase compared with the signal S<b>1</b>. Alternatively, an additional RF signal, phase coherent with S<b>1</b>, may be generated in base station <b>100</b> and be used to do the phase comparison with S<b>2</b>. This arrangement obviates the need to frequency convert S<b>2</b> before performing the phase comparison.
P-0041[0041] Phase comparison of the corresponding frequency increments of signal S<b>1</b> and frequency converted signal S<b>2</b> provides a phase offset Θi for each of the frequencies. The relative phase offsets φi between the frequency increments is calculated by subtracting phase offsets Θi of the carriers of S<b>2</b> having adjacent frequencies. A software implemented phase ambiguity algorithm is applied during the calculation to account for the phase folding resulting from any repeated cycling of the phase difference from −π to +π. Once the relative phase offset information is obtained, the distance D can be calculated from the slope of the relative phase offsets (φi) v. frequency data.
P-0042[0042] The embodiment illustrated in FIG. 2 is directed to a full-duplex system in which signal transmission and reception occur simultaneously requiring the frequencies of S<b>1</b> to be different from the frequencies of S<b>2</b>. However, as will be described later, the present invention could also be implemented, for example, in a half-duplex manner allowing the use of the same frequencies for signals S<b>1</b> and S<b>2</b>, thereby obviating the need to convert the frequencies of signal S<b>2</b> to the frequencies of S<b>1</b>, or the frequencies of signal S<b>1</b> to the frequencies of S<b>2</b>, for phase comparison.
P-0043[0043] RF communications, control, and processing functionality of the base station <b>100</b> may be performed by common equipment, for example, under different software control, or may be performed by different equipment. Examples are described below in connection with FIG. 3A, 3B, and <b>3</b>C. However, it should be understood that control, processing, and RF communications functionality may be performed by various equipment configurations depending on the type of device that base station <b>100</b> embodies and the degree of overlap and compatibility between the distance measurement functionality and other functionality of the base station <b>100</b>.
P-0044[0044] For example, if the base station <b>100</b> is a Bluetooth-enabled mobile telephone, the base station <b>100</b> requires RF communications for mobile telecommunications, distance measurement, and Bluetooth communications. The same or different control and/or RF equipment may be used for wireless communications to network infrastructure (e.g., mobile telephone to cellular base station), for distance measurement, and for direct wireless device-to-wireless device (e.g., Bluetooth) communications. The same may be true of a Bluetooth-enabled laptop with a RF modem for linking to an ISP and many other devices equipped for wireless communications using multiple different protocols. On the other hand, the base station <b>100</b> may embody a wireless device that supports distance measurement and a single wireless communications protocol (e.g., a Bluetooth-equipped vending machine, a mobile telephone, laptop with an RF modem, etc.). The same or different control and/or RF equipment may be used for wireless communications and for distance measurement. Finally, the base station <b>100</b> may be equipped for RF communication only to perform wireless distance measurement. In this case, only a single RF communications equipment for distance measurement need be provided.
P-0045[0045]FIG. 3A is a functional block diagram illustrating some of the components of the base station <b>100</b> according to an exemplary embodiment. As shown, base station <b>100</b> includes a user interface <b>101</b>, a processor <b>102</b>, and an RF transceiver <b>103</b>. The processor <b>102</b> further includes a central processing unit (CPU) <b>102</b>, memory <b>105</b>, e.g., DRAM, and data storage medium <b>106</b>. The user operates the base station through the user interface <b>101</b>. User interface <b>101</b> can include any number of input controls and output devices, such as a visual display, a keypad, pointer, a mouse, tracking ball, a four-button pad, speaker(s), a microphone, or any combination of the foregoing.
P-0046[0046] Processor <b>102</b> is coupled between the user interface <b>101</b> and the RF transceiver <b>103</b>. Processor <b>102</b> receives phase and amplitude data (e.g., I and Q data, as will be used in the following examples) from the RF transceiver <b>103</b> and calculates distance, which can be displayed on the user interface or used to control a distance-based process. The processor also controls the transceiver <b>103</b> and receives control information from the user interface <b>101</b>. The I/Q data from the RF transceiver <b>103</b> is typically stored in memory <b>105</b> for processing by CPU <b>104</b>. Further, storage space <b>106</b> contains program instructions for the CPU as well as other static data such as the device ID information. In handheld devices, storage <b>106</b> is typically a non-volatile read only memory. In larger base station implementations, the storage space can be a hard disk drive. It is anticipated that the program instructions for the processor <b>102</b> can be embedded for storage, transport, or sale, in any suitable computer readable mediums, such as a floppy diskette, optical disk, a memory chip or a memory portion of a chip, or can be stored on a server and downloaded to the processor for use. The RF transceiver <b>103</b> is typically implemented as a combination of discrete components or a smaller number of integrated chipsets.
P-0047[0047] In addition to calculating the distance, for example, as described below, the processor <b>102</b> and the transceiver <b>103</b> may operate to communicate according to one or more communication protocols using the same or different frequencies than used for distance measurement. For example, if the base station <b>100</b> were a mobile telephone, the processor <b>102</b> and transceiver <b>103</b> may be used to handle mobile telephone communications. For example, the base station may transmit and receive communications signals with a cellular station, a satellite, or other network switching infrastructure. In addition, the processor <b>102</b> and transceiver <b>103</b> may be used to handle other communications protocol(s), such as Bluetooth, for example. The base station <b>100</b> may communicate directly with other wireless devices. In this regard, the base station <b>100</b> may use common equipment for distance measurement and for other communications. Alternatively, the RF transceiver <b>103</b> may be used solely for distance measurement.
P-0048[0048]FIG. 3B illustrates a further exemplary embodiment of a base station <b>100</b>. FIG. 3B is similar to FIG. 3A, but includes RF transceiver <b>103</b>-<b>1</b> and RF transceiver <b>103</b>-<b>2</b>. In accordance with the embodiment of FIG. 3B, the RF transceiver <b>103</b>-<b>1</b> may be used for communications according to a first set of one or more communications protocols and RF transceiver <b>103</b>-<b>2</b> may be used for distance measurements and possibly communications according to a second set of one or more communications protocols. Processor <b>102</b> controls transceivers <b>103</b>-<b>1</b> and <b>103</b>-<b>2</b> and may process information received from either or both transceivers. In accordance with FIG. 3B, the base station <b>100</b> may be, for example, a mobile telephone. RF transceiver <b>103</b>-<b>1</b> may handle telephone communications and RF transceiver <b>103</b>-<b>2</b> may handle distance measurement RF transmissions and possibly other communications, such as Bluetooth communications.
P-0049[0049]FIG. 3C illustrates a further exemplary embodiment of a base station <b>100</b>. FIG. 3C is similar to FIG. 3A, but includes processors <b>102</b>-<b>1</b> and <b>102</b>-<b>2</b> and transceivers <b>103</b>-<b>1</b> and <b>103</b>-<b>2</b>. In accordance with the embodiment of FIG. 3C, the processor <b>102</b>-<b>1</b> and RF transceiver <b>103</b>-<b>1</b> may be used for communications according to a first set of one or more communications protocols and processor <b>102</b>-<b>2</b> and RF transceiver <b>103</b>-<b>2</b> may be used for distance measurements and possibly communications according to a second set of one or more communications protocols. Processor <b>102</b>-<b>1</b> controls and may process data from transceiver <b>103</b>-<b>1</b> and processor <b>102</b>-<b>2</b>. Processor <b>102</b>-<b>2</b> controls and processes information from RF transceiver <b>103</b>-<b>2</b>. Processor <b>102</b>-<b>2</b> also communicates with processor <b>102</b>-<b>1</b>. In accordance with FIG. 3C, the base station <b>100</b> may be, for example, a mobile telephone. RF transceiver <b>103</b>-<b>1</b> may handle telephone communications and RF transceiver <b>103</b>-<b>2</b> may handle distance measurement RF transmissions and other communications, such as Bluetooth communications. Processor <b>102</b>-<b>1</b> may be used to control mobile telephone communications and perform overall device control. Processor may be used for controlling distance measurement control, such as mathematical processing, and perform control operations for another communications protocol, e.g., Blueooth. The embodiments of FIGS. 3B and 3C are useful, for example, where the distance measurement functionality is added to an existing device design. In the embodiment of FIG. 3B, the processor <b>102</b> of the existing device may be loaded with software for performing distance measurement calculations. FIG. 3C provides an alternative where the processor <b>102</b>-<b>1</b> is not capable or would not be efficient for performing the distance measurement calculations.
P-0050[0050]FIGS. 4A and 4B show two alternative implementations of the present invention in base station <b>100</b>. As shown in FIG. 4A, the distance measurement functionality may be implemented as a separate processor chip <b>108</b> and used in conjunction with a RF transceiver chip <b>107</b>. The processor chip <b>108</b> may be, for example, a general purpose microprocessor, a math processor, or an ASIC built using, for example, CMOS technology. The RF transceiver chip <b>107</b> may be, for example, a Bluetooth chip or other RF communications chip. The RF transceiver chip <b>107</b> may be built using bipolar technology or BiCMOS technology.
P-0051[0051] Alternatively, as shown in FIG. 4B, the RF transceiver chip <b>107</b> may include memory <b>109</b> and processor circuitry <b>110</b> for performing distance measurement calculations. The processor circuitry <b>110</b> may be general purpose processing circuitry or a specially-designed circuit for performing distance measurement calculations. Accordingly, the RF transceiver chip <b>107</b> may output a distance value directly. The RF transceiver chip <b>107</b> may be a Bluetooth chip. Other platforms will be known to those skilled in the art and are within the scope of the present invention.
P-0052[0052]FIG. 5 illustrates exemplary RF circuitry that may be included in the base station <b>100</b> and the remote station <b>200</b>. FIG. 5 has been simplified for purposes of explanation and is not intended to show every feature of the base station <b>100</b> and the remote station <b>200</b>. As shown, the base station <b>100</b> includes a local oscillator <b>103</b>-<b>1</b>, divider <b>103</b>-<b>2</b>, synthesizer <b>103</b>-<b>3</b>, synthesizer <b>103</b>-<b>4</b>, power amplifier <b>103</b>-<b>5</b>, phase detector <b>103</b>-<b>6</b>, and receiver <b>103</b>-<b>7</b>. Local oscillator <b>103</b>-<b>1</b> generates a system clock, or reference frequency f<sub>ref</sub>, which is coupled to the reference inputs of synthesizers <b>103</b>-<b>3</b> and <b>103</b>-<b>4</b>. In this example, the value of f<sub>ref </sub>will be set to 0.5 MHz. System clock f<sub>ref </sub>is also divided by divider (÷M) <b>103</b>-<b>2</b> to generate a modulation signal f<sub>m</sub>. Integer M can be set to an integer value of at least one or higher. In this case, M will be set to a value of 1. Consequently, in this example, f<sub>m </sub>is also equal to 0.5 MHz. Modulation signal f<sub>m </sub>is coupled to the modulation input of synthesizer <b>103</b>-<b>5</b>. Because modulation signal f<sub>m </sub>is derived from f<sub>ref</sub>, it maintains phase coherency with f<sub>ref</sub>. Likewise, because the carriers having frequencies f<sub>t1</sub>, f<sub>t2</sub>, . . . f<sub>tn </sub>are derived from f<sub>ref</sub>, phase coherency between these carriers having frequencies f<sub>t1</sub>, f<sub>t2</sub>, . . . f<sub>tn</sub>, and signals f<sub>ref</sub>, and f<sub>m </sub>is maintained.
P-0053[0053] Synthesizer <b>103</b>-<b>3</b> generates a frequency hopping spread spectrum (FHSS) signal S<b>1</b>, which is comprised of a sequence of carriers at different frequencies. Each carrier is a multiple of the reference frequency f<sub>ref</sub>. Signal S<b>1</b> is modulated by f<sub>m </sub>and coupled to the input of power amplifier <b>103</b>-<b>5</b>. Signal S<b>1</b> is therefore comprised of a sequence of carriers, each modulated by f<sub>m</sub>. Power amplifier <b>103</b>-<b>5</b> amplifies S<b>1</b> to produce amplified signal S<b>1</b>A. Signal S<b>1</b>A is propagated over distance D to the remote unit <b>200</b>.
P-0054[0054] Synthesizer <b>103</b>-<b>4</b> generates an FHSS signal S<b>3</b>, which is comprised of a sequence of carriers at different frequencies. Each carrier is a multiple of the reference frequency f<sub>ref</sub>. Each of the carriers in the sequence of carriers of signal S<b>3</b> has a corresponding carrier from the sequence of carriers of S<b>1</b>. Typically, in a full duplex design, signals S<b>1</b> and S<b>3</b> are required to be within different frequency bands.
P-0055[0055] Receiver <b>103</b>-<b>7</b> receives external FHSS signal S<b>2</b>A′ (transmitted from remote station <b>200</b>). Signals S<b>2</b>A′ and S<b>3</b> have the same carrier frequencies. Signal S<b>2</b>A′ is comprised of a sequence of phase shifted carriers corresponding to the carriers of signal S<b>3</b> generated by synthesizer <b>103</b>-<b>4</b>. Further, the sequence of carriers of signal S<b>2</b>A′ are equal in frequency to the sequence of carriers of signal S<b>3</b> generated by the synthesizer <b>103</b>-<b>4</b>. Signal S<b>2</b>′ and S<b>3</b> are coupled to the inputs of phase detector <b>103</b>-<b>6</b> for phase comparison. Phase detector <b>103</b>-<b>6</b> generates a sequence of DC I/Q outputs corresponding to the phase and amplitude of the sequence of carriers of S<b>2</b>′.
P-0056[0056] Also shown in FIG. 5 is the remote station <b>200</b>. Remote station <b>200</b> includes a receiver/discriminator <b>200</b>-<b>2</b>, synthesizer <b>200</b>-<b>3</b>, and power amplifier <b>200</b>-<b>1</b>. The receiver/discriminator <b>200</b>-<b>2</b> receives FHSS signal S<b>1</b>A′ (comprised of a sequence of carriers having frequencies f<sub>t1</sub>, f<sub>t2</sub>, . . . f<sub>tn</sub>) from the RF transceiver <b>103</b> of the base station <b>100</b> and recovers the modulation signal f<sub>m</sub>′. Modulation signal f<sub>m</sub>′ is coupled to the input of synthesizer <b>200</b>-<b>3</b>. Synthesizer <b>200</b>-<b>3</b> multiplies f<sub>m</sub>′ by a sequence of integers to generate FHSS signal S<b>2</b>, which is comprised of a sequence of frequencies f<sub>r1</sub>, f<sub>r2</sub>, . . . f<sub>m</sub>. In this example, N will be a sequence of integers from 4804-4960. Signal S<b>2</b> is coupled to the input of power amplifier <b>200</b>-<b>1</b>, amplified, and transmitted to receiver <b>103</b>-<b>7</b> of base station <b>100</b>.
P-0057[0057] As shown in FIG. 5, modulated signal f<sub>m </sub>is transmitted from base station <b>100</b> to remote unit <b>200</b> using a frequency hopping scheme. For purposes of obtaining the distance measurement, the message content and method of modulation are academic (requiring only that phase coherency be maintained) and are dependent on the specific application and platform used. For example, if using the Bluetooth™ technology the method of modulation used would most likely be gaussian frequency shift keying. Other modulation techniques will be known to those skilled in the art and are within the scope of the present invention.
P-0058[0058] Once the signal S<b>1</b>′ is received at the remote unit <b>200</b> by receiver <b>200</b>-<b>2</b>, it is frequency discriminated to obtain a received version of original modulation signal signal f<sub>m</sub>′. Modulation signal f<sub>m</sub>′ contains the phase information of the received signal S<b>1</b>A′. Modulation signal f<sub>m </sub>can therefore be used to synchronize a voltage controlled oscillator (VCO) within the synthesizer <b>200</b>-<b>3</b>. More specifically, modulation signal f<sub>m</sub>′ can be used as a reference signal for the synthesizer <b>200</b>-<b>3</b> to generate FHSS signal S<b>2</b>, comprising carriers having frequencies (f<sub>r1</sub>, f<sub>r2</sub>, . . . f<sub>m</sub>). To accomplish this, synthesizer <b>200</b>-<b>3</b> multiplies f<sub>m</sub>′ (in this case, 0.5 MHZ) by a sequence of integers N (in this case, 4804=>8960). Each of the frequencies of S<b>2</b> is therefore phase coherent with modulation signal f<sub>m</sub>. S<b>2</b> is amplified by power amplifier <b>200</b>-<b>1</b> to generate signal S<b>2</b>A and transmitted back to the base station <b>100</b>.
P-0059[0059] At base station <b>100</b>, FHSS signal S<b>2</b>A′ is received by receiver <b>103</b>-<b>7</b> and amplified to produce FHSS signal S<b>2</b>′. The signal S<b>2</b>A′ is the same frequency as S<b>3</b> (generated by synthesizer <b>103</b>-<b>4</b>), except for a difference in the phase angle due to the propagation distance experienced by signal S<b>1</b>A′ and S<b>2</b>A′. Signal S<b>2</b>′ is phase compared with the S<b>3</b> by phase detector <b>103</b>-<b>6</b>. The phase comparison is performed by generating In-phase (I) and Quadrature (Q) DC signals and performing a simple arithmetic calculation to find the phase shift. I/Q data is stored in memory <b>105</b> of the processor <b>102</b> (shown in FIG. 3). After I/Q data is collected for a sufficient number of adjacent carrier frequencies, CPU <b>104</b> executes a distance measurement algorithm that operates on the stored I/Q data to calculate the distance between the base station <b>100</b> and remote station <b>200</b>.
P-0060[0060] Notably, in this embodiment, the carrier frequencies of S<b>1</b>A are different from the carrier frequencies comprising S<b>2</b>A. Consequently, this embodiment is well suited for, but not limited to, full-duplex operation. Moreover, the full-duplex transmission scheme described herein need not transmit carrier frequencies in incrementing or decrementing order, and in practice, the sequential order of carrier frequency transmission may be quite random. In operation, it is only necessary that the base station and the remote station follow the same hopping sequence of carrier frequencies. Many other transmission schemes are known and could take advantage of other variation of the full-duplex operation of this embodiment of the present invention.
P-0061[0061] In alternative embodiments, synthesizer <b>103</b>-<b>4</b> generates a FHSS signal having a sequence of carriers (S<b>3</b>) at different frequencies than those of S<b>2</b>A′. This requires that S<b>2</b>A′ be frequency-converted by receiver <b>103</b>-<b>7</b> to the same frequency as the FHSS signal output from synthesizer <b>103</b>-<b>4</b>. This frequency-conversion is necessary because of the requirement that the two inputs to phase detector <b>103</b>-<b>6</b> be at the same frequency for meaningful phase comparison. Generally, any transceiver arrangement that allows a phase detector to compare phases of equal frequency signals will suffice.
P-0062[0062]FIG. 6 is a detailed illustration of one example of phase detector <b>103</b>-<b>6</b>. As shown, phase detector <b>103</b>-<b>6</b> includes a 90 degree phase shifter <b>103</b>-<b>14</b>, RF mixers <b>103</b>-<b>12</b> and <b>103</b>-<b>13</b>, and low pass filters (LPFs) <b>103</b>-<b>10</b> and <b>103</b>-<b>11</b>. Mixer <b>103</b>-<b>12</b> receives input signal S<b>3</b> (sin [2πf<sub>t </sub>t]) from the synthesizer <b>103</b>-<b>4</b> and input signal S<b>2</b>′ (sin [2πf<sub>t </sub>(t−2τ)]) from receiver <b>103</b>-<b>7</b>. Mixer <b>103</b>-<b>12</b> mixes these two signals and sends the result to low pass filter <b>103</b>-<b>10</b> to remove unwanted harmonics. Mixer <b>103</b>-<b>13</b> receives input signal S<b>2</b>′ (sin [2πf<sub>t </sub>(t−2τ)]) from receiver <b>103</b>-<b>7</b> and S<b>3</b> (cos [2πf<sub>t </sub>t]) from the 90 degree phase shifter <b>103</b>-<b>14</b>. The 90 degree phase shifter <b>103</b>-<b>14</b> receives as an input S<b>3</b> (sin [2πf<sub>t </sub>t]) from synthesizer <b>103</b>-<b>14</b>. Mixer <b>103</b>-<b>13</b> mixes these two signals and sends the result to low pass filter <b>103</b>-<b>11</b> to remove unwanted harmonics. The inphase and quadrature signals I and Q are thereby output from low pass filters <b>103</b>-<b>10</b> and <b>103</b>-<b>11</b>, respectively. The phase differences (I and Q components) are forwarded to the CPU <b>103</b> (Shown in FIG. 3) for further processing, e.g., calculation of the phase/frequency slope.
P-0063[0063] The I and Q components are generated by mixing the received signal sin [2πf<sub>t </sub>(t−2τ)] with the locally generated signal sin [2πf<sub>t </sub>t] as illustrated in FIG. 6, where τ is the one-way time delay. Using the resulting I and Q components (stored in memory <b>105</b>) to solve for τ yields:
<i>Q/I</i>=tan [2<i>πf</i><sub>t</sub>*2τ]
τ=<i>arc </i>tan(<i>Q/I</i>)/4<i>πf</i><sub>t</sub>
P-0064[0064] Once an ambiguous value for τ (τ*) is determined, the phase shift Θ<sub>1</sub>:=2πf<sub>i</sub>τ* may be calculated. After the data (phase shift v. frequency) on the various frequencies is collected, a least mean square (LMS) error criteria is used to estimate the expected straight line curve. Figure <b>10</b> illustrates one example of a plotting of the phase shift v. frequency data using τ:=130 ns and a starting frequency F:=76 MHz with increments of ΔF:=1 MHz such that f<sub>i</sub>:=F+ΔFi.
P-0065[0065] As indicated in the graph of FIG. 10, a sawtooth curve results as the phase shift value “drops” to −π each time the phase shift cycles through π. To straighten out the angle v. frequency data, the following phase ambiguity algorithm is applied to a sequence of carriers having frequencies f<sub>r1</sub>, f<sub>r2</sub>, . . . f<sub>m</sub>:
φ(<i>n</i>):=0 if <i>n</i>=0; (1)
P-0066[0066] otherwise,
φ(<i>n</i>):=(Θ<i>n−Θn</i>−1)+φ(<i>n</i>−1)+π if Θ<i>n−Θn</i>−1<0 (2)
φ(<i>n</i>):=(Θ<i>n−Θn</i>−1)+φ(<i>n</i>−1) otherwise. (3)
P-0067[0067] At step (1), the value of φ(n) is initialized to equal 0 for the first carrier frequency f<sub>r0 </sub>thereby establishing a baseline for calculating the next plotted phase value.
P-0068[0068] At step (2), the algorithm checks for the negative slope (Θn−Θn−1<0) which would occur as the estimate drops to −π; as the phase difference cycles through +π. When the negative slope is detected, the algorithm adds the relative phase offset (Θn−Θn−1) of the points to the previous data point (φ(n−1)) +π and substitutes the resulting value for the zero estimate.
P-0069[0069] At step (3), if the algorithm determines that the slope is not negative, the algorithm adds the relative phase offset (Θn−Θn−1) of the points to the previous data point (φ(n−1)) and substitutes the resulting value for the zero estimate.
P-0070[0070] The modified data is then plotted using the parameters of a line <i>Φ</i><sub>1</sub>:=φ(<i>i</i>); <i>m:</i>=slope (<i>f</i>,Φ); <i>b</i>:=intercept(<i>f</i>,Φ); <i>y</i>(<i>i</i>) :=<i>mf</i><sub>i</sub>+<i>b </i>
P-0071[0071] to provide the phase v. frequency line shown in FIG. 11. The distance D in meters is determined from the slope (m) of the phase v. frequency line which is proportional to the delay T, i.e. T=m/2π;. In the example of FIG. 11, D:=cT, where c:=3×10<sup>8 </sup>m/s and T:=m/2π. Consequently, for the line illustrated in FIG. 11, T=130 ns resulting in a distance D=39 m. Subsequently, the calculated distance data can be used to implement any number of distance-based processes as described above.
P-0072[0072]FIG. 7 is a functional block diagram of a second embodiment of the present invention. This embodiment can operate either in half-duplex or in full-duplex modes. FIG. 7 illustrates circuitry that may be included in the RF transceiver portion of base station <b>300</b> and the remote station <b>400</b>. As shown, the base station <b>300</b> includes a local oscillator <b>300</b>-<b>1</b>, synthesizer <b>300</b>-<b>2</b>, synthesizer <b>300</b>-<b>3</b>, power amplifier <b>300</b>-<b>4</b>, phase detector <b>300</b>-<b>5</b>, and receiver <b>300</b>-<b>6</b>. Local oscillator <b>300</b>-<b>1</b> generates a system clock, or reference signal f<sub>ref</sub>, which is coupled to the reference inputs of synthesizers <b>300</b>-<b>2</b> and <b>300</b>-<b>3</b>. In this example, f<sub>ref</sub>=0.5 MHz.
P-0073[0073] Synthesizer <b>300</b>-<b>2</b> generates a single carrier signal S<b>1</b>(f0), which is coupled to the input of power amplifier <b>300</b>-<b>5</b>. S<b>1</b>(f0) is a multiple of the reference frequency f<sub>ref</sub>. In this example, synthesizer <b>300</b>-<b>2</b> multiplies f<sub>ref </sub>by an integer value R, where R=200. Power amplifier <b>300</b>-<b>4</b> amplifies S<b>1</b>(f0) and produces amplified signal S<b>1</b>A(f0), which may be, for example, 100 MHz. Signal S<b>1</b>A(f0) is propagated over distance D to the remote unit <b>400</b>. Synthesizer <b>300</b>-<b>3</b> generates an FHSS signal S<b>3</b>, which is comprised of a sequence of carriers at different frequencies. Each carrier is a multiple of the reference frequency f<sub>ref</sub>. In this example, f<sub>ref </sub>is multiplied by a sequence of integers N, where N varies between 4800 and 4960. As previously mentioned, N need not vary in ascending or descending order.
P-0074[0074] Receiver <b>300</b>-<b>6</b> receives external FHSS signal S<b>2</b>A′ (transmitted from remote station <b>200</b>) to produce return signal S<b>2</b>′. Signal S<b>2</b>′ is comprised of a sequence of phase shifted carriers corresponding to FHSS signal S<b>3</b> generated by synthesizer <b>300</b>-<b>3</b>. Further, the sequence of carriers of FHSS signal S<b>2</b>′ are equal in frequency to the sequence of carriers of signal S<b>3</b> generated by the synthesizer <b>300</b>-<b>3</b>. Signals S<b>2</b>′ and S<b>3</b> are coupled to the inputs of phase detector <b>300</b>-<b>5</b> for phase comparison. Phase detector <b>300</b>-<b>5</b> generates a sequence of DC I/Q outputs corresponding to the carriers of S<b>2</b>′ and S<b>3</b>. The internal details of phase detector <b>300</b>-<b>5</b> are the same as described in the previous embodiment.
P-0075[0075] Also shown in FIG. 7 is the remote station <b>400</b>. Remote station <b>400</b> includes a receiver <b>400</b>-<b>2</b>, divider <b>400</b>-<b>3</b>, synthesizer <b>400</b>-<b>4</b>, and power amplifier <b>400</b>-<b>1</b>. The receiver <b>400</b>-<b>2</b> receives single carrier signal S<b>1</b>A′(f0) from the base station <b>300</b> to produce S<b>1</b>′(f0). Divider <b>400</b>-<b>3</b> divides signal S<b>1</b>′(f0) to produce reference signal f<sub>ref</sub>. For purposes of example, R=200. Reference signal f<sub>ref </sub>is coupled to the input of synthesizer <b>400</b>-<b>4</b>. Synthesizer <b>400</b>-<b>4</b> multiplies f<sub>ref </sub>by a sequence of integers N to generate FHSS signal S<b>2</b>, which is comprised of a sequence of frequencies f<sub>r1</sub>, f<sub>r2</sub>, . . . f<sub>m</sub>. In this example, N is a sequence of integers between 4800 and 4960. Signal S<b>2</b> is coupled to the input of power amplifier <b>400</b>-<b>1</b>, amplified, and transmitted to receiver <b>300</b>-<b>6</b> in the RF transceiver <b>300</b> of the base station.
P-0076[0076] As shown in FIG. 7, single carrier signal S<b>1</b>A(f0)is transmitted from transceiver <b>300</b> to remote station <b>200</b>. As will be described, this embodiment does not require that a spread spectrum signal be used for the outgoing transmission from the base station. Further, the invention could be modified to work with a modulated carrier transmitted from the base station, although modulation is not a requirement for this embodiment
P-0077[0077] As shown in FIG. 7, signal S<b>1</b>A′ is received at the remote unit <b>400</b> by receiver <b>400</b>-<b>2</b> to produce single frequency signal S<b>1</b>(f0)′. S<b>1</b>(f0)′ is then used by the divider to generate a reference signal f<sub>ref</sub>. Reference signal f<sub>ref </sub>is used to synchronize a VCO in synthesizer <b>400</b>-<b>4</b> to generate S<b>2</b> which is comprised of a sequence of carriers (f<sub>r1</sub>, f<sub>r2</sub>, . . . f<sub>m</sub>). FHSS signal S<b>2</b> is amplified by power amplifier <b>400</b>-<b>1</b> to generate signal S<b>2</b>A and transmitted back to the RF transceiver <b>300</b> of the base station.
P-0078[0078] At the base station transceiver <b>300</b>, FHSS signal S<b>2</b>A′ is received by receiver <b>103</b>-<b>7</b> and amplified to produce FHSS signal S<b>2</b>′. Signal S<b>2</b>′ is phase compared with the signal S<b>3</b> originally generated by synthesizer <b>300</b>-<b>3</b>. As in the previous embodiment, phase comparison is performed by generating In-phase (I) and Quadrature (Q) DC signals and performing a simple arithmetic calculation to find the phase shift. I/Q data is stored in memory <b>105</b> of the processor <b>102</b> (shown in FIG. 3). After I/Q data is collected for a sufficient number of adjacent carrier frequencies, CPU <b>104</b> executes the distance measurement algorithm described in the previous embodiment. Notably, in the second embodiment, the carrier frequency of S<b>1</b>A(f0) was different from the frequencies comprising S<b>2</b>A. Consequently, the second embodiment is well suited for, but not limited to, full duplex operation. Further, as mentioned before, any transceiver implementation that provides for phase detection of equal frequency signals is sufficient.
P-0079[0079]FIG. 8 is a function block diagram of a further embodiment of the present invention. FIG. 8 illustrates circuitry that may be included in the base station transceiver <b>500</b> and the remote station <b>600</b>. As shown, the base station transceiver <b>500</b> includes a local oscillator <b>500</b>-<b>1</b>, synthesizer <b>500</b>-<b>2</b>, power amplifier <b>500</b>-<b>3</b>, phase detector <b>500</b>-<b>4</b>, and receiver <b>500</b>-<b>5</b>. Local oscillator <b>500</b>-<b>1</b> generates a system clock, or reference frequency f<sub>ref</sub>, which is coupled to the reference input of synthesizer <b>500</b>-<b>2</b>. N this example, f<sub>ref </sub>is set to 0.5 MHz.
P-0080[0080] Synthesizer <b>500</b>-<b>2</b> generates a frequency hopping spread spectrum (FHSS) signal S<b>1</b>, which is comprised of a sequence of carriers at different frequencies. Each carrier is a multiple of the reference frequency f<sub>ref</sub>. In this example, the multiplication factor N is used by synthesizer <b>500</b>-<b>2</b>, and is a sequence of values between 4800 and 4960. Signal S<b>1</b> is coupled to the input of power amplifier <b>500</b>-<b>3</b>. Power amplifier <b>500</b>-<b>3</b> amplifies signal S<b>1</b> and produces amplified FHSS signal S<b>1</b>A. Signal S<b>1</b>A is propagated over distance D to the remote unit <b>600</b>.
P-0081[0081] Receiver <b>500</b>-<b>5</b> receives external FHSS signal S<b>2</b>A′ (transmitted from remote station <b>600</b>). Signal S<b>2</b>A′ is comprised of a sequence of phase shifted carriers corresponding to the carriers of signal S<b>1</b> generated by synthesizer <b>500</b>-<b>2</b>. Further, the sequence of carriers of signal FHSS S<b>2</b>A′ are equal in frequency to the sequence of carriers of signal S<b>1</b> generated by the synthesizer <b>500</b>-<b>2</b>. Signal S<b>2</b>′ and S<b>1</b> are coupled to the inputs of phase detector <b>500</b>-<b>4</b> for phase comparison. Phase detector <b>500</b>-<b>4</b> generates a sequence of DC I/Q outputs corresponding to the carriers of S<b>2</b>′.
P-0082[0082] Also shown in FIG. 8 is the remote station <b>600</b>. Remote station <b>600</b> includes a receiver <b>600</b>-<b>1</b>, divider <b>600</b>-<b>2</b>, synthesizer <b>600</b>-<b>3</b>, and power amplifier <b>600</b>-<b>4</b>. The receiver <b>600</b>-<b>1</b> receives FHSS signal S<b>1</b>A′ (comprised of a sequence of carriers having frequencies f<sub>t1</sub>, f<sub>t2</sub>, . . . f<sub>tn</sub>) from the base station RF transceiver <b>500</b> and generates signal S<b>1</b>′. Divider <b>600</b>-<b>2</b> divides S<b>1</b>′ by a factor R to generate a sequence of reference signals f<sub>ref</sub>′. For purposes of example, let R sequence through the range of integers 4800=>4960. Reference signal f<sub>ref </sub>is coupled to the input of synthesizer <b>600</b>-<b>3</b>. Synthesizer <b>600</b>-<b>3</b> multiplies f<sub>ref </sub>to generate FHSS signal S<b>2</b>, which is comprised of a sequence of frequencies f<sub>r1</sub>, f<sub>r2</sub>, . . . f<sub>m</sub>. FHSS signal S<b>2</b> is coupled to the input of power amplifier <b>600</b>-<b>1</b>, amplified, and transmitted to receiver <b>500</b>-<b>5</b> of base station transceiver <b>500</b>.
P-0083[0083] The operation of this embodiment will be described with reference to FIGS. <b>8</b>-<b>9</b>. As shown in FIG. 8, FHSS signal S<b>1</b>A is transmitted from base station transceiver <b>500</b> to remote unit <b>600</b>. As shown in the timing diagram of FIG. 9, the S<b>1</b>A is comprised of a sequence of carriers f<b>1</b>, f<b>2</b>, f<b>3</b> . . . fn. To implement a half-duplex system, where the return transmit carriers have the same frequency as the base station transmit carriers, transmit and receive operations must be time multiplexed. In this example, the carrier of S<b>1</b>A having a frequency of f0 is transmitted by the base station to the remote station during a first time interval (B=>R). Subsequently, the same phase-shifter carrier is received by the base station during a second time interval (R=>B). Next, f1 is transmitted and received during alternating time intervals (B=>R) and (R=>B). In this way, the base station and remote station can utilize the same transmit band without interference.
P-0084[0084] The half-duplex transmission scheme described herein need not transmit carrier frequencies in incrementing order, and in practice, the sequential order of carrier frequency transmission may be quite random. In operation, it is only necessary that the base station and the remote station follow the same hopping sequence of carrier frequencies. Many other transmission schemes are known and could take advantage of other variation of the half-duplex operation of this embodiment of the present invention.
P-0085[0085] As shown in FIG. 8, once the signal S<b>1</b>A′ is received at the remote unit <b>600</b> by receiver <b>600</b>-<b>1</b>, it is divided down by divider <b>600</b>-<b>2</b> to generate the reference frequency f<sub>ref</sub>′. Divider <b>600</b>-<b>2</b> includes a phase locked loop for generating f<sub>ref</sub>′. The phase locked loop contains a VCO which is locked by the input signal S<b>1</b>′. In this example, the dividing factor R is selected from a sequence of integers ranging from 4800 to 4960. Each integer is selected according to the given transmit frequency. After the transmission of signal S<b>1</b>A(f0) from the transceiver <b>500</b> of the base station ceases, divider <b>600</b>-<b>2</b> maintains the control voltage on the VCO such that the reference signal f<sub>ref </sub>continues with minimal frequency and phase drift. One or more techniques to maintain a stable reference signal after the input locking signal ceases to exist can be implemented, for example, as suggested in related U.S. Application No. [Attorney Docket No. 52625-5002], filed concurrently herewith and expressly incorporated by reference herein.
P-0086[0086] Reference signal f<sub>ref </sub>contains the phase information of the received signal S<b>1</b>′. It can therefore be used to synchronize a VCO within the synthesizer <b>600</b>-<b>3</b>. More specifically, the signal f<sub>ref</sub>′ is used as a reference signal for the synthesizer <b>600</b>-<b>3</b> to generate signal S<b>2</b> comprising carriers having frequencies (f<sub>r1</sub>, f<sub>r2</sub>, . . . f<sub>m</sub>). Each of the frequencies of S<b>2</b> are phase coherent with reference signal f<sub>ref</sub>′. After transmission of S<b>1</b> by the base station transceiver <b>500</b> is complete, return signal S<b>2</b> is amplified by power amplifier <b>600</b>-<b>1</b> to generate signal S<b>2</b>A and transmitted back to the base station transceiver <b>500</b>.
P-0087[0087] At base station <b>500</b>, FHSS signal S<b>2</b>A′ is received and by receiver <b>500</b>-<b>5</b> and amplified to produce signal S<b>2</b>′. Signal S<b>2</b>′ is phase compared with the S<b>1</b> originally generated signals by synthesizer <b>500</b>-<b>2</b>. The phase comparison is performed by the same methods previously described.
P-0088[0088] There are any number of physical implementations capable of practicing the inventive methods described herein. For example, FIG. 12 illustrates the process steps used to perform distance measurement in accordance with an embodiment of the present invention. The steps could be applied to any number of system implementations. While steps <b>700</b>-<b>1</b> through <b>700</b>-<b>14</b> will produce the desired result, i.e. an accurate distance measurement between a base station and a remote station, the invention may be practiced without including each and every step shown.
P-0089[0089] At step <b>700</b>-<b>1</b>, a first FHSS signal is generated at a base station. At step <b>700</b>-<b>2</b>, a third FHSS signal is generated at the base station. The third FFHS signal has a different frequency structure than the first FHSS signal. As will be discussed below, step <b>700</b>-<b>2</b> is not required. Step <b>700</b>-<b>3</b> involves modulating the first FHSS signal with a modulation signal fm. The modulated signal is transmitted to a remote station in step <b>700</b>-<b>4</b>.
P-0090[0090] At step <b>700</b>-<b>5</b>, the modulation signal fm is recovered at the remote station. For example, the received signal may be discriminated at the remote station to recover the modulation signal. As noted above, the modulated signal fm received at the remote station approximates the signal fm transmitted by the base station time-shifted as a result of the transmission delay. Step <b>700</b>-<b>6</b> includes generating a second FHSS signal using the recovered modulation signal fm as a reference signal. At step <b>700</b>-<b>7</b>, the remote station transmits the second FHSS signal to the base station. At step <b>700</b>-<b>8</b>, the base station receives the second FHSS signal. At step <b>700</b>-<b>9</b>, the phase of the second and third FHSS signal are compared to generate I/Q phase data. Alternatively, the received second FFHS signal may be converted to a time-delayed version of the first FFHS signal. In such a case, the first FFHS signal and the time-delayed version may be compared. Moreover, both of the first and second FFHS signals may be converted to a fourth and fifth FFHS signals for comparison. The above steps may be repeated several times to obtain multiple data points for statistical correction.
P-0091[0091] Step <b>700</b>-<b>10</b> includes storing I/Q data in memory. At step <b>700</b>-<b>11</b>, the phase offsets for adjacent frequencies are calculated. At step <b>700</b>-<b>12</b>, a straight line curve is estimated using the phase offsets. Of course, a straight line curve need not be actually plotted, but the estimation may be performed by manipulating data sets. For example, a least mean square error criteria may be used to estimate the straight line curve. At step <b>700</b>-<b>13</b>, a phase ambiguity algorithm is applied to obtain phase v. frequency line. As above, the phase v. frequency line need not be actually plotted, but may be represented in data. Finally, at step <b>700</b>-<b>14</b>, the distance between the base station and the remote station is calculated based on the slope of the phase/frequency line.
P-0092[0092]FIG. 13 illustrates the process steps used in performing distance measurement in accordance with an embodiment of the present invention. As above, the steps could be applied to any number of system implementations. While steps <b>800</b>-<b>1</b> through <b>800</b>-<b>13</b> will produce the desired result, i.e. an accurate distance measurement between a base station and a remote station, the invention may be practiced without including each and every step shown.
P-0093[0093] Step <b>800</b>-<b>1</b> includes transmitting a single frequency carrier from a base station to a remote station. At the remote station, a reference signal is generated by dividing the received single carrier signal by a constant, as shown in step <b>800</b>-<b>2</b>. At step <b>800</b>-<b>3</b>, an FHSS signal is generated from the reference signal. The FHSS signal is transmitted from the remote to the base station at step <b>800</b>-<b>4</b> and received at the base station at step <b>800</b>-<b>5</b>. Step <b>800</b>-<b>6</b> includes generating another FHSS signal at the base station that is phase coherent with the single carrier signal. At step <b>800</b>-<b>7</b>, the phases of the two FHSS signals are compared to generate I/Q phase data. At step <b>800</b>-<b>8</b>, the I/Q data is stored in memory. Step <b>800</b>-<b>9</b> includes calculating phase offsets for adjacent frequencies. At step <b>800</b>-<b>10</b>, a straight line curve is estimated, e.g., using a least mean square error criteria. As above, the straight line curve may be represented in data. Step <b>800</b>-<b>11</b> includes applying a phase ambiguity algorithm to obtain phase v. frequency line. Step <b>800</b>-<b>12</b> includes calculating the distance between the base station and the remote station based on the slope of the phase/frequency line.
P-0094[0094]FIG. 14 illustrates the process steps used in performing distance measurement in accordance with an embodiment of the present invention. The steps could be applied to any number of system implementations. While steps <b>900</b>-<b>1</b> through <b>900</b>-<b>13</b> will produce the desired result, i.e. an accurate distance measurement between a base station and a remote station, the invention may be practiced without including each and every step shown.
P-0095[0095] Step <b>900</b>-<b>1</b> includes generating a first FHSS signal at a base station. At step <b>900</b>-<b>2</b>, the first FHSS signal is transmitted to a remote station. At the remote station, the received FHSS signal is divided by a series of integers to generate a reference signal, as provided in step <b>900</b>-<b>3</b>. Step <b>900</b>-<b>4</b> includes halting the transmission of the first FHSS signal and maintaining the reference signal. Step <b>900</b>-<b>5</b> includes multiplying the reference signal by a series of constants to produce a second FHSS signal. The multiplied second FHSS signal is transmitted to the base station at step <b>900</b>-<b>6</b> and received at the base station at step <b>900</b>-<b>7</b>. At step <b>900</b>-<b>8</b>, the phase of the first and second FHSS signals are compared to generate I/Q phase data. Step <b>900</b>-<b>9</b> includes storing the I/Q data in memory and step <b>900</b>-<b>10</b> includes calculating phase offsets for adjacent frequencies. At step <b>900</b>-<b>11</b>, a straight-line curve is estimated, e.g., using least mean square error criteria. Step <b>900</b>-<b>12</b> includes applying a phase ambiguity algorithm to obtain phase v. frequency line. The distance between the base station and the remote station is calculated based on the slope of the phase/frequency line at step <b>900</b>-<b>13</b>.
P-0096[0096] Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
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19 legal events, as the office reported them to INPADOC
Over the term
Point at a mark for the eventEvents
| Event | Code | |
|---|---|---|
| Lapsed due to failure to pay maintenance feeLapsedFP | FP | |
| Information on status: patent discontinuationPATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362STCH | STCH | |
| Information on status: patent discontinuationPATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362STCH | STCH | |
| Lapse for failure to pay maintenance feesLapsedLAPS | LAPS | |
| Maintenance fee reminder mailedREMI | REMI | |
| Fee payment procedurePAT HOLDER NO LONGER CLAIMS SMALL ENTITY STATUS, ENTITY STATUS SET TO UNDISCOUNTED (ORIGINAL EVENT CODE: STOL); ENTITY STATUS OF PATENT OWNER: LARGE ENTITYFEPP | FEPP | |
| AssignmentAS | AS | |
| Fee paymentFPAY | FPAY | |
| AssignmentAS | AS | |
| AssignmentAS | AS | |
| AssignmentAS | AS | |
| AssignmentAS | AS | |
| AssignmentAS | AS | |
| AssignmentAS | AS | |
| Fee paymentFPAY | FPAY | |
| AssignmentAS | AS | |
| AssignmentAS | AS | |
| AssignmentAS | AS | |
| AssignmentAS | AS |
Numbers
- Application
- 75960101
Titles
- English
- Accurate distance measurement using RF techniques
Patent term adjustment
- A delay
- +275 daysthe office missed an examination deadline
- B delay
- +128 dayspendency past three years
- Applicant delay
- −120 days
- Net adjustment
- 283 days
Classification
- CPC, 1
- G01S13/84
- IPC, 1
- G01S13 84