Reduced-complexity antenna system using multiplexed receive chain processing

Antenna system with reduced complexity using multiplexed receiving chain processing

Technical field

The present invention relates to an antenna diversity receiver used in a radio communication system, and in particular to an antenna device that uses a signal processing chain of a joint diversity receiver to reduce complexity.

Background technique

It has recently been proposed that the performance and capacity of existing wireless systems can be improved by using so-called "smart" antenna technology. In particular, a technique combining spatio-temporal signal processing has been proposed, which can be used to resist the desired harmful effects of multipath attenuation of the introduced signal and to suppress interference signals. In this way, the performance and capacity of digital wireless systems in existing or to be developed (for example, CDMA-based systems, TDMA-based systems, WLAN systems, and OFDM-based systems such as IEEE802.11a/g systems) can be Be improved.

It can be expected that smart antenna technology will be increasingly applied to the configuration of base station facilities and individual mobile users (such as mobile phones) connected to cellular systems, in order to locate the increasing demand for configuration in such systems. These requirements are partly caused by the transition from current voice-based services to next-generation wireless multimedia services in use, and the accompanying blurring of the differences between voice, image, and data transfer modes. Individual users using such next-generation systems will have to demonstrate higher sound quality and provide high-speed data services (for example, 10 Mbits/s high speed) compared to the existing cellular mobile radio standards. However, it is complicated to obtain high-speed and high-quality services, because individual mobile users want to be compact and light, and in various environments (such as cellular/one-hundredth-cell/one-mega-cell, urban/ Suburban/rural and indoor/outdoor) stable operation capability. In addition, in addition to providing high-quality communications and coverage, next-generation systems expect to get more effective use of available bandwidth and acceptable prices to ensure widespread market adoption.

In some wireless systems, three main factors tend to take up most of the performance and reduce capacity: multipath attenuation, propagation delay between components of the received multipath signal, and co-channel interference (CCI). As we all know, multipath attenuation is caused by a transmitted signal traveling through multiple paths back and forth on its way to the receiving antenna. Signals with different phases from these paths are superimposed together, causing the amplitude and phase of the received signal to change with the position, direction, and polarization of the antenna, and time (as caused by traveling in the environment). In order to eliminate the effects of multipath attenuation and improve quality or reduce the influential error rate has proven to be very difficult. Although it is theoretically feasible to reduce the impact of multipath attenuation by using higher generation energy or increasing bandwidth, these methods are usually in contradiction with the requirements of next-generation systems.

As mentioned above, "delay propagation" or the difference in propagation delay in composite components receiving multipath signals tends to constitute a major obstacle to improving the capacity and performance of wireless communication systems. It has been reported that when the delay propagation exceeds approximately ten percent (10%) of the symbol period, the resulting significant inter-symbol interference (ISI) usually limits the maximum data speed. It has been noted that this type of trouble frequently occurs in narrow bandwidth systems, such as the Global System for Mobile Communications (GSM).

The existence of co-channel interference also adversely affects the performance and capacity of the cellular system. The operation of the existing cellular system is to divide the available channels into channel groups, each unit uses a channel group, and frequency reuses. Time division multiple access (TDMA) systems use a frequency reuse with a usage factor of 7, while most code division multiple (CDMA) systems use a frequency reuse with a usage factor of 1. These frequency reuses lead to CCI, which increases when the channel group decreases (for example, the capacity of each unit increases). In the TDMA system, the CCI mainly comes from one or two different users; while in the CDMA system, there may be some strong interference in the unit and from adjacent units. For a given CCI level, capacity can be improved by shortening the size of the unit, but it increases the cost of adding base stations.

The performance impairment of the cellular system described above can be partially improved by using a multi-element antenna system designed to introduce diversity gain into the signal reception process. There are at least three main methods for achieving diversity gain through the anti-correlation interference of the received signal of each antenna element: space diversity, polarization diversity, and angle diversity. In order to understand the spatial diversity, the antenna elements are sufficiently separated to obtain a lower attenuation correlation. The separation requirement depends on the angular spread, which refers to the angle at which the signal reaches the receiving antenna.

In the case where a mobile subscriber unit (such as a mobile phone) is surrounded by other scattered objects, the antenna spacing is only a quarter of a wavelength, which is usually sufficient to obtain a lower attenuation correlation. This allows multiple spatial diversity antennas to be combined on a mobile phone, particularly at higher frequencies (because the reduction in antenna size is a function of increasing frequency). Furthermore, dual-polarized antennas can be placed close together, have lower attenuation correlation, and can be regarded as antennas with different styles (angle or direction diversity). However, each antenna element configuration in the wireless phone requires a separate electronic signal processing chain, which increases the cost and energy consumption of the phone.

Summary of the invention

In one embodiment, the present invention is embodied as a method for receiving signals and a device for implementing the method. The method includes the following steps: receiving each of the multiple copies through each of the corresponding majority antenna elements, so as to generate multiple received signal copies; orthogonally multiplexing the multiple received signal copies into one The multiplexed signal supplied to the signal processing chain; in the signal processing chain, the multiplexed signal is transformed into a plurality of separate signals, where each separate signal corresponds to one of the copies of the signal.

Alternatively, orthogonal multiplexing is implemented according to complex Walsh coding scheduling. Other alternatives are that each converts the signal into a multiplexed signal copy, the signal copies are offset by 90 degrees from each other.

In another embodiment, the present invention is expressed as a method for receiving signals, including the steps of: receiving each of a large number of signal replicas through one of the corresponding antenna elements, thereby generating multiple received signal replicas; The antennas in the first subnet of the element exchange signal energy to generate a first signal that includes the signal energy from each antenna of the first subnet of the plurality of antenna elements; from the first subnet of the plurality of antenna elements The antennas in the two subnets exchange signal energy to generate a second signal that includes the signal energy from each antenna of the second subnet of multiple antenna elements; the second signal is changed from the phase of the first signal Offset; combining the second signal with the first signal to form a multiplexed signal including the information expression of each independent copy of the signal; and transforming the multiplexed signal into multiple signals in the signal processing chain Independent signals, where each independent signal corresponds to one of the copies of the signal.

In still another embodiment, the present invention can be embodied as a device for receiving a signal, including: a plurality of antenna elements are spatially arranged to receive one of the corresponding multiple copies of the signal, so that multiple copies of the received signal can be generated A signal processing chain; and an orthogonal multiplexer, which is connected between a plurality of antenna elements and a signal processing chain, wherein the orthogonal multiplexer is used to receive the plurality of received signal copies and orthogonal Multiplex the plurality of received signal copies as a multiplexed signal on the signal processing chain; wherein the signal processing chain includes a signal separation for converting the multiplexed signal into a plurality of independent signals Device, where each independent signal corresponds to one of the copies of the signal.

In still another embodiment, the present invention can be expressed as a method for orthogonal multiplexing signals, including the following steps: generating multiple orthogonal signals; multiplexing the multiple signals through one of the corresponding multiple signal copies. Each of the orthogonal signals is thereby generated to generate multiple copies of the coded signal, wherein each of the multiple signal copies is received by one of the corresponding multiple antenna elements; and the multiple copies of the coded signal are combined into a multiplexed signal.

Description of the drawings

In the drawings: Figure 1 is a block diagram of a traditional diversity receiver, in which signals received by multiple antenna elements are weighted and combined to produce an output signal; Figure 2 is a traditional spatial-temporal (st) filtering device Block diagram; Figure 3 is a schematic diagram of a multiple input/multiple output antenna device in a wireless communication system; Figure 4 is a block diagram describing the structure of an existing multiple receiving antenna system in the RF field; Figure 5 is the same as Figure 4 Fig. 6 is a block diagram of a multi-element antenna processing module according to the first embodiment of the present invention; Fig. 7 is a block diagram of a multi-element antenna processing module according to the first embodiment of the present invention when receiving a signal. A flow chart of steps traversed by the antenna processing module of each element; FIGS. 8A and 8B show the antenna processing modules of multiple elements in the time domain and the frequency domain according to an embodiment, respectively, as shown in FIG. 6 Fig. 9 is a waveform graph showing the multiplexed output of the antenna processing module with multiple elements according to an embodiment of Fig. 6; Fig. 10 is a graph depicting when the converted tone and the next When harmonics are admitted, the output curve of a low-pass filter of the antenna processing module of multiple elements is shown in Fig. 6;

Fig. 11 is a graph depicting the output of a low-pass filter of the antenna processing module with multiple elements as shown in Fig. 6 when only the basic conversion tone is admitted; Figs. 12A and 12B are graphs depicting their respective in the time domain and In the frequency domain, the pulse shape curve of the matched filter can be simulated by the antenna processing module with multiple elements as shown in Fig. 6; Figs. 13A and 13B depict the respective in the time domain and the frequency domain as shown in Fig. 6 A graph showing the output of a matched filter that can be simulated by an antenna processing module with multiple elements; Figure 14 is a diagram depicting the implementation of five conversion operations for each symbol when the antenna processing module with multiple elements in Figure 6 is converted A group budget (constellation estimate) graph; Fig. 15 is a graph depicting another group budget when the antenna processing module of multiple elements in Fig. 6 realizes twenty conversion operations per symbol; Fig. 16 is a graph depicting the current constellation estimate. Converting the antenna processing module of multiple elements in Fig. 6 is a graph of another group of budgets for fifty conversion operations per symbol; Fig. 17 is a graph depicting the average bit error rate of a single antenna system; Fig. 18 is Depict the antenna processing module in Figure 6 at the available symbol rate (symbol A graph of the average bit error rate operating at a conversion frequency fs of 20 times (20X) of the rate); Fig. 19 depicts the antenna processing module in Fig. 6 at a conversion frequency fs of 2 times (2X) the available symbol rate A graph of the average bit error rate of operation; Fig. 20 is another embodiment of an antenna processing module configured to operate with more than two antenna elements; Fig. 21 is a diagram depicting an embodiment of the present invention when a signal is received through Fig. 20 is a flow chart of the steps through which the multiple element antenna processing module passes; Fig. 22 is a time vector diagram of applying the converted signal to the two antenna elements in Figs. 6 and 21 according to an embodiment; Fig. 23 is a time vector diagram according to one The embodiment applies the converted signal to the time vector diagrams of the two antenna elements in Figs. 6 and 21; Fig. 24 is yet another embodiment of an antenna processing module configured with more than two antenna elements operating; Figs. 25A and Figs. 25B is a complex Walsh coding matrix and a joint time vector diagram according to an embodiment, used to provide a converted signal to the mixer of the antenna processing module in FIG. 24; and FIGS. 26A and 26B are according to another embodiment The complex Walsh coding matrix and the joint time vector diagram are used to provide the converted signal to the mixer of the antenna processing module in Figure 24.

detailed description

In the following description, a number of different aspects of the present invention will be described. However, it is obvious to those skilled in the art that the present invention may only implement some or all aspects of the present invention. For the purpose of illustration, the description of specific numbers, materials and shapes is to provide a thorough understanding of the present invention. However, the present invention can be implemented without special details that are obvious to those skilled in the art. In another example, in order not to obscure the present invention, well-known features are omitted or simplified.

Various operations will be described as multiple discrete steps executed in sequence, which is more helpful to understand the present invention. However, the described order will not be explained, which means that these operations must depend on the order, in particular, the embodiment steps Order. Furthermore, the phrase "in one embodiment" will be used repeatedly, but this phrase is not designated for the same embodiment, although it may refer to the same.

In order to configure a mobile device to process signals from multiple antenna elements, the cost and energy consumption of the combined electronic components within the device are expected to be implemented in a cost-effective way. In this regard, the present invention is dedicated to a system and method for realizing multiple antenna elements, especially multi-element antenna devices, in a mobile device with a potentially low-cost means. The present invention is not limited to mobile devices, but can also be applied to infrastructure elements (such as base stations and access points). In addition, the present invention can be applied to almost all known wireless standards and modulation devices (for example, GSM, CDMA2000, WCDMA, WLAN, fixed wireless standards, OFDM and CDMA). As described below, the multiple advantages provided by the present invention derive from the multiplexing technology of receiving signals from multiple antenna elements to the ordinary receiving chain processing path, in order to reduce the energy consumption and cost.

For example, a plurality of embodiments according to the present invention provide a multi-element antenna device and a joint receiver with reduced complexity and low cost design. In some embodiments, the design of the antenna device and the receiver does not substantially increase the energy consumption compared to the single-element method, thus showing that it can be well applied in wireless mobile phones.

According to one aspect of the present invention, an example of multiple antenna elements is time division multiplexed onto a single RF processing path using orthogonal transfer functions. Then with channel selection and space and time processing, demultiplexing is performed in the digital domain.

In order to easily and correctly evaluate the main tasks of the present invention, a brief overview of a variety of existing multi-element antenna systems designed to reduce the effects of delay propagation, interference and attenuation, please refer to Figures 1 to 4.

First, please refer to FIG. 1, which shows a block diagram of an existing diversity receiver 100, in which in order to generate an output signal, signals received by multiple antenna elements are weighted and combined. The existing diversity receiver 100 in the figure is a collection of M-shaped antenna elements 102, and parallel receiving chains 104, 106, and 108 including weighting parts 110, 112, and 114 connected to each individual antenna element. The receiving chains 104, 106, 108 are all connected to the combiner 116 and the mixed signal 118 extending from the connection 116.

With M-shaped antenna elements, such an arrangement usually provides "M" antenna gain and diversity gain against multipath attenuation in the associated attenuation between the antenna elements. In this context, antenna gain is defined as the amount of reduction in the required received signal energy for a given average output signal-to-noise ratio (SNR); while diversity gain is defined as the amount of reduction in the required bit error rate (BER) for a given average output signal-to-noise ratio (SNR). The amount of reduction in the required average output signal-to-noise ratio.

In order to alleviate interference, each M-shaped antenna element 102 is weighted in a respective weighting part 110, 112, 114 and incorporated into the combiner 116 to maximize the signal-to-interference and noise ratio (SINR). This weighting process usually minimizes mean squared error (MMSE) and uses related interference to reduce the energy of interference.

Now referring to FIG. 2, a block diagram shows an existing spatial-temporal (st) filtering device 200. The first antenna 202 and the second antenna 204 shown in the figure are connected to a first linear equalizer 206 and a second linear equalizer 208, respectively. The output terminal of each of the first and second equalizers 206, 208 is connected to the combiner 210, and the output terminal of the combined 10 is connected to the MLSE/DFE section 212.

The filtering device of Figure 2 is designed to use joint real-time spatial processing to eliminate delay propagation. Generally, since CCI is not known by the receiver, the most ideal real-time spatial (ST) equalizer, or is perceived by Minimized Intermediate Error (MMSE) or Signal to Interference and Noise Ratio (SINR), it typically includes a whitening filter ( Whitening filter), such as linear equalizers (LE) 206, 208 whitening the CCI in time and space, and the filtering device in FIG. 2 are typical of such a system. As shown in Figure 2, the linear equalizer (LE) 206, 208 is a non-linear filter, which is represented by the MLSE/DFE part 212, using a decision feedback equalizer (DFE) or most probably a sequence estimator ( MLSE) to achieve.

A common technology is known in the art. The turbo principle (TurboPeinciple) with higher performance can also be used to replace the non-linear filter, but it requires higher computational complexity. Using ST processing (STP) technology, SNR gains up to 4dB and SINR gains up to 21dB have been reported to be available with a moderate number of antenna elements.

Next, please refer to FIG. 3, which shows a general multiple-input/multi-output antenna device in a wireless communication system. The transmitter (TX) 302 in the figure is connected to a plurality of transmitting antennas 304, and the plurality of transmitting antennas 304 transmit signals to a plurality of receivers (RX) 310 connected to the receiver (RX) 310 through time varying obstructions (time varying obstructions) 306. Receiving antenna 308. As shown in the figure, multiple antenna elements are arranged on the transmitter (TX) 302 and the receiver (RX) 310 of the wireless communication system.

In addition to multiple input/multiple output antenna (MIMO) devices, other antenna devices can be classified based on the "input" and "output" to the number of channels connecting the transmitter and receiver, as follows: Single input/single The output (SISO) system includes transceivers (such as mobile units and base stations) with separate antennas for uplink and downlink communications.

Multiple input/single output (MISO) system, including one or more receivers, which input downlink through multiple antennas, and one or more transmitters, output uplink through separate antennas.

Single input/multiple output (SIMO) system, including one or more receivers, through a single antenna input downlink, and one or more transmitters, through multiple antenna output uplink.

Especially in MIMO systems, one of the most attractive aspects of multiple element antenna devices is that these configurations can be used to achieve a significant increase in system capacity. A superior evaluation of the available channels in the transmitter and receiver can be obtained. The signal received in a MIMO system with M receiving antennas is decomposed into M independent channels. The result of the M-folding increases the capacity of the SISO system. For a fixed total transmission energy, the capacity provided by the MIMO system is used to increase the SNR proportionally, but in practice, it is limited by the number of M-shaped antenna elements.

In the special case of multipath channel attenuation, it was found that the use of MIMO devices allows the capacity to be limited by almost M extra bits/cycle for every 3dB increase in SNR. This MIMO range characteristic is compared with the baseline configuration. When M=1, one or more bits/cycles are changed by the Shannons classic equation every time the SNR increases by 3dB. Note that the increase in the capacity of the MIMO system can be obtained without the additional bandwidth of the baseline device of any related separate components.

However, multi-element antenna devices widely deployed in wireless communication systems (especially in wireless mobile phones) are restricted due to the increase in complexity and the related increase in energy consumption, cost and size. In some requirements, each antenna element provides a recommended structure for separate receiving chains, which leads to an increase in at least some of these parameters.

For example, Figure 4 depicts an existing multiple receiving antenna system in the RF field. As shown in the figure, the implementation of FIG. 4 includes separate receiving chains 402, 404, 406 corresponding to each M-shaped antenna element, and each receiving chain 402, 404, 406 includes elements that perform amplification, filtering, and mixing. Therefore, the cost of implementing a system with such a structure is higher than the cost of a system with only one receiving chain.

A further disadvantage of this method is the use of analog phase adjusters and variable gain amplifiers, which are relatively expensive and suffer from performance degradation due to aging, temperature changes and deviations from specified tolerances. In addition, since the implementation of FIG. 4 utilizes the phase relationship between the receiving and transmitting antenna elements (for example, the differential delay of the channel runs through each receiving processing chain), rigid adhesion to tolerances and precise calibration are required in each RF processing chain.

Please refer to FIG. 5 below, which shows a block diagram in a digital form equivalent to the circuit form of FIG. 4. Generally, the degradation of the performance of the digital circuit device in FIG. 5 is basically the same as the reason described above in conjunction with FIG. 4. That is, each antenna element associated with the doubler of the entire receiving chain (for example, from RF to baseband) results in an increase in size, cost, complexity, and energy consumed relative to a single antenna approach. Therefore, the multi-element antenna structure is not suitable for deployment in mobile phones and other mobile terminals used in wireless communication systems so far.

Overview and system structure As in the following detailed description, several embodiments of antenna devices and receivers with reduced complexity are proposed in the present invention to incorporate the radio frequency processing associated with each antenna unit into the signal processing chain. Once radio frequency processing is available in some embodiments, it is incorporated into the signal processing chain.

In some embodiments, this merging is achieved by multiplexing samples onto a single radio frequency processing chain, the samples coming from a switch element connected to a pair of antenna elements. Once the single radio frequency processing chain completes radio frequency processing, the associated signal passes through a matched filter that is used to reduce the available sample frequency of the appropriate baseband ratio. Once the signal originally received by each antenna element in the digital domain is restored, the restored signal is subjected to conventional spatial processing. This structure can be extended to systems that use more than one pair of antenna elements by changing the multiplexer/signal separator and the sample interval of the signal stream provided to the matched filter (associated with each antenna).

FIG. 6 is a block diagram illustrating a receiver front end incorporating a plural-element antenna processing module 600 according to an embodiment of the present invention. The complex element antenna processing module 600 includes first and second antenna elements 602 and 604, and the first and second antenna elements 602 and 604 are connected to the radio frequency processing chain 610 through a multiplexer switch 608. When referring to FIG. 6, refer to FIG. 7 at the same time. FIG. 7 is a flowchart illustrating the steps performed by the complex element antenna processing module 600.

In operation, the first and second antenna elements 602 and 604 first receive signals from two spatial locations. In this way, each of the first and second antenna elements 602 and 604 receives a replica of the signal (step 702). In some embodiments, the copies received by the first and second antenna elements 602 and 604 are uncorrelated copies of the signal.

Then, copies of the signals received by the first and second antenna elements 602 and 604 are orthogonally multiplexed to the processing chain 610 (step 704). In some embodiments, by multiplying the first received signal by one copy of the received signal (such as the first antenna 602), and multiplying the second exchange signal by another copy of the received signal (such as the second antenna 604) Realize quadrature multiplexing, in which the phase difference between the second exchange signal and the first exchange signal is 90 degrees.

Referring briefly to FIG. 23, there is shown two square waves, 90 degrees apart in phase, which is an exemplary exchange of signals for multiple signal copies received by the first and second antennas 602, 604 according to an embodiment of the present invention. Square wave. As shown in Figure 23, each square wave reverses its polarity during each cycle. However, it is well-known that the exchange square wave does not need to be inverted during each cycle, and by using a square wave that reverses the polarity in each cycle period (that is, closer to the sine wave), less production is generated during multiplexing. Harmonics, which only require less filtering of multiplexed signals.

In some embodiments (which will be further described with reference to Figures 24 and 25), frequency propagation will be performed according to complex Walsh coding principals.

As is well known to those skilled in the art, the multiplexer 608 can be implemented using different hardware and software/firmware. For example, in one embodiment, a single-pole double-throw (SPDT) switch is used in conjunction with a frequency offset technique to orthogonally multiplex the copies of the signal. Alternatively, as will be described in detail in FIG. 24, a mixer is used to provide a copy of the exchange signal to the received signal.

Briefly referring to FIGS. 8A and 8B, there is shown as an exemplary embodiment the expression of the output of the multiplexing switch 608 in the time domain and the frequency domain, respectively, in which the copy of the signal has no phase shift, and the switching process is realized The basic tone required for oscillation is offset by 218 kHz from the carrier fc. In the time domain representation of FIG. 8A, the time multiplexing of the signals received from the first and second antenna elements 602, 604 of the radio frequency processing chain 610 is obvious, and in this example, it is necessary to clarify the received signal Mainly only the intensity is different. The emission of the signals received by the antenna elements 602 and 604 due to the operation of the multiplexer 608 is clearly shown by the energy spectrogram in FIG. 8B. The high-order harmonics in the energy spectrogram of FIG. 8B are also clear, and in general only the center frequency and each offset in those 218 kHz are transmitted to ADCs (Analog-to-Digital Converters) 634, 636.

Multiplexing can be expressed mathematically as the application of exchanging signals s1(t) and s2(t) to the signal energy r1(t) received by the first antenna element 602 "Ant 1", and to the second antenna element 604" Application of signal energy r2(t) received by Ant2", the result is: m(t)=r1(t)s1(t)+r2(t)s2(t) where: s1(t)=1+cos(2πfs /2t)s2(t)=1+cos(2πfs/2t+π)r1(t)=sin(2πfct+p1(t))r2(t)=sin(2πfct+p2(t))p1(t) = Baseband phase process received on Ant 1 p2(t) = Baseband phase process received on Ant 2 Note that in the above mathematical expression, a sine wave instead of a square wave is used as the exchange function. As a result, the calculation is simplified due to the low harmonic content of the sine wave compared to the square wave.

As mentioned earlier, in some embodiments, the exchange signal (such as a square wave) that reverses polarity in each cycle generally approximates a sine wave more closely. It fully reduces or eliminates the potential generation of false harmonic energy and returns to the mathematical expression again, the expansion of m(t) output: m(t)=r1(t)+r2(t)+sin(2π(fc- fs/2)t+p1(t))/2+sin(2π(fc-fs/2+π)t+p2(t))/2+sin(2π(fc+fs/2)t+p1( t))/2+sin(2π(fc+fs/2+π)t+p2(t))/2 The frequency spectrum of the signal m(t) appears as a peak at the center of the carrier frequency fc, and has a peak on both sides of fc The side lobe shift of the identity of fs/2.

In an exemplary embodiment, the multiplexer 608 exchanges at a rate that is at least 20 times the symbol rate of the information received by the antenna elements 602 and 604. However, in the antenna embodiment, the switching rate of the orthogonal multiplexer 608 ranges from approximately twice the available symbol rate to more than 20 times the symbol rate.

Next, the multiplexed signal from the multiplexer 608 is down-converted from the radio frequency (step 706). Those of ordinary skill in the art know that a single side lobe described above includes the sum of two signals of interest with a phase offset signal of π radians, and one side lobe reduces the usable expression to two sinusoidal phase offsets. The sum of the shifts is: sin(2π(fc-fs/2)t+p1(t))/2+sin(2π(fc-fs/2+π)t+p2(t))/2 when p1( When t)=p2(t), this part is zero and cannot be actually used. Thus, in some embodiments, since m(t) is the signal of interest, the received signal energy is down-mixed to the carrier frequency.

In one embodiment, such as shown in FIG. 6, the RF processing chain 610 includes an in-phase (I) branch 614 and a quadrature-phase (Q) branch 618, which respectively include a first The mixing device 620 and the second mixing device 624. As shown in the figure, a mixed signal cos(fc) is provided to the first mixing device 620, where fc represents the frequency of the received carrier signal. Similarly, the mixed signal sin(fc) is provided to the second mixing device 624. The mixing devices 620 and 624 are used to down-mix the received signal energy to the carrier frequency fc, which results in the generation of a central peak at DC, and a pair of sub-pairs at half the switching frequency of the multiplexer 608 (fs/2). The petals "superimpose" each other at the apex.

As shown in FIG. 6, the signal energy from the first mixing device 620 and the second mixing device 624 is provided to the first low-pass filter 630 and the second low-pass filter 632, respectively, and in one embodiment, in the phase ( The signal energy in the I) branch 614 and the quadrature phase (Q) branch 618 is filtered at the cut-off point of fs.

After low-pass filtering at the separation point of fs (which keeps s1(t) and s2(t) intact), the I and Q parts of m(t) are obtained as follows: m_b_I(t)=m(t)*cos (2πfct)=s1(t)r1(t)cos(2πfct)+s2(t)r2(t)cos(2πfct)=s1(t)sin(p1(t))+s2(t)sin(p2( t))m_b_Q(t)=m(t)*sin(2πfct)=s1(t)r1(t)sin(2πfct)+s2(t)r2(t)sin(2πfct)=s1(t)cos( p1(t))+s2(t)cos(p2(t)) These results are expected because the functions s1(t) and s2(t) can be considered square.

Figures 9-11 provide exemplary representations of the different signals closest to the low pass filters 630 and 632 that exist. In particular, FIG. 9 shows the waveform of the output of the multiplexer switch 608 before being filtered by one of the low-pass filters 630 and 632.

FIG. 10 depicts the output of one of the low pass filters 630 and 632 in the case where the exchange tone and the next harmonic are accepted.

In contrast, Fig. 11 shows the signal at the output of one of the low-pass filters in the case where only the basic exchange tones are accepted.

The filtered signals from the first and second low-pass filters 630 and 632 are supplied to the signal separator 638 through the first analog-to-digital converter (ADC) 634 and the second ADC 636, where the filtered signals are converted from analog signals Is a digital signal (step 708). Then, the digital signals from the first analog-to-digital converter (ADC) 634 and the second ADC 636 are separated by a signal separator 638.

The signal separator 638 is used to route the samples from the first antenna element 602 to the first slot buffer 642 and to route the samples from the second antenna element 604 to the second slot buffer 644. In this way, the signal splitter 638 provides an independent signal that is representative of a copy of the signal received by the first and second antenna elements 602, 604. Then, the buffer samples from the first slot buffer 642 and the second slot buffer 644 are respectively passed through the first matching filter 650 and the second matching filter 654 for pulse matching filtering (step 712). After the pulse matching and filtering, the independent signals from the first and second pulse matching filters 650, 654 are spatially processed by the spatial processing module 660 (step 714). In an exemplary embodiment, the spatial processing module 660 executes a known spatial operation algorithm in the data domain.

12A and 12B describe the pulse shape of an exemplary operation of the matching filters 650 and 654 in the time domain and the frequency domain, respectively. Figures 13A and 13B depict the output of the matched filters 650 and 654 in the time domain and the frequency domain.

In one embodiment, the pulse matching filters 650 and 654 are not configured in a manner that takes into account the interruption in the independent demultiplexer signal. The interruption is caused by the multiplexing switch 608 during the multiplexing operation. The result of sampling of the received signals r1(t) and r2(t). When the exchange frequency fs grows to a symbol frequency whose order size exceeds the received energy, however, any loss that occurs during this effective sampling process tends to be negligible.

For example, Figures 14-16 depict baseband group estimates generated with exchange operations of 5, 20, and 50 per signal based on the operation, respectively. As shown in the figure, when the exchange frequency increases, the loss due to sampling processing becomes negligible.

In other embodiments, the pulse matching filters 650, 654 are configured in a manner that takes into account the interruption in the independent demultiplexer signal. The interruption is performed by the multiplexing switch 608 during the multiplexing operation. The result of sampling of the received signals r1(t) and r2(t). The pulse matching filters 650 and 654 in these embodiments synthesize the buffered samples from the first slot buffer 642 and the second slot buffer 644 (ie, low-pass filtering, signal separation, and buffered dispersed low-pass signals) to The maximum amount of energy is concentrated at the moment of sampling. This is achieved by filters 650, 654 matched to the independent low-pass signals as a complex conjugate of the independent low-pass signals.

The signal-to-noise characteristics of a receiver with a processing module (such as a processing module 600 configured with two such as first and second antenna elements 602, 604) are compared with the characteristics obtained using a receiver including only a single antenna element. In general, it can be found that the spatially different output levels formed by the configuration of the present invention lead to the appearance of signal fading. In the presence of such interference with linearly independent spatial sign differences, the configuration of the present invention for providing substantial improvements in signal-to-noise characteristics can be found.

Next, referring to Figs. 17-19, for example, simulation scenarios are described respectively (1) a single antenna, (2) an antenna operation module 600 configured with two antennas and operating at an exchange frequency fs of 20 times (20X) the available symbol rate, And (3) the average error rate in the antenna operation module 600 configured with two antennas and operating at a switching frequency fs that is twice (2X) the available symbol rate.

Next, referring to FIG. 18, it can be observed that the significant advantages in the medium switching frequency fs of the 20X symbol rate can be obtained with a single antenna (FIG. 17). On the contrary, FIG. 19 shows that in the exchange frequency fs of 2X symbol rate, the performance will be degraded from that in FIG. 18. Nevertheless, the performance in the switching frequency fs of the 2X symbol rate appears to be higher than that of the single antenna case (Figure 17). It should be noted that the proper design of each matched filter 650, 654 can substantially reduce or eliminate any difference in performance, which is a function of the switching frequency fs.

Next, referring to FIG. 20, another embodiment of the antenna processing module 2000 is shown. The antenna processing module 2000 is configured with more than two antenna elements. As shown in the figure, the multi-element antenna processing module 2000 includes first, second, third, and fourth antenna elements 2002, 2004, 2006, and 2008 connected to a multiplexer 2001, where the multiplexer 2001 is connected To the RF processing chain 2016. When referring to FIG. 20, refer to FIG. 21 at the same time, wherein FIG. 21 is a flowchart illustrating steps performed by the antenna processing module 2000.

In operation, the antennas 2002, 2004, 2006, and 2008 receive signals at different spatial locations, and as a result, each antenna 2002, 2004, 2006, and 2008 receives each copy of the signal (step 2102). In some embodiments, the antennas 2002, 2004, 2006, and 2008 are adjusted so that each receives an unrelated copy of the signal.

In some embodiments, as shown in FIG. 20, the multiplexer 2001 includes first and second multiplexer switches 2010, 2012, which operate as single-pole double-throw switches. The first and second antennas 2002, 2004 are connected to the first multiplexing switch 2010 as the first subnet of the four antennas 2002, 2004, 2006, and 2008, and the third and fourth antennas 2006, 2008 are used as The second subnet of four antennas 2002, 2004, 2006 and 2008 is connected to the second multiplex switch 2012.

In the current embodiment, the first multiplexing switch 2010 exchanges between the first and second antenna elements 2002 and 2004 at a rate of fs/2 to generate the first signal 2014 (step 2104). Similarly, the second multiplexing switch 2012 exchanges between the third and fourth antenna elements 2006 and 2008 at the same fs/2 rate to generate the second signal 2016 (step 2106). Then the second signal 2016 undergoes a phase shift, which is 90 degrees from the first signal (step 2108).

Briefly referring to FIG. 22, there is shown two exchange signals in one embodiment, the exchange signals used in the first and second antenna elements 2002, 2004 (and between the third and fourth antenna elements 2006, 2008) The exchange is provided to form the first and second signals 2014, 2016 in FIG. 20, respectively. In this embodiment, the format of the first signal is realized by multiplying the copy of the signal received at the first antenna 2002 by the first square wave, and multiplying the copy of the signal received by the second antenna 2004 by the second square wave. The phase difference between the square wave and the first square wave is 180 degrees. The same switching schedule is applied to the second and third antennas to form a second signal, and then, as described above, the second signal 2016 is offset by 90 degrees from the first signal.

Briefly referring to FIG. 13, there is shown two exchange signals in another embodiment. The exchange signals are used between the first and second antenna elements 2002 and 2004, and between the third and fourth antenna elements 2006 and 2008. The exchange is provided to form the first and second signals 2014, 2016 in FIG. 20, respectively. As shown in FIG. 23, the two exchange signals are converted into square waves that are 90 degrees out of phase with each other and change polarity in each cycle.

In this embodiment, the format of the first signal is realized by multiplying the copy of the signal received at the first antenna 2002 by the first square wave, and multiplying the copy of the signal received by the second antenna 2004 by the second square wave. The phase difference between the square wave and the first square wave is 90 degrees. The same switching schedule applied to the second and third antennas to form the second signal is offset by 90 degrees from the first signal.

Next, the first and second signals 2014, 2016 are combined to form an orthogonal multiplexed signal on the processing chain 2016 (step 2110). In this way, the four antenna elements are multiplexed into a universal receiver chain with the desired bandwidth, as in a two antenna element embodiment. Therefore, the current embodiment can be implemented at a lower cost than other designs.

For example, compared to a switch that includes a single-pole four-throw (single-pole four-throw) switch to provide switching between four antennas, the current embodiment uses half the bandwidth, so the current embodiment is more cost-effective.

The multiplexed signal is then down-converted by the mixing device 2018 (step 2112), and is filtered by the low-pass filter 2020 before being converted from an analog signal to a digital signal by the digital converter 2022.

After being converted into digital representation, the multiplexed signal is divided into four independent signals by a signal separator 2024, each of which represents a copy of the corresponding signal, which is divided by four antenna elements 2002, 2004, 2006 And the corresponding one in 2008 is received (step 2114). Then, the four independent signals are filtered by the pulse matching filters 2026, 2028, 2030, and 2032 before being received by the spatial processing part 2034.

Referring to FIG. 24, another embodiment of an antenna processing module 2400 is shown, which operates using more than two antenna elements. As shown in the figure, the multi-element antenna processing module 2400 includes first, second, third, and fourth antenna elements 2402, 2404, 2406, 2408 connected to the multiplexer 2410, the multiplexer 2410 and the radio frequency The processing chain 2016 is connected.

In operation, antennas 2402, 2404, 2406, and 2408 receive signals at different spatial locations. As a result, each antenna 2402, 2404, 2406, and 2408 receives each copy of the signal (step 2102). In some embodiments, the antennas 2402, 2404, 2406, and 2408 are adjusted so that each antenna receives an unrelated copy of the signal.

As shown in FIG. 24, the multiplexer 2410 includes first, second, third, and fourth mixing units 2412, 2414, 2416, 2418 connected to antennas 2402, 2404, 2406, and 2408, respectively. The mixing unit 2412, 2414, 2416, 2418 is used to inject the exchanged signal into each copy of the signal received by each antenna 2402, 2404, 2406, 2408. In some embodiments, the switched signals provided by each mixer are quadrature switched signals.

For example, in one embodiment, the exchange of signals is performed according to a complex Walsh coding schedule. For example, briefly refer to FIGS. 25A and 25B, which respectively show a complex Walsh coding matrix and a corresponding signal timing diagram. It should be noted that each element in the complex coding matrix of FIG. 25 is a complex number. In this embodiment alone, for the sake of simplicity, the imaginary part of each element is zero. It should be noted that, in this embodiment, the elements in the matrix can be zero or one, corresponding to the "off" or "on" state, respectively.

In operation, each row in the complex Walsh matrix is interpreted by, for example, a CPU (not shown), and a corresponding exchange signal is generated, as shown in FIG. 25B, which is provided to a corresponding mixing unit 2412, 2414, 2416 , 2418. Then, the mixing units 2412, 2414, 2416, and 2418 use the copies of the signals received by the antennas 2402, 2404, 2406, and 2408 to mix and exchange signals. For example, the first row in the complex Walsh matrix of FIG. 25A is 0, 0, 0, 1. As a result, in the first three cycles (as shown in FIG. 25B), the mixer 2412 receives the signal through the first antenna 2402. A copy of the signal is mixed into an "off" signal.

Referring to FIGS. 26A and 26B, another embodiment of a complex Walsh coding matrix and a corresponding signal timing diagram are respectively shown. As shown in FIG. 26A, the elements of the complex Walsh coding matrix are 1 or -1. As a result, the corresponding signal (as shown in FIG. 26B) reverses polarity from cycle to cycle. As a result, when the signals as shown in FIG. 26B are mixed, less harmonics than the signals in FIG. 25B are generated.

After the signal copies from the antenna signals 2402, 2404, 2406, and 2408 are mixed by a switching signal (such as the switching signal described with reference to FIGS. 25B and 26B), the encoded signal copies 2420, 2422, 2424, 2426 are combined by the signal synthesizer 2428 , To generate an orthogonal multiplexed signal on the processing chain 2430.

It should be noted that the orthogonal multiplexing scheduling in this embodiment is an embodiment that implements step 704 in FIG. 7.

After multiplexing, in some embodiments, the multiplexed signal is down-converted by the mixer 2430, filtered by the low-pass filter 2432, converted into a digital signal by the analog-to-data converter 2434, and then separated by the signal The processor 2436 is separated into the expression of the four original signal copies received by the antennas 2402, 2404, 2406, and 2408. Then the independent signal is passed through the pulse matching filters 2438, 2440, 2442, 2444 for pulse matching filtering before being passed through the spatial processing unit 2446 for spatial processing.

The described and other embodiments may include, but are not limited to, Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA) Or use in any of these synthetic systems. It can also include systems that use any type of modulation to encode data signals.

The foregoing description encompasses explanations and uses specific terminology to provide a complete understanding of the present invention. However, it is obvious to those skilled in the art that specific details are not required to implement the present invention. In other instances, well-known circuits and devices are shown as block diagrams to avoid unnecessary interference with the essence of the invention. Therefore, the description of the foregoing specific embodiments of the present invention is for the purpose of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise form disclosed. Obviously, many modifications and changes can be made according to the above-mentioned professors. The selected and described embodiments are used to best explain the principles of the present invention and its practical application, so that other persons familiar with the art can best use the present invention and different embodiments with different modifications to suit specific uses purpose.