Programmable transponder system

0001This invention relates to a reader, transpondes and system according to the preamble parts of claims 1, 10 and 14 respectively. In such a system the transponder is displaced from the reader identifying the transponder to the reader in accordance with a code individual to the transponder and transmitted to the reader at the command of the reader. The system is able to provide such identification without interference from extraneous noise, even at high levels, or small obstacles in the path of data transmission between the transponder and the reader. More particularly, the invention relates to a system for initially transmitting an identifying code from the reader to the transponder and programming this code into the transponder to identify the transponder.

0002As our society becomes increasingly complex, it becomes increasingly important to be able to identify different objects. For example, in an aircraft plant for manufacturing a jet airplane, thousands, and even tens of thousands, of different tools are required to manufacture the different parts incorporated into the airplane. It is accordingly important to be able to identify the individual tools quickly and reliably. One reason is that a fast and reliable identification of each individual tool is cost-efficient because it minimizes the time needed to identify such tool. Another reason is that a fast and reliable identification of each individual tool minimizes the possibility that the wrong tool will be selected and used on a workpiece, thereby causing the workpiece to be ruined or damaged.

0003It has been known for an extended period of time that it would be desirable to provide a system for obtaining a fast and reliable indication of objects such as tools. An extensive effort has accordingly been made by a wide variety of different parties to provide a satisfactory system. Such efforts have not been productive for a number of reasons. As a result, a satisfactory system still does not exist for identifying objects such as tools.

0004The systems now in use are undesirable for a number of reasons. They are not fast. For example, some of the systems use a transponder which stores energy received from a displaced reader and which then generates a code after such storage of energy. The energy is stored by charging a capacitance at the transponder. Other systems sweep a range of frequencies and detect the perturbations produced at individual frequencies in such frequency range. As will be appreciated, both types of systems are relatively slow.

0005The systems now in use have other severe limitations. The systems are not self synchronous. In other words, the systems do not operate on the basis of clock signals internally generated in the system. As a result, the systems sometimes provide the reader with false and inaccurate indications of the code identifying the object at the transponder. This causes an improper object to be identified sometimes at the reader.

0006The systems now in use also have other critical limitations. For example, the systems now in use are sometimes responsive to extraneous signals. Furthermore, in the systems now in use, members in the path between the transponder and the reader sometimes block the reception by the reader of the identifying signals transmitted by the transponder. This blockage has occurred even when the members in the path are relatively small. These problems have been exacerbated by the fact that the systems now in use are not self-synchronous. This has caused the systems now in use to identify objects improperly.

0007The systems now in use are also relatively complicated. This has caused the systems now in use to be excessively large from the standpoint of the space occupied by such systems. It has also prevented the systems now in use from taking advantage of integrated circuit technology. For example, it would be desirable to dispose the transponder on a single integrated circuit chip and to dispose all, or at least substantially all, of the reader components on another integrated circuit chip.

0008From EP-A-082 690 a transmitter/responder system is known. A transmitter means can be embodied in any suitable manner, at least one responder and at least one transmitter means can be movable relative to each other. At least one transmitter means can be a programmer for initially programming at least one memory means provided in the responder. At least a portion of code from the transmitted coded signals can be utilized for providing the memory means with storable code or for modifying at least a portion of code when already stored in the memory means.

0009European Patent application EP-A-245 605 discloses and claims a system which overcomes the above disadvantages. The system is fast, accurate and reliable. It operates on a self-synchronous and passive basis. It is immune to extraneous signals and it is effective even when small members are disposed between the transponder and the reader. It is simple and compact such that the transponder is disposed on a single integrated circuit chip and all, or substantially all, of the reader circuit is disposed on another single integrated circuit chip. It is quite tolerant of variations in the values of components so that it can be produced economically in quantity.

0010In one embodiment of the system disclosed and claimed in EP-A- 245 605 a reader (which can also be considered to be an interrogator) identifies information, such as the identity of an object at a transponder, provided in binary form at the transponder. The reader initially generates a pulse which activates the transponder into transmitting a series of signals, such as by magnetic induction, to the reader. Upon each count of a particular number of signals in the reader, the reader generates a new pulse which causes the transponder to produce a new series of signals. The generation of the pulses by the reader may occur through the charge and discharge of energy in a storage member such as a capacitance.

0011The series of signals produced by the transponder in EP-A- 245 605 may have either a first frequency or second frequency. The signals may be generated at the first and second frequencies in each sequence in an order dependent upon (a) the binary code provided at the transponder and (b) the polarity of the pulse produced by the reader in such sequence. The signals may be generated at the second frequency by connecting a capacitance across a coupling coil at the transponder. The reader then identifies the information by demodulating the signals received by it at the first and second frequencies.

0012The reader in EP-A- 245 605 is able to interrupt at any time the generation of the sequences of signals at the transponder when it does not receive the signals transmitted by the transponder. The reader then operates on a free running basis to generate pulses of opposite polarity at a relatively low frequency. In this way, the reader is constantly prepared to activate the transponder when the transponder becomes subsequently disposed within the effective range of the reader.

0013The memory storing the code in the transponder may be programmable. This invention provides a system operable at the reader for programming a binary code into such memory from the reader to constitute the binary information thereafter identifying the object. The code is transmitted from the reader to the object by sequences of pulses similar to the pulses described above as being transmitted from the reader to the transponder to interrogate the transponder as to the code in the transponder.

0014To program the memory with such a code, the reader in this invention generates, and transmits to the transponder, sequences of pulses, each sequence coding for a programmable item of information (e.g. binary "1", binary "0" and reset). Depending upon the individual programmable item, the coded sequence may have pulses of the same polarity or pulses of opposite polarity. At a time related to each such sequence, the reader produces a sequence different from the coded sequence and indicating that pulses coding for a programmable item follow.

0015The transponder in this invention demodulates and decodes the transmitted pulses to recover the identifying code. This code is then recorded in the programmable memory and is used thereafter to identify the transponder when the reader interrogates the transponder as described above. <ul id="ul0001" list-style="none"><li>1 is a circuit diagram, partially in block form, of one embodiment of a system at the reader for transmitting pulses to the transponder to program the programmable memory in the transponder;</li><li>Figure 2 illustrates sequences of signals for programming individual items (e.g. binary "1", binary "0" and rese) in the programmable memory in the transponder);</li><li>Figure 3 illustrates the voltages produced at strategic terminals in the system of Figure 1 when the system is operating to program a particular sequence of programmable items into the memory at the transponder;</li><li>Figure 4 is a schematic circuit diagram illustrating how an identifying code for a transponder is produced at the reader;</li><li>Figure 5 is a circuit diagram, partially in block form, schematically illustrating a system at the transponder for demodulating and then decoding the programmable pulses received at the transponder and for recording the decoded information in the memory in the transponder; and</li><li>Figure 6 is a table illustrating the operation of the transponder of Figure 5 in responding to the programmable pulses to record the decoded information in the memory in the transponder.</li></ul>

0016A system at the reader for programming the programmable information in the transponder memory 104 is shown in Figure 1. The system shown in Figure 1 may include a pair of transistors 200 and 202. The transistor 200 may be a pnp transistor and the transistor 202 may be an npn transistor. The emitter of the transistor 200 may receive a positive voltage from a power supply 204 and the emitter of the transistor 202 may receive a reference voltage such as a ground 206.

0017The collectors of the transistors 200 and 202 may be connected to a resistor 208 which is in series with a capacitance 210. A coil 212 is connected between the capacitance 210 and the reference potential such as ground. A connection is made from the ungrounded terminal of the coil 212 to one terminal of a resistance 216. The other terminal of the resistence 216 is common with the anode of a diode 218 and the cathode of a diode 220. The cathode of the diode 218 and the anode of the diode 220 are common with the reference potential such as the ground 206.

0018The voltage on the anode of the diode 218 and the cathode of the diode 220 is introduced to one input terminal of a comparator 222. A second input terminal of the comparator 222 receives the reference potential such as the ground 206. The output from the comparator 222 is introduced to one input terminal of an exclusive "or" network 224. A second input terminal of the exclusive "or" network 224 receives the voltage on the output terminal of one stage (designated as the "false" stage) in a bistable member such as a flip-flop generally indicated at 226.

0019The signals from the exclusive "or" network 224 are introduced to a counter 228. The counter 228 may be programmed at each instant to count to a particular value dependent upon the programmable item to be inserted into the programmable memory in the transponder. Upon each count of the particular count in the counter 228, a signal is introduced to the input terminals in the flip-flop 226 to trigger the flip-flop from one state of operation to the other. The output terminals of the true and false stages in the flip-flop 226 are respectively connected to the bases of the transistors 220 and 202.

0020Figure 2 illustrates the sequence (or pattern) of signals produced in the reader for each different type of programmable information. In Figure 2, the pulses move from right to left at progressive instants of time so that the most recent pulse in a sequence is at the right. For example, to program a binary "0" in the programmable memory in the transponder, a sequence of signals generally indicated at 230 is produced. This sequence includes a first pair of pulses 231a and 231b alternately with positive and negative polarities. The sequence also includes a second pair of pulses 230a and 230b of positive and negative polarities. The second pair of pulses 230a and 230b indicates that programmable information is contained in the preceeding sequence. The preceeding pair of pulses 231a and 231b indicates a binary "0".

0021In like manner, a binary "1" is indicated in Figure 2 by a second pair of pulses 233a and 233b alternately of positive and negative polarities. This indicates that signals representing a programmable item is contained in the preceeding sequence. The programmable item constituting a binary "1" is indicated by a pair of pulses 234a and 234b, both of negative polarity. The pulses of positive and negative polarity preceeded by two pulses of negative polarity are generally indicated at 235 in Figure 2.

0022A sequence of pulses to initialize a code sequence identified as "Reset" is generally indicated at 236 in Figure 2. This sequence includes a pair of pulses 237a and 237b, first of positive polarity and then of negative polarity, to indicate that a programmable item is contained in the preceeding sequence. This pair of pulses follows a single pulse 238a of positive polarity. When a programmable item constituting a reset is produced, it may indicate that the following sequences individually represent binary "1's" and binary "0's" to be programmed into the memory.

0023The system shown in Figure 1 operates to produce the sequences of pulses indicated at 230, 235 and 236 in Figure 13. When the flip-flop 226 is in the false state of operation, a voltage of relatively low polarity is introduced to the gate of the transistor 200 to make the transistor conductive. A pulse of current accordingly flows through a circuit including the power supply 204, the transistor 200, the resistance 208, the capacitance 210 and the coil 212 to charge the capacitance. This current produces a voltage pulse, such as a pulse 240 in Figure 3, in the coil 212. The coil 212 is coupled to the transponder which incorporates a tuned circuit so as to produce ringing signals as indicated at 244 in Figure 3.

0024When the true state of the flip-flop 226 becomes operative, voltage of a relatively high polarity is produced on the output terminal of the left stage in the flip-flop. This causes the transistor 202 to become conductive. The capacitance 210 accordingly discharges through a circuit including the capacitance, the resistance 208, the transistor 202 and the coil 212. This flow of current produces a pulse of a negative polarity in the coil 212, as indicated at 242 in Figure 3. This pulse is followed by ringing signals as indicated at 246 in Figure 3.

0025The diode 218 operates to limit the amplitude of the positive pulses, such as the pulse 240, produced by the coil 212 and the diode 220 operates to limit the amplitude of the pulses of negative polarity, such as the pulse 242, produced by the coil. The pulses of limited amplitude are indicated at 247 in Figure 3. Because of this limitation in the amplitude of the pulses such as the pulses 240 and 242, the amplitudes of the ringing signals 244 and 246 more nearly approach those of the pulses 240 and 242.

0026The pulses, such as the pulses 247, of limited amplitude are introduced to the comparator 222 which operates to saturate the pulses such as the pulses 240 and 242 and the ringing signals such as the ringing signals 244 and 246. The resultant pulses from the comparator 222 are as indicated at 248 in Figure 3. As will be appreciated, all of the pulses now have substantially the same amplitude.

0027The saturated pulses from the comparator 222 and the voltage on the output terminal of the false stage in the flip-flop 226 are introduced to the exclusive "or" network 224. The network 224 is constructed in a conventional manner to pass a pulse only when one of the input voltages introduced to the network is low and the other input voltage introduced to the network is high. The pulses passing through the exclusive "or" network 224 are indicated at 250 in Figure 3.

0028The pulses passing through the network 224 are introduced to the counter 228. As will be seen from the subsequent discussion, the counter 228 is set at each instant to count to a value dependent upon the programming operation at that instant. When the particular count is reached in the counter 228, the counter becomes reset to start a new count. This causes a triggering signal to be introduced to the flip-flop 226 to set the flip-flop from its previous state of operation to the other state of operation. The triggering signals introduced to the flip-flop 226 are indicated at 252 in Figure 3.

0029In the representations shown in Figure 3, the first pulse in a sequence appears at the left and successive pulses appear progressively toward the right. In Figure 3, the pulses 240 and 242 constitute a pair for synchronizing the operation of the system shown in Figure 1 . These pulses are separated by a particular number such as ten (10) ringing cycles. A reset is then programmed by the production of pulses 260, 262, 264 and 266. The pulses 264 and 266 indicate that a programming item is contained in the preceeding pulses in time and the pulse 260 indicates that the programming item constitutes a reset. The pulses 260 and 262 provide such an indication since there is the particular separation of one (1) ringing cycles between these two (2) pulses. In this way, only the pulse 260 is considered at the transponder in providing the initialization reset and the pulse 262 is disregarded at the transponder.

0030In like manner, pulses such as the pulses 282 and 284 separated by the particular number such as ten (10) ringing cycles and having opposite polarities indicate that a programmable item is contained in the preceeding pulses. This programmable item is indicated by pulses 276, 278 and 280. The pulses 274 and 276 are separated by the particular number such as ten (10) clock signals. The pulse 278 is accordingly disregarded at the transponder in a manner similar to the way that the transponder disregards the pulse 262 in the previous paragraph.

0031In Figure 3, the pulses 264 and 266 also represent a binary "0". The reason is that the pulses 264 and 266 are followed by the pulses 274 and 276 respectively having a positive and negative polarity. Thus, as will be seen it is not necessary to send a separate pair of pulses for each programmable item, such as the pulses 264 and 266, respectively having positive and negative polarities. Specifically, the pulses 264 and 266 indicate that a reset is represented by the pulses 260. The pulses 264 and 266 also represent a binary "0" since they are followed by the pulses 274 and 276.

0032In considering Figure 3 in relation to Figure 5, it will be seen that the letter "A" through "F" are shown at strategic terminals in Figure 5. The voltages or signals produced at these terminals are shown in the rows "A" through "F" in Figure 6. Figure 3 also indicates the value for the letter "N" indicated in Figure 1 . This indicates a preselected number of ringing cycles to be produced at each instant.

0033Figure 4 is a schematic diagram of how the system shown in Figure 3 operates at the reader to obtain the generation by the circuitry shown in Figure 1 of the patterns of signals for programming the programmable memory at the transponder. The system shown in Figure 4 includes a microcomputer 300 which generates an individual code to be recorded in the memory at the transponder. This code controls at each instant the count to be provided in the counter 228 (also shown in Figure 1 ). As will be appreciated, every time that a count has been completed, a signal is introduced from the counter to the flip-flop 226 in Figure 1 to obtain the generation of a pulse which is transmitted by the coil 212 to the transponder.

0034Figure 16 schematically illustrates a system at the transponder for demodulating and detecting the programming pulses from the reader . The programming pulses from the reader are received by a coil 302 at the transponder. The coil 302 may be the same as the coil described in EP-A- 245 605. The pulses in the coil 302 are introduced to a clock separator 304 which determines whether a pulse is derived from a positive or negative signal in the coil 302. The positive pulses from the clock separator 304 are introduced on one line to a shift register 306 and the negative pulses are introduced on another line to the shift register. The pulses representing each programmable item are then shifted through the shift register 306 to obtain an identification of the programmable item (e.g. binary "1", binary "0" and reset) in accordance with the relative polarities of the pulses in the shift register 306. This identification is provided by a decoder 308 in accordance with a truth table in Figure 6. The programmable items (e.g. binary "1" or binary "0") may then be recorbed in the appropriate positions in the programmable memory . It will be appreciated that the clock separator 304, the shift register 306 and the decoder 308 may be included in a microprocessing unit at the transponder.

0035Figure 6 constitutes a table illustrating how signals are produced in the shift register 306 for the different programmable items constituting a binary "1", a binary "0" and a reset. In Figure 6, the successive stages in the shift register 306 are respectively illustrated at A, B, C and D to correspond to the designations for the shift registers in Figure 5. As will be seen, the signals are shifted progressively from the stage A to the stage B, then to the stage C and finally to the stage D. The decoder 308 examines the four (4) signals in parallel in the stages A, B, C and D in the shift register 306. A positive signal in the stage A and a negative signal in the stage B indicate that a programmable item is represented by the signals in the stages C and D. A positive signal in the stage C indicates a reset. When a reset is produced, this indicates that the following individual sequences represent binary "1's" or binary "0's" which may be recorded in the programmable memory in a pattern represented by such signals. Two negative signals in the stages C and D represent a binary "1". A positive signal in the stage C and a negative signal in the stage D represent a binary "0".

0036The apparatus disclosed above and shown in Figures 1 - 5 has certain important advantages. One advantage is that it is able to program the memory in the transponder by using the same types of pulse transmission as are used subsequently in identifying the transponder in accordance with the operation of the circuitry and apparatus shown in EP-A- 245 605.

0037Another advantage to the programming system and method of this invention is that the communication between the reader and the transponder is substantially foolproof during the programming of the transponder. This results in part from the characteristics of the coils as shown in EP-A- 245 605. It also results in part from the inclusion of the pair of pulses of opposite polarity following the pair of pulses identifying each programmable item. By including this pair of pulses, the transponder is able to identify that the preceeding pair of pulses represents a programmable item and is able to identify such programmable item from such preceeding pair of pulses.

0038There is another important advantage to the programming system and method of this invention. This results from the fact that the programming pulses are produced on a self synchronizing basis at the reader and that the pulses are produced after particular counts in the counter 228. This facilitates the identification and decoding of the programming pulses at the transponder 20.

0039The programming is also relatively fast. This results in part from the use of integrated circuit chips for the reader and the transponder. It also results in part from the generation of the programming pulses at the reader in accordance with the counts provided in the counter 228.