JP3586294B2 - Method and apparatus for interrogating a remote transponder - Google Patents

Description

【図面の簡単な説明】
【図１】好ましい質問器およびベースユニットのブロック回路図。
【図２】好ましいトランスポンダのブロック回路図。
【図３】最も顕著な特徴を示す好ましい装置のより一般的なブロック図。
【図４】近接したトランスポンダからの影響がない通常のトランスポンダと、非常に近接した他のトランスポンダに対するトランスポンダとに応じたアンテナ信号の信号波形図。
【符号の説明】
１０ 質問器
１２ 第１トランスポンダ
１２ａ 第２トランスポンダ
１３０ 共振回路[0001]
[Industrial applications]
The present invention relates generally to a method and apparatus for detecting adjacent transponders.
[0002]
[Prior art]
The preferred embodiment of the present invention detects the presence of adjacent transponders by measuring the duration of response signals from a plurality of transponders. Examples described in U.S. Pat. No. 5,053,774 and patent application Ser. No. 07 / 981,635, both assigned to Texas Instruments, Inc. by Joseph H. Schumann. In a typical response period to the RF interrogation pulse is about 20 ms, during which the transponder can operate to generate a response message, typically 128 bits. After this 20 ms period, the output of the transponder is squelched. Squelching of the response signal is performed by a transponder timer triggered by the end of the burst (when the excitation signal ends). This timer counts up to 128 (bits) and then discharges the transponder charging capacitor.
[0003]
[Problems to be solved by the invention]
There is a great demand for a device or apparatus that enables identification or detection of an object provided with the device or apparatus at a predetermined position in a non-contact state and at a predetermined distance with respect to its existence. Furthermore, it can be determined whether two or more transponders are adjacent to each other. To There is another request to do so.
[0004]
[Means for Solving the Problems]
The present invention is the first to utilize the coupling between adjacent transponders to determine if two or more transponders are adjacent. When two transponders are adjacent, both are charged up and respond separately to the RF interrogation pulse. Thus, one transponder sends a response signal and the other transponder enters this signal field. This radiated signal interferes with the vibration maintained in the other transponder's resonant circuit. This interference of the cross-coupled response causes a beat in each resonant circuit of the transponder. This beat phenomenon is similar to what a musician listens to when tuning an out-of-tune instrument. If the instrument frequencies are different, cooperative interference (the sound signals are in phase and the sound intensity increases) and destructive interference (the sound signal is 180 degrees out of phase and the sound intensity decreases) You can hear the patterns that change over time. Such a pattern that changes with time is called a beat.
[0005]
Such a beat effect can occur in both transponders. During the period of destructive interference, any transponder stimulates the end-of-burst effect, causing the timer to be reset repeatedly (because the end-of-burst resets the timer). Resetting the timer opens a new 128 ms window for the logic and transponder to transmit the data signal. Therefore, the transponder's discharging function is repeatedly disabled by this beat effect, and the transponder transmits until the charging capacitor is completely discharged.
[0006]
Beat effects also occur between the transponder of the preferred embodiment and other transponders, such as those manufactured by manufacturers other than the applicant of the present invention. Interference with other types of transponders causes beats in the resonant circuit, causing the timer to reset repeatedly.
[0007]
【Example】
Referring to FIG. 1, the transponder device to be described includes an interrogator 10 and a transponder 12. Interrogator 10 is preferably held in the hands of an operator and is manufactured to transmit an RF interrogation pulse when key 14 is pressed. The interrogator 10 can receive an RF signal and detect information included in the signal. An RF signal is transmitted from the transponder 12, which in this embodiment is responsive to the transmission of the RF interrogation pulse, preferably by returning an RF signal having the same frequency as the interrogation pulse. The RF signal is data modulated by transponder 12 using frequency shift keying (FSK) modulation. A base unit 16 manufactured as a fixed unit is linked to the interrogator 10. The functions of the interrogator 10, transponder 12, and base unit 16 and their interaction will be described in more detail below. First, the configuration of these units will be described.
[0008]
The interrogator 10 includes a microprocessor 18 for controlling a function sequence as a central control unit. The RF oscillator 20 generates an RF oscillation signal as soon as it is set to the active state by a signal at the output 22 of the microprocessor 18. The output signal of the RF oscillator 20 can be supplied to a coupling coil 32 via a switch 24 and an amplifier 26 or via a switch 28 and an amplifier 30. Switches 24 and 28 are controlled by the microprocessor, respectively, with the aid of signals generated at the outputs 34 and 36 of the microprocessor. A coil 38 of a resonance circuit including a coil 38 and a capacitor 40 is coupled to the coupling coil 32. A resistor 44 that can be bridge-connected to the coil 38 and the capacitor 40 by a switch 42 is in series, and another switch 46 is provided between the resistor 44 and the ground. Switches 42 and 46 are controlled by a microprocessor which generates control signals corresponding to its outputs 48 and 50. When switch 46 is closed, the resonant circuit consisting of coil 38 and capacitor 40 operates as a parallel resonant circuit, while when switch 46 is open, the resonant circuit operates as a series resonant circuit. Coil 38 operates as a transmit / receive coil, which transmits RF interrogation pulses supplied to the coil by oscillator 20 and receives RF signals returned by transponder 12.
[0009]
The RF signal received by the resonant circuit is supplied to two amplifiers 52, 54 which amplify the received RF signal and limit these signals for pulse shaping. A parallel resonance circuit 56 that guarantees necessary reception sensitivity is connected to these amplifiers. The output terminal of the amplifier 54 is a clock generator 58 The clock generator generates a clock signal from the supplied signal and supplies the clock signal to the input terminal 60 of the microprocessor 18.
[0010]
Further, the output signal of the amplifier 54 is supplied to a demodulator 62, which demodulates the signal applied thereto and supplies the demodulated signal to an input terminal 64 of the microprocessor 18.
[0011]
After the information contained in the received RF signal is demodulated by the demodulator 62, it is supplied to the random access memory 66 via the microprocessor 18, and this information can be stored in the memory 66. Between the microprocessor 18 and the random access memory 66, a bidirectional connection circuit 68 is arranged, which inputs information from the microprocessor 18 to the random access memory 66 and transfers information in the reverse direction. Is also possible. Information stored in the random access memory 66 can be taken out at the jack 70.
[0012]
A display unit 72, supplied with a signal by the microprocessor 18, allows an operator to view the data contained in the received RF signal.
Since the interrogator 10 is a portable device, a rechargeable battery 74 is provided as a power source. After the switch 76 is closed, the output voltage of the battery 74 is supplied to a terminal of the predetermined chip in the interrogator 10 which is indicated by “+”. However, this supply voltage is supplied to the two amplifiers 52, 54, the clock generator 58 and the demodulator 62 via a separate switch 78 controlled by the microprocessor 18.
[0013]
Battery 74 can be charged with a voltage induced in coil 80, rectified in rectifier 82, and smoothed by capacitor 84. This voltage is preferably induced in coil 80 via coil 112 in base unit 16. The charging sensor 86 detects that a charging voltage has been induced in the coil 18, ie, that the battery 74 is being charged, and then the input 88 of the microprocessor 18 generates a corresponding message signal.
[0014]
Another switch 90 controlled by a signal from the output end 92 of the microprocessor 18 can supply the output signal of the RF oscillator 20 to the coupling coil 96 via the amplifier 94 in the closed state. The switch 90 is typically used to activate the transponder 12 to transmit RF interrogation pulses to initiate data transfer to and from the transponder 12. .
[0015]
The RF oscillator 20 can be modulated by the modulator 98. The modulation signal required for this purpose can be supplied by the microprocessor 18 to the modulator 98 via the switch 100, which is controlled by a signal from the output 102 of the microprocessor. The modulation signal from the microprocessor 18 is supplied to the coupling coil 104 when the switch 100 is also closed.
[0016]
The base unit 16 also shown in FIG. 1 is a fixed unit, which is connected via a jack 106 to the mains network. The power supply 108 generates an operating voltage for the charging voltage generator 110, and the output signal of the generator is supplied to the coil 112. A switch 114 is inserted between the power supply 108 and the charging voltage generator 110, and the switch 114 is closed whenever the interrogator 10 is installed on the base unit 16. This switch is shown in FIG. 1 as a kind of activation button 116 provided at the border of the interrogator 10. When the interrogator 10 is installed on the base unit 16, the coils 112 and 80 are spaced within the base unit and the interrogator 10 so that the coils 112 and 80 cooperate like primary and secondary windings of a transformer. It is arranged in a way. Thus, the battery 74 can be charged in a non-contact state when necessary. The coils 96 and 104 in the interrogator 10 are disposed so as to be spatially very close to the coil 118 when the interrogator 10 is installed on the base unit 16. Thus, signals can be transmitted in a non-contact state between one coil 96 and coil 104 and the other coil 118. Demodulator 120 operates to demodulate the signal resulting from coil 118.
[0017]
The transponder 12 of the preferred embodiment shown in FIG. 2 includes a parallel resonant circuit 130 having a coil 132 and a capacitor 134 for receiving RF interrogation pulses. A capacitor 136 that operates as an energy storage is connected to the parallel resonance circuit 130. Further, the parallel resonance circuit 130 is also connected to the RF bus 138. This resonant circuit 130 acts as a receiver / transmitter, as is well known to those skilled in the art. The clock recovery circuit receives the RF signal from the RF bus 138 and recovers a clock signal 139 having a substantially square waveform. The burst end unit detector 142 connected to the RF bus 138 has a function of monitoring the power level of the RF carrier on the RF bus 138. Such an RF carrier is generated on the RF bus 138 upon receiving an RF interrogation pulse from the interrogator 10. As soon as the power level of the RF carrier on the RF bus 138 falls below a predetermined threshold value, the burst end detector 142 generates a predetermined value of an RF threshold signal at its output. This RF carrier is rectified by connecting the diode 144 to the RF bus 138, thereby charging the capacitor 136. The energy stored in this capacitor 136 is proportional to the energy contained in the RF interrogation pulse. Therefore, a DC voltage can be extracted from the capacitor 136 after receiving the RF interrogation pulse. The function of the Zener diode 146 connected to the capacitor 136 is to ensure that the DC voltage that can be extracted from the tap does not exceed the value determined by the actual configuration, for example, the Zener voltage of the diode 146 in the integrated circuit. The function of diode 146 can be accomplished by a number of circuits known to those skilled in the art to limit the voltage. Zener diode 146 performs a similar function to prevent the voltage on RF bus 138 from becoming too large. First, when the interrogator 12 is interrogated, the interrogator 10 sends an RF signal to the transponder 12 to charge the transponder 12. This operation is called a charging phase.
[0018]
A power-on reset (POR, not shown) circuit sends a POR signal to the start detection circuit 154. The POR signal monitors the Vcc level, and is activated when the Vcc level rises from a level lower than a predetermined DC threshold to a level higher than the predetermined DC threshold. Generally, this POR signal occurs during the transponder charging phase. POR circuits are well known to those skilled in the art and are commonly used in almost all classes of circuits, known as "state machines," so that the circuit can be initialized to a known state. Upon receiving the POR signal, the start detection circuit 154 monitors the output terminal 150 at the end of the burst detection circuit 142. At the output terminal 150, an end portion (EOB) of the burst signal is generated. When a positive state EOB is detected after the positive state power-on reset signal, the start detection circuit 154 switches to send power to the clock recovery circuit 140 via the switch 156. The clock recovery circuit 140 preferably cleans up the signal from the resonance circuit 130 and generates a recovered RF clock. The reproduced RF clock is preferably a rectangular wave. The output signal of start detection circuit 154 remains positive until a subsequent POR is received. All components of the transponder except for the clock regenerator 140 are continuously supplied with Vcc, but by utilizing low power CMOS technology, the inactive state (ie, the clock regenerator 140 is activated). ), It is preferable that only negligible amount of power be consumed.
[0019]
Referring to FIG. 2, frequency divider 158 receives clock signal 139 and divides its frequency by eight. Preferably, the pluck circuit 192 sends a short pulse each time triggered by a divided clock signal received from the divider 158. This plaque circuit 192 momentarily turns on the field effect transistor or FET 190 and conducts between the resonant circuit 130 and ground via the RF bus 138 so that the resonant circuit obtains electrical energy from the charging capacitor 136. By forming the passage, the vibration of the resonance circuit 130 is maintained. This plaque circuit 192 is metaphorically named to describe maintaining the vibration of the resonance circuit 130, such as maintaining the vibration of the guitar string by performing a tracking operation on the guitar string. is there. This plucking operation temporarily reduces the voltage on the RF bus 138 below the threshold, causing the burst detection circuit 142 End of Part of The pulse width is not sufficient for the given channel resistance of FET 190 to trigger and energize this circuit. The second frequency divider 160 further divides the frequency of the clock signal 139 into two so that the clock frequency at the output terminal of the frequency divider 160 becomes 1/16 of the original clock frequency.
[0020]
Next, the readout circuit of the preferred embodiment will be described with further reference to FIG. The output terminal of the second frequency divider 160 receives the shift clock input signal of the output shift register 172 and passes data through the register 172 at a frequency that is 1/16 of the original clock frequency. Output shift register 172 receives a parallel load from memory 168 or another source via data bus 220 upon receipt of a "load" signal from the output of start detector 154 at its shift / load input 174. After this loading of the output shift register 172, the signal from the start detection circuit 154 is positive, so that a shift signal is received at the shift / load input 174 of the register 172. While this shift signal is positive, the data is shifted by the clock signal received at shift clock input 176 through the output shift register at 1/16 of the original clock frequency. As shown, data recirculates through output shift register 172 via data path 182 and sends a signal via data path 182 to the gate of the FET or modulator 200. The data of the output shift register is preferably at a low level for a predetermined time (pre-bit-time), and is at a high level or a low level according to the data loaded therein. In the present embodiment, this pre-bit time is used so that the interrogator's receive coil 38 can recover from a power burst overload (charging phase), as described below with read and write functions. Used to separate While the output signal of output shift register 172 is low, FET 200 is not conducting. While the output of the output shift register 172 is high, the FET 200 is conductive and thus the capacitor 198 is connected to the resonant circuit. 130 To reduce its resonance frequency. In essence, FET 200 operates as a switch under the control of output shift register 172, connecting and leaving capacitor 198 to modulate the frequency of resonant circuit 130. As described above, the frequency modulation of the resonance frequency of the resonance circuit 130, that is, the carrier frequency is performed in response to the data applied to the FET 200. If the original resonant frequency of the resonant circuit 130 is maintained for one bit period, a low level or zero signal will be displayed and a new parallel resonant frequency of the original resonant circuit 130 parallel to the capacitor 198 will occur within one bit period. In this case, a high level, that is, a "1" signal is displayed.
[0021]
Next, the operation of the discharge logic circuit will be described with reference to FIG. Timer 184 receives the output signal of divider 160 at input 186 and divides the frequency of the clock signal by some other 128 minutes. Since the preferred data transmission bit length is 128, the timer 184 Is some 128 times in this example. When changing the bit length, it is preferable to change the division ratio of the timer 184 accordingly. Diode 210 maintains a unidirectional current from timer 184 to a parallel RC network of capacitor 212 and resistor 214 that maintains the charge on the gate of the field effect transistor, FET 216, for a known period of time. The capacitor 212 can be charged by the timer 184 via the diode 210 but must be discharged via the resistor 214. The gate of the FET 216 is a resistor 214 and a capacitor 212 When maintained above the threshold voltage by a parallel circuit with, FET 216 acts on charging capacitor 136 to create a low impedance discharge path to ground. Thus, after the entire data frame (in this example, 128 bits (readout phase)) has been transmitted from the transponder 12 to the interrogator 10, the residual energy in the transponder 12 is removed by the short circuit across the charging capacitor 136. . Such an operation ensures that the transponder is correctly initialized during the next charging phase and does not remain in an indeterminate or incorrect state so that subsequent charging can be blocked. Furthermore, with this function, each transponder 12 in the field of the interrogator 10 has the same activation condition.
[0022]
Next, a circuit (write function) capable of writing data to the transponder 12 will be described with further reference to the circuit of the transponder 12 shown in FIG. In a preferred embodiment of the present invention, the interrogator 10 converts the RF interrogation pulse as shown in FIG. modulation , PPM). This signal is displayed on the RS bus 138. As is well known to those skilled in the art, pulse pause modulation systems operate by alternately energizing and deenergizing a carrier wave. While the carrier is de-energized, burst end detector 142 detects a decrease in RF energy and is energized. After the start section detection circuit 154 is enabled by the POR signal, the start section detection circuit 154 is started by the first EOB signal generated by the start bit (see FIG. 4). As will be described later, since each data bit status (data bit status) is transmitted according to the presence or absence of a phase shift of the carrier wave, a start bit is used in this preferred embodiment, but another bit that does not need to transmit the start bit is used. Embodiments are also possible. The period during which the carrier known as the phase shift is energized is shorter than the pre-bit time of the readout phase. During the phase shift, the output shift register 172 starts shifting, so this embodiment uses this specific condition. However, since the pre-bit time is longer than the phase shift time, none of the output shift registers can shift, and shifts zero, so that the actual FET 200 Does not cause unwanted modulation of the carrier 138 without being activated or inverted. When the carrier returns, the EOB signal is deenergized. Due to the energization and de-energization of the EOB signal, regardless of the switching of the EOB signal, the start detection circuit 154 keeps the output active until a new POR signal is received. Maintain power to the.
[0023]
A fourth frequency divider 162 is provided. The frequency divider receives the clock signal from the second frequency divider 160, divides the frequency of the clock signal by 16 again, and outputs the clock of the input shift register 228. An input clock signal is supplied to the input terminal 227. In the preferred embodiment, the percentage of write data is at the resonance frequency, ie, one-265th of the receive clock frequency. Steps must be taken to shift the data into the input shift register 228 while the data is stable. This can be guaranteed as follows. The fourth frequency divider 162 is energized by the start detecting circuit 154 via the AND gate 155. Each successive zero bit, or low bit, received by the burst end detection circuit 142 makes the output 150 of the burst detection circuit positive. This positive signal is received at the negative logic input of AND gate 155. This negative logic input is indicated by a circle at the input of AND gate 155, as is well known to those skilled in the art. Since the output signal of the AND gate 155 is made negative by the definition of the AND function, the fourth frequency divider 162 is cleared and the input clock is synchronized with the input data.
[0024]
The end detection circuit 234 detects the end of the data frame when a combination of bits in the input shift register 228 is input, and activates the programming logic 232 if a programming command has been received by the command recorder 230 first. I do. This data is then transferred from input shift register 228 to memory 168 or other memory via parallel data bus 220. The memory for transferring data is preferably an electrically erasable programmable read only memory (EEPROM).
[0025]
Burst end detector 142 generally operates as a pulse pause modulation (PPM) demodulator. Many other modulation methods are known in the field of wireless communication, and it is possible to use another demodulator for such another modulation method instead of the burst end detector.
[0026]
In the preferred embodiment, there is also a provision for initializing the test sequence via the test logic 236. Test logic 236 can receive signals from command recorder 230 and data from data bus 220 and initialize a number of test routines such as those commonly implemented in the field of logic circuit design. The results of these test routines can be placed on the data bus 220 and output to the modulation circuit via the field effect transistor 200 by the shift register 172.
[0027]
In the preferred embodiment of the present invention, a programmable tuning (tuning) network 238 is provided. This programmable tuning network 238 operates by switching a network of parallel capacitors 240, each of which is a field effect transistor, or FET. 242 Grounded through. Each field effect transistor is connected to a latch 244 that receives data from memory 168 or command recorder 230 via data bus 220 under the control of latch signal 246 from command recorder 230, I do. By switching the field effect transistor 242 to the on state of conducting, the associated capacitor 240 is connected in parallel with the parallel resonant circuit 130. As the capacitance increases, the resonance frequency of the parallel resonance circuit 130 decreases. When the field effect transistor 242 is switched to a non-conducting off state, the capacitor associated therewith is in a floating state and does not affect the parallel resonance circuit 130. The network 238 of FET and capacitor pairs 240, 242 can provide many different values with increased capacitance, depending on the combination of the relative values of each capacitor 240, as is well known to those skilled in the art. Alternatively, the latch 244 can be a one-time programmable (OTP) memory to permanently store data internally, and the device can be programmed with a programmable tuning network (OTP). Programmable (tuning network) 238 can be permanently programmed to be set.
[0028]
The divider ratios of the dividers in the embodiments described herein are selected to suit the details of each design. This division ratio must in each case be chosen so as to perform optimally the task of designing them.
[0029]
Referring to FIG. 3 in conjunction with FIGS. 1-2, assume that there are at least two transponders 12, 12a within range of the coil 38 transmitting the RF interrogation pulse. Power / transmission circuit 300 is provided to drive coil 38. Alternatively, a separate antenna is used as the transmit antenna. Na And the coil 38 is And It is also possible to use it. However, the coil 38 preferably operates as a transmitting and receiving antenna. The power / transmitter circuit 300 preferably comprises the oscillator 20 of the interrogator 10 of the preferred embodiment of FIG. The coil 132 of the parallel resonant circuit 130 (FIG. 2) of the transponders 12, 12a receives this RF interrogation pulse so that the resonant circuit 130 is stimulated and vibrates. The part of the RF bus 138 by the rectifier diode 144 In minutes The RF vibrations are rectified and the capacitor 136 is charged by DC. After that, only the energy charged in the capacitor 136 is used for supplying the energy of the transponders 12 and 12a. The read circuit 302 is provided to receive the transponder response. The read circuit 302 preferably comprises a clock generator 58 that can generate a carrier detect (CD) signal to the microprocessor, ie, the microprocessor 18 can interpret the presence or absence of the clock signal as carrier detection. The timer 304 is preferably provided in the microprocessor 18 of the interrogator 10. Timer 304 measures the period during which the clock signal is present. When a data signal is obtained from the output terminal of the read circuit 302 and the timer 304, the decoder 304 reads a) whether the data is valid and a good read is performed with CD ≦ 20 ms, and b) a read such that the CD is not detected. C) to determine if CD ≧ 20 ms and therefore more than two transponders were present in close proximity to the interrogator Ruko It is possible. The function of the decoder 306 is preferably within the microprocessor 18 of the preferred interrogator 10.
[0030]
Referring now to FIG. 4, the RF level on the RF bus 138 begins to drop when the RF interrogation pulse has been received. Burst end detector 142 Detects this level increase and generates an EOB signal of a predetermined value at its output 150 as soon as the power level drops below a predetermined level. Timer 184 is reset by EOB.
[0031]
In the plaque circuit 192, after the end of the excitation pulse, the field effect transistor 190 is turned off, so that no more current can flow through the coil 132. However, since the parallel resonance circuit 130 is of high quality, the vibration of the RF carrier does not stop immediately, and the resonance circuit continues to vibrate while damping. The frequency divider 158 that halves the frequency of the RF carrier wave sends a signal to the monoflop 192 after the second oscillation period, so that the flop 192 Is triggered. This monoflop 192 applies a sustain pulse to the field effect transistor 190 during the hold time. A current is supplied to the coil 132 by a holding pulse from the plaque circuit 192 during the holding time. This means that energy is pumped into the RF carrier wave generator for a short time. Because of the use of the divider 158, this pumping effect occurs after one nth oscillation period of the RF carrier wave.
[0032]
It is assumed that the data is permanently stored in the memory 168 and that these data are uniquely assigned to the transponders 12 and 12a. This data can be composed of, for example, 128 bits. At the timing of the clock signal applied to the clock input 176, the information in the memory 168 is transferred to the output shift register 172. To perform this transfer operation, 128 pulses are required. The reason is that the shift register 172 contains all information of 128 data bits. The timer 184 determines that the data transfer has been completed by counting the clock pulses. After receiving the 128 pulses, timer 184 generates a signal at its output 188 that is sent to FET 216 via diode 210. Since the preferable data transmission bit length is 128, in this example, the frequency division ratio of the timer 184 is 1/128. If the bit length needs to be changed, it is preferable to change the frequency division ratio of the third timer 184 accordingly. Diode 210 is a field effect transistor, a capacitor that maintains the charge on the gate of FET 216 for a known time from timer 184. 212 And maintain a unidirectional current to the parallel RC circuit of resistor 214. Capacitor 212 can be charged by timer 184 via diode 210, but must be discharged via resistor 214. FET 216 is connected to ground for charging capacitor 136 to ground when the gate of FET 216 is maintained above the threshold voltage by a parallel circuit of resistor 214 and capacitor 212. Low It works to form an impedance discharge path. After all data frames (in this example, 128 bits (readout phase)) have been transmitted from the transponder 12 to the interrogator 10, the remaining energy in the transponder is typically reduced by a short circuit across the charging capacitor 136. Removed. This action causes the transponder to initialize properly during the next charging phase, so that it is indeterminate, i.e. incorrect, so that the next charging is not prevented. Status Is guaranteed not to stay.
[0033]
If two or more transponders 12, 12a are adjacent, the interrogator 10 preferably detects such a condition so as to prevent the interfering signal from the transponders 12, 12a from being considered valid data. By utilizing the result of cross-coupling between adjacent transponders 12, 12a, the interrogator 10 can detect that the transponders 12, 12a are adjacent. When such a condition is detected, the interrogator 10 can take action such as more powerful or selective addressing of the transponders 12, 12a, or notification to the user. If two transponders 12, 12a are adjacent, both are charged and respond separately. For example, due to the tight coupling between the two, one transponder 12 answers and the other transponder 12a enters its electric field. Such tight coupling produces a beat in each of the transponder's resonant circuits 130, because their frequencies are only slightly different. Such destructive interference (ie, , Resonant circuit of one transponder 12 130 The burst end detector 142 resets the timer 184 due to the interference of the signal at (1) being 180 degrees out of phase with the combined signal from the other transponder 12a). Resetting the timer 184 opens a new 128-bit window for a response. This occurs continuously within each transponder 12, 12a. Thus, instead of the signal vibration energy in the resonant circuit 130 attenuating after 20 ms, natural vibrations can be attenuated by the normal parasitic damping effect. In an embodiment, this new time is about 40 ms.
[0034]
It can be determined whether there is another type of transponder, that is, a transponder that is not of the type described herein as a preferred embodiment adjacent to the preferred transponder 12. In such a case, the other transponder is more lossy (i.e., operates at a lower Q value and consumes more energy between functions from the preferred transponder 12), so that the transponder loses more energy from its own oscillations. Send to adjacent transponder and discharge faster than adjacent transponder. Therefore, in the embodiment, the transponder can discharge in about 30 ms instead of 40 ms. In any case, the discharge time is longer than 20 ms and the oscillations decay during a normal interrogation cycle.
[0035]
Although several preferred embodiments have been described above, it should be understood that the scope of the present invention is defined by the appended claims, and includes embodiments different from the above-described embodiments.
[0036]
For example, microcomputers are used in some contexts to mean that microcomputers require memory while microprocessors do not require memory. In this specification, such terms are synonymous and use of the terms are intended to mean equivalents. The phrase or processing or control circuit may be an ASIC (Special Purpose Integrated Circuit), PAL (Programmable Logic Array), PLA (Programmable Logic Array), decoder, memory, non-software based processor or other circuit, or any type of Includes an architecture microprocessor and a microcomputer digital computer, or a combination thereof. Memory devices are SRAM (static random access memory), DRAM (dynamic random access memory), pseudo static RAM, latch, EEPROM (electrically erasable programmable read only memory), EPROM (erasable programmable read only memory), Includes registers or other memory devices known to those skilled in the art. These terms should not be construed as limiting in interpreting the present invention.
[0037]
It is also possible to configure a full-duplex (full-duplex) transponder structure or a half-duplex (half-duplex) structure. Frequency shift keying (FSK) modulation is considered as a possible data modulation method, but is not limited to this, but also includes pulse pause modulation, amplitude shift keying (ASK), quadrature AM (QAM) modulation, quadrature phase shift keying (QPSK). Or other modulation methods are possible. Different types of multiplexing, such as time or frequency modulation, can be performed to prevent cross signal interference. Not only can it be composed of discrete components or fully integrated circuits composed of silicon, gallium arsenide or other electronic material families, but also in a light-based or other technology-based form Is also possible. It should also be understood that various embodiments of the present invention may employ or be embodied in hardware, software or microcoded hardware.
[0038]
Although the invention has been described with reference to the illustrated embodiment, this description is not to be construed as limiting. With reference to this description, those skilled in the art will be able to contemplate other embodiments of the present invention, as well as various modifications and combinations of the embodiments shown. It is therefore intended that the appended claims encompass any such modifications or embodiments.
[0039]
With respect to the above description, the following items are further disclosed.
(1) a) Send an RF interrogation pulse from the interrogator,
b) receiving the RF interrogation pulse by first and second transponders;
c) terminating the RF interrogation pulse;
d) detecting the end of the RF interrogation pulse with the first transponder;
e) initializing an RF response having a predetermined period with the first transponder;
f) detecting the RF signal from the second transponder with the first transponder;
g) A method of interrogating a remote transponder upon detecting the RF signal from the second transponder, comprising changing a duration of the RF response at the first transponder.
[0040]
(2) receiving the RF response by the interrogator and analyzing a period of the RF response to determine whether both the first and second transponders are near the interrogator. 2. The method according to claim 1.
3. The method of claim 2, further comprising the step of selectively addressing one of said first and second transponders with said interrogator.
The method of claim 1, wherein the first transponder is a half-duplex transponder.
(5) The method according to (1), wherein the second transponder is a half-duplex transponder.
[0041]
(6) The method according to (1), wherein the second transponder is a full-duplex transponder.
(7) The method according to claim 1, wherein the first transponder receives the RF interrogation pulse and has a resonance circuit for performing oscillation in response to the RF interrogation pulse.
(8) Detecting the RF signal from the second transponder in the first transponder includes destruction of the oscillation generated in the resonance circuit of the first transponder and the RF signal from the second transponder. 8. The method of claim 7, wherein said method is performed by detecting severe interference.
(9) The method according to (1), wherein the period is selected by a counter that counts a predetermined number of oscillations in the resonance circuit.
[0042]
(10) a) Send an RF interrogation pulse from the interrogator,
b) Providing first and second transponders (each of said first and second transponders having a resonant circuit including a parallel circuit of a coil and a capacitor) near said interrogator;
c) receiving the RF interrogation pulse by each coil of the transponder;
d) generating in the resonance circuit of each of the transponders an oscillation caused by coupling of signal energy from the RF interrogation pulse to the resonance circuit;
e) terminating the RF interrogation pulse from the interrogator;
f) detecting the end of the RF interrogation pulse in the first transponder;
g) initializing an RF response having a predetermined time period in said first transponder;
h) detecting destructive interference between the oscillation generated in the resonance circuit of the first transponder and the RF signal from the second transponder;
i) changing the duration of the RF response within the first transponder;
j) receiving the RF response by the interrogator and analyzing the duration of the RF response to determine whether the first and second transponders are near the interrogator; Way to ask a question.
[0043]
(11) a) an interrogator operable to transmit RF interrogation pulses and receive an RF response;
b) first and second transponders approaching the interrogator, wherein at least the first transponder is operable to receive the RF interrogation pulse from the interrogator and oscillate with signal energy in the RF interrogation pulse; Having a resonant circuit that can
c) a transponder burst end detector that is electrically coupled to the resonant circuit to receive an RF interrogation pulse end;
d) a transponder transmitter electrically coupled with the burst end detector for transmitting an RF response to the RF interrogator;
e) a transponder counter for determining that the response message from the transponder has been completed and disabling the transmitter;
f) A device for interrogating a remote transponder, comprising a response signal detector provided on said transponder to detect a response from an adjacent transponder and reset a counter of said transponder.
[0044]
(12) The apparatus according to (11), wherein the transponder burst end detector and the transponder transmitter have an intervention control circuit for controlling them.
(13) The apparatus according to (11), wherein the interrogator has an antenna for receiving the RF response.
14. The apparatus of claim 13, wherein said interrogator further comprises a readout circuit electrically coupled to said antenna for detecting valid data returned from said transponder.
[0045]
15. The transponder of claim 14, wherein said interrogator further comprises a timer circuit electrically coupled to said antenna for measuring a duration of said RF response from said first transponder.
(16) The transponder according to (15), wherein the interrogator further includes a decoder electrically coupled to the read circuit and the timer circuit.
[0046]
(17) An interrogator for determining whether an RF interrogator pulse from an interrogator has been received by more than one transponder, comprising: a) a transmitting antenna for transmitting an RF interrogator pulse to the transponder;
b) a receiving antenna for receiving an RF response from at least one of said transponders;
c) a readout circuit electrically coupled to the receiving antenna and operable to extract a data signal from the RF response;
d) a timer electrically coupled to the receiving antenna and operable to measure a duration of the RF response;
e) electrically coupled with the readout circuit and the timer and interpreting the signals received from the readout circuit and the timer as to whether a valid response has been received from a single transponder without interfering with other transponders; An interrogator with a decoder operable to execute.
(18) The interrogator according to (17), wherein the transmitting antenna is the same antenna as the receiving antenna.
[0047]
(19) A method of interrogating the remote transponder includes transmitting an RF interrogation pulse from the interrogator (10), receiving the RF interrogation pulse by the first and second transponders (12, 12a), and transmitting each of the transponders (12, 12a). Generating a vibration in the resonance circuit (130). The oscillation is caused by the coupling of signal energy from the RF interrogation pulse into the resonant circuit (130). When the RF interrogation pulse ends, the first transponder (12) detects the end of the pulse and initializes a first RF response having a predetermined period. The first transponder (12) also detects a second RF response from the second transponder (12a), but the response of the first transponder is affected by the second RF response. The response time difference at the first transponder (12) for the response affected and the response not affected by the adjacent transponder can be detected in the interrogator, so that the interrogator can detect the case where the RF responses received by it do not match.
[0048]
Related patent references
The following U.S. patents and patent applications assigned to the assignee of the present application are incorporated by reference.

[Brief description of the drawings]
FIG. 1 is a block circuit diagram of a preferred interrogator and base unit.
FIG. 2 is a block diagram of a preferred transponder.
FIG. 3 is a more general block diagram of a preferred device showing the most salient features.
FIG. 4 is a signal waveform diagram of an antenna signal according to a normal transponder having no influence from a nearby transponder and a transponder with respect to another very close transponder.
[Explanation of symbols]
10 Interrogator
12 First transponder
12a Second transponder
130 Resonant circuit

Claims (2)

In the method of asking the remote transponder,
a) sending an RF interrogation pulse from the interrogator,
b) receiving the RF interrogation pulse by first and second transponders;
c) terminating the RF interrogation pulse;
d) detecting the end of the RF interrogation pulse with the first transponder;
e) initializing an RF response having a predetermined period with the first transponder;
f) detecting the RF signal from the second transponder with the first transponder;
g) upon detection of said RF signals from said second transponder, to change the period of the RF response definitive to the first transponder, the method comprising the. In an apparatus for interrogating a remote transponder,
a) having an interrogator operable to transmit RF interrogation pulses and receive an RF response;
b) having first and second transponders approaching the interrogator, at least the first transponder has a resonance circuit, the resonance circuit receiving the RF interrogation pulse from the interrogator, and the RF interrogation Operate to oscillate by the signal energy in the pulse ,
to receive an end portion of c) RF interrogation pulse has an end portion of burst detector of the resonant circuit and electrically coupled transponder,
d) it has a transmitter of the burst end portion detector electrically coupled to the transponder for transmitting an RF response to the RF interrogator,
e) determining that the response message from the first transponder is finished, a counter of the transponder for disabling said transmitter,
f) An apparatus comprising a response signal detector provided on the first transponder to detect a response from an adjacent transponder and reset a counter of the transponder.

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