JP2006005392A - Interrogator for wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interrogator for a wireless communication system capable of realizing smooth and highly reliable wireless communication control by preventing a converging time for antenna directivity control from getting longer. <P>SOLUTION: The interrogator 100 includes reception antennas 2A to 2C for receiving a signal transmitted or returned from a wireless tag T. Multiplier sections 52a to 52c apply a weight to a signal received by the reception antennas 2A to 2C so as to change the directivity by the elements of the reception antennas 2A to 2C in a way of optimizing the reception sensitivity to the wireless tag T and output the signal after weighting from an adder section 53. Then an adaptive control section 51 determines the weight so that a signal level of a composite output signal Y after the weighting approaches a prescribed reference level outputted from a reference level control section 54. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wireless communication apparatus that performs wireless communication of information with the outside, and more particularly to an interrogator of a wireless communication system.

  RFID (Radio Frequency Identification) that reads / writes information of a wireless tag by transmitting and receiving an inquiry and receiving a response from a reader / writer as an interrogator to a small wireless tag as a responder The system is known.

  For example, a wireless tag circuit element included in a label-like wireless tag includes an IC circuit unit that stores predetermined wireless tag information and an antenna that is connected to the IC circuit unit and transmits / receives information. The IC circuit unit demodulates and interprets the signal received by the antenna, reflects and modulates the received carrier wave based on the information signal stored in the memory, and returns it to the interrogator via the antenna.

  On the other hand, in general radio communication systems including the interrogator, a so-called adaptive control technique called AAA (Adaptive Array Antenna) processing has been known in order to perform demodulation processing in the above-described radio communication with high sensitivity. (For example, refer to Patent Document 1).

  In this prior art, a plurality of reception antennas are provided, weight vectors (weight values) are added to the reception signals received by the plurality of antennas, and the adaptive array processed reception signals are demodulated by a demodulation circuit. Then, by changing the weight vector so that the error between the demodulated signal and a predetermined reference signal is as small as possible, the directivity by the plurality of antennas is transmitted on the plurality of mobile terminal devices on the transmission side. It is changed so that the reception sensitivity to the optimum.

JP 2002-280945 A (paragraph numbers 0036 to 0069, FIG. 1)

  In the above prior art, the weight vector is changed so that the error between the received signal demodulated by the demodulation circuit and the reference signal becomes small. Usually, the demodulation circuit includes a filter having a relatively large number of taps, and a certain amount of time is required for the filtering process. Therefore, a delay occurs between the input of the antenna reception signal and the output of the decoded signal. For this reason, the weight update interval must be equal to or longer than the delay time, and there is a disadvantage that it takes time for the convergence calculation.

  In particular, with respect to a reception signal including a relatively short information signal used for the RFID (Radio Frequency Identification) communication or the like, the adaptive array processing does not end during the continuation of the information signal, and the demodulated signal cannot be read sufficiently. there is a possibility. As a result, it has been difficult to realize smooth and reliable wireless communication control.

  An object of the present invention is to provide an interrogator of a wireless communication system that can prevent the convergence time of antenna directivity control from becoming long and can realize wireless communication control that is smooth and highly reliable.

  In order to achieve the above object, the first invention provides a plurality of antenna elements for receiving signals transmitted or returned from a responder, and the plurality of antenna elements for signals received by the plurality of antenna elements. Weighting signal output means for applying a weighting for changing the directivity so that the receiving sensitivity to the responder is optimized, and outputting the weighted signal; and the weighted signal from the weighted signal output means Weighting determining means for determining the weighting to be output to the weighting signal output means so that the signal level approaches a predetermined target signal level.

  In the first invention of this application, when a signal transmitted or returned from the responder is received by a plurality of antenna elements, the weighting signal output means applies the weighting from the weighting determination means and outputs a weighted signal. So-called adaptive control is performed to change the directivity of the antenna element so that the reception sensitivity to the transponder is optimized. In the first invention of this application, when determining the weighting, the weighting determining means determines the weighting so that the weighted signal level (for example, absolute value) from the weighting signal output means approaches the predetermined target signal level (absolute value). . In this way, by adopting adaptive control by comparing signal levels, the signal waveform obtained by demodulating the weighted signal is compared with a predetermined reference signal waveform so that the demodulated signal waveform approaches the reference signal waveform. As in the conventional adaptive control for determining the weighting, it is possible to prevent the convergence time of the antenna directivity control from becoming long due to the influence of a large calculation time necessary for signal demodulation. As a result, the convergence time of antenna directivity control can be shortened, and smooth and highly reliable wireless communication control can be realized.

  According to a second invention, in the first invention, there is provided target signal level setting means for setting the predetermined target signal level.

  By setting a predetermined target signal level with the target signal level setting means, the target signal level used when determining the weight with the weight determination means is set by an external signal, appropriately changed, or received by the antenna element. It can be set according to the signal.

  According to a third invention, in the second invention, there is provided edge detection means for detecting a rising edge or a falling edge of an envelope of the signal received by the plurality of antenna elements, and the target signal level setting means includes the target signal level setting means, The predetermined target signal level is set according to the detection result of the edge detection means.

  By setting a predetermined target signal level with the target signal level setting means in accordance with the edge of the signal detected by the edge detection means, the start / end points of adaptive control can be correctly recognized, and normal by comparing waveforms It is possible to reliably perform adaptive control by comparing levels different from those of the adaptive control.

  According to a third invention, in the second or third invention, the target signal level setting means has a plurality of target signals respectively corresponding to a plurality of level values of an envelope of the weighted signal as the target signal level. Level values are respectively set, and the weight determination means determines the weights so that each of the plurality of level values of the weighted signal approaches the corresponding target signal level value.

  By weighting each of the plurality of level values so as to approach the corresponding target signal level, more precise adaptive control can be performed, and directivity by the plurality of antenna elements can be quickly optimized.

  According to a fifth invention, in any one of the second to fourth inventions, the target signal level setting means sets the target signal level to a high level portion and a low level portion of an envelope of the weighted signal, respectively. Corresponding high target signal level and low target signal level are respectively set, and the weight determination means is configured such that the high level portion of the weighted signal approaches the high target signal level and the low level portion is the low target signal. The weighting is determined so as to approach the level.

  By weighting the low-level part closer to the low target signal level so that the high-level part approaches the high target signal level, more precise adaptive control is performed, and the directivity by multiple antenna elements is quickly optimized. Can be

  According to a sixth aspect of the present invention based on the fifth aspect, the target signal level setting means is a high-level positive target that is a target for each of a positive value and a negative value of the high-level portion of the weighted signal as the high target signal level. A low-level positive target value and a low-level negative target value, which are targets for the positive value and negative value of the low-level portion of the weighted signal, respectively. The weight determination means sets the positive value and the negative value of the high level portion of the weighted signal as approaching the high level positive target value and the high level negative target value, respectively. The weighting is determined so that the positive value and the negative value of the low level portion of the later signal approach the low level positive target value and the low level negative target value. The features.

  By setting the high and low level positive and negative target values for the positive and negative values in the high and low level parts and weighting them accordingly, more precise adaptive control is performed, and the directivity by multiple antenna elements Can be optimized more quickly.

  According to a seventh aspect, in the sixth aspect, the sampling means for sampling the signals from the responders received by the plurality of antenna elements at a predetermined time interval (rate) and sequentially outputting the sampling values to the weight determining means. And the weight determination means is configured so that the sample value corresponding to the high level portion approaches the high target signal level and the sample value corresponding to the low level portion approaches the low target signal level. The weighting is determined.

  The values sampled at a predetermined interval by the sampling means are sequentially output to the weight determining means, and using this, the weight is determined by the weight determining means so that the sample values of the high and low level portions approach the high and low target signal levels. be able to.

  An eighth invention is characterized in that, in the seventh invention, a storage means for storing the sampling value by the sampling means in a readable manner is provided.

  The sampling value from the sampling means is stored in the storage means, and then read out at an appropriate timing, so that it can be used in the weight determination means.

  In a ninth aspect based on the seventh aspect, the sampling means receives the signal of the period T from the transponder received by the plurality of antenna elements when n is a positive integer (1 / 2n) T. It is characterized by sampling at intervals (rates).

  The sampling means samples the signal of period T at a time interval of (1 / 2n) T and sequentially outputs it to the weighting determination means. Using this, the sample values of the high and low level portions are set to the high and low targets by the weighting determination means. The weight can be determined to approach the signal level.

  In a tenth aspect based on the ninth aspect, the signal having the period T from the transponder is an intermediate frequency signal obtained by converting signals from the transponders received by the plurality of antenna elements so that the frequency thereof is lowered. It is characterized by being.

  An intermediate frequency signal obtained by converting the signal from the transponder received by the antenna element into a low frequency is sampled by the sampling means at a time interval of (1 / 2n) T and sequentially output to the weight determining means, and using this, the weight determining means is used. The weighting can be determined so that the sample values of the high and low level portions approach the high and low target signal levels.

  In an eleventh aspect based on the ninth or tenth aspect, the target signal level setting means corresponds to the high level positive target value or the low level positive corresponding to one positive value in each period T among the sampling values. A target value is set, and the corresponding high level negative target value or low level negative target value is set for one negative value in each cycle T, and the interval between each positive value negative value in which the target value is set is the same sample It is a number.

  If the sampling value is in the high level part, the high level positive target value is set as one positive value in each period T, and the high level negative target value is set in one negative value. A low level positive target value is set for one positive value in the period T, and a low level negative target value is set for one negative value, and these are used to determine the positive and negative sample values of the high and low level portions by the weight determination means. Can be determined so as to approach the corresponding high / low level positive / negative target values.

  In a twelfth aspect based on the eleventh aspect, the target signal level setting means performs the setting in association with the sample value of a predetermined sample number determined in advance in each period T. .

  In each period T, a positive target value and a negative target value are set for each of a positive value and a negative value of a predetermined predetermined sample number, and these positive / negative sample values are used by the weight determination means using these. Can be determined so as to approach the corresponding positive / negative target values.

  In a thirteenth aspect based on the eleventh aspect, the target signal level setting means calculates the absolute value as the one positive value from an average value for each sample number in one period T or a plurality of periods T. The high level positive target value or the low level positive target value is set in association with a large positive value, and the high level negative target value or the low level is associated with the negative value having the largest absolute value as the one negative value. A negative target value is set.

  A positive target value and a negative target value are set for one positive value and one negative value having the largest absolute value among the sample values from an average value for each sample number in one period T or a plurality of periods T. By using these, the weight determination unit can determine the weights so that the positive / negative sample values approach the corresponding positive / negative target values.

  In a fourteenth aspect based on any one of the eleventh to thirteenth aspects, the received signal is sampled at (1 / 4n) T, and the target signal level setting means is in each period T of the sampling values. The target signal level is set to 0 for a value between the one positive value and the one negative value or a central value thereof.

  The target signal level is set to 0 for a value between one positive value and one negative value for which a positive target value and a negative target value are set in each period T, or a sample value in the center thereof, and weighting is performed using these target signal levels. The weighting can be determined by the determining means so that these sample values approach zero.

  In a fifteenth aspect based on any one of the fifth to fourteenth aspects, the target signal level setting means has a phase substantially inverted with respect to the low level portion of the weighted signal as the low target signal level. Such a target signal level is set.

  As a result, the target value is set so as to be the same absolute value toward the negative side for the positive value of the low level portion and toward the positive side for the negative value of the low level portion. The weight is determined by the weight determination means. As a result, since the low-level portion is controlled more quickly in the direction of attenuation, the directivity by the plurality of antenna elements can be optimized more quickly.

  A sixteenth aspect of the invention is characterized in that, in the fifteenth aspect of the invention, when the ratio of the signal component transmitted from the responder that is outputting the weighted signal exceeds a predetermined value, the weight updating process is terminated. .

  As described above, the target value is set so that the positive value of the low level part becomes the negative side and the negative value becomes the same absolute value toward the positive side, the weight is determined, and the low level part is quickly attenuated. If the control is continued as it is when the control is performed, the amplitude ratio of the signal component (= reflected wave component) transmitted from the transponder will eventually become almost zero. In the fourteenth invention of the present application, the antenna element directivity can be quickly optimized while avoiding the above-described adverse effects by terminating the weighting update when the ratio of the reflected wave in the middle of attenuation reaches a predetermined value or more.

  In a seventeenth aspect based on any one of the first to sixteenth aspects, the responder is a wireless tag, and a predetermined transmission signal is transmitted to the wireless tag by a transmission antenna, and in response to the transmission signal. Information is communicated with the wireless tag by receiving return signals returned from the wireless tag by the plurality of antenna elements.

  In the seventeenth invention of the present application, signals returned from the wireless tag are received by a plurality of antenna elements, and a weighted signal output means applies a weight from the weight determining means to output a weighted signal, and a plurality of antennas Adaptive control for optimizing the reception sensitivity to the wireless tag is executed to change the directivity by the element so that the reception sensitivity to the wireless tag is optimized.

  ADVANTAGE OF THE INVENTION According to this invention, it can prevent that the convergence time of antenna directivity control becomes long by using adaptive control by the comparison of signal levels, and can implement | achieve smooth and reliable wireless communication control.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a system configuration diagram showing an overall outline of a wireless communication system (wireless tag communication system) to which this embodiment is applied.

  In FIG. 1, the RFID tag communication system S includes an interrogator 100 of the present embodiment (only one is shown, but a plurality of interrogators may be present) and an RFID tag T as a responder corresponding thereto. This is a so-called RFID (Radio Frequency Identification) communication system.

  The wireless tag T includes a wireless tag circuit element To including an antenna 151 and an IC circuit unit 150.

  The interrogator 100 has a directivity within a predetermined plane and is configured to be variable in the direction in which transmission or reception can be performed with the maximum power. The interrogator 100 transmits a signal by wireless communication with the antenna 151 of the RFID circuit element To. In this example, transmission / reception is performed. One transmission antenna 1 and three reception antennas (antenna elements) 2A, 2B, and 2C, and the IC circuit unit 150 of the RFID circuit element To through the antennas 1 and 2A to C are used. A transmission signal (transmission wave Fc) that is provided for accessing (reading or writing) and modulated in a predetermined manner is output as a digital signal, or a return signal (reflection wave Fr) from the RFID circuit element To. DSP (Digital Signal Processor) 10 that performs digital signal processing such as demodulation) and the transmission signal output by the DSP 10 A transmission signal D / A conversion unit 11 that converts the received signal to the transmission antenna 1 and converts the reception signal at the reception antennas 2A to 2C into a digital signal and supplies the digital signal to the DSP 10, and the received signal is transmitted at a predetermined time interval. Received signal A / D converter 12 having a sampling function for sampling in the above-described manner (which will be composed of received signal A / D converters 12a, 12b, and 12c as will be described later. Signal A / D converter 12).

  When a transmission wave Fc, which is a transmission signal, is transmitted from the interrogator 100, the transmission wave Fc is modulated based on a predetermined information signal in the RFID circuit element To of the RFID tag T that has received the transmission wave Fc. Information is transmitted and received by the interrogator 100 receiving and demodulating the reflected wave Fr.

  FIG. 2 is a block diagram illustrating an example of a functional configuration of the RFID circuit element To provided in the RFID tag T.

  In FIG. 2, the RFID circuit element To receives the transmission wave Fc and transmits the reflection wave Fr in a non-contact manner using the antennas 1, 2 </ b> A to 2 </ b> C on the interrogator 100 side and a high frequency such as a UHF band. The antenna 151 is configured to be connected to the antenna 151 and the IC circuit unit 150 is connected to the antenna 151 and performs digital signal processing.

  The IC circuit unit 150 includes a rectifying unit 152 that rectifies the carrier wave received by the antenna 151, a power source unit 153 that accumulates energy of the carrier wave rectified by the rectifying unit 152 and serves as a driving power source, and the antenna 151. A clock extraction unit 154 that extracts a clock signal from the received carrier wave and supplies the clock signal to the control unit 157; a memory 155 that functions as an information storage unit that can store a predetermined information signal; and a modulation / demodulation unit connected to the antenna 151 156, and a control unit 157 for controlling the operation of the RFID circuit element To via the rectification unit 152, the clock extraction unit 154, the modulation / demodulation unit 156 and the like based on the power supply from the power supply unit 153. Yes.

  The modem 156 demodulates the communication signal received from the antenna 151 from the transmission antenna 1 of the interrogator 100 and reflects and modulates the carrier wave received from the antenna 1 based on the return signal from the controller 157. To do.

  The control unit 157 interprets the received signal demodulated by the modulation / demodulation unit 156, generates a return signal based on the information signal stored in the memory 155, and performs basic control such as control of returning by the modulation / demodulation unit 156. Execute control.

  The above description has been made by taking the RFID tag circuit element To of the type that does not use a subcarrier as an example. However, the present invention is not limited to this, and a subcarrier oscillation unit and a subcarrier modulation unit (both not shown) are provided. The subcarrier generated by the oscillating unit may be modulated by the subcarrier modulating unit based on a predetermined information signal input via the control unit 157 and returned from the antenna 151.

  FIG. 3 is a functional block diagram showing a functional configuration of the interrogator 100.

  In FIG. 3, the interrogator 100 outputs the above-described antennas 1, 2 </ b> A to 2 </ b> C, the DSP 10, the transmission signal D / A conversion unit 11, and the reception signal A / D conversion units 12 a to 12 c and a predetermined frequency conversion signal. The frequency of the transmission signal from the converted signal output unit 13 and the DSP 10 converted into the analog signal by the transmission signal D / A conversion unit 11 is increased by the frequency of the frequency conversion signal output from the frequency conversion signal output unit 13. The frequency of the received signal received by the up-converter 14 that outputs to the transmitting antenna 1 and each of the receiving antennas 2A, 2B, 2C is lowered by the frequency of the frequency converted signal output from the frequency converted signal output unit 13, and Down converters 15a, 15b, 15c that output to the received signal A / D converters 12a, 12b, 12c (hereinafter particularly distinguished) And it has simply referred to as down-converter 15 in the case), a band-pass filter 18,19a for removing unnecessary frequency signal components, 19b, and 19c. A known direct modulation circuit may be used instead of the bandpass filter.

  The DSP 10 is a so-called microcomputer system that includes a CPU, a ROM, a RAM, and the like in hardware and performs signal processing according to a program stored in advance in the ROM while using a temporary storage function of the RAM. The DSP 10 functionally outputs a transmission digital signal output unit 16 that outputs a transmission signal to the RFID circuit element To as a digital signal, and a transmission digital signal output from the transmission digital signal output unit 16. A modulator 17 that modulates based on a predetermined information signal (transmission information) and supplies the modulated signal to the transmission signal D / A converter 11, and a memory that stores reception signals respectively received by the reception antennas 2A, 2B, and 2C A memory 20 functioning as a unit, an adaptive array processing unit 50 for applying a predetermined weight (weighting value; weighting) to the received signal read from the memory 20 and performing an adaptive array processing, and processing performed by the adaptive array processing unit 50 A received signal is demodulated and a predetermined information signal (= a modulated signal by the RFID circuit element To) The AM demodulator 30 for reading out the signal, the FSK decoder 40 for decoding the demodulated signal, the received signal output from the memory 20 according to the instruction signal from the FSK decoder 40, and the antennas 2A to 2C, respectively. Circuit switching units 60a, 60b, and 60c are provided for switching circuits so as to supply any one of the received signals to the adaptive array processing unit 50.

  The memory 20 preferably stores the received signals received by the plurality of receiving antennas 2A to 2C for a time longer than a demodulation delay time, which will be described later, and erases unnecessary received signals after the time has elapsed. For example, a RAM or a hard disk is preferably used.

  The adaptive array processing unit 50 includes an adaptive control unit (LMS) 51 that controls the value of the weight given to the received signal read from the memory 20 using, for example, a least square method, and the circuit switching unit. Multipliers 52a to 52c for multiplying the signals input through 60a to 60c by the weights from the adaptive controller 51, an adder 53 for adding the outputs from the multipliers 52a to 52c, and a reference signal level (target An output signal level (described later in detail) and a reference level control unit 54 for setting and controlling the value of r.

  Specifically, the adaptive control unit 51 specifically relates to the combined output signal added by the adding unit 53 so that the receiving sensitivity of the receiving antennas 2A to 2C is optimal with respect to the direction in which the wireless tag T is disposed. In the present embodiment, the antennas 2A to 2A are arranged so that the amplitude of the reflected wave component by the RFID circuit element To is as high as possible (or low) and approaches the predetermined reference signal level output from the reference level control unit 54. The directivity is controlled by changing the amplitude and phase of each received signal received by 2C. For this purpose, a weight value is calculated for each of the antennas 2A, 2B, and 2C in the phase control signal from the adaptive control unit 51 to the multiplication units 52a to 52c. As a result, the accuracy of demodulation processing by the AM demodulator 30 is increased as much as possible. The reception signals subjected to the adaptive array processing in the multipliers 52 a to 52 c by the control signal of the adaptive controller 51 are added together in the adder 53 as described above, and then output to the AM demodulator 30.

  The AM demodulator 30 preferably performs IQ quadrature demodulation, that is, after converting the input signal into an I phase (In phase) and a Q phase (Quadrature phase) signal that are 90 ° out of phase with each other, The received signal is demodulated by synthesizing the phase synthesized signal and output to the FSK decoding unit 40.

  In the above configuration, a transmission digital signal is output from the transmission digital signal output unit 16, the signal is modulated based on predetermined transmission information by the modulation unit 17, and then converted into an analog signal by the transmission signal D / A conversion unit 11. Is done. The frequency of the transmission signal converted into the analog signal is increased by the up-converter 14 by the frequency of the frequency conversion signal output from the frequency conversion signal output unit 13 and is supplied to the transmission antenna 1 and wirelessly transmitted as a transmission wave Fc. It is transmitted toward the tag circuit element To.

  When the transmission wave Fc from the transmission antenna 1 of the interrogator 100 is received by the antenna 151 of the RFID circuit element To, the transmission wave Fc is supplied to the modulation / demodulation unit 156 and demodulated. Further, a part of the transmission wave Fc is rectified by the rectification unit 152 and is used as an energy source (power source) by the power supply unit 153. The IC circuit unit 150 is operated by this power source. Further, the control unit 155 generates a reply signal from the information signal in the memory 155 based on the demodulated data of the modulation / demodulation unit 156, and the modulation / demodulation unit 156 modulates the transmission wave Fc based on the return signal and reflects the reflected wave from the antenna 151. It is sent back to the interrogator 100 as Fr. The clock extraction unit 154 extracts a clock component from the received signal and outputs it to the control unit 157.

  When the reflected wave Fr from the antenna 151 of the RFID circuit element To is received by the receiving antennas 2A to 2C of the interrogator 100, the reflected wave Fr is supplied from the antennas 2A to 2C to the down converter 15, and each received signal The frequency is converted into an intermediate frequency signal that is lower by the frequency of the frequency conversion signal output from the frequency conversion signal output unit 13. The down-converted received signals are converted into digital signals by the corresponding received signal A / D converters 12, supplied to the memory 20, stored in the memory 20, and via the circuit switching units 60 a to 60 c. Are supplied to the AM demodulator 30.

  Here, first, in a state where the information signal start point is not detected (first pass), the circuit switching units 60a to 60c are respectively received by the output of the reception signal A / D conversion unit 12, that is, the reception antennas 2A to 2C. The received signal is connected to the AM demodulator 30 so that the output of the memory 20 is not input to the AM demodulator 30 (the state shown in FIG. 3). In this state, when the received signals output from the received signal A / D converter 12 are input to the AM demodulator 30, the received signals are, for example, I-phase and Q-phase signals whose phases are different from each other by 90 ° as described above. Respectively. Then, the I-phase signals from the antennas 2A to 2C are combined, and only signals having a predetermined frequency or less are passed through an LPF (not shown), and the Q-phase signals from the antennas 2A to 2C are combined. At the same time, only a signal having a predetermined frequency or less is passed by an LPF (not shown). Then, the extracted I-phase combined signal and Q-phase combined signal are further combined (square root of the sum of squares) to generate a demodulated signal, and the demodulated signal has a predetermined frequency that is passed by an HPF (not shown). Is output as an AM demodulated wave. The signal thus output from the AM demodulator 30 is further decoded by the FSK decoder 40, and the decoded data is output.

  FIG. 4 is a diagram for explaining the information signal start point detection process by the adaptive array processing unit 50.

  A reflected wave Fr (received signal) from the RFID circuit element To received by the receiving antennas 2A to 2C is converted into a transmission wave Fc (direct wave) transmitted from the transmitting antenna 1 by a modulated signal (predetermined by the RFID circuit element To). For example, a portion having a relatively large amplitude in the input data shown in FIG. 4A corresponds to the modulated signal. The received signal is demodulated by the AM demodulator 30 as described above, and is output as a demodulated signal as shown in the output data of FIG. The portion of the demodulated signal shown in FIG. 4B that oscillates corresponds to the modulated signal by the RFID circuit element To, but the demodulation processing by the AM demodulator 30 takes a predetermined time. A predetermined initial delay (initial delay) is generated after a received signal including a modulated signal by To is input to the AM demodulator 30 until a portion corresponding to the modulated signal is demodulated and output by the AM demodulator 30. To do.

  In this embodiment, in order to perform adaptive array processing corresponding to this initial delay, the FSK decoding unit 40 also functions as an information signal start point detection unit, and the modulation signal of the RFID circuit element To included in the received signal is transmitted. Detect the starting point. That is, based on the output data of the FSK decoding unit 40 as shown in FIG. 4B, the leading edge of the modulation signal by the RFID circuit element To included in the decoded signal is detected. For example, the FSK decoding unit 40 detects whether the interval between the change points of the amplitude or phase of the information signal is within a predetermined range, and the interval between the change points is predetermined after the adaptive array processing unit 50 starts weight control. If it is out of the range, the setting of the adaptive array processing unit 50 is initialized, and a start point detection restart instruction is issued to the information signal start point detection unit.

  In this information signal start point detection control, as shown in FIG. 4 (c), when one or a plurality of signals having a predetermined pulse width are detected, this is detected as an information signal (modulated signal) from the RFID circuit element To. And the start point of the pulse having the predetermined width is detected as the leading edge. Since this detection takes a predetermined time including the LPF and the delay time of the LPF, the modulation signal from the RFID circuit element To is input to the AM demodulator 30 until the start point of the modulation signal is detected. Causes the above-described predetermined initial delay (initial delay). The FSK decoding unit 40 connects the circuit switching units 60a to 60c so that the received signal corresponding to the modulation signal after the start point is read from the memory 20 and input to the AM demodulation unit 30 when the start point of the modulation signal is detected. Switch. That is, among the received signals stored in the memory 20, the delay (delay 1) due to the demodulation process (temporary demodulation) in the first path, the delay (delay 2) due to the modulation signal start point detection process included in the decoded signal, and the start point detection process The received signals after the portion calculated by the amount of delay (delay 3) corresponding to the number of the predetermined pulse width signals (number of samples) used (for example, about 100 samples in total) are read and supplied to the AM demodulator 30. The process of demodulating the received signal read from the memory 20 corresponds to this demodulation. In the above, the initial delay occurs only when the information signal start point is detected, and no delay occurs during subsequent weight updates.

  After the information signal start point is detected (after the second pass), the AM demodulator 30 performs the main demodulation as described above. That is, the circuit switching units 60 a to 60 c are switched so as to input the output of the memory 20 to the AM demodulating unit 30, and reception signals corresponding to the start point of the modulation signal by the RFID circuit element To read from the memory 20 are received. The adaptive array processing unit 50 performs adaptive array processing.

  On the other hand, in the adaptive array processing executed by the adaptive array processing unit 50, the reception sensitivity of the reception antennas 2A to 2C is controlled by controlling the weight (weight value) given to the reception signal read from the memory 20, and the RFID circuit element. The directivity is controlled so as to be optimal with respect to the direction in which To is arranged. Specifically, for the signal from the memory 20, for example, the amplitude of the modulation component (reflected wave component) by the RFID circuit element To is made as high as possible (or low) so as to approach a predetermined reference signal level. In addition, the amplitude and phase of each received signal received by each of the receiving antennas 2A to 2C is changed, and the accuracy of the demodulation processing by the AM demodulator 30 is increased as much as possible. In this state, as described above, the outputs of the reception signal A / D conversion units 12a to 12c, that is, the reception signals respectively received by the reception antennas 2A to 2C are not directly input to the AM demodulation unit 30.

  The received signal subjected to adaptive array processing by the control signal of the adaptive control unit 51 and demodulated by the AM demodulating unit 30 is finally converted into a decoded signal by the FSK decoding unit 40 and is output as data.

  In the above basic configuration, the main part of the present invention is the adaptive array processing technique executed by the adaptive array processing unit 50.

  That is, in this embodiment, attention is paid not to the waveform of the reference signal as used in normal adaptive array processing but to the level of the signal (reference signal level), and this is used as the target signal level so that the weighted signal level is as close as possible. By performing the control, it is possible to perform a rapid convergence calculation process.

  FIG. 5 is an explanatory diagram for conceptually explaining the adaptive array processing technique forming the main part of the present invention.

  In FIG. 5, as described above, the combined output signal Y based on the received signals received by the receiving antennas 2A to 2C has a sinusoidal amplitude (absolute value) corresponding to the reflected wave Fr from the RFID circuit element To. Large portion (= high level portion of sine wave signal envelope, expressed as “H” or “H level” in the figure), and other small portion of sine wave amplitude (absolute value) (= sine wave signal envelope) Low-level portion, which is represented by “L” or “L level” in the figure). Since a large number of sine wave envelopes (substantially rectangular wave shapes) that can be read due to the difference in level correspond to the transmitted predetermined information signals, this rectangular wave shape is used to obtain information signals quickly. It is enough to make it stand out (sharp). In this embodiment, from this viewpoint, the adaptive array processing unit 50 updates the weight so that the amplitude is further increased in the high level portion and the amplitude is further decreased in the low level portion. Do.

  Specifically, as shown in the figure, the positive value of the high level portion (the portion above the amplitude center line 0 in the figure) has a higher absolute value than the reference level for the high level positive value. (High-level positive target value) is set, and the weight update is performed so as to match or approach this reference level (see the white arrow). For negative values in the high-level part (the part below the amplitude center line 0 in the figure), a reference level for high-level negative values with a higher absolute value (high-level negative target value) is set. Then, the weight update is performed so as to match or approach this reference level (see the white arrow). These two reference levels correspond to the high target signal level described in each claim.

  For the low level part, the positive value (the part above the amplitude center line 0 in the figure) and the negative value (the part below the amplitude center line 0 in the figure) are both absolute Set a reference level for low level positive value (low level positive target value) and a reference level for low level negative value (low level negative target value, 0 in this example) with a small value so as to match or approach this reference level The above weight update is performed (see the white arrow). These two reference levels correspond to the low target signal level described in each claim.

  FIGS. 6A and 6B are explanatory diagrams showing an example of the convergence operation by updating the weights. For example, in the initial weight setting (weight initial value), as shown in FIG. 6A, the amplitude difference between the high level portion H and the low level portion L is not large in the composite output signal Y, and as a result, these differences are different. The reflected wave component corresponding to is not very clear. However, by performing the control by the adaptive array processing unit 50 as described above with reference to FIG. 5, the combined output signal Y after weighting using the weight after completion of the convergence calculation (weight convergence value) is: As shown in FIG. 6B, the amplitude difference between the high level portion H and the low level portion L is increased. In this case, the directivity null portion of the antennas 2A to 2C is directed to the interfering wave, and the directional main beam is directed to the direction of the wireless tag T, thereby increasing the ratio of the reflected wave component of the combined output signal Y. ing. As a result, the substantially rectangular wave shape of the envelope is clarified (prominently), and the reflected wave component corresponding to the difference between these is clarified, making it possible to perform a suitable demodulation process that is less susceptible to noise.

  FIG. 7 is a diagram illustrating an example of sampling performed by the reception signal A / D conversion unit 12 when performing adaptive array processing using the reference level as described above as a target signal level. The received signal A / D converter 12 receives a signal (in this example, a sine wave) having a periodicity of frequency f (period T = 1 / f) from the antenna 151 of the RFID tag circuit element To of the RFID tag T as a responder. ) Is transmitted, the received sine wave signal is sampled at a time interval of (1 / 2n) T (n: positive integer), for example.

  That is, in this example, with respect to the sinusoidal received signals input by the receiving antennas 2A to 2C, a ratio of four per one period T, with T / 4 being 1/4 of the period T of the sinusoidal wave as a sampling interval. Thus, sampling is performed as sample values Y1, Y2, Y3, Y4, Y5, Y6, Y7,.

  Here, the sine wave waveform of the example shown in FIG. 7 may correspond to the above-described high level portion or the low level portion.

  In the case of corresponding to the high level portion, as described above with reference to FIG. 5, for example, regarding the even-numbered composite outputs Y0, Y2, Y4, Y6, the positive values Y0, Y4 are absolute values from them. Convergence calculation is performed so as to match or approach a large (corresponding to the upper side in the figure) high-level positive value reference level, and Y2 and Y6 that are negative values have larger absolute values (lower in the figure). Convergence calculation is performed so as to match or approach the reference level for high-level negative values (corresponding to the side).

  In the case of corresponding to the low level portion, as described above with reference to FIG. 5, for example, regarding the even-numbered combined outputs Y0, Y2, Y4, Y6, the positive values Y0, Y4 are absolute values. Convergence calculation is performed so as to match or approach a small (corresponding to the lower side in the figure) low-level positive reference level, and Y2 and Y6 that are negative values have smaller absolute values than those (in the figure, The convergence calculation is performed so as to match or approach the reference level for low level negative values (corresponding to the upper side).

  In addition, in any case corresponding to either the high level side or the low level side, it is not necessary to perform the convergence calculation using the target signal for the odd-numbered combined outputs Y1, Y3, Y5, Y7, or refer to them separately. A convergence calculation may be performed by setting level 0 as a target signal level.

  FIG. 8 is a flowchart showing a control procedure of the adaptive array processing operation executed by the adaptive array processing unit 50 based on the received signal data stored in the memory 20 as described above.

  In FIG. 8, first, in step S5, the adaptive control unit 51 reads the received signal data stored in the memory 20 as described above.

  Next, the process proceeds to step S10, where the adaptive control unit 51 uses the appropriate method (for example, comparing the average value of a large number of data with a threshold value as a threshold value) to read the received signal data as described above. Whether it corresponds to a level signal or a low level signal is detected.

  In step S15, the reference level control unit 54 starts the first edge of the decoded received signal (the rising edge or the rising edge of the decoded rectangular wave signal) based on the signal input from the FSK decoding unit 40 described above. It is determined whether the first falling edge) is detected. If the determination is not satisfied until an edge is detected, the process returns to step S5 and the same procedure is repeated. When an edge is detected and the determination in step S15 is satisfied, the process proceeds to next S20.

  In step S20, when the adaptive control unit 51 and the reference level control unit 54 perform the adaptive array processing using the above-described reference level for each sample value of the received signal data read from the memory 20, in order to distinguish in arithmetic processing. The reference level that must be set separately (high level reference level or low level reference level) and the initial value of the sign (positive / negative) of the composite output signal Y after adaptive array processing are set ( Initialization; detailed procedure is described later).

  Thereafter, the process proceeds to step S30, where the reference level control unit 54 performs the convergence calculation in the adaptive array processing as described above according to the previous reference level setting and the sign (positive / negative) setting of the combined output signal Y. A reference level as a level is set (details will be described later).

  In step S35, the adaptive control unit 51 determines whether the sample value previously read from the memory 20 in step S5 satisfies a predetermined sample number condition appropriately determined in advance for adaptive array control. In this example, the high level positive target value or the low level positive target value corresponding to one positive value in each period T of the sine wave waveform is set, and the high level corresponding to one negative value in each period T is set. For the purpose of setting a negative target value or a low-level negative target value and setting the same number of samples as the interval between the positive and negative values for which the target value has been set, the first sample (for example, FIG. 8) (Y0, Y2, Y4, Y6,...). If it is the first sample value, the determination is satisfied, and the routine goes to Step S40. If it is not the first sample value, the process proceeds to step S55 described later.

  In step S40, according to the setting of the reference level in step S30, the adaptive control unit 51 and the reference level control unit 54 change the value of the high level portion H of the composite output signal Y to the reference level value for the high level. A weight is calculated so that the value of the level portion L matches (or approaches) the value of the reference level for the low level, and the combined output signal Y added by the adder 53 is connected to the receiving antennas 2A to 2C. The directivity is controlled by changing the amplitude and phase of each of the reception signals received by the antennas 2A to 2C so that the reception sensitivity is optimized with respect to the direction in which the wireless tag T is disposed.

  In step S50, the adaptive control unit 51 determines whether the weight of the adaptive array process in step S40 has converged. If the weights have converged, the determination is satisfied, and this flow ends. If the weight has not yet converged, the determination is not satisfied, and the routine goes to Step S55.

  In step S55, as in step S5, the adaptive control unit 51 reads the received signal data stored in the memory 20.

  After that, in step S60, the reference level control unit 54, based on the signal input from the FSK decoding unit 40 described above, the next edge of the decoded received signal (of the decoded rectangular wave signal, the next It is determined whether a rising edge or a falling edge is detected. Until the next edge is detected, the determination is not satisfied and the process returns to step S35 and the same procedure is repeated. If the next edge is detected, the determination is satisfied, the process returns to step S30, and the same procedure is repeated.

  As described above, on the basis of the reference level value set in step S30, decoding is performed by repeating the convergence calculation in steps S35, S40, S50, S55, S60, S35, and so on. Calculation so that the high-level part (or low-level part, the same correspondence relationship) of the received sine wave signal corresponding to the period from one edge of the rectangular wave signal to the next edge is higher (or lower level). I will go. If the next edge is detected during this period, the reference level is switched from the reference level for high level to the reference level for low level in step S30 through step S60 (or switched from the reference level for low level to the reference level for high level). The calculation is performed so that the low level portion (or high level portion, the same correspondence relationship below) of the received sine wave signal corresponding to the edge from that edge to the next edge becomes a lower level (or high level). . In this way, adaptive array processing is implemented to increase the sensitivity of the received signal as shown in FIGS.

  FIG. 9 is a flowchart showing a detailed control procedure of step S20 executed by the adaptive control unit 51 and the reference level control unit 54 shown in FIG.

  In FIG. 9, when the leading edge of the rising edge or falling edge of the rectangular wave signal is detected in step S15 as described above, the value of the combined output signal Y after that edge is first determined in step S21 of this flow. Whether it corresponds to a high-level signal or a low-level signal is determined by an appropriate method (for example, comparing an average value of a large number of data as a threshold value with a magnitude).

  If the combined output signal Y after the leading edge is a low level signal (as will be described later, the control procedure proceeds from step S32 in FIG. 10 to reverse the high level ← → low level), the process proceeds to step S22. The positive reference level that should be referred to in the positive value among the sampling values is set to the reference level for the high level positive value, and the negative reference level that should be referred to in the negative value among the sampling values is used for the high level negative value The reference level is set (see also FIG. 5 above).

  On the contrary, if the composite output signal Y after the leading edge is a high level signal, the process proceeds to step S23, and the positive value reference level to be referred to in the positive value of the sampling value is set as the reference level for the low level positive value. At the same time, the negative value reference level to be referred to in the negative values of the sampling values is set to the low level negative value reference level (see also FIG. 5 described above).

  When step S22 or step S23 is completed as described above, the process proceeds to step S24. In step S24, it is determined whether the sign of the combined output signal Y after the leading edge is positive or negative.

  If the sign of the composite output signal Y after the leading edge is negative (since the control procedure reverses positive ← → negative in step S43 and step S45 in FIG. 11 as described later), the process proceeds to step S25. A sign for adding to the composite output signal Y is set to be positive.

  Conversely, if the sign of the composite output signal Y after the leading edge is positive, the process proceeds to step S26, and the sign attached to the composite output signal Y is set to negative.

  When step S25 and step S26 are finished, this routine is finished, and the routine proceeds to step S30 in FIG.

  FIG. 10 is a flowchart showing the detailed control procedure of step S30 executed by the reference level control unit 54 shown in FIG.

  In FIG. 10, when step S25 or step S26 of FIG. 9 is completed, in step S31 of this flow, the reference level set at the previous time (at this time) is for the high level or for the low level. It is determined whether it is.

  If the previously set reference level is for the low level, the process proceeds to step S32, where the positive value reference level to be referred to in the positive value among the sampled values is set to the high level positive value reference level, and the sampling value The negative value reference level to be referred to in the negative value is set to the high level negative value reference level (see also FIG. 5 described above).

  On the other hand, if the previously set reference level is for the high level, the process proceeds to step S33, and the positive value reference level to be referred to in the positive value among the sampling values is set to the low level positive value reference level. The negative value reference level to be referred to in the negative values among the sampling values is set to the low level negative value reference level (see also FIG. 5 described above).

  When step S32 or step S33 is completed, this routine is ended, and the process proceeds to step S35 in FIG.

  When the next rising edge or falling edge of the rectangular wave signal is detected in FIG. 8 by resetting the current reference level opposite to the previous reference level, the process returns from step S60 to step S30. Execute switching from low level reference level before rising edge to high level reference level after rising edge, or switching from high level reference level before falling edge to low level reference level after falling edge .

  Further, in FIG. 8, when the process proceeds from step S5 to step S15 to step S30 through the initial setting in step S20, the level of the composite output signal Y after the edge detected in step S15 is handled. Thus, the reference level for high level or the reference level for low level is set correctly.

  FIG. 11 is a flowchart showing a detailed control procedure of step S40 executed by the adaptive control unit 51 and the reference level control unit 54 shown in FIG.

  In FIG. 11, when step S35 of FIG. 8 is completed, first in step S41 of this flow, it is determined whether the sign attached to the combined output signal Y at the previous time (at this time) is positive or negative.

  If the previous sign was negative, the process proceeds to step S42, the reference level to be referred to the sampled value is set to the positive value reference level, and the sign attached to the composite output signal Y is set to positive in step S43. cure.

  On the other hand, if the previous sign is positive, the process proceeds to step S44, where the reference level to be referred to the sampled value is set to the negative value reference level, and the sign attached to the composite output signal Y is made negative in step S45. Set again.

  When step S43 or step S45 is completed as described above, the process proceeds to step S46.

  In step S46, the difference between the value obtained by adding the sign set in step S43 or step S45 to the combined output signal Y input from the adder 53 and the reference level value set in step S42 or step S44 ( Error) to generate an error signal.

  After that, in step S47, the error signal generated in step S46 and the combined output signal Y (input signal to the adaptive control unit 51) input from the adder 53 are publicly known, such as a preset LMS algorithm. Substituting into the recurrence formula for updating the weights, the weight values up to that time are updated.

  In step S48, the weight value updated in step S47 is newly set in a wait register (not shown) provided in the adaptive control unit 51.

  As a result, the phase control signals from the adaptive control unit 51 to the multiplication units 52a to 52c are weighted by the weights calculated for each of the receiving antennas 2A, 2B, and 2C, and multiplied by the corresponding phase and amplitude (gain). Set in the sections 52a to 52c. As a result, the directivity generated by the antennas 2 </ b> A to 2 </ b> C is sought so that the received signal strength becomes the maximum value, that is, the optimum sensitivity.

  While the weights have not yet converged by the control as described above, the weights are repeatedly updated in the order of step S40 → step S50 → step S55 → step S60 → (or via step S30) S35 → step S40 in FIG. While searching for the directivity that optimizes the reception sensitivity. At this time, the weight value (or error signal value) is stored in an appropriate storage means such as a RAM in the DSP 10 and the size thereof is compared with that stored so far, and is converged as described above. If the change is considered to be equal to or less than a predetermined value when the calculation is repeated, it is determined in step S50 in FIG. 8 that the calculation has converged. When the optimum weight is found in this way, the convergence calculation ends, the determination in step S50 is satisfied, and the optimum directivity is realized.

  In the above, the multipliers 52a to 52c and the adder 53 provided in the adaptive array processing unit 50 respond to the directivity by the plurality of antenna elements with respect to the signals received by the plurality of antenna elements according to the claims. The weighting signal output means for applying the weighting for changing the receiving sensitivity to the optimum signal and outputting the weighted signal is configured, and the adaptive control unit 51 receives the weighted signal from the weighting signal output means. The weight determining means for determining the weight to be output to the weighted signal output means is configured so that the signal level approaches the predetermined target signal level.

  Further, the reference level control unit 54 constitutes target signal level setting means for setting a predetermined target signal level, and the FSK decoding unit 40 has rising edges or falling edges of envelopes of signals received by a plurality of antenna elements. Constitutes edge detecting means for detecting.

  The received signal A / D conversion unit 12 constitutes sampling means for sampling the signals from the responders received by the plurality of antenna elements at predetermined intervals and sequentially outputting the sampled values to the weighting determination means. Constitutes storage means for storing the sampling value by the sampling means in a readable manner.

  The operational effects of the present embodiment configured as described above will be described below.

  In the interrogator 100 of the present embodiment, when the signals from the radio tags T that are responders are received by the receiving antennas 2A to 2C, the multipliers 52a to 52c of the adaptive array processing unit 50 are determined by the adaptive control unit 51. After weighting by applying a weight, so-called adaptive control is performed to change the directivity of the receiving antennas 2A to 2C so that the receiving sensitivity to the RFID circuit element To is optimized. Here, in this embodiment, when the adaptive control unit 51 determines the weighting, the high level portion of the combined output signal Y weighted by the multiplying units 52a to 52c and summed by the adding unit 53 is a high level reference level ( The weight is determined so as to be close to the reference level for high level positive value or negative value in detail) and the reference level for low level (specifically, reference level for low level positive value or negative value) in the low level part. In this way, by adopting adaptive control by comparing signal levels, the signal waveform obtained by demodulating the weighted signal is compared with a predetermined reference signal waveform so that the demodulated signal waveform approaches the reference signal waveform. As in the conventional adaptive control for determining the weighting, it is possible to prevent the convergence time of the antenna directivity control from becoming long due to the influence of a large calculation time necessary for signal demodulation. That is, unlike the above-described prior art, the delay occurs in this embodiment only in the initial delay when the information signal start point is detected (delay 1 + delay 2 + delay 3 described above) and does not occur during the subsequent weight update. The weight can be minimized and the weight can be converged in as short a time as possible. As a result, it is possible to shorten the convergence time of directivity control of the receiving antennas 2A to 2C, and to realize smooth and reliable wireless communication control.

  At this time, the reference level as the target signal level is set by the reference level control unit 54 in accordance with the edge of the composite output signal Y detected by the FSK decoding unit 40, so that the starting point / end at which adaptive control is to be performed. A point etc. can be recognized correctly, and adaptive control by comparison between levels different from normal adaptive control by comparison between waveforms can be reliably performed.

  Further, in the adaptive array processing in the adaptive array processing unit 50, the combined output signal from the adding unit 53 (that is, the output before demodulating by the AM demodulating unit 30) is supplied to the adaptive control unit 51 to set / update the weight. As a result, it is possible to prevent the influence of delay due to the number of taps of the LPF and HPF, which can occur when the output after demodulation is supplied.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit and technical idea of the present invention. Hereinafter, such modifications will be described.

(1) Variation of reference level setting according to sampling (1)
That is, in the above embodiment, the adaptive control unit 51 and the reference level control unit 54 set the reference level so as to be associated with the sample value of a predetermined sample number determined in advance in each cycle T. Specifically, the process proceeds to step S40 only when the first sample in the half cycle T / 2 in step S35 in FIG. 8, and the reference level is set in step S42 or step S44 in FIG. The application mode of the present invention is not limited to this.

  That is, in a certain period T, the reference level for high level positive value (= high level positive target value) or the positive value having the largest absolute value (for example, Y0 in the first period of FIG. 7 described above) or A reference level for low level positive value (= low level positive target value) is set, and a reference value for high level negative value is associated with the negative value having the largest absolute value (for example, Y2 in the first cycle of FIG. 7). A level (high level negative target value) or a reference level for low level negative values (low level negative target value) may be set.

  FIG. 12 is a flowchart showing a control procedure of the adaptive array processing operation executed by the adaptive array processing unit 50 in such a modification, and corresponds to FIG. 8 of the above embodiment. The same steps as those in FIG. 8 are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 12, step S20A is newly provided between step S20 and step S30. That is, after setting the initial value of the reference level and the initial value of the sign of the composite output signal Y as described above in step S20, the process proceeds to step S20A.

  In step S20A, the adaptive control unit 51 detects sample data having the maximum absolute value in the half cycle T / 2, and stores, for example, the sample number in an appropriate unit.

  Thereafter, as described above in step S30, after setting the reference level, the process proceeds to step S35 ′ provided in place of step S35.

  In step S35 ', the sample value previously read from the memory 20 in step S5 by the adaptive control unit 51 is changed to a predetermined sample number condition appropriately determined for adaptive array control, that is, in this modification, the half cycle described above. It is determined whether or not the sample (number) has the maximum absolute value during T / 2.

  Then, the determination is satisfied only when the absolute value is the maximum sample value, the process proceeds to step S40, and the same adaptive array processing is performed thereafter.

  In addition, instead of the maximum value in one period, an average value for each corresponding sample number in a plurality of periods T may be obtained, and the reference level may be set by the same method.

(2) Variation of reference level setting according to sampling (part 2)
Further, for example, the received signal A / D converter 12 receives (1 / 4n) T (where n = 1, 3, 5,...; Signals received by the receiving antennas 2A to 2C at different sampling intervals, as shown in FIG. n = 1), and the adaptive control unit 51 and the reference level control unit 54 determine a value between one positive value and one negative value during each period T. Alternatively, the target signal level may be set to 0 for the central value (for example, Y1 between Y0 and Y2, Y3 between Y2 and Y4 in the case of FIG. 7).

  FIG. 13 is a flowchart showing the control procedure of the adaptive array processing operation executed by the adaptive array processing unit 50 in such a modification, and corresponds to FIG. 8 of the above embodiment. The same steps as those in FIG. 8 are denoted by the same reference numerals, and the description thereof is omitted.

  13, step S35 ″ and step S40 ′ are provided instead of step S35 and step S40. That is, after setting the reference level as described above in step S30, the process proceeds to step S35 ′. The sample value previously read from the memory 20 in step S5 by the adaptive control unit 51 is a predetermined sample number condition that is appropriately determined in advance for adaptive array control, that is, of the half cycle T / 2 in this modification. It is determined whether it is the first sample (for example, Y0, Y2, Y4, Y6,... In FIG. 7) or an intermediate sample having a half period T / 2 (for example, Y1, Y3, Y5, Y7,... In FIG. 7).

  Then, the determination is satisfied only when the sample value is satisfied, and the process proceeds to step S40 ′.

  FIG. 14 is a flowchart showing a detailed control procedure of step S40 ′ executed by the adaptive control unit 51 and the reference level control unit 54 in this modification, and corresponds to FIG. 11 of the above embodiment. The same steps as those in FIG. 11 are denoted by the same reference numerals, and description thereof is omitted.

  In FIG. 14, when step S35 ″ in FIG. 13 is completed, the process proceeds to step S40A newly provided before step S41.

  In step S40A, it is determined whether the sample value previously read from the memory 20 in step S5 is an intermediate sample of the half cycle T / 2.

  If it is the first sample in the half cycle T / 2, the determination is not satisfied, and the process proceeds to step S41 similar to FIG. 11, and thereafter the same procedure is performed.

  If it is an intermediate sample of half cycle T / 2, the determination is satisfied and the routine goes to Step S49B, the reference level is set to 0, and the routine goes to Step S46. As a result, arithmetic processing for weight calculation is performed using a predetermined reference level for high level or low level for the first sample of the half cycle T / 2 and using reference level 0 for the intermediate sample.

(3) Variation at First Convergence Calculation That is, in the above embodiment, while the weight does not converge in the flow of FIG. 8 (during the convergence calculation), as described above, step S35 → step S40 → step S50. → Step S55 → Step S60 → Step S35 →... Here, at the beginning after this adaptive array processing is started, the weight also starts calculation from the initial value, and in many cases it takes a relatively long time for convergence. Data portion (= so-called preamble) may end. In such a case, although the calculation has progressed to some extent from the initial weight initial value due to the repetition and the weight has been updated toward the optimum weight value, the weight optimization history is wasted due to the end of the preamble. In addition, the weight is updated from the beginning.

  In this modification, the weight optimization history is utilized as it is even after the preamble is completed, so that the weight calculation can be converged more quickly.

  FIG. 15 is a flowchart showing a control procedure of the adaptive array processing operation executed by the adaptive array processing unit 50 in such a modification, and corresponds to FIG. 8 of the above embodiment. The same steps as those in FIG. 8 are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 15, step S56 is newly provided between step S55 and step S60. That is, after the adaptive control unit 51 reads the received signal data stored in the memory 20 as described above in step S55, the process proceeds to step S56.

  In step S56, the adaptive control unit 51 determines whether or not the preamble has been completed based on the received signal data read in step S55. For example, after the first rising edge is detected by the FSK decoding unit 40 (in other words, the start point of the modulation signal is detected), it may be determined whether or not the number of edges corresponding to the preamble data has been detected.

  If the preamble has not ended, the determination in step S56 is not satisfied, and the process proceeds to step S60 similar to FIG. 8, and thereafter the same procedure is repeated.

  When the preamble is completed, the determination in step S56 is satisfied, the process proceeds to step S57, the setting for repeated reading for reuse of the above-described weight update history is performed, and the process proceeds to step S60. Step S60 and subsequent steps are the same as described above.

  FIG. 16 is a flowchart showing the detailed procedure of step S57 executed by the adaptive control unit 51.

  First, in step S58, the previous weight value (calculated so far) is set as the next weight initial value and stored in an appropriate means.

  In step S59, the read pointer (read instruction identifier) used for reading data from the memory 20 in step S55 described above is returned to the position of the first edge (that is, the rising edge at the start of the preamble), and this routine is terminated. To do.

  When the preamble is finished during the convergence calculation by the above procedure, the next sample becomes the first edge, so step S60 is satisfied and the process returns to step S30. After step S30 → step S35, step S40 again. The calculation of the weight is started. At this time, the weight value at the start of the calculation can be set as the stored value in step S58, not the initial weight value. As a result, the calculation can be restarted using the weight optimization calculation history so far, so that the weight calculation can be converged more quickly.

(4) When the phase of the low-level component is inverted That is, in the above-described embodiment, in order to clarify the substantially rectangular wave shape of the sinusoidal signal envelope, the high-level positive value having a larger absolute value is used for the high-level portion. Set the reference level for the value to increase the level absolute value more, and for the low level part, set the reference level for the low level positive value with a smaller absolute value to reduce the level absolute value more, A weight convergence calculation was performed.

  However, the low level portion is not limited to the direction of decreasing the absolute value as described above, and as shown in FIG. 17 corresponding to FIG. 5, if the level is reversed, that is, the low level positive value. Just like setting the reference level on the negative side and changing the composite output signal level in the negative direction, if the negative value is a low level, set the reference level on the positive side and change the composite output signal level in the positive direction The weight is calculated so that the phase is reversed (so that the phase is reversed). By doing so, the state of the weight initial value shown in FIG. 18A becomes the optimum weight value state shown in FIG. 18B in a relatively short time, and the directivity optimum state should be realized more quickly. It is.

  This modification is based on such consideration. However, in this case, since the control is performed to change the positive / negative of the level to the opposite side for the low level part where the absolute value is to be reduced as much as possible, as described above, the convergence calculation continues further as it is, Passing through the optimum weight value state (the reflected wave component ratio is the largest and clarified state) shown in FIG. 18 (b), the reflected wave component ratio is reduced as shown in FIG. 18 (c). . Therefore, in this modification, unlike the control procedure described so far, the reflected wave component of the composite output signal Y is monitored, and when the ratio of the reflected wave component reaches a predetermined value, the above-described FIG. It is assumed that the optimal state as shown in b) has been realized, and the convergence calculation is terminated halfway.

  FIG. 19 is a flowchart showing a control procedure of the adaptive array processing operation executed by the adaptive array processing unit 50 in such a modification, and corresponds to FIG. 8 of the above embodiment. The same steps as those in FIG. 8 are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 19, step S30 ′ is provided instead of step S30. In step S30, detailed contents are omitted. For example, a low level positive reference level and a low level negative reference level are set as follows. The level is set so that the sine wave waveform of the low level portion is a substantially inverted phase waveform.

  Thereafter, Step S35 and Step S40 are the same as those in FIG. 8, and Step S51 is newly provided after Step S40. That is, when the update wait register setting in step S48 is completed in the adaptive array processing shown in FIG. 11, the process proceeds to step S51.

  In step S51, the adaptive control unit 51 calculates the above-described reflected wave component ratio by an appropriate method based on the combined output signal Y input from the addition unit 53. Thereafter, in step S50 ′ provided in place of step S50, it is determined whether or not the ratio of the reflected wave component calculated in step S51 is equal to or greater than a predetermined value. If it is equal to or greater than the predetermined value, the determination is satisfied and the flow ends. If it is less than the predetermined value, the process proceeds to step S55, and thereafter the same procedure is performed.

  In this modification, the reference level value is set so as to have the same absolute value toward the negative side for the positive value of the low level portion and toward the positive side for the negative value of the low level portion, The weight is determined based on this. As a result, since the low level portion is controlled more quickly in the direction of attenuation, the directivity by the receiving antennas 2A to 2C can be optimized more quickly.

(4) Others In the above, the memory 20, the AM demodulating unit 30, the FSK decoding unit 40, the adaptive control unit 51, and the reference level control unit 54 are provided in the DSP 10. It may be provided as an independent control device as a separate body.

  In the above, the interrogator 100 includes the transmission antenna 1 that transmits the transmission wave Fc toward the RFID circuit element To, and the reception antennas 2A to 2A that receive the reflected wave Fr returned from the RFID circuit element To. 2C is provided as a separate body, but the present invention is not limited to this, and a transmission / reception antenna that transmits a transmission wave Fc toward the RFID circuit element To and receives a reflected wave Fr returned from the RFID circuit element To It may be provided with. In this case, a transmission / reception separator such as a circulator is provided corresponding to the transmission / reception antenna.

  Further, in the above, the interrogator 100 has been used as an interrogator in the communication system S of FIG. 3, but the present invention is not limited to this, and the present invention writes a predetermined information to the RFID circuit element To and uses the RFID tag. The present invention is also suitably applied to a wireless tag creation device that creates T and a wireless tag reader / writer that reads and writes information.

  In addition, although not illustrated one by one, the present invention is implemented with various modifications within a range not departing from the gist thereof.

1 is a system configuration diagram showing an overall outline of a wireless communication system to which an embodiment of the present invention is applied. FIG. 2 is a block diagram illustrating an example of a functional configuration of a wireless tag circuit element provided in the wireless tag illustrated in FIG. 1. It is a functional block diagram showing the functional structure of the interrogator shown in FIG. It is a figure explaining the information signal starting point detection process by the adaptive array process part shown in FIG. It is explanatory drawing which illustrates notionally the technique of the adaptive array process which makes the principal part of this invention. It is explanatory drawing showing an example of the behavior of convergence by the update of a weight. It is a figure showing an example of the sampling which a received signal A / D conversion part performs when performing adaptive array processing which made the reference level the target signal level. It is a flowchart showing the control procedure of the adaptive array processing operation which an adaptive array process part performs. It is a flowchart showing the detailed control procedure of step S20 shown in FIG. It is a flowchart showing the detailed control procedure of step S30 shown in FIG. It is a flowchart showing the detailed control procedure of step S40 shown in FIG. It is a flowchart showing the control procedure of the adaptive array processing operation in the modified example in which the reference level is set in association with the sample value having the largest absolute value. It is a flowchart showing the control procedure of the adaptive array processing operation in a modification in which the target signal level is set to 0 for a value between one positive value and one negative value or a central value in each period. It is a flowchart showing the detailed control procedure of step S40 'shown in FIG. 10 is a flowchart showing a control procedure of an adaptive array processing operation executed by an adaptive array processing unit in a modified example in which the history of weight optimization up to that time is used as it is even if the preamble is terminated. It is a flowchart showing the detailed procedure of step S57 shown in FIG. It is explanatory drawing which illustrates notionally the technique of the adaptive array process which makes the principal part of the modification which inverts a phase of a low level component. It is explanatory drawing showing an example of the behavior of convergence by the update of a weight. It is a flowchart showing the control procedure of the adaptive array processing operation in the modification shown in FIG.

Explanation of symbols

1 Transmitting antenna 2A to C Receiving antenna (antenna element)
12 Received signal A / D converter (sampling means)
20 memory (storage means)
40 FSK decoding unit (edge detection means)
50 Adaptive array processing unit 51 Adaptive control unit (weighting determination means)
52a-c Multiplier (weighting signal output means)
53 Adder (weighting signal output means)
54 Reference level control unit (target signal level setting means)
100 Interrogator T Wireless tag (responder)
To RFID tag circuit element

Claims (17)

A plurality of antenna elements for receiving signals transmitted or returned from the responders;
Weighting is applied to signals received by the plurality of antenna elements so as to change the directivity of the plurality of antenna elements so that the reception sensitivity with respect to the responder is optimized, and the weighted signal is output. Weighting signal output means;
Weighting determining means for determining weights to be output to the weighting signal output means so that the signal level of the weighted signal from the weighting signal output means approaches a predetermined target signal level. Interrogator for wireless communication systems. The interrogator of the wireless communication system according to claim 1,
An interrogator for a wireless communication system, comprising target signal level setting means for setting the predetermined target signal level. The interrogator of the wireless communication system according to claim 2,
Edge detection means for detecting a rising edge or a falling edge of an envelope of the signal received by the plurality of antenna elements;
The interrogator of a radio communication system, wherein the target signal level setting means sets the predetermined target signal level according to a detection result of the edge detection means. The interrogator of the wireless communication system according to claim 2 or 3,
The target signal level setting means sets a plurality of target signal level values respectively corresponding to a plurality of level values of an envelope of the weighted signal as the target signal level,
The interrogator of a wireless communication system, wherein the weight determination means determines the weight so that each of the plurality of level values of the weighted signal approaches the corresponding target signal level value. The interrogator of the wireless communication system according to any one of claims 2 to 4,
The target signal level setting means sets, as the target signal level, a high target signal level and a low target signal level respectively corresponding to a high level portion and a low level portion of an envelope of the weighted signal,
The weight determination means determines the weight so that the high level portion of the weighted signal approaches the high target signal level and the low level portion approaches the low target signal level. Interrogator for wireless communication systems. The interrogator of the wireless communication system according to claim 5,
The target signal level setting means sets, as the high target signal level, a high level positive target value and a high level negative target value, which are targets of the positive value and negative value of the high level portion of the weighted signal, respectively. The low target signal level is set to a low level positive target value and a low level negative target value, which are targets of the positive value and negative value of the low level portion of the weighted signal, respectively.
The weight determination means includes the positive value and the negative value of the high level portion of the weighted signal approaching the high level positive target value and the high level negative target value, respectively. The interrogator of a wireless communication system, wherein the weighting is determined so that the positive value and the negative value of the low level portion approach the low level positive target value and the low level negative target value. The interrogator of the wireless communication system according to claim 6,
Sampling means for sampling signals from the responders received by the plurality of antenna elements at predetermined intervals, and sequentially outputting the sampling values to the weighting determination means,
The weight determination means determines the weighting so that the sample value corresponding to the high level portion approaches the high target signal level and the sample value corresponding to the low level portion approaches the low target signal level. An interrogator for a wireless communication system. The interrogator of the wireless communication system according to claim 7,
An interrogator for a wireless communication system, comprising storage means for storing the sampling value obtained by the sampling means in a readable manner. The interrogator of the wireless communication system according to claim 7,
The sampling means samples the signal of the period T from the responder received by the plurality of antenna elements at a time interval of (1 / 2n) T, where n is a positive integer. System interrogator. The interrogator of the wireless communication system according to claim 9,
The signal of the period T from the transponder is an intermediate frequency signal obtained by converting the signal from the transponder received by the plurality of antenna elements so that the frequency thereof is lowered. Interrogator. The interrogator of the wireless communication system according to claim 9 or 10,
The target signal level setting means sets the corresponding high-level positive target value or low-level positive target value for one positive value in each cycle T among the sampling values, and sets a negative value 1 in each cycle T. The interrogator of the wireless communication system, wherein the corresponding high-level negative target value or low-level negative target value is set, and the interval between the positive and negative values set with the target value is the same number of samples . The interrogator of the wireless communication system according to claim 11,
The interrogator of a wireless communication system, wherein the target signal level setting means performs the setting in association with the sample value of a predetermined sample number determined in each period T. The interrogator of the wireless communication system according to claim 11,
The target signal level setting means associates the high level with the positive value having the largest absolute value as the one positive value from an average value for each sample number in one period T or a plurality of periods T. A positive target value or a low level positive target value is set, and the high level negative target value or the low level negative target value is set in association with the negative value having the largest absolute value as the one negative value. Interrogator for wireless communication systems. The interrogator of the wireless communication system according to any one of claims 11 to 13,
Sampling the received signal at (1 / 4n) T;
The target signal level setting means sets the target signal level to 0 for a value between the one positive value and the one negative value or a value in the middle thereof in each cycle T among the sampling values. An interrogator for a wireless communication system. The interrogator of the wireless communication system according to any one of claims 5 to 14,
The target signal level setting means sets a target signal level as the low target signal level so as to have a phase substantially inverted from the low level portion of the weighted signal. Interrogator. The interrogator of the wireless communication system according to claim 15,
The interrogator of a wireless communication system, wherein the weight updating process is terminated when the ratio of the signal component transmitted from the responder that is outputting the weighted signal exceeds a predetermined value. The interrogator of the wireless communication system according to any one of claims 1 to 16,
The responder is a wireless tag;
A predetermined transmission signal is transmitted to the wireless tag by a transmission antenna, and a response signal returned from the wireless tag in response to the transmission signal is received by the plurality of antenna elements. An interrogator for a wireless communication system, wherein information is communicated between the wireless communication systems.

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