JP4591770B2 - Interrogator for wireless communication apparatus and wireless tag communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the amount of operation processing for preparing an imaginary part necessary for complex signalling and to realize smooth and highly reliable radio communication control. <P>SOLUTION: A radio communication device comprises: receiving antennas 2A to 2C which receive signals of a frequency f transmitted from a radio tagged circuit element To without contact; a memory 20 which samples the received signals at a rate of 4nf (n is an integer) and outputs the latest memory data and memory data before the n sampling; and an input signal real number-a complex number converting part 41 which performs complex signal conversion using the latest memory data and the memory data before the n sampling for a real number part and an imaginary number part, respectively. An adaptive control part 50 changes the directivity of the receiving antennas 2A to 2C based on the data converted to complex signals so that the receiving sensitivity to an antenna 151 becomes optimal. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

  The present invention relates to a wireless communication device that performs wireless communication of information with the outside, and an interrogator of a wireless tag communication system that reads or writes information with respect to a wireless tag that is a type of the wireless communication device.

  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 wireless communication devices 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 wireless communication as described above with high sensitivity. It has been. In this method, a plurality of antenna elements are provided as antennas (reception antennas), weights (weight values) are added (adaptive processing) to the reception signals received by the plurality of antenna elements, and this adaptive processing reception is performed. Demodulate the signal. Then, by changing the weight so that the error between the demodulated signal and the reference signal is as small as possible, the directivity by multiple antenna elements is changed so that the reception sensitivity to the transmission side is optimized. It is something to be made.

  In order to perform such adaptive control, the phase information of each received signal from the plurality of antenna elements is required, and thus it is necessary to convert the signal into a complex signal. Usually, since the received signal is a digital signal and is only a real part of a complex signal composed of a real part and an imaginary part, processing such as Hilbert transform described in Non-Patent Document 1 is performed on the received signal. Therefore, the imaginary part is created separately.

Marvin E. Frerking, Kluwer Academic Publishers "Digital Signal Processing in Communication Systems" p.138

  As described above, in the prior art, complicated processing such as Hilbert transform is required to create an imaginary part that is not included in the received signal from the antenna. For this reason, the amount of calculation in the central processing unit (CPU) of the interrogator of the wireless communication device or the wireless tag communication system is enormous, and it takes a lot of time for the arithmetic processing, making smooth wireless communication control difficult. It was. As a result, it has been difficult to improve the reliability of wireless communication control.

  An object of the present invention is to provide an interrogator for a wireless communication device and a wireless tag communication system that can reduce the amount of calculation processing for creating an imaginary part necessary for complex signalization and realize smooth and reliable wireless communication control. It is to provide.

In order to achieve the above object, the first invention provides a plurality of antenna elements that receive the modulated signal of frequency f transmitted from the transmitting means in a contactless manner, and the modulated signals received by the plurality of antenna elements or the The modulation signal frequency-converted from the modulation signal to fi is sampled and stored sequentially at a rate of 4nf or 4nfi, where n is a positive integer, and the latest storage data and the storage data before n sampling can be output. Means, conversion means for performing complex signal conversion using the latest storage data output from the storage means and the storage data before n sampling in the real part or imaginary part, respectively, and the complex signal by the conversion means Control for changing the directivity of the plurality of antenna elements based on the converted data so that the reception sensitivity with respect to the transmission means is optimized. Possess a stage, said control means is sampled at a rate of 4nf or 4Nfi, a signal based on the synthesized composite output signal stored modulated signal in the storage means, and the target output signal to a predetermined, the Complex weight converted data is input, and weighting determining means for determining weights used for generating the combined output signal so that the combined output signal approaches the target output signal, and determined by the weight determining means Combined output signal generation means for generating the combined output signal using the weighted data, and the storage means inputs and stores the latest stored data, while storing and holding the latest stored data and so far The shift register is capable of sequentially outputting the stored data before n sampling, and the shift register includes two registers. The latest stored data is input to and stored in one of the two registers, and the data stored in the one register is output to the conversion means for the real part, while the two registers Of these, the data before n sampling stored and held in the other register is output to the conversion means for the imaginary part .

In general, a signal having periodicity such as a sine wave signal has a characteristic that the imaginary number component and the imaginary number component have the same waveform in which the phase of the imaginary number component is delayed by 90 ° from the real number component. In the first invention of the present application, using this correlation, the received modulation signal of the frequency f is sampled at a 4nf (or 4nfi) rate and stored in the storage means, which corresponds to the latest data and its phase exactly 90 ° behind. and n sampling before data is outputted from the storage means to the converting means. The conversion means performs complex signal conversion using the latest data for the real part and the data before n sampling for the imaginary part. Then, the control means performs so-called adaptive control that changes the directivity of the plurality of antenna elements so that the reception sensitivity to the transmission means is optimized using the data after the complex signal conversion.

In this way, the imaginary part necessary for complex signal conversion for adaptive control is obtained by simply diverting the data before the phase delay, so that it is more computationally processing than conventional methods using complicated methods such as Hilbert transform. Can be significantly simplified. As a result, the amount of calculation in the central processing unit of the wireless communication device can be reduced, and smooth and reliable wireless communication control can be realized.

Further, the weighting determining means determines the weighting so that the combined output signal from the control means approaches the target output signal, and using the weighting, the combined output signal generating means generates a combined output signal, and the generated combined output The signal is fed back to the weight determination means. By optimizing the weighting in this way, the directivity by the plurality of antenna elements can be changed so that the reception sensitivity with respect to the transmission means is optimized.

Further, each time the latest storage data is sequentially stored by the shift register, the data and the storage data before n sampling can be output to the conversion means.

Also, each time the latest stored data is sequentially stored in one register using a shift register having two registers , the data and the stored data before n sampling stored in the other register are converted together. Can be output to the means.

In a second aspect based on the first aspect , the combined output signal generating means uses the latest stored data output from the storage means and the weighting from the weight determining means, and outputs the combined output. Signal generation is performed.

  By using the latest storage data of the real number component output from the storage means and the weighting from the weight determination means, it is possible to generate a composite output signal in the real number format.

A third invention is characterized in that, in the above-mentioned second invention, there is provided coefficient multiplication means for multiplying the data subjected to complex signal conversion by the conversion means by a predetermined dimension conversion coefficient and outputting the result to the control means. .

  As a result, when the synthesized output signal generation means multiplies the latest storage data from the storage means by the weight determined by the weight determination means to generate a composite output signal in real number format, the dimension of the latest storage data and the weight is set. Matching and smooth calculation can be performed.

In a fourth aspect based on the first aspect , the combined output signal generation means outputs the latest stored data output from the storage means and subjected to the complex signal conversion by the conversion means, and the weight determination means The composite output signal in a complex signal format is generated using weighting.

  A composite output signal in the form of a complex signal can be generated using the latest stored data subjected to complex signal conversion and the weighting from the weighting determining means.

According to a fifth invention, in any one of the first to fourth inventions, there is provided demodulating means for demodulating the combined output signal generated by the combined output signal generating means.

That is, in the fifth invention of this application, the weighting determining means inputs the combined output signal output from the combined output signal generating means before demodulating by the demodulating means, and performs weighting determination so as to approach the target output signal. . Thereby, compared with the case where weighting is performed on the basis of the demodulated signal, the calculation procedure can be simplified and the calculation amount can also be reduced.

In order to achieve the above object, a sixth aspect of the invention relates to a plurality of antenna elements that contactlessly receive a modulation signal having a frequency f transmitted from the IC circuit portion of the RFID tag circuit element to be interrogated, and the plurality of antennas. The modulation signal received by the element or the modulation signal frequency-converted from the modulation signal to fi is sequentially sampled and stored at a rate of 4nf or 4nfi, where n is a positive integer, and the latest stored data and before n sampling of the memory means capable of outputting stored data, conversion means the latest stored data and the n sampling before storing data output from the storage means, performs complex signal conversion using respectively the real part or the imaginary part If, on the basis of the complex signal converted data in the conversion unit, the directivity by the plurality of antenna elements, receiving for said RFID circuit element Sensitivity have a control means for changing to be optimum, the control means includes a signal is sampled at a rate of 4nf or 4Nfi, based on the synthesized composite output signal stored modulated signal to said memory means, A weighting for inputting a predetermined target output signal and the complex signal-converted data and determining a weight used for generating the synthesized output signal so that the synthesized output signal approaches the target output signal Determining means and combined output signal generating means for generating the combined output signal using the weight determined by the weight determining means, and the storage means inputs and stores the latest stored data, A shift register capable of sequentially outputting the latest storage data and the storage data before n sampling stored and held so far; The shift register includes two registers, the latest stored data is input to and stored in one of the two registers, and the data stored in the one register is used for the real part as the conversion means. On the other hand, the data before n sampling stored and held in the other of the two registers is output to the conversion means for the imaginary part.

In the sixth invention of this application, the received modulation signal of the frequency f is sampled at a 4nf (or 4nfi) rate and stored in the storage means. The latest data and the data before n sampling corresponding to the phase 90 ° delay ( Or data after n sampling) is output from the storage means to the conversion means. The conversion means performs complex signal conversion using the latest data for the real part and the data before (or after) n samplings for the imaginary part. Then, the control means performs so-called adaptive control using the data after the complex signal conversion to change the directivity of the plurality of antenna elements so that the reception sensitivity with respect to the RFID circuit element is optimized. As described above, the imaginary part necessary for complex signal conversion for performing adaptive control is acquired by simply diverting data before (or after) the phase delay, thereby using a complicated method such as Hilbert transform. Compared with the above, the arithmetic processing can be remarkably simplified. As a result, the amount of calculation in the central controller of the interrogator can be reduced, and smooth and reliable wireless communication control can be realized.

Further, the weighting determining means determines the weighting so that the combined output signal from the control means approaches the target output signal, and using the weighting, the combined output signal generating means generates a combined output signal, and the generated combined output The signal is fed back to the weight determination means. By optimizing the weighting in this way, the directivity by the plurality of antenna elements can be changed so that the reception sensitivity with respect to the RFID circuit element is optimized.
Further, each time the latest storage data is sequentially stored by the shift register, the data and the storage data before n sampling can be output to the conversion means. Since the shift register includes two registers, each time the latest stored data is sequentially stored in one register, the data and the stored data before n sampling stored in the other register are converted together. Can be output.

  ADVANTAGE OF THE INVENTION According to this invention, the amount of arithmetic processings for producing the imaginary part required for complex signal conversion can be reduced, and smooth and reliable wireless communication control can be implement | achieved.

  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 an RFID tag communication system to which this embodiment is applied.

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

  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 an IC circuit unit 150 of the RFID circuit element To through the antennas 1 and 2A to 2C. Provided for accessing (reading or writing), outputting a transmission signal (transmission wave Fc) as a digital signal, demodulating a return signal (reflection wave Fr) from the RFID circuit element To, etc. A DSP (Digital Signal Processor) 10 that executes digital signal processing, and a transmission signal output from the DSP 10 is converted into an analog signal to transmit the signal. Transmission signal D / A converter 11 to be output to the tener 1 and received signal A / D converters 12a, 12b, 12c (hereinafter referred to as "converted signals") received by the receiving antennas 2A to 2C and converted to digital signals. If there is no particular distinction, it is simply referred to as a received 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 unit 155 that functions as an information storage unit that can store a predetermined information signal; and a modem that is connected to the antenna 151 And a controller 157 for controlling the operation of the RFID circuit element To through the rectifier 152, the clock extractor 154, the modulator / demodulator 156 and the like based on the power from the power supply 153. ing.

  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 unit 155, and performs basic control such as returning by the modulation / demodulation unit 156. Execute proper 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 the figure, the thick solid line represents the signal flow after the complex transformation, and the thin solid line represents the flow of the real number signal.

  In FIG. 3, the interrogator 100 includes the antennas 1, 2A to 2C, the DSP 10, the transmission signal D / A conversion unit 11, and the reception signal A / D conversion unit 12, and a frequency conversion signal that outputs a predetermined frequency conversion signal. The frequency of the transmission signal from the DSP 10 converted to an analog signal by the output unit 13 and 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, and the transmission is performed. The frequency of the received signal received by the up-converter 14 that outputs to the antenna 1 and each of the receiving antennas 2A, 2B, and 2C is lowered by the frequency of the frequency converted signal output from the frequency converted signal output unit 13, and the received signal Down converters 15a, 15b, 15c for output to the A / D converters 12a, 12b, 12c (hereinafter, unless otherwise distinguished) Simply referred to as down-converter 15) and the band-pass filter 18,19a for removing unnecessary frequency signal components comprises 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, 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 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 as a predetermined information signal (transmission information). And a memory 20 that functions as a storage unit for storing received signals respectively received by the receiving antennas 2A, 2B, and 2C. The AM demodulator 30 and the FSK decoder 40 that demodulate the received signal read from the memory 20 and read a predetermined information signal (= modulated signal by the RFID circuit element To) included in the received signal, and the memory Input signal real number-complex number conversion unit that receives a received signal (real number format) read from 20 and converts complex signal format complex signal 1 and multipliers 42a, 42b, 42c for multiplying the complex signal transformed data by a predetermined dimension transformation coefficient (cos ωt in this example), and the data after being multiplied by the coefficient are input, An adaptive control unit (LMS (= LeastMeanSquare) control unit) 50 for determining (controlling) a weight (weight) to be given to the received signal read from the memory 20 in the AM demodulating unit 30; An input signal combined output real number-complex number converting unit 51 that inputs a combined output signal (real number format) and performs complex signal conversion in a complex number format is provided.

  The AM demodulator 30 preferably performs IQ quadrature demodulation, that is, converts the input signal into an I phase (In phase) signal and a Q phase (Quadrature phase) signal whose phases are 90 ° different from each other, and then the I phase combined signal Yi And the Q-phase combined signal Yq are combined to demodulate the received signal.

  The AM demodulator 30 includes I-phase converters 31a to 31c that convert the received signals of the antennas 2A to 2C into I-phase signals, and receptions converted into I-phase signals by the I-phase converters 31a to 31c. An I-phase signal synthesizer 32 that synthesizes the signals into an I-phase synthesized signal Yi, and an I-phase LPF that passes a signal having a predetermined frequency or less out of the I-phase synthesized signal output from the I-phase signal synthesizer 32 ( Low-Pass Filter) 33, Q-phase converters 34a to 34c for converting received signals of the antennas 2A to 2C into Q-phase signals, and Q-phase signals converted by the Q-phase converters 34a to 34c, respectively. A Q-phase signal synthesizer 35 that synthesizes the received signal to obtain a Q-phase synthesized signal Yq, and a Q-phase LPF 36 that passes a signal having a predetermined frequency or less among the Q-phase synthesized signal output from the Q-phase signal synthesizer 35. And from the above I-phase LPF33 A demodulated signal generator 37 that generates a demodulated signal by combining the output I-phase composite signal and the Q-phase composite signal output from the Q-phase LPF 36 (square root of the sum of squares), and the demodulated signal generator 37 outputs the demodulated signal. And an HPF (High-Pass Filter) 38 that passes a signal having a predetermined frequency or higher among the demodulated signals.

  The I-phase conversion units 31a to 31c and the Q-phase conversion units 34a to 34c also function as phase / amplitude control units that control the phase and amplitude of each input using the weights instructed by the adaptive control unit 50.

  The I-phase synthesized signal Yi outputted from the I-phase signal synthesizing unit 32 and the Q-phase synthesized signal Yq outputted from the Q-phase signal synthesizing unit 35 are respectively complexed in complex form in the input signal synthesized output real-complex number converting unit 51. The signal is converted and supplied to the adaptive control unit 50.

  The AM demodulated signal output from the HPF 38 is decoded by the FSK decoding unit 40 and output as decoded information (information regarding modulation by the radio tag T).

  The multiplication units 42a to 42c multiply the weight data determined by the adaptive control unit 50 with respect to the latest stored data from the memory 20 in the I-phase conversion units 31a to 31c and Q-phase conversion units 34a to 34c. When generating Yi and Yq, the dimensions of the latest stored data and the weight are matched to perform smooth calculation.

  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 modem 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. With this power supply, the control unit 155 generates a reply signal based on the information signal of the memory unit 155, and the modulation / demodulation unit 156 modulates the transmission wave Fc based on the return signal, and the interrogator as the reflected wave Fr from the antenna 151. Reply to 100.

  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 to receive each received signal. Is reduced 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, and stored in the memory 20.

  Thereafter, the received signals read from the memory 20 are supplied to the AM demodulator 30, and these received signals are I-phase signals whose phases are different from each other by 90 ° by the I-phase converters 31 a to 31 c and the Q-phase converters 34 a to 34 c. Each is converted into a Q-phase signal. The received signal converted to the I-phase signal is synthesized by the I-phase signal synthesis unit 32 to be an I-phase synthesized signal Yi, and the received signal converted to the Q-phase signal is synthesized by the Q-phase signal synthesis unit 35. Q-phase composite signal Yq.

  A demodulated signal generating unit is a signal having a predetermined frequency or less that is passed by the I-phase LPF 33 in the I-phase synthesized signal Yi and a signal having a frequency that is less than or equal to the predetermined frequency that is passed by the Q-phase LPF 36 in the Q-phase synthesized signal Yq. 37 is combined (the square root of the sum of squares) to generate a demodulated signal. Of the demodulated signal output from the demodulated signal generation unit 37, a signal having a predetermined frequency or higher that is passed by the HPF 38 is output as an AM demodulated wave, and further the data decoded by the FSK decoding unit 40 is output.

  FIG. 4 is a flowchart showing the control procedure of the adaptive processing operation by the DSP 10 which is the main part of the above operation.

  In FIG. 4, first, in step S110, the phase and gain (signal amplitude) set by the control signals from the adaptive control unit (LMS) to the I-phase conversion units 31a to 31c and the Q-phase conversion units 34a to 34c are set to predetermined values. Set to the initial value.

  Thereafter, in step S120, the signal from the transmission digital signal output unit 16 is modulated by the modulation unit 17, and is transmitted to the RFID circuit element To of the target RFID tag T via the transmission signal D / A conversion unit 11 and the transmission antenna 1. It transmits as a transmission wave Fc. After the transmission of the transmission wave Fc modulated by the modulation unit 17 is completed, the process proceeds to step S125, and the transmission wave Fc of only the carrier wave is transmitted to the RFID circuit element To for power supply or the like.

  In step S130, the reflected wave Fr transmitted from the RFID circuit element To corresponding to the transmission wave Fc is received by the reception antennas 2A to 2C, and further received in the memory 20 via the reception signal A / D conversion unit. Capture and memorize. Step S125 and step S130 represent processing for one sample.

  In this case, the directivity by each of the receiving antennas 2A to 2C is changed so that the receiving sensitivity is optimized. Specifically, with respect to the combined signals Yi and Yq after conversion input from the I-phase signal combining unit 32 and the Q-phase signal combining unit 35 via the input signal combined output real-complex number converting unit 51, the receiving antennas 2A to 2A. In order to optimize the 2C reception sensitivity in the direction in which the RFID tag T is arranged (= the amplitude of the modulation component by the RFID circuit element To is made as high as possible, and a predetermined reference signal (target output) Signal) (approaching r) By changing the amplitude and phase of each of the received signals received by the antennas 2A to 2C and controlling the directivity, the accuracy of demodulation processing by the AM demodulator 30 is made as much as possible. Increase. Therefore, predetermined weighting is performed for each antenna 2A, 2B, 2C in the phase / amplitude control signals from the adaptive control unit 50 to the I-phase conversion units 31a to 31c and the Q-phase conversion units 34a to 34c. The update of the value (weight) is performed until the weight converges.

  Therefore, after step S130 is completed, in step S140, the weights related to the antennas 2A to 2C are determined and output to the I-phase conversion units 31a to 31c and the Q-phase conversion units 34a to 34c, and then correspond to step S150. The phase and amplitude (gain) are set by the I-phase converters 31a to 31c and the Q-phase converters 34a to 34c.

  The weight value at this time is stored in an appropriate storage means such as a RAM in the DSP 10 and compared with the size stored so far, and the determination in step S160 is not satisfied as will be described later. When the same calculation is repeated after returning to S125, it is determined that the calculation has converged if the change is considered to be equal to or less than a predetermined value compared to the stored value so far. The adaptive control unit 50 searches for the directivity generated by the antennas 2A to 2C so that the reflected wave component from the RFID circuit element To has the maximum value, that is, the optimum sensitivity. In addition, when a jamming signal is detected, the directivity is further optimized so that the jamming signal becomes small. If the weight value is substantially constant and the calculation converges, the determination in step S160 is satisfied. If not, the determination is not satisfied, and the process returns to step S120 and the same calculation procedure is repeated.

  In this way, when the directivity with the optimum reception sensitivity is found for each of the antennas 2A to 2C by repeating Step S125, Step S130, Step S140, Step S150, and Step S160, the calculation ends and the determination in Step S160 is satisfied. Then, the process proceeds to step S170. At this time, when there is an interference signal source in the same direction as the wireless tag T, the tag direction and the antenna directivity may deviate. Moreover, it may become directivity which shows maximum in several directions. For this reason, the direction of the tag is an estimated value or a probability value.

  In step S170, the direction in which the wireless tag T exists is estimated based on the convergence result, and in step S180, the coordinate position where the wireless tag T exists is estimated based on the signal strength when the convergence is performed.

  As described above, adaptive array control is performed to change the directivity synthesized by the antennas 2A to 2C so that the reception sensitivity of the RFID circuit element To with respect to the antenna 151 is optimized, and the demodulation processing by the AM demodulator 30 is performed. The target RFID circuit element To is detected with high sensitivity. The received signal that has been adaptively processed and demodulated by the AM demodulator 30 according to the control signal of the adaptive controller 50 is finally converted into a decoded signal by the FSK decoder 40 and is output as data. As a result, a predetermined information signal included in the reception signals of the antennas 2A to 2C, that is, a modulation signal by the RFID circuit element To can be reliably and quickly read out.

  In the above basic configuration, the main part of the present invention is a method of complex signal conversion of signals received by the antennas 2A to 2C, which is necessary for the above-described weight determination in the adaptive control unit 50.

That is, in the adaptive control unit 50 that performs adaptive control, an analysis signal including phase information and amplitude information of the received signal, that is,
X (t) = Xi (t) + jXq (t) (Formula 1)
A signal represented by a complex expression such as

  Here, the output received by the antenna and subjected to A / D conversion is usually only the real part (the first term part of Equation 1 above), and there is no imaginary part (the second term part of Equation 1 above). Therefore, it is necessary to create this imaginary part signal separately (perform complex signal conversion).

  In this embodiment, the signal waveform having a periodicity such as a sine wave is focused on the fact that the imaginary part signal is delayed by 90 ° in phase from the real part signal. The stored data for 90 degrees before is extracted from the memory 20 as a set of real part data and imaginary part data and used as a set, whereby complex signal conversion is executed by a very simple method.

  FIG. 5 is an explanatory view for conceptually explaining the complex signal conversion technique which forms the main part of the present invention. In FIG. 5, in this embodiment, a signal (in this example, a sine wave) having a periodicity of frequency f (period T = 1 / f) is transmitted from the antenna 151 of the RFID circuit element To as a transmission means. On the premise of this, the memory 20 samples and sequentially stores the received sine wave signal at a rate of 4 nf (n: positive integer) (that is, period ¼ nf = T / 4n).

For example, in the illustrated example, in one waveform, signal values at five points at intervals of T / 4 (corresponding to n = 1) are Xi (0), Xi (1), Xi (2), Xi ( 3), Xi (4). As described above, the value of the imaginary part of the analytic signal is nothing but the value obtained by delaying the phase of the signal of the real part by 90 °, so that Xi (0), Xi (1), Xi (2), Xi (3) Is equal to the imaginary part of the real part Xi (1), Xi (2), Xi (3), Xi (4), respectively. Therefore, each analytic signal value is
X (1) = Xi (1) + j Xi (0)
X (2) = Xi (2) + j Xi (1)
X (3) = Xi (3) + j Xi (2)
X (4) = Xi (4) + j Xi (3)
In general,
X (t) = Xi (t) + j Xi (t-1) (however t ≧ 1)
It becomes.

The above is the case of n = 1, and when it is expanded including n,
X (t) = Xi (t) + j Xi (t-n) (where t ≧ n)
It becomes.

  In the present embodiment, based on the above considerations, the memory 20 can output the latest stored data and the stored data before n sampling while sequentially sampling and storing at the 4f rate as described above. Yes.

  FIG. 6 is an explanatory diagram showing the functional configuration of such a memory 20 by taking n = 1 as an example.

  In FIG. 6, the memory 20 has a so-called two-stage shift register function composed of a register 0 and a register 1. That is, when data is written to the register 0, the data is shifted to the register 1. As a result, the value of the register 0 (current data) is a real number by fetching the signal data from the received signal A / D converter 12 into the register 0 every time at a rate of 4f (n = 1) (1/4 cycle). By simply outputting the value of register 1 (shift register output, data before sampling) as imaginary part Xq to input signal real number-complex number conversion unit 41 as part Xi, input signal real number-complex number conversion unit 41 Values of the real part and imaginary part corresponding to the data can be obtained, and complex signal conversion can be performed using these values.

  Although the case where n = 1 has been described above as an example, it is needless to say that the same function may be achieved even when n ≧ 2.

  In the above, the memory 20 according to each claim samples the signals received by a plurality of antenna elements, sequentially stores them by sampling at a rate of 4 nf, where n is a positive integer, and stores the latest stored data and its previous n samples. The storage means capable of outputting the storage data, and the input signal real number-complex number conversion unit 41 outputs the latest storage data output from the storage means and the storage data before n sampling to the real number part and the imaginary number part, respectively. A conversion means for performing complex signal conversion is used.

  Further, the adaptive control unit 50, the I-phase conversion units 31a to 31c and the Q-phase conversion units 34a to 34c, the I-phase signal synthesis unit 32 and the Q-phase signal synthesis unit 35 are subjected to complex signal conversion by the conversion unit. Based on the data, a control unit is configured to change the directivity of the plurality of antenna elements so that the reception sensitivity with respect to the transmission unit is optimized. Among them, the adaptive control unit 50 inputs a signal based on the combined output signal from the control means, a predetermined target output signal, and the complex signal converted data so that the combined output signal approaches the target output signal. And a weight determining means for determining weights used for generating the synthesized output signal, and comprising I-phase converters 31a-c and Q-phase converters 34a-c, I-phase signal synthesizer 32 and Q-phase signal synthesizer The unit 35 constitutes a combined output signal generating unit that generates a combined output signal using the weight determined by the weight determining unit.

  Further, the multipliers 42a, 42b, and 42c constitute coefficient multiplying means for multiplying the data subjected to complex signal conversion by the converting means by a predetermined dimension conversion coefficient and outputting the result to the control means. The I-phase LPF 33 and Q-phase LPF 36 provided in the AM demodulator 30 and the demodulated signal generator 37 constitute a demodulator that demodulates the combined output signal generated by the combined output signal generator.

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

  In the present embodiment, in a signal having periodicity such as a sine wave signal, the correlation between the imaginary component and the imaginary component having the same waveform delayed by 90 ° from the real component is used for the real component and the imaginary component. Sampling at a rate and storing it in the memory 20, the latest data and data before n sampling corresponding to the phase 90 ° delay (or data after n sampling corresponding to phase 90 ° advance) may be stored in the memory 20, the input signal is output to the real number-complex number conversion unit 41. The input signal real number-complex number conversion unit 41 performs complex signal conversion using the latest data for the real number part and the data before n sampling for the imaginary number part. The adaptive control unit 50 uses the data after the complex signal conversion to change the directivity of the plurality of antenna elements so that the reception sensitivity of the RFID circuit element To to the antenna 151 is optimized. I do.

  As described above, the imaginary part necessary for complex signal conversion for adaptive control is acquired by simply diverting the data before the phase delay (or the data after the phase advance), so that complicated Hilbert conversion or the like is required. Compared to the conventional method using a simple technique, the arithmetic processing can be remarkably simplified. As a result, the amount of computation in the central processing unit (CPU) of the DSP 10 can be reduced, and smooth and reliable wireless communication control can be realized.

  At this time, the synthesized output signals Yi and Yq (that is, the output before demodulation) from the I-phase signal synthesis unit 32 and the Q-phase signal synthesis unit 35 are sent to the adaptive control unit 50 via the input signal synthesis output real-complex number conversion unit. By supplying, it is possible to prevent the influence of delay due to the number of taps of the I-phase LPF 33, Q-phase LPF 36, and HPF 38, compared to the case where weighting is performed based on the demodulated signal, and the calculation procedure is reduced. This simplifies and reduces the amount of calculation.

  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) When the AM demodulation unit is provided separately from the phase amplitude control unit In other words, in the above-described embodiment, the I-phase conversion units 31a to 31c and the Q-phase conversion units 34a to 34c that form the main part of the AM demodulation function. However, it also functions as a phase / amplitude control unit that controls the phase and amplitude of each input with the weights instructed by the adaptive control unit 50, but this is a case where these are provided separately and independently.

  FIG. 7 is a functional block diagram showing the main part of the configuration of the interrogator 100 ′ according to such a modification, and corresponds to FIG. 3 of the above embodiment. The same parts as those in the above embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate. In the figure, the thick solid line represents the signal flow after the complex transformation, and the thin solid line represents the flow of the real number signal.

  The interrogator 100 ′ shown in FIG. 7 performs only the phase amplitude control function in the DSP 10 ′, and performs AM demodulation in the AM demodulator 130 newly provided separately.

  In the DSP 10 ′, the received signal (real number format) read from the memory 20 is input to the input signal real number-complex number conversion unit 41 and converted into a complex number format complex signal, and this complex signal is converted into the adaptive control unit 50 ′ and It is supplied to the multipliers 131a, 131b, 131c. The adaptive control unit 50 is functionally equivalent to the adaptive control unit 50 of the above-described embodiment, and the combined output signals summed by the addition unit 132 from the multiplication units 131a to 131c are received by the receiving antennas 2A to 2C. A reference signal (target output signal) determined in advance so that the reception sensitivity is optimized in the direction in which the RFID tag T is arranged (= the amplitude of the modulation component by the RFID circuit element To is as high as possible) The accuracy of demodulation processing by the AM demodulator 130 is increased as much as possible by changing the amplitude and phase of each of the received signals received by the antennas 2A to 2C (to approach r) and controlling the directivity. is there. Therefore, predetermined weighting is performed for each of the antennas 2A, 2B, and 2C in the phase / amplitude control signal from the adaptive control unit 50 'to the multiplication units 131a to 131c. Do until it converges. The reception signals adaptively processed by the multipliers 131a to 131c according to the control signal of the adaptive controller 50 ′ are summed by the adder 132 and then output to the AM demodulator 130.

  Similarly to the above embodiment, the memory 20 samples the sine wave signals received by the antennas 2A to 2C at a rate of 4 nf and sequentially stores them, and stores the latest stored data and the data before n sampling (or after n sampling). The stored data is output to the input signal real-complex number conversion unit 41 as the real part Xi and the imaginary number part Xq, respectively, and the input signal real-complex number conversion unit 41 performs complex signal conversion using these.

  Although the detailed description is omitted, the AM demodulator 130 converts the input signal from the DSP 10 ′ into an I phase (In phase) and a Q phase (Quadrature phase) signal, similarly to the AM demodulator 30 in FIG. 3. By synthesizing these I-phase synthesized signal Yi and Q-phase synthesized signal Yq, the received signal is subjected to IQ quadrature demodulation and output to FSK decoding section 40.

  In the above, the adaptive control unit 50 'inputs the signal based on the combined output signal, the predetermined target output signal, and the complex signal converted data described in each claim, and the combined output signal is the target output. Weighting determining means for determining the weighting used for generating the synthesized output signal is configured to approach the signal.

  Further, the multiplication units 131a to 131c and the addition unit 132 use the latest storage data output from the storage unit and subjected to the complex signal conversion by the conversion unit, and the weighted signal from the weight determination unit, and the composite output signal in the complex signal format. The composite output signal generating means for generating the above is configured.

  Further, the AM demodulating unit 130 constitutes a demodulating unit that demodulates the combined output signal generated by the combined output signal generating unit.

  According to this modification as well as the above-described embodiment, it is possible to simplify the arithmetic processing and reduce the amount of calculation in the central processing unit (CPU) of the DSP 10 ′, thereby realizing an effect of realizing smooth and highly reliable wireless communication control.

(2) Other Memory Formats In the above embodiment and the modified example of (1), the memory 20 has a shift register function, but is not limited thereto. That is, a two-stage memory that selectively stores alternately in the first storage unit (memory 1) and the second storage unit (memory 2) may be used.

  FIG. 8 is an explanatory diagram conceptually showing the function of the memory 20 'according to this modification. As shown in FIG. 8, in this case, the memory 20 ′ alternately writes the output signals of the reception signal A / D conversion units 12 a, 12 b, and 12 c into the memory 1 and the memory 2. When writing to the memory 1 as shown in FIG. 8A, the latest data in the memory 1 is output to the input signal real-complex number conversion unit 41 as the real part signal of the received signal, and the previous time (when n = 1); The written data in the memory 0 (generally before n sampling) is output to the input signal real-complex number conversion unit 41 as an imaginary part signal of the received signal. Similarly, when data is written to the memory 0 as shown in FIG. 8B, the data in the memory 0 becomes the real part signal of the received signal, and the previous time (when n = 1; generally before n sampling). The written data in the memory 0 becomes an imaginary part signal.

  The memory 20 ′ of this modification can also perform the same function as the memory 20 described above. As described above, data after n samplings may be used.

(3) Others In the above, the memories 20, 20 ′, the AM demodulator 30, the FSK decoder 40, and the adaptive controllers 50, 50 ′ are provided in the DSP 10, 10 ′. The DSPs 10 and 10 'may be provided as independent control devices as separate bodies.

  In the above, the interrogators 100 and 100 ′ receive the transmission antenna 1 that transmits the transmission wave Fc toward the RFID circuit element To and the reflected wave Fr that is returned from the RFID circuit element To. Although the antennas 2A to 2C are provided separately, the present invention is not limited to this, and the transmission wave Fc is transmitted to the RFID circuit element To and the reflected wave Fr returned from the RFID circuit element To is received. It may be provided with a transmitting / receiving antenna. In this case, a transmission / reception separator such as a circulator is provided corresponding to the transmission / reception antenna.

  Further, in the above, the interrogators 100 and 100 ′ are used as interrogators in the communication system S of FIG. 1, but the present invention is not limited to this, and the present invention provides predetermined information to the RFID circuit element To. The present invention is also suitably applied to a wireless tag creation device that creates a write wireless tag 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.

It is a system configuration figure showing the whole outline of the RFID tag communications system which is an application object of this embodiment. 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. 4 is a flowchart showing a control procedure of adaptive processing operation by the DSP shown in FIG. 3. It is explanatory drawing which illustrates the method of complex signal conversion notionally. It is explanatory drawing which showed the functional structure of the memory shown in FIG. It is a functional block diagram showing making the principal part of the structure of the interrogator by the modification which provided AM demodulation part separately from the phase amplitude control part. It is explanatory drawing which represented the function in the modification regarding memory conceptually.

Explanation of symbols

1 Transmitting antenna 2 Receiving antenna (antenna element)
20 memory (storage means)
20 'memory (storage means)
31a-c I-phase converter (synthetic output signal generating means, control means)
32 I-phase signal synthesizer (synthesized output signal generation means, control means)
33 I-phase LPF (demodulation means)
34a-c Q-phase conversion unit (combined output signal generation means, control means)
35 Q-phase signal synthesis unit (synthesis output signal generation means, control means)
36 Q-phase LPF (demodulation means)
37 Demodulated signal generator (demodulating means)
41 Input signal real number-complex number conversion unit (conversion means)
42a-c Multiplier (coefficient multiplying means)
50 Adaptive control unit (weighting determination means, control means)
50 'adaptive control unit (weighting determination means, control means)
100 Interrogator (wireless communication device)
100 'interrogator (wireless communication device)
130 AM demodulator (demodulator)
131a-c Multiplying unit (combined output signal generating means, control means)
132 Adder (combined output signal generating means, control means)
151 Antenna (transmission means)
S RFID tag communication system

Claims (6)

A plurality of antenna elements for receiving the modulated signal of the frequency f transmitted from the transmission means in a contactless manner;
The modulation signals received by the plurality of antenna elements or the modulation signals frequency-converted from the modulation signals to fi are sequentially sampled and stored at the rate of 4nf or 4nfi, where n is a positive integer, and the latest stored data and Storage means capable of outputting storage data before n sampling;
Conversion means for performing complex signal conversion by using the latest storage data output from the storage means and the storage data before n sampling, respectively, for a real part or an imaginary part;
Based on the complex signal converted data in the conversion unit, the directivity by the plurality of antenna elements, the receiving sensitivity with respect to the transmission means have a control means for changing to the optimum,
The control means includes
A signal based on a combined output signal sampled at a rate of 4 nf or 4 nfi and combined with the modulation signal stored in the storage means, a predetermined target output signal, and the complex signal converted data are input, Weight determining means for determining a weight used for generating the combined output signal so that the combined output signal approaches the target output signal;
A combined output signal generating means for generating the combined output signal using the weight determined by the weight determining means;
The storage means
A shift register capable of sequentially inputting and storing the latest stored data and sequentially outputting the latest stored data and the stored data stored and held before n sampling.
The shift register includes two registers,
The latest stored data is input to and stored in one of the two registers, and the data stored in the one register is output to the conversion means for the real part, while the two registers The wireless communication apparatus , wherein data before n sampling stored and held in the other register is output to the conversion means for the imaginary part . The wireless communication device according to claim 1 , wherein
The synthesized output signal generating means includes
A wireless communication apparatus that generates the combined output signal using the latest stored data output from the shift register and the weighting from the weighting determination unit. The wireless communication device according to claim 2 , wherein
A wireless communication apparatus comprising: coefficient multiplication means for multiplying the data subjected to complex signal conversion by the conversion means by a predetermined dimension conversion coefficient and outputting the result to the control means. The wireless communication device according to claim 1 , wherein
The synthesized output signal generating means includes
Using the latest storage data output from the shift register and subjected to the complex signal conversion by the conversion unit, and the weighting from the weight determination unit, the composite output signal in a complex signal format is generated. A wireless communication device. The wireless communication device according to any one of claims 2 to 4 ,
A radio communication apparatus comprising demodulating means for demodulating the combined output signal generated by the combined output signal generating means. A plurality of antenna elements for receiving the modulated signal of the frequency f transmitted from the IC circuit portion of the RFID tag circuit element to be interrogated in a non-contact manner;
The modulation signals received by the plurality of antenna elements or the modulation signals frequency-converted from the modulation signals to fi are sequentially sampled and stored at the rate of 4nf or 4nfi, where n is a positive integer, and the latest stored data and Storage means capable of outputting storage data before n sampling;
Conversion means for performing complex signal conversion by using the latest storage data output from the storage means and the storage data before n sampling, respectively, for a real part or an imaginary part;
Based on the complex signal converted data in the conversion unit, the directivity by the plurality of antenna elements, the reception sensitivity with respect to the RFID circuit element have a control means for changing to the optimum,
The control means includes
A signal based on a combined output signal that is sampled at a rate of 4 nf or 4 nfi and combined with the modulated signal stored in the storage means, a predetermined target output signal, and the complex signal converted data are input; Weight determining means for determining a weight used for generating the combined output signal so that the combined output signal approaches the target output signal;
A combined output signal generating means for generating the combined output signal using the weight determined by the weight determining means;
The storage means
A shift register capable of sequentially inputting and storing the latest stored data and sequentially outputting the latest stored data and the stored data stored and held before n sampling.
The shift register includes two registers,
The latest stored data is input to and stored in one of the two registers, and the data stored in the one register is output to the conversion means for the real part, while the two registers The interrogator of the RFID tag communication system, wherein data before n sampling stored and held in the other register is output to the conversion means for the imaginary part .

Images