TWI427537B - RF tag reader circuit - Google Patents

Description

Radio frequency tag reader circuit

The present invention relates to a technique for receiving data (signals) transmitted by a so-called tag. In particular, it relates to a receiving circuit of a radio frequency (RF) tag reader that receives a signal transmitted by an active tag by a Low-IF method.

In recent years, RF type electronic tags (hereinafter referred to as RF tags) have been widely used in terms of means for memorizing various information. The RF tag has a passive tag and an active tag. Passive tags do not require a battery and communicate by backscatter. In the backscattering mode, the RF tag receives the supply of power according to the unmodulated signal sent by the RF tag reader, so that the amount of reflection of the unmodulated signal is changed, thereby maintaining the retained data. Send to the RF tag reader. Active tags, although they require a power supply and an oscillator alone, can communicate over long distances compared to passive tags.

In addition, in the communication with the passive tag, the RF tag reader must transmit the unmodulated wave while receiving the data. Therefore, in the communication with the passive tag, in many cases, the same frequency as the unmodulated wave sent to the passive tag can be used as the direct conversion mode of the local signal frequency. On the other hand, in the communication with the active tag, since it is not necessary to perform the simultaneous transmission and reception, many cases adopt the Low-IF method with high reception performance. For example, in the following Non-Patent Document 1, a configuration of an RFIC using a Low-IF method is disclosed.

[Previous Technical Literature] [Non-patent literature]

[Non-Patent Document 1] J. Crols, et al., "Low-IF Topologies for High-Performance Analog Front Ends of Fully Integrated Receivers", IEEE Transactions on Circuits and Systems II, Vol. 45, No. 3, pp. 269-282, March 1998.

However, the passive tag transmits the data holding the data internally by reflecting the unmodulated wave from the RF tag reader, so there is no untuned wave that is transmitted by the RF tag reader. The case of frequency offset. However, the active tag is independent of the RF tag reader and additionally has an oscillator, so the frequency of the signal transmitted by the active tag may be offset from the frequency of the signal that the RF tag reader imaginarily receives. If the two frequencies are offset, the reception characteristics in the RF tag reader are degraded.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve reception characteristics in radio wave reception by an active tag.

In order to solve the above problems, in the present invention, the local signal frequency of the RF tag reader or the center frequency of the band pass filter is adjusted based on the unmodulated signal from the active tag.

For example, the first aspect of the present invention is a radio frequency tag reader circuit, which is a receiving circuit of a radio frequency (RF) tag reader that receives a signal transmitted by an active tag by a Low-IF method. The utility model is characterized in that: a programmable PLL for outputting a local frequency signal of a frequency division ratio set by a signal outputted by a reference oscillator; and a non-modulation signal to be transmitted by the active label is used by the foregoing a mixer that can be programmed to down-convert the local signal output by the PLL; a band pass filter that passes a signal of a predetermined frequency band among the output signals from the mixer; An amplifier that amplifies an output signal of the band pass filter; a demodulation unit that performs demodulation after converting the output of the amplifier into digital data; calculates a frequency indicating an output signal from the band pass filter, and pre-orders a frequency difference calculation unit for determining a frequency difference of the difference between the reference frequencies; and calculating a frequency division ratio corresponding to the difference calculated by the frequency difference calculation unit, and setting the calculated frequency division ratio Programmable PLL frequency-division ratio control unit.

In addition, the second aspect of the present invention is a radio frequency tag reader circuit, which is a receiving circuit of a radio frequency (RF) tag reader that receives a signal transmitted by an active tag by a Low-IF method. The present invention is characterized in that: the local signal generating unit that outputs the local signal of the preset frequency; and the unmodulated signal sent by the active tag is down-converted using the local signal output by the local signal generating unit. (down-converting) mixer; in the center frequency corresponding to the input control signal, a band pass of a signal of a predetermined frequency band is passed among the output signals from the mixer a filter; an amplifier that amplifies an output signal of the band pass filter; a demodulation unit that demodulates the output of the amplifier after converting the output of the amplifier; calculates a frequency of the output signal from the band pass filter, and a frequency difference calculation unit that sets a difference between the reference frequency; and a center frequency for controlling a frequency band of the band pass filter according to the difference calculated by the frequency difference calculation unit The control signal is supplied to the band pass filter of the band-pass filter control unit.

With the RF tag reader circuit of the present invention, the reception characteristics can be improved in the reception of radio waves transmitted by the active tag.

First, a first embodiment of the present invention will be described.

Fig. 1 is a system configuration diagram showing an example of an RFID system 10 according to an embodiment of the present invention. The RFID system 10 includes an active tag 11, a data processing device 12, and an RF tag reader 20.

In the present embodiment, when the active tag 11 receives the Wake UP message from the RF tag reader 20, for example, as shown in FIG. 2, the transmission includes the unmodulated wave (CW) 30 and the pilot tone. 31. Messages of preamble 32 and data 33.

A switch 13 is provided in the RF tag reader 20, and the user presses the switch 13 when receiving data from the active tag 11. When the switch 13 is pressed, the RF tag reader 20 of the present embodiment transmits a Wake UP message, and then adjusts the message transmitted by the active tag 11 based on the unmodulated wave transmitted by the active tag 11. The frequency of the local signal used by the radio wave demodulation. Next, the RF tag reader 20 demodulates the pilot tone, preamble signal, and data transmitted after the unmodulated wave, and transmits the demodulated data to the data processing device 12.

Fig. 3 is a block diagram showing an example of the functional configuration of the RF tag reader 20 in the first embodiment. The RF tag reader 20 includes an antenna 200, an LNA (Low Noise Amplifier) 201, a mixer 202, a mixer 203, a BPF (Band Pass Filter) 204, and a BPF 205. AGC (Automatic Gain Control) amplifier 206, AGC amplifier 207, ADC (Analog to Digital converter) 208, ADC 209, LPF (Low Pass Filter) 210, LPF 211, solution The modulator 212, the phase shifter 213, the PLL (Phase Locked Loop) 214, the frequency division ratio control unit 215, the Δf calculation unit 216, and the control unit 217.

The PLL 214 generates a local signal of a frequency division ratio set by the frequency division ratio control unit 215 or the control unit 217 by a reference signal source such as a crystal vibrator, and supplies the generated local signal to the mixer 202, and It is supplied to the mixer 203 through the phase shifter 213. In the present embodiment, since the RF tag reader 20 receives the signal from the active tag 11 in the Low-IF mode, the local signal generated by the PLL 214 is offset by the frequency of the signal to be transmitted by the active tag 11. Move a predetermined frequency share (for example, 100 kHz).

The LNA 201 transmits the signal received by the active tag 11 through the antenna 200, and supplies it to the mixer 202 and the mixer 203. The mixer 202 supplies the I component of the received signal to the BPF 204 by down-converting the signal supplied from the LNA 201 by multiplying the local signal supplied from the PLL 214. The mixer 202 multiplies the local signal shifted by π/2 by the phase shifter 213, thereby down-converting the signal supplied from the LNA 201 to supply the Q component of the received signal to the BPF 205.

The BPF 204 passes the frequency components of the predetermined frequency band among the signals supplied from the mixer 202. The BPF 205 passes the frequency components of the predetermined frequency band among the signals supplied from the mixer 203.

The received signal of the one component outputted by the BPF 204 is amplified by the AGC amplifier 206, converted into a digital signal by the ADC 208, and is removed from the harmonics by the LPF 210, and then supplied to the demodulator 212. The received signal of the Q component outputted by the BPF 205 is amplified by the AGC amplifier 207, converted into a digital signal by the ADC 209, and is removed from the harmonics by the LPF 211, and then supplied to the demodulator 212. The demodulator 212 demodulates the data bits based on the received signals of the I component and the Q component, and supplies the demodulated data bits to the data processing device 12.

When the control unit 217 is instructed, the Δf calculating unit 216 calculates the frequency difference Δf between the frequency of the received signal and the predetermined frequency, and supplies the calculated value of Δf to the frequency dividing ratio control unit 215. In the present embodiment, the Δf calculating unit 216 monitors the Q component of the received signal, and counts the number of times of repetition of the first wavelength of the received signal in the predetermined time interval Tc. Next, the Δf calculating unit 216 calculates (α - β) ÷ Tc as Δf based on the difference from the number of times of repetition of the one wavelength to be counted in the signal of the frequency set in advance.

In the present embodiment, the Δf calculating unit 216 calculates the value of Δf based on the Q component of the received signal, but may calculate the value of Δf based on the I component of the received signal. Further, for example, as shown in FIG. 4, the Δf calculating unit 216 may count the number of peaks of the received signal at the predetermined time interval Tc by the number of times of repetition of the one wavelength.

However, in another aspect, the Δf calculating unit 216 may calculate the frequency difference Δf by the analog PLL or the digital PLL by using the I component and the Q component of the received signal. Fig. 5 shows an example in which the Δf calculating unit 216 is constructed by a digital PLL.

In Fig. 5, in the phase comparator 40, the Cosine wave is multiplied by the multiplier 41 of the I component output signal outputted by the LPF 210, and the Q component outputted by the LPF 211 is received. The signal number is multiplied by the multiplier 42 and inverted by the inverter 44. The output of the multiplier 41 and the output of the inverter 44 are added by the adder 43 and output.

The signal output from the phase comparator 40 is output to the frequency division ratio control unit 215 as a frequency difference Δf after passing through the loop filter 45. In addition, the output from the loop filter 45 is in an NCO (numeric controlled oscillator) 46, and a reference value indicating a predetermined frequency is added by the adder 47, which is integrated by the integrator 48 and fed back. To phase comparator 40. Here, the reference value indicates the mixer 202 and the mixer 203 when the frequency of the signal transmitted by the active tag 11 is not different from the frequency of the imaginary received signal of the RF tag reader 20. The digit value of the intermediate frequency of the signal being output.

Here, if the signal frequency output by the LPF 210 or the LPF 211 is ω _S /2π and the predetermined intermediate frequency is ω _IF /2π, the frequency difference can be calculated by the following calculation formula (1). Δf(=(ω _S -ω _IF )/2π).

[Number 1]

The PLL 214 includes, as shown in FIG. 6, a phase comparator 60, a charge pump 61, a loop filter 62, a VCO (voltage controlled oscillator) 63, and a variable frequency divider 64. The variable frequency divider 64 is provided by the frequency division ratio control unit 215 when the frequency of the output signal of the _VCO 63 is f _VCO and the frequency of the output signal of the variable frequency divider 64 is f _OUT . frequency division ratio set value of parameter a, parameter B, and the parameter N, the output is calculated according to the following formula (2) frequency f _OUT signal.

[Number 2]

f _OUT =( A × N + B ) f _VCO …(2)

Train output of the phase comparator 60 with the reference signal from the reference source and the phase difference signal from the variable frequency divider 64 is f _OUT signal corresponding to the charge pump 61 to the signal line 60 from the phase comparator into a voltage. The loop filter 62 averages the output voltage of the charge pump 61, and the VCO 63 outputs a signal of a frequency corresponding to the output voltage of the loop filter 62. In the present embodiment, an integer frequency divider is used as the variable frequency divider 64 as an example. However, the PLL 214 may be configured as a fractional PLL (fractional PLL) using a frequency divider as the variable frequency divider 64. ).

The frequency division ratio control unit 215 has a frequency division ratio table 50 and a frequency division ratio setting unit 51 as shown in FIG. 7, for example. In the frequency division ratio table 50, for example, as shown in FIG. 8, a value 501 corresponding to each parameter to be set in the PLL 214 is stored in advance in correspondence with the frequency difference 500. When the value 501 of each parameter in the frequency division ratio table 50 is calculated by the Δf calculation unit 216, the value of the PLL 214 should be set in order to generate the local signal frequency with the frequency difference set to 0. The measurement is performed in advance by a manufacturer or the like using an experiment and stored.

When the Δf calculating unit 216 receives the signal indicating the frequency difference Δf, the frequency dividing ratio setting unit 51 extracts each parameter of the frequency dividing ratio corresponding to the received frequency difference Δf from the frequency dividing ratio table 50, and The extracted parameters are set to the variable frequency divider 64 of the PLL 214.

Here, by the offset between the reference signal in the active tag 11 and the reference signal in the RF tag reader 20, if the frequency of the signal transmitted by the active tag 11 is the same as that of the RF tag reader 20 If the frequency of the imaginary received signal is shifted by more than the predetermined frequency, or if the offset of the frequency is less than the predetermined frequency, the signal is transmitted by the Low-IF method, and the frequency is mixed. The frequency of the down-converted signal by the 202 and the mixer 203 is separated from the passband of the BPF 204 and the BPF 205, respectively.

Since the signal from the passband of the BPF 204 and the BPF 205 is not supplied to the AGC amplifier 206 and the AGC amplifier 207, the demodulator 212 cannot directly demodulate the signal from the active tag 11.

On the other hand, the frequency division ratio control unit 215 changes the frequency of the local signal obtained by the PLL 214 to the signal frequency offset of the active tag 11 in accordance with the frequency difference Δf calculated by the Δf calculating unit 216. Set the frequency of the specified frequency share. Thereby, the frequency of the signal down-converted by the mixer 202 and the mixer 203 is not separated from the pass band of the BPF 204 and the BPF 205, and is supplied to the AGC amplifier 206 and the AGC amplifier 207.

Therefore, the RF tag reader 20 of the present embodiment can correct the signal from the active tag 11 even when the reference signal in the active tag 11 is offset from the reference signal in the RF tag reader 20. Demodulation is performed.

Next, the operation of the control unit 217 will be described with reference to the flowchart of Fig. 9. Fig. 9 is a flow chart showing an example of the operation of the RF tag reader 20 in the first embodiment. When the user receives the reception of the material from the active tag 11 through the switch 13 provided in the RF tag reader 20, the RF tag reader 20 starts the operation shown in this flowchart.

First, the control unit 217 sets an initial value of the frequency division ratio in the PLL 214 (S100), and transmits a Wake UP message by a transmitter (not shown). Next, the control unit 217 determines whether or not the unmodulated signal is output by the LPF 211 (S101). When the no-modulation signal is not output (S101: No), the control unit 217 repeats the step S101 until the no-modulation signal is output.

When the unmodulated signal is output (S101: Yes), the control unit 217 activates the frequency division ratio control unit 215 and the Δf calculation unit 216 (S102), and calculates the frequency difference Δf by the Δf calculation unit 216. The predetermined time (for example, several tens of μs) is reserved by the setting of the frequency division ratio by the frequency division ratio control unit 215 and the period until the switching of the local signal frequency by the PLL 214 is completed.

The Δf calculating unit 216 performs a frequency difference Δf between the frequency at which the received signal is calculated and a predetermined frequency, and supplies the calculated Δf value to the frequency dividing ratio control unit 215. The PLL 214 extracts each parameter of the frequency division ratio corresponding to the frequency difference Δf received by the Δf calculation unit 216 from the frequency division ratio table 50, and sets the extracted parameters to the variable frequency divider 64 of the PLL 214. (S103).

Next, the control unit 217 stops the frequency division ratio control unit 215 and the Δf calculation unit 216 (S104). Next, the PLL 214 continues to operate by the frequency division ratio set by the frequency division ratio control unit 215 in step S103, and the demodulator 212 decodes the data transmitted by the active tag 11 following the unmodulated wave. To adjust (S105), the RF tag reader 20 ends the operation shown in this flowchart.

The first embodiment of the present invention has been described above.

As apparent from the above description, the RF tag reader 20 of the present embodiment can improve the reception characteristics in the reception of radio waves transmitted by the active tag 11.

Next, a second embodiment of the present invention will be described.

Fig. 10 is a block diagram showing an example of the functional configuration of the RF tag reader 20 in the second embodiment. The RF tag reader 20 of the present embodiment includes an antenna 200, an LNA 201, a mixer 202, a mixer 203, a BPF 204, a BPF 205, an AGC amplifier 206, an AGC amplifier 207, an ADC 208, an ADC 209, an LPF 210, an LPF 211, and demodulation. The device 212, the phase shifter 213, the PLL 214, the frequency division ratio control unit 215, the Δf calculation unit 216, the control unit 217, the switch 220, the switch 221, the LPF 222, and the LPF 223.

The RF tag reader 20 in the present embodiment has the switch 220, the switch 221, the LPF 222, and the LPF 223, which is different from the RF tag reader 20 in the first embodiment described with reference to Fig. 3. In addition, in the tenth figure, the member which has the same code|symbol is attached|subjected by FIG. 3, and has the same or the same function as the member of FIG. 3, and the description is abbreviate|omitted.

The switch 220 transmits the output signal of the mixer 202 to the LPF 222 or the BPF 204 in accordance with an instruction from the control unit 217. The switch 221 transmits the output signal of the mixer 203 to the LPF 223 or the BPF 205 in accordance with an instruction from the control unit 217.

The LPF 222 extracts a signal of a frequency band below a predetermined frequency from among signals supplied from the switch 220 and supplies it to the AGC amplifier 206. The LPF 223 extracts a signal of a frequency band equal to or lower than a predetermined frequency from the signal supplied from the transmission switch 221, and supplies it to the AGC amplifier 207.

Next, the operation of the control unit 217 in the present embodiment will be described with reference to the flowchart of Fig. 11. Fig. 11 is a flow chart showing an example of the operation of the RF tag reader 20 in the second embodiment. In the present embodiment, the switch 13 provided in the RF tag reader 20 can instruct the RF tag reader 20 to indicate either the reception of the active tag or the reception of the passive tag. The RF tag reader 20 starts the operation shown in this flowchart when the switch 13 is operated.

First, the control unit 217 determines whether or not the operation by the user through the switch 13 is a receiver indicating the active tag (S200). When the user is instructed to receive the reception of the active tag (S200: Yes), the control unit 217 switches the switch 220 by sending the output signal of the mixer 202 to the BPF 204, and the mixer 203 is switched. The way in which the output signal is sent to the BPF 205 switches the switch 221 (S201).

Next, the control unit 217 sets an initial value of the frequency division ratio of the local signal frequency in the reception of the Low-IF mode reception to the PLL 214 (S202), and transmits the Wake UP message by a transmitter (not shown). . Next, the control unit 217 determines whether or not the presence or absence of the modulation signal is outputted by the LPF 211 (S203). When the no-modulation signal is not output (S203: No), the control unit 217 repeats the step S203 until the no-modulation signal is output.

When the no-modulation signal is output (S203: Yes), the control unit 217 activates the frequency division ratio control unit 215 and the Δf calculation unit 216 (S204), and calculates the frequency difference Δf by the Δf calculation unit 216. The predetermined time (for example, several tens of μs) is reserved by the setting of the frequency division ratio by the frequency division ratio control unit 215 and the period until the switching of the local signal frequency by the PLL 214 is completed.

The Δf calculating unit 216 calculates the frequency difference Δf between the frequency of the received signal and the predetermined frequency, and supplies the calculated Δf value to the frequency dividing ratio control unit 215. The frequency division ratio control unit 215 extracts each parameter of the frequency division ratio corresponding to the frequency difference Δf received by the Δf calculation unit 216 by the frequency division ratio table 50, and sets each of the extracted parameters to the variable value of the PLL 214. The frequency converter 64 (S205).

Next, the control unit 217 stops the frequency division ratio control unit 215 and the Δf calculation unit 216 (S206). Next, the PLL 214 continues to operate by the frequency division ratio set by the frequency division ratio control unit 215 in step S205, and the demodulator 212 decodes the data transmitted by the active tag 11 following the unmodulated wave. After the adjustment (S207), the RF tag reader 20 ends the operation shown in this flowchart.

In step S200, when the operation of the switch 13 by the user is to indicate the receiver of the passive tag (S200: No), the control unit 217 switches the output signal of the mixer 202 to the LPF 222. The switch 220 is switched, and the switch 221 is switched in such a manner that the output signal of the mixer 203 is transmitted to the LPF 223 (S208).

Next, the control unit 217 sets the initial value of the division ratio of the local signal frequency in the reception for generating the direct conversion method to the PLL 214 (S209). Next, the control unit 217 performs carrier sense (carrier sense) to determine whether or not there is another RF tag in communication (S210). If there is another RF tag in communication (S210: Yes), the control unit 217 repeats step S210 until the RF tag in communication is not present.

If there is no RF tag in communication (S210: No), the control unit 217 causes the transmitter (not shown) to start transmitting radio waves to the passive tag (S211), and the demodulator 212 is sent by the passive tag. The data is demodulated (S212), and the RF tag reader 20 ends the operation shown in this flowchart.

The second embodiment of the present invention has been described above.

As apparent from the above description, the RF tag reader 20 of the present embodiment can improve the reception characteristics in the radio wave reception transmitted by the active tag 11, and can extract the data from the active tag with the passive tag. The data is switched by one RF tag reader 20 for receiving.

Next, a third embodiment of the present invention will be described.

Fig. 12 is a block diagram showing an example of the functional configuration of the RF tag reader 20 in the third embodiment. The RF tag reader 20 of the present embodiment includes an antenna 200, an LNA 201, a mixer 202, a mixer 203, an AGC amplifier 206, an AGC amplifier 207, an ADC 208, an ADC 209, an LPF 210, an LPF 211, a demodulator 212, and a shifter. The phaser 213, the PLL 214, the frequency division ratio control unit 215, the Δf calculation unit 216, the control unit 217, and the filter circuit 230.

The RF tag reader 20 of the present embodiment has a filter circuit 230 instead of the BPF 204 and the BPF 205, and is different from the RF tag reader 20 of the first embodiment described with reference to Fig. 3 in this respect. In addition, in the tenth figure, the member which has the same code|symbol is attached|subjected by FIG. 3, and has the same or the same function as the member of FIG. 3, and the description is abbreviate|omitted.

The filter circuit 230 operates as either a BPF or an LPF by an instruction from the control unit 217. The filter circuit 230 has a configuration as shown in FIG. 13, for example, when the switches 231 to 236 are all turned off (OFF), and as the LPF, when the switches 231 to 236 are all turned on (ON), they are used as complex filters. The BPF of the device operates. The control unit 217 controls all of the switches 231 to 236 to be turned off during passive tag reception, and controls all of the switches 231 to 236 to be turned on when the active tag is received.

The third embodiment of the present invention will be described above.

As apparent from the above description, the RF tag reader 20 of the present embodiment can improve the reception characteristics in the radio wave reception transmitted by the active tag 11, and can make the data from the active tag and the passive The data of the tag is miniaturized when the one RF tag reader 20 is switched to perform reception.

Next, a fourth embodiment of the present invention will be described.

Fig. 14 is a block diagram showing an example of the functional configuration of the RF tag reader 20 in the fourth embodiment. The RF tag reader 20 of the present embodiment includes an antenna 200, an LNA 201, a mixer 202, a mixer 203, an AGC amplifier 206, an AGC amplifier 207, an ADC 208, an ADC 209, an LPF 210, an LPF 211, a demodulator 212, and a shifter. The phaser 213, the PLL 214, the Δf calculation unit 216, the control unit 217, the variable BPF 240, the variable BPF 241, and the BPF control unit 242.

The RF tag reader 20 of the present embodiment includes a variable BPF 240, a variable BPF 241, and a BPF control unit 242 instead of the BPF 204, the BPF 205, and the frequency division ratio control unit 215. In this regard, the description will be made using FIG. The RF tag reader 20 in the first embodiment is different. In the fourth embodiment, the components having the same reference numerals as those in the third embodiment have the same or similar functions as those of the members in the third embodiment, and therefore the description thereof will be omitted.

The variable BPF 240 directly changes the center frequency of the pass band while maintaining the bandwidth of the pass band in accordance with the control signal from the BPF control unit 242. The variable BPF 240 is configured, for example, as shown in Fig. 15. The BPF control unit 242 can change the center frequency of the pass band of the variable BPF 240 by changing the resistance values of the variable resistor 243-1 and the variable resistor 243-2.

Here, the respective variable resistors 243 can be configured as shown in, for example, FIG. The BPF control unit 242 can change the resistance value of the entire variable resistor 243 by turning on or off the respective switches 244. The BPF control unit 242 may also change the capacitance of the capacitor in the variable BPF 240 in place of the change in the resistance value of the variable resistor 243 or together with the change in the resistance value of the variable resistor 243. Further, in the example of Fig. 16, the variable BPF 240 is constituted by a resistor and a capacitor, but in other forms, the variable BPF 240 may be constituted by a coil and a capacitor. Since the variable BPF 241 has the same configuration as that of the variable BPF 240, description thereof will be omitted.

For example, as shown in FIG. 17, the BPF control unit 242 has a control signal table 70 and a control signal supply unit 71. In the control signal table 70, for example, as shown in FIG. 18, a control signal 701 indicating control of each of the switches in the variable BPF 240 and the variable BPF 241 is stored in advance in association with the frequency difference 700. When the control signal 701 in the control signal table 70 calculates the corresponding frequency difference by the Δf calculating unit 216, it should be supplied to shift the frequency difference, the center frequency of the pass band of the variable BPF 240 and the variable BPF 241. The values up to the variable BPF 240 and the variable BPF 241 are measured and stored in advance by an experimenter or the like using an experiment.

When the control signal supply unit 71 receives the signal indicating the frequency difference Δf by the Δf calculation unit 216, the control signal table 70 extracts the control signal corresponding to the received frequency difference Δf, and supplies the extracted control signal to the control signal. Variable BPF240 and variable BPF241.

Here, by the offset between the reference signal in the active tag 11 and the reference signal in the RF tag reader 20, if the frequency of the signal transmitted by the active tag 11 is the same as that of the RF tag reader 20 If the frequency of the imaginary received signal is shifted by more than the predetermined frequency, or if the offset of the frequency is less than the predetermined frequency, the signal is transmitted by the Low-IF method, and the frequency is mixed. The frequency of the signal down-converted by the device 202 and the mixer 203 is separated from the passband of the variable BPF 240 and the variable BPF 241, respectively.

Since the signal of the passband of the variable BPF 240 and the variable BPF 241 is not supplied to the AGC amplifier 206 and the AGC amplifier 207, the demodulator 212 cannot directly demodulate the signal from the active tag 11.

On the other hand, the BPF control unit 242 shifts the center frequency of the pass band of the variable BPF 240 and the variable BPF 241 in accordance with the frequency difference Δf calculated by the Δf calculating unit 216 to offset the frequency difference Δf. The control signals are supplied to the variable BPF 240 and the variable BPF 241, respectively. Thereby, the frequency of the signal down-converted by the mixer 202 and the mixer 203 is not separated from the pass band of the variable BPF 240 and the variable BPF 241, and is supplied to the AGC amplifier 206 and the AGC amplifier 207, respectively. Therefore, the RF tag reader 20 of the present embodiment can correctly demodulate the signal from the active tag 11.

Next, the operation of the control unit 217 in the present embodiment will be described with reference to the flowchart of Fig. 19. Fig. 19 is a flow chart showing an example of the operation of the RF tag reader 20 in the fourth embodiment. When the user is instructed to receive the data from the active tag 11 via the switch 13 provided in the RF tag reader 20, the RF tag reader 20 starts the operation shown in this flowchart. It is to be noted that the processing of the same reference numerals as in the ninth embodiment is the same as the processing in the ninth embodiment except for the contents described below, and therefore the description thereof will be omitted.

When the unmodulated signal is output from the LPF 211 in the step S101 (S101: Yes), the control unit 217 activates the Δf calculating unit 216 and the BPF control unit 242 (S110), and the Δf calculating unit 216 determines The calculation of the frequency difference Δf and the period until the supply of the control signal by the BPF control unit 242 is completed wait for a predetermined time (for example, several tens of μsec).

The Δf calculating unit 216 calculates the frequency difference Δf between the frequency of the received signal and the predetermined frequency, and supplies the calculated value of Δf to the BPF control unit 242. The BPF control unit 242 extracts the control signal corresponding to the frequency difference Δf received by the Δf calculating unit 216 from the control signal table 70, and supplies the extracted control signals to the variable BPF 240 and the variable BPF 241 (S111), respectively. .

Next, the control unit 217 stops the Δf calculation unit 216 and the BPF control unit 242 (S112). Next, the demodulator 212 demodulates the data transmitted by the active tag 11 following the unmodulated wave (S105), and the RF tag reader 20 ends the operation shown in this flowchart.

The fourth embodiment of the present invention has been described above.

As apparent from the above description, in the RF tag reader 20 of the present embodiment, the reception characteristics can be improved in the reception of radio waves transmitted by the active tag 11.

Next, a fifth embodiment of the present invention will be described.

Fig. 20 is a block diagram showing an example of the functional configuration of the RF tag reader 20 in the fifth embodiment. The RF tag reader 20 of the present embodiment includes an antenna 200, an LNA 201, a mixer 202, a mixer 203, an AGC amplifier 206, an AGC amplifier 207, an ADC 208, an ADC 209, an LPF 210, an LPF 211, a demodulator 212, and a shifter. The phaser 213, the PLL 214, the Δf calculation unit 216, the control unit 217, the variable BPF 240, the variable BPF 241, the BPF control unit 242, the switch 250, the switch 251, the LPF 252, and the LPF 253.

The RF tag reader 20 of the present embodiment includes the switch 250, the switch 251, the LPF 252, and the LPF 253. In this respect, the RF tag reader 20 of the fourth embodiment described with reference to Fig. 14 is used. In addition, in the 20th drawing, the member which has the same code|symbol is attached|subjected by FIG. 14 is the same or the same function as the member of FIG.

The switch 250 transmits the output signal of the mixer 202 to the LPF 252 or the variable BPF 240 in accordance with an instruction from the control unit 217. The switch 251 transmits the output signal of the mixer 203 to the LPF 253 or the variable BPF 241 in accordance with an instruction from the control unit 217.

The LPF 252 extracts a signal of a frequency band below a predetermined frequency from the signal supplied through the switch 250 and supplies it to the AGC amplifier 206. The LPF 253 extracts a signal of a frequency band equal to or lower than a predetermined frequency from the signal supplied from the switch 251 and supplies it to the AGC amplifier 207.

Next, the operation of the control unit 217 in the present embodiment will be described with reference to the flowchart of Fig. 21. Fig. 21 is a flow chart showing an example of the operation of the RF tag reader 20 in the fifth embodiment.

In the present embodiment, the switch 13 provided in the RF tag reader 20 can instruct the RF tag reader 20 to indicate either the reception of the active tag or the reception of the passive tag. The RF tag reader 20 starts the operation shown in this flowchart when the switch 13 is operated. In the above, the processing of the same reference numerals as in the eleventh embodiment is the same as the processing in the eleventh embodiment, and therefore the description thereof is omitted.

In step S203, when the LPF 211 is outputted with the no-modulation signal (S203: Yes), the control unit 217 activates the Δf calculation unit 216 and the BPF control unit 242 (S220) to the frequency determined by the Δf calculation unit 216. The calculation of the difference Δf and the period until the supply of the control signal by the BPF control unit 242 is completed wait for a predetermined time (for example, several tens of μsec).

The Δf calculating unit 216 calculates the frequency difference Δf between the frequency of the received signal and the predetermined frequency, and supplies the calculated value of Δf to the BPF control unit 242. The control signal corresponding to the frequency difference Δf received by the Δf calculating unit 216 is extracted from the control signal table 70, and the extracted control signals are supplied to the variable BPF 240 and the variable BPF 241, respectively (S221).

Next, the control unit 217 stops the Δf calculation unit 216 and the BPF control unit 242 (S222). Next, the demodulator 212 demodulates the data transmitted by the active tag 11 following the unmodulated wave (S207), and the RF tag reader 20 ends the operation shown in this flowchart.

The fifth embodiment of the present invention has been described above.

As can be seen from the above description, in the RF tag reader 20 of the present embodiment, the reception characteristics can be improved in the reception of the radio waves transmitted by the active tag 11, and the data from the active tag can be The data from the passive tag is switched by one RF tag reader 20 for switching.

Next, a sixth embodiment of the present invention will be described.

Fig. 22 is a block diagram showing an example of the functional configuration of the RF tag reader 20 in the sixth embodiment. The RF tag reader 20 of the present embodiment includes an antenna 200, an LNA 201, a mixer 202, a mixer 203, an AGC amplifier 206, an AGC amplifier 207, an ADC 208, an ADC 209, an LPF 210, an LPF 211, a demodulator 212, and a shifter. The phaser 213, the PLL 214, the Δf calculation unit 216, the control unit 217, the BPF control unit 242, and the filter circuit 260.

The RF tag reader 20 of the present embodiment has a filter circuit 260 instead of the variable BPF 240 and the variable BPF 241. In this regard, the RF tag reader of the fourth embodiment described with reference to Fig. 14 is used. 20 different. In addition, in the 22nd drawing, the member which has the same code|symbol with the code|symbol of FIG. 14 has the same or the same function as the member of FIG.

The filter circuit 260 operates as either a BPF or an LPF by an instruction from the control unit 217. The filter circuit 260 is configured as shown in Fig. 23, and operates as an LPF when all of the switches 261 to 266 are turned off, and operates as a BPF of a complex filter when all of the switches 261 to 266 are turned on. The control unit 217 controls all of the switches 261 to 266 to be turned off during passive tag reception, and controls all of the switches 261 to 266 to be turned on when the active tag is received.

Further, when all of the switches 261 to 266 are turned on and the BPF as the complex filter operates, the BPF control unit 242 supplies the variable resistors connected to the switches 261 to 266 and the Δf calculating unit 216. The control signal corresponding to the frequency difference Δf is generated, whereby the center frequency of the pass band of the filter circuit 260 operating as the BPF is shifted by the frequency difference Δf calculated by the Δf calculating unit 216.

The sixth embodiment of the present invention has been described above.

As apparent from the above description, in the RF tag reader 20 of the present embodiment, the reception characteristics can be improved in the reception of the radio waves transmitted by the active tag 11, and the data from the active tag can be obtained. The data from the passive tag is miniaturized when the RF tag reader 20 is switched and the reception is performed.

However, the present invention is not limited to the above embodiments, and various modifications are possible within the scope of the gist of the invention.

For example, in the filter circuit 230 of the third embodiment and the filter circuit 260 of the sixth embodiment, the LPF of the I component and the Q component are set to have a single end as a three-time actual filter. The example is explained, but the invention is not limited thereto. In other aspects, the I component of the filter circuit and the LPF of the Q component may be formed by differential, or may be formed by an actual filter that is not three or more times.

Further, the I component of the filter circuit and the LPF of the Q component can be configured by using an actual filter that is differentially used five times, as disclosed in Japanese Laid-Open Patent Publication No. 2008-205962. When the filter circuit disclosed in Japanese Laid-Open Patent Publication No. 2008-205962 is used as the filter circuit 260 in the sixth embodiment, the resistor inserted between the LPF of the I component and the LPF of the Q component is formed as The variable resistor whose resistance value is changed by the control of the control unit 217 may be used.

10. . . RFID system

11. . . Active label

12. . . Data processing device

13. . . switch

20. . . RF tag reader

30. . . CW

31. . . Guiding tone

32. . . Preamble signal

33. . . data

41. . . Multiplier

42. . . Multiplier

43. . . Adder

44. . . inverter

45. . . Loop filter

46. . . NCO

47. . . Adder

48. . . Integrator

50. . . Divide ratio table

51. . . Frequency division ratio setting unit

60. . . Phase comparator

61. . . Charge pump

62. . . Loop filter

63. . . VCO

64. . . Variable divider

70. . . Control signal form

71. . . Control signal supply

200. . . antenna

201. . . LNA

202. . . Mixer

203. . . Mixer

204. . . BPF

205. . . BPF

206. . . AGC amplifier

207. . . AGC amplifier

208. . . ADC

209. . . ADC

210. . . LPF

211. . . LPF

212. . . Demodulator

213. . . Phase shifter

214. . . PLL

215. . . Frequency division ratio control unit

216. . . Δf calculation unit

217. . . Control department

220. . . switch

221. . . switch

222. . . LPF

223. . . LPF

230. . . Filter circuit

231~236. . . switch

240. . . Variable BPF

241. . . Variable BPF

242. . . BPF Control Department

243. . . Variable resistance

244. . . switch

250. . . switch

251. . . switch

252. . . LPF

253. . . LPF

260. . . Filter circuit

500. . . Frequency difference

501. . . Parameter value

700. . . Frequency difference

701. . . Control signal

Fig. 1 is a system configuration diagram showing an example of an RFID system 10 according to an embodiment of the present invention.

Fig. 2 is a view showing an example of the specifications of the signal transmitted by the active tag 11.

Fig. 3 is a block diagram showing an example of the functional configuration of the RF tag reader 20 in the first embodiment.

Fig. 4 is a conceptual diagram for explaining a calculation method of the frequency difference Δf.

Fig. 5 is a block diagram showing another example of the Δf calculating unit 216.

Fig. 6 is a block diagram showing an example of the functional configuration of the PLL 214.

Fig. 7 is a block diagram showing an example of the functional configuration of the frequency division ratio control unit 215.

Fig. 8 is a view showing an example of the construction of the data stored in the frequency division ratio table 50.

Fig. 9 is a flow chart showing an example of the operation of the RF tag reader 20 in the first embodiment.

Fig. 10 is a block diagram showing an example of the functional configuration of the RF tag reader 20 in the second embodiment.

Fig. 11 is a flow chart showing an example of the operation of the RF tag reader 20 in the second embodiment.

Fig. 12 is a block diagram showing an example of the functional configuration of the RF tag reader 20 in the third embodiment.

Fig. 13 is a circuit diagram showing an example of the circuit configuration of the filter circuit 230.

Fig. 14 is a block diagram showing an example of the functional configuration of the RF tag reader 20 in the fourth embodiment.

Fig. 15 is a circuit diagram showing an example of the circuit configuration of the variable BPF 240.

Fig. 16 is a circuit diagram showing an example of a circuit configuration of a variable resistor.

Fig. 17 is a block diagram showing an example of the functional configuration of the BPF control unit 242.

Fig. 18 is a view showing an example of the construction of the data stored in the control signal table 70.

Fig. 19 is a flow chart showing an example of the operation of the RF tag reader 20 in the fourth embodiment.

Fig. 20 is a block diagram showing an example of the functional configuration of the RF tag reader 20 in the fifth embodiment.

Fig. 21 is a flow chart showing an example of the operation of the RF tag reader 20 in the fifth embodiment.

Fig. 22 is a block diagram showing an example of the functional configuration of the RF tag reader 20 in the sixth embodiment.

Fig. 23 is a circuit diagram showing an example of the circuit configuration of the filter circuit 260.

11. . . Active label

12. . . Data processing device

13. . . switch

20. . . RF tag reader

200. . . antenna

201. . . LNA

202. . . Mixer

203. . . Mixer

204. . . BPF

205. . . BPF

206. . . AGC amplifier

207. . . AGC amplifier

208. . . ADC

209. . . ADC

210. . . LPF

211. . . LPF

212. . . Demodulator

213. . . Phase shifter

214. . . PLL

215. . . Frequency division ratio control unit

216. . . Δf calculation unit

217. . . Control department

Claims (7)

A radio frequency tag reader circuit is a receiving circuit of a radio frequency (RF) tag reader that receives a signal transmitted by an active tag by a Low-IF method, and is characterized in that: The signal output by the device outputs a programmable PLL of the local signal of the set frequency division ratio; the unmodulated signal sent by the active tag uses the local signal outputted by the programmable PLL a mixer for down-converting; a band pass filter for passing a signal of a predetermined frequency band among output signals from the mixer; an amplifier for amplifying an output signal of the band pass filter; a demodulation unit that converts an output of the amplifier into digital data and demodulates; and calculates a frequency difference calculation unit that displays a frequency difference between a frequency of an output signal from the band pass filter and a predetermined reference frequency; And calculating a frequency dividing ratio corresponding to the difference calculated by the frequency difference calculating unit, and setting the calculated frequency dividing ratio to the frequency dividing ratio control unit of the programmable PLL. The radio frequency tag reader circuit according to claim 1, wherein the frequency division ratio control unit has a value of each different frequency difference, and when the frequency difference is output by the frequency difference calculation unit, Storing a frequency division ratio table that should be set to a parameter value of a frequency division ratio of the aforementioned programmable PLL; and When the frequency difference calculation unit outputs a frequency difference, the parameter of the frequency division ratio corresponding to the frequency difference is extracted by the frequency division ratio table, and the parameter of the extracted frequency division ratio is set to the programmable PLL. The division ratio setting unit. The radio frequency tag reader circuit according to claim 1, wherein the signal from the frequency band below the predetermined frequency is passed through the output signal from the mixer to be supplied to the amplifier a low pass filter; supplying the output signal of the mixer to the switch of any one of the band pass filter or the low pass filter according to the supplied switching signal; and when the user is instructed to be passive At the time of receiving the tag, the frequency division ratio is set by outputting the frequency of the predetermined carrier to the programmable PLL, and the output signal of the mixer is supplied to the low-pass filter to switch the signal. When the switch is supplied to the switch, the operation of the frequency difference output unit and the frequency division ratio control unit is stopped, and when the user instructs the reception of the active tag, the predetermined frequency portion of the frequency offset of the carrier is output. The frequency of the method is set in the aforementioned programmable PLL to set the frequency division ratio, and the output signal of the mixer is supplied to the band pass filter to supply the switching signal to the foregoing The reception mode switching unit that starts the operation of the frequency difference output unit and the frequency division ratio control unit. A radio frequency tag reader circuit connected by a Low-IF method A receiving circuit of a radio frequency (RF) tag reader that receives a signal transmitted by an active tag, and is characterized in that: a local signal generating unit that outputs a local signal of a predetermined frequency; The unmodulated signal for transmission is a mixer that is down-converted by the local signal outputted by the local signal generating unit; in the center frequency corresponding to the input control signal, from the aforementioned mixer Among the output signals, a band pass filter that passes a signal of a predetermined frequency band; an amplifier that amplifies an output signal of the band pass filter; and demodulation after demodulation of the output of the aforementioned amplifier into digital data a frequency difference calculation unit that calculates a difference between a frequency of an output signal of the band pass filter and a predetermined reference frequency, and a difference calculated by the frequency difference calculation unit to generate a control The control signal of the center frequency of the band of the band pass filter is supplied to the band pass filter control unit of the band pass filter. The radio frequency tag reader circuit of claim 4, wherein the band pass filter changes a part of a constant of a component constituting the band pass filter according to the input control signal, thereby making a pass The center frequency of the frequency band is changed, and the band pass filter control unit has a value for each frequency difference. When the frequency difference is output by the frequency difference calculation unit, the band pass filter should be supplied to the band pass in advance. a control signal table for the value of the control signal of the filter; and When the frequency difference calculation unit outputs a frequency difference, the control signal table extracts a value of the control signal corresponding to the frequency difference, and inputs the extracted control signal to the control signal supply unit of the band pass filter. . The radio frequency tag reader circuit of claim 4, wherein the local signal generating unit outputs a local frequency signal of the set frequency dividing ratio to a signal output by the reference oscillator. The PLL, the RF tag reader circuit further includes: a low-pass filter that supplies a signal of a frequency band equal to or lower than a predetermined frequency among the output signals from the mixer to the amplifier; Supplying the output signal of the mixer to the switch of any one of the band pass filter or the low pass filter according to the supplied switching signal; and when the user is instructed to receive the passive tag, Setting a frequency dividing ratio by outputting a frequency of a predetermined carrier to the programmable PLL, and supplying a switching signal to the switch in such a manner that an output signal of the mixer is supplied to the low pass filter, so that a switching signal is supplied to the switch The operation of the frequency difference output unit and the band pass filter control unit is stopped. When the user is instructed to receive the active tag, the frequency of the carrier is shifted in advance. Given to the frequency of the output of the programmable PLL frequency division ratio is set to the output signal of the mixer is supplied to a bandpass filter preceding the switching signal supplied to said switch, and A reception mode switching unit that starts the operation of the frequency difference output unit and the band pass filter control unit. The radio frequency tag reader circuit according to any one of claims 1 to 6, wherein the frequency difference calculating unit outputs the band pass filter from the predetermined time interval. The frequency difference is obtained by dividing the difference between the number of repetitions of one wavelength of the signal of the reference frequency in the time interval by the number of times of repetition of the wavelength of the modulation signal, and dividing the time interval to calculate the frequency difference.