JP2006120090A - Interrogator and method for setting receiving sensitivity of interrogator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely read storage information from a target transponder. <P>SOLUTION: An RFID (radio frequency identification) reader/writer 10 (interrogator) having a transmitting circuit 12 for transmitting a request radio wave for transmitting storage information stored in an IC tag 5 (transponder), and a receiving circuit 14 for receiving and demodulating a response radio wave transmitted from the transponder 5 that has received the request radio wave is provided with a sensitivity setting circuit 141 for setting the receiving sensitivity of the receiving circuit 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an interrogator such as an RFID reader device and a reception sensitivity setting method for the interrogator, and more particularly to a technique for reliably reading stored information from a target responder.

The frequency bands used by RFID (Radio Frequency IDentification) used in a system for reading information without contact (hereinafter referred to as an information reading system) are currently 13.56 MHz band and 2.45 GHz band. Recently, in addition to these, introduction of RFID using the UHF band (communication distance 3 to 6 m) has been studied, and in Japan, research is being conducted in various places to introduce RFID using the UHF band, such as revision of the Radio Law. Has been done. RFID using the UHF band has a longer communication distance (about 3 to 6 m) compared to the conventional 13.56 MHz band (communication distance of about 80 cm) or 2.45 GHz band (communication distance of about 1.5 m). There is a feature. In the RFID using the UHF band, information (hereinafter referred to as storage information) recorded in a plurality of responders (for example, IC tags) can be read at a time by a reader device (interrogator). Further, it is possible to read information of an IC tag that is in a place that cannot be seen from the reader device.
JP 2004-38574 A Japanese Patent Laid-Open No. 9-18183

  By the way, the reception sensitivity of RFID reader devices that are currently in widespread use is set and shipped on the assumption of general usage conditions. However, RFID is applied to the reach of radio waves transmitted from the reader device to the IC tag (hereinafter referred to as request radio waves) and radio waves transmitted from the IC tag that has received the request radio waves (hereinafter referred to as response radio waves). The reception sensitivity set at the time of shipment of the reader device or the like is not always set to an appropriate state at each site where the reader device is used. For this reason, when information stored in an IC tag (hereinafter referred to as storage information) is read from one of a plurality of IC tags arranged close to each other, A response radio wave transmitted from an IC tag that is not configured may be picked up, which causes a malfunction of the system.

  For example, as shown in FIG. 9, in a system using RFID in which a plurality of reader devices 10 are arranged adjacent to each other, information stored in the IC tag 5 (1) is stored for the reader device 10 (1) of the first system 91. However, if the range (service area) from which the reader device 10 (1) can read the stored information is too wide, the information stored in the IC tag 5 (2) of the second system 92 is read. Become. Such a problem is particularly serious in an RFID system that uses a wide frequency band of a service area such as the UHF band.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide an interrogator capable of reliably reading stored information from a target responder and a method for setting the reception sensitivity of the interrogator.

  In order to achieve the above object, the invention according to the first aspect of the present invention includes a transmission circuit that transmits a request radio wave that transmits stored information stored in a responder, and the request radio wave is received. An interrogator having a receiving circuit that receives and demodulates a response radio wave transmitted from a responding device, and includes a sensitivity setting circuit for setting the receiving sensitivity of the receiving circuit.

  Thus, by providing the sensitivity setting circuit in the interrogator, it becomes possible to freely change the reception sensitivity of the interrogator. For this reason, it becomes possible to set so that the response radio wave transmitted from the responder which is not targeted by the interrogator is not received. Accordingly, it is possible to reliably and stably read out stored information from only the answering machine targeted by the interrogator. In addition, the service area can be freely set within a necessary range.

The invention according to a second aspect of the present invention is the interrogator according to the first aspect, wherein the sensitivity setting circuit includes a user interface that receives designation of the reception sensitivity, and the sensitivity setting circuit Includes a circuit for setting the receiving sensitivity of the receiving circuit so as to be the receiving sensitivity received from the user interface.
The user can easily set the receiving sensitivity of the receiving circuit using this user interface.

The invention according to the third aspect of the present invention is the interrogator according to claim 1, further comprising a signal strength measuring circuit that outputs a signal indicating the strength of the received signal based on the response radio wave, The sensitivity setting circuit includes a circuit that automatically sets the reception sensitivity of the reception circuit in accordance with the signal output from the signal strength measurement circuit.
As described above, the interrogator includes a circuit for automatically setting the reception sensitivity, thereby reducing the burden on the user for setting the reception sensitivity.

The invention according to a fourth aspect of the present invention is the interrogator according to the fourth aspect, wherein the circuit that automatically sets the reception sensitivity has a reception sensitivity of the reception circuit. The threshold value is obtained from the sum of the noise intensity contained in the received signal and the signal-to-noise ratio required by the demodulator, and only the value obtained by subtracting the threshold value from the signal intensity measured by the signal strength measurement circuit. A circuit for attenuating the signal strength of the received signal is included.
Thus, the threshold value obtained from the sum of the noise intensity and the signal-to-noise ratio contained in the received signal of the receiving circuit is obtained, and the value obtained by subtracting the threshold value from the signal intensity at each time point is used as the attenuation amount. It is possible to automatically estimate the amount of attenuation.

A fifth aspect of the present invention is the interrogator according to any one of the first to fourth aspects, wherein the receiving circuit amplifies a received signal based on the response radio wave. The sensitivity setting circuit includes a circuit for setting the receiving sensitivity of the receiving circuit by switching whether to amplify the received signal by the low noise amplifier circuit.
As described above, the reception sensitivity can be changed by switching whether or not the received signal is passed through the low-noise amplifier circuit.

The invention according to a sixth aspect of the present invention is the interrogator according to the fifth aspect, wherein the sensitivity setting circuit controls the gain of the low noise amplifier to control the reception sensitivity of the reception circuit. It is assumed that a circuit for setting is included.
Thus, by controlling the gain, the receiving sensitivity can be set finely.

A seventh aspect of the present invention is the interrogator according to any one of the first to fourth aspects, wherein the receiving circuit includes an attenuator circuit that attenuates a received signal based on the response radio wave. And the sensitivity setting circuit includes a circuit for setting the reception sensitivity of the receiving circuit by switching whether to attenuate the received signal based on the response radio wave by the attenuator circuit.
As described above, the reception sensitivity can be changed by switching whether or not the reception signal is passed through the attenuator circuit.

The invention according to an eighth aspect of the present invention is the interrogator according to the seventh aspect, wherein the sensitivity setting circuit controls reception of the reception circuit by controlling an attenuation amount by the signal attenuation circuit. Sensitivity is set.
In this way, by controlling the attenuation amount, the receiving sensitivity can be set finely.

The ninth aspect of the present invention is the interrogator according to any one of the first to fourth aspects, wherein the receiving circuit amplifies a received signal based on the response radio wave. A low noise amplifier circuit and an attenuator circuit for attenuating the received signal based on the response radio wave, and the sensitivity setting circuit performs only amplification of the received signal based on the response radio wave by the low noise amplifier circuit or the response Including a circuit for switching to a state in which a reception signal based on a radio wave is allowed to pass only through the attenuator or whether the reception signal is not amplified by the low noise amplifier circuit or attenuated by the attenuator circuit. And
In this way, the sensitivity setting circuit changes the reception sensitivity by providing a circuit that switches whether the received signal passes only through the low-noise amplifier circuit, only through the attenuator circuit, or none of them. Can be made. As a result, the stored information can be reliably and stably read from only the responding machine targeted by the interrogator.

The tenth aspect of the present invention is the interrogator according to the ninth aspect, wherein the sensitivity setting circuit controls the gain of the low noise amplifier circuit and the attenuation amount of the attenuator circuit. It is supposed to include a circuit to perform.
Thus, since the sensitivity setting circuit includes a circuit for controlling the gain of the low noise amplifier circuit and the attenuation amount of the attenuator circuit, the sensitivity setting circuit can change the reception sensitivity from the maximum gain of the low noise amplifier circuit to the maximum of the attenuator circuit. The range up to the attenuation can be changed continuously. As a result, it is possible to reliably and stably read stored information from only the responding machine targeted by the interrogator.

  The eleventh aspect of the present invention is the interrogator according to any one of the first to tenth aspects, wherein the responder is an IC tag in RFID, and the interrogator is the IC tag. It is assumed that it is an RFID reader device that reads out the stored information from.

  A twelfth aspect of the present invention is the interrogator according to the third aspect, wherein the signal strength measurement circuit is an RSSI (Radio Signal Strength Indicator) circuit.

The thirteenth aspect of the present invention is the interrogator according to the fourth aspect, wherein the threshold value is a predetermined offset to a value obtained from a sum of the noise intensity and a signal-to-noise ratio. The value is the sum of the values.
In this way, by adding the offset value, it is possible to prevent the service area of the interrogator from becoming unnecessarily narrow.

  According to the fourteenth aspect of the present invention, there is provided a transmission circuit for transmitting a request radio wave for transmitting stored information stored in a responder, and a response transmitted from the responder that has received the request radio wave. A receiving circuit for receiving and demodulating radio waves, the receiving circuit amplifying a received signal based on the response radio wave, and an attenuator for attenuating the received signal based on the response radio wave And a reception sensitivity setting method for an interrogator configured to include a circuit, wherein the sensitivity setting circuit performs only amplification by the low noise amplification circuit of a reception signal based on the response radio wave or reception based on the response radio wave Either the signal is passed only through the attenuator, or the received signal is neither amplified by the low noise amplifier circuit nor attenuated by the attenuator circuit. With switching state, and setting the receiver sensitivity by controlling the attenuation amount of the gain of the low noise amplifier circuit, and the attenuator circuit.

  According to the present invention, it is possible to reliably read stored information from a target responder.

  Hereinafter, embodiments of the present invention will be described. FIG. 1 is a block configuration of an RFID reader device 10 (interrogator), which will be described as the present embodiment. As shown in the figure, the reader device 10 of this embodiment includes a transmission antenna 11, a transmission circuit 12, a reception antenna 13, a reception circuit 14, a baseband processing circuit 15, an arithmetic circuit 16, and the like.

  The transmission circuit 12 generates a transmission signal that is a source of a radio wave (hereinafter referred to as a request radio wave) for causing the IC tag 5 to transmit information stored in the IC tag 5 (hereinafter referred to as storage information), thereby transmitting antennas. 11 is supplied. The frequency of the request radio wave transmitted from the transmission antenna 11 is, for example, the UHF band.

  The transmission circuit 12 includes a BB (Base Band) amplifier 121, a low-pass filter (LPF) 122, a modulation circuit 123, a local oscillator 124, a band-pass filter (BPF) 125, a power amplifier 126, and a low-pass filter 127. . The BB amplifier 121 amplifies the transmission data output from the baseband processing circuit 15. The low-pass filter 122 limits the band of the transmission data amplified by the baseband processing circuit 15. The modulation circuit 123 modulates the band-limited transmission data and generates a transmission signal having the frequency of the requested radio wave. The band pass filter 125 limits the band of the transmission signal output from the modulation circuit 123. The power amplifier 126 amplifies the transmission signal to a predetermined power. The amplified transmission signal passes through the low-pass filter 127 and is supplied to the transmission antenna 11.

  The receiving circuit 14 is a direct conversion type circuit. The receiving circuit 14 demodulates a radio wave (hereinafter referred to as a response radio wave) transmitted from the IC tag 5 that has received the requested radio wave and is received by the receiving antenna 13. The frequency of the response radio wave is, for example, the UHF band. The reception circuit 14 includes circuits such as a front end circuit 141, a quadrature detection circuit 142, a demodulation circuit 143, and an RSSI (Radio Signal Strength Indicator) circuit 144.

  The front end circuit 141 includes a circuit (sensitivity setting circuit) for setting the receiving sensitivity of the receiving circuit 14. The front end circuit 141 includes a low noise amplifier circuit 1411 (hereinafter referred to as LNA (Low Noise Amplifier) 1411), a through output circuit 1412, an attenuator circuit 1413 (hereinafter referred to as ATT (Attenuator) circuit 1413), and a switch circuit 1414. Consists of. Among these, the LNA circuit 1411 amplifies the reception signal (RF signal) of the reception antenna 13 at the first stage of the reception circuit 14 and improves the S / N (signal-to-noise ratio) of the reception circuit 14. Note that the LNA circuit 1411 includes a circuit for controlling the gain (hereinafter referred to as a gain control circuit). An example of an LNA circuit 1411 configured using an FET (Field Effect Transistor) is shown in FIG. 2, and the relationship between the voltage applied to the second gate of the FET of the LNA circuit 1411 and the gain is shown in FIG. In the LNA circuit 1411, the gain is controlled by changing the voltage applied to the gate G2. In FIG. 2, L1 to L4 are matching elements. The through output circuit 1412 is a circuit for performing through output to the subsequent circuit as it is without attenuating the amplification of the reception signal of the reception antenna 13.

  The ATT circuit 1413 is a circuit for attenuating the signal strength of the reception signal supplied to the subsequent circuit. The ATT circuit 1413 is realized by, for example, a circuit of T-type, π-type, bridge T-type, reflection type, balance type, or the like. The ATT circuit 1413 includes a circuit for controlling the amount of attenuation (hereinafter referred to as an attenuation amount control circuit). FIG. 4 shows an example of an ATT circuit 1413 configured using a T-shaped circuit and capable of controlling the attenuation. This circuit uses V1 as a fixed voltage and V2 as a variable voltage. In this circuit, when V1> V2, the current flowing through D1 is large (that is, D1 is a low resistance value) and the current flowing through D2 is small (that is, D2 is a high resistance value). As a result, the ATT circuit 1413 The amount of attenuation of the received signal is small. On the other hand, when V2> V1, the current flowing through D1 is small (that is, D1 is a high resistance value) and the current flowing through D2 is large (that is, D2 is a low resistance value). As a result, the received signal by the ATT circuit 1413 The amount of attenuation increases.

  The switch circuit 1414 switches which of the LNA circuit 1411, the through output circuit 1412, and the ATT 1413 is supplied to the subsequent circuit. The switch circuit 1414 is configured using an element such as an FET or a PIN diode. The switch circuit 1414 has three positions of “LNA”, “through”, and “ATT” corresponding to outputs from the above circuits as contact states. The switch circuit 1414 also includes a user interface (not shown) that accepts user manual settings. Details of the specific function and usage of the switch circuit 1414 will be described later.

  The quadrature detection circuit 142 of the circuits constituting the reception circuit 14 is a circuit that detects a reception signal output from the switch circuit 1414 and generates a baseband signal. The quadrature detection circuit 142 includes a first DBM (Double Balanced Mixer) 1421, a second DBM 1422, a local oscillator 1423, and a π / 2 phase shifter 1424. The local oscillator 1423 can be shared with the local oscillator 124 of the transmission circuit 12. The first DBM 1421 receives the reception signal output from the switch circuit 1414 and the oscillation signal of the local oscillator 1423, and the first DBM 1421 outputs an I (In-phase) signal. The second DBM 1422 receives a signal obtained by shifting the phase of the reception signal output from the switch circuit 1414 and the oscillation signal of the local oscillator 1423 output from the π / 2 phase shifter 1424 by 90 degrees (π / 2). And outputs a Q (Quadrature-phase) signal. The I signal output from the first DBM 1421 passes through the first filter 1425, is amplified by the first amplifier circuit 1426, and is input to the demodulation circuit 143. On the other hand, the Q signal output from the second DBM 1422 passes through the second filter 1427, is amplified by the second amplifier circuit 1428, and is input to the demodulation circuit 143.

  The demodulation circuit 143 performs A / D conversion of the I signal and Q signal input from the quadrature detection circuit 142, demodulation processing, and the like to generate demodulation data, and outputs this to the baseband processing circuit 15.

  The RSSI circuit 144 is a circuit (signal strength measuring circuit) that outputs a voltage corresponding to the strength of the input signal. The RSSI circuit 144 has a signal (hereinafter referred to as a combined signal) obtained by combining a part of the Q signal amplified by the second amplifier circuit 1428 and a part of the I signal amplified by the first amplifier circuit 1426. The received RSSI circuit 144 outputs a voltage corresponding to the intensity of the combined signal to the arithmetic circuit 15. The RSSI circuit 144 has a built-in A / D converter, and the output voltage of the RSSI circuit 144 is output to the arithmetic circuit 15 as a digital value. FIG. 5 shows an example of the RSSI circuit 144 (excluding the A / D converter), and FIG. 6 shows the relationship between the combined signal (RF-in) input to this circuit and the output voltage. The input signal is amplified stepwise by a limiter saturated RF amplifier 1441 connected in series, and the output of each limiter saturated RF amplifier 1441 is amplitude detected by a detector 1442 provided at each stage. And the voltage output from each detector 1442 is synthesize | combined, The voltage amplified by the amplifier 1443 is made into the output.

  The baseband processing circuit 15 generates digital data by performing frame removal, data assembly, frame synchronization, error control, and the like on the demodulated data input from the receiving circuit 14 and outputs the digital data to the arithmetic circuit 16. On the other hand, the baseband processing circuit 15 generates transmission data by adding a frame or adding an error control code to the digital data input from the arithmetic circuit 16, and outputs this to the transmission circuit 12.

  The arithmetic circuit 16 includes a CPU 161, a memory 162 such as a ROM / RAM, an input device 163 such as a key input panel or a switch, a display device 164 such as an LCD, and the like. The memory 162 stores programs and data that realize various functions of the reader device 10. The arithmetic circuit 16 outputs digital data that is the source of the requested radio wave to the baseband processing circuit 15. On the other hand, the arithmetic circuit 16 receives digital data input from the demodulation circuit from the baseband processing circuit 15. The arithmetic circuit 16 is connected to a gain control circuit of the LNA 1411, an attenuation control circuit of the ATT 1413, and a switch circuit 1414 via a control line, and gain control of the gain control circuit, attenuation control of the attenuation control circuit, switch Processing such as position switching of the circuit 1414 is performed.

  In the reader device 10 of this embodiment, the sensitivity of the receiving circuit can be set by the switch circuit 1414 provided in the receiving circuit 14, the gain control circuit of the LNA 1411, and the attenuation control circuit of the ATT 1413. FIG. 7 shows an example of a user interface provided in the reader device 10 for this setting. Hereinafter, the processing procedure when the reception sensitivity is set by the user interface will be described with reference to the flowchart shown in FIG.

  When setting the receiving sensitivity, the user first selects whether to set the receiving sensitivity manually or automatically (S811). This selection is performed by operating the method selection switch 71 in the user interface shown in FIG. If manual is selected here (S811: manual), the user next operates the function selection switch 72 to set the reception sensitivity by the LNA 1411 (position "LNA"), or does not use the LNA 1411 or the ATT 1413? (“THRU” position) or whether the reception sensitivity is set by ATT 1413 (“ATT” position) is selected (S812). If the “LNA” position is selected (S812: LNA), the user further operates the gain adjustment knob 73 to set the gain of the LNA 1411 (S813). When the “ATT” position is selected (S812: ATT), the user operates the attenuation adjustment knob 73 to set the attenuation by the ATT 1413 (S815).

  Here, at the time of selection in the processing of S812, the setting of the gain of the LNA 1411, and the setting of the attenuation amount of the ATT 1413, the user performs the receiving sensitivity of the reader device 10 in a desired state. That is, the user sets the reader apparatus 10 to receive only response radio waves transmitted only from the target IC tag 5. This is performed, for example, by repeatedly performing the operation of making the setting and actually making the reader device 10 receive the response radio wave and confirming it.

  On the other hand, when the user selects automatic in S811 (S811: automatic), the user further presses the calculation button 73 to give an instruction to calculate the amount of attenuation. When the arithmetic circuit 16 detects that the calculation button 73 has been pressed (S816: YES), it obtains the signal intensity from the RSSI 144 (S817) and calculates the attenuation (S818). The calculation of the attenuation amount here is performed by the following procedure, for example.

That is, assuming that the noise in the receiving antenna 13 is generated only by thermal noise, the noise intensity N is N = kTBF (k: Boltzmann constant, T: absolute temperature, B: bandwidth required for communication, F : Noise figure of the receiving circuit 14). Here, for example, assuming that the bandwidth required for communication between the reader device 10 and the IC tag 5 is 500 (kHz), room temperature 25 (° C.), and noise figure 7 (dB), the noise intensity N included in the received signal Is
N = 10 log (1.38 × 10 ⁻²³ (J / K)) + 10 log (298 (K))
+10 log (500 × 10 ³ (kHz)) +7 (dB)
= -228.6 (dBW) + 24.7 (dB) + 57 (dB) + 7 (dB)
= -139.9 (dBW) ...... Formula 1
It becomes. This value is converted to dBm.
N = −139.9 (dBW) +30 (dB) = − 109.9 (dBm) ≈−110 (dBm) (2)
It is.

Here, if the C / N (signal to noise ratio) necessary for the receiving circuit 14 to demodulate the response signal from the IC tag 5 is 13 (dB), the receiving circuit 14 demodulates the response signal. The signal strength required for
Signal strength = N + C / N = −110 (dBm) +13 (dB) = − 97 (dBm) …… Equation 3
It is.

As a result, in this example, if the signal strength (hereinafter referred to as reception sensitivity) is greater than −97 (dBm) (hereinafter referred to as threshold), the reception circuit 14 can demodulate the response signal from the IC tag 5. Accordingly, the attenuation amount in S818 can be obtained from the signal intensity acquired from the RSSI 144 in S817 by the following equation.
Attenuation = acquired signal strength−threshold ...... Equation 4
Here, for example, when the signal strength acquired from RSSI 144 is −82 (dBm),
Attenuation = −82 (dBm) − (− 97 (dBm)) = 15 (dB).
It becomes. For example, when the signal intensity acquired from RSSI 144 is −62 (dbm),
Attenuation = −62 − (− 97) = 35 (dB) …… Equation 6
It becomes.

  If the threshold value is set too strictly, the service area of the reader device 10 may be unnecessarily narrowed. Therefore, a value obtained by adding an offset value to the signal intensity obtained by Expression 3 may be used as a threshold value.

When the attenuation amount is obtained as described above, the arithmetic circuit 16 next controls the switching of the position of the switch circuit 1414, the gain control of the gain control circuit, and the attenuation control of the attenuation control circuit, so that the received signal is attenuated. The amount is attenuated by the amount (S819). The arithmetic circuit 16 can change the attenuation within a predetermined range by such control. For example, when the gain can be varied in the range of 0 to 15 (dB) and the attenuation amount of the ATT 1413 in the range of 25 (dB) by the control of the gain control circuit of the LNA 1411, the arithmetic circuit 16 In relation to the position of the switch circuit 1414, the attenuation can be changed in the range of 40 (dB) as follows.
0 to 15 (dB): Position is “LNA”
15 (dB): Position is “THRU”
15-40 (dB): Position is “ATT”

  When performing the above control, the arithmetic circuit 16 displays information indicating that the control has been executed on the display device 164 (S820). When the user confirms that the message is displayed on the display device 164, the reader device 10 is used to check whether or not the reception sensitivity of the reception circuit 14 is set to a desired value. The display device 164 displays information indicating that the above control has been executed, as well as the attenuation amount set by the arithmetic circuit 16, and the user sees this to set the sensitivity of the receiving circuit 14 to a desired value. You can also know if you are.

  When confirming that the reception sensitivity is set to a desired value, the user presses the light button 75. When the arithmetic circuit 75 detects that the light button 75 has been pressed (S821), it writes the attenuation amount obtained in the process of S818 into the memory 162 (S822). On the other hand, when the reception sensitivity is not set to a desired value, the user presses the calculation button 74 again to reset the attenuation amount (the processing from S817 is performed again). In this case, the user changes the attenuation calculated by the reader device 10 by changing the positional relationship between the reader device 10 and the IC tag 5, for example. The user repeats the above operation so that the receiving sensitivity of the reader device 10 becomes a desired value.

  In the above-described embodiment, when the reader device 10 is started up such as when the power is turned on, the arithmetic circuit 16 reads the attenuation amount already stored in the memory 162 before the previous operation, so that such an attenuation amount is obtained. It is also possible to automatically switch the position of the switch circuit 1414, control the gain of the gain control circuit, and control the attenuation amount of the attenuation amount control circuit.

  The above description of the embodiment is for facilitating understanding of the present invention, and does not limit the present invention. It goes without saying that the present invention can be changed and improved without departing from the gist thereof, and that the present invention includes equivalents thereof. For example, the reader device 10 may be a reader / writer device.

It is a figure which shows the block configuration of the reader apparatus 10 by one Embodiment of this invention. It is a figure which shows an example of the LNA circuit 1411 by one Embodiment of this invention. It is a figure which shows the relationship between the voltage applied to the 2nd gate of FET in LNA circuit 1411 shown in FIG. 2 by one Embodiment of this invention, and a gain. It is a figure which shows an example of the ATT circuit 1413 by one Embodiment of this invention. It is a figure which shows an example of the RSSI circuit 144 by one Embodiment of this invention. It is a figure which shows the relationship between the synthesized signal (RF-in) and output voltage by one Embodiment of this invention. It is a figure which shows an example of the user interface provided in the reader apparatus 10 in order to perform the setting of the receiving sensitivity by one Embodiment of this invention. It is a figure which shows the flowchart explaining the process sequence in the case of setting reception sensitivity with the user interface by one Embodiment of this invention. It is a figure explaining the system using the conventional RFID.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Reader apparatus 11 Transmission antenna 12 Transmission circuit 121 Amplifier circuit 122 Low pass filter 123 Modulation circuit 124 Local oscillator 13 Reception antenna 14 Reception circuit 141 Front end circuit 142 Quadrature detection circuit 143 Demodulation circuit 144 RSSI circuit 1411 Low noise amplification circuit 1412 Through output circuit 1413 Attenuator circuit 1414 Switch circuit 15 Baseband processing circuit 16 Arithmetic circuit 161 CPU 162 Memory

Claims (14)

  An interrogator having a transmission circuit that transmits a request radio wave that transmits stored information stored in a responder, and a reception circuit that receives and demodulates a response radio wave transmitted from a responder that has received the request radio wave An interrogator comprising a sensitivity setting circuit for setting the receiving sensitivity of the receiving circuit. The interrogator according to claim 1,
The sensitivity setting circuit includes a user interface that receives designation of the reception sensitivity, and the sensitivity setting circuit includes a circuit that sets the reception sensitivity of the reception circuit so that the reception sensitivity is received from the user interface. Interrogator characterized by that. The interrogator according to claim 1,
A signal strength measuring circuit that outputs a signal indicating the strength of the received signal based on the response radio wave;
The interrogator, wherein the sensitivity setting circuit includes a circuit that automatically sets the reception sensitivity of the reception circuit in accordance with the signal output from the signal strength measurement circuit. The interrogator according to claim 4, wherein
The circuit that automatically sets the reception sensitivity obtains a threshold value based on the sum of the noise intensity included in the reception signal of the reception circuit and the signal-to-noise ratio required by the demodulation unit. An interrogator comprising a circuit for attenuating the signal strength of the received signal by a value obtained by subtracting the threshold value from the signal strength measured by the signal strength measuring circuit. The interrogator according to any one of claims 1 to 4,
The reception circuit includes a low noise amplification circuit that amplifies a reception signal based on the response radio wave, and the sensitivity setting circuit switches whether the reception signal is amplified by the low noise amplification circuit or not. An interrogator comprising a circuit for setting reception sensitivity. The interrogator according to claim 5, wherein
The interrogator, wherein the sensitivity setting circuit includes a circuit that sets a reception sensitivity of the reception circuit by controlling a gain of the low noise amplifier. The interrogator according to any one of claims 1 to 4,
The reception circuit includes an attenuator circuit that attenuates a reception signal based on the response radio wave, and the sensitivity setting circuit switches whether the reception signal based on the response radio wave is attenuated by the attenuator circuit or not. An interrogator comprising a circuit for setting reception sensitivity. The interrogator according to claim 7,
The interrogator, wherein the sensitivity setting circuit sets the reception sensitivity of the reception circuit by controlling an attenuation amount by the signal attenuation circuit. The interrogator according to any one of claims 1 to 4,
The reception circuit includes a low noise amplification circuit that amplifies the reception signal based on the response radio wave, and an attenuator circuit that attenuates the reception signal based on the response radio wave,
Whether the sensitivity setting circuit only amplifies the reception signal based on the response radio wave by the low noise amplification circuit, or passes the reception signal based on the response radio wave only to the attenuator, or the low noise amplification circuit of the reception signal An interrogator comprising a circuit for switching to any state of whether to amplify by the attenuator or to attenuate by the attenuator circuit. The interrogator according to claim 9, wherein
The interrogator characterized in that the sensitivity setting circuit includes a circuit for controlling a gain of the low-noise amplifier circuit and an attenuation amount of the attenuator circuit. The interrogator according to any one of claims 1 to 10,
The interrogator is an IC tag in RFID, and the interrogator is an RFID reader device that reads the stored information from the IC tag. The interrogator according to claim 3,
The interrogator characterized in that the signal strength measuring circuit is an RSSI (Radio Signal Strength Indicator) circuit. The interrogator according to claim 4, wherein
The threshold is a value obtained by adding a predetermined offset value to a value obtained from the sum of the noise intensity and the signal-to-noise ratio. A transmission circuit that transmits a request radio wave that transmits stored information stored in the responder, and a reception circuit that receives and demodulates the response radio wave transmitted from the responder that has received the request radio wave,
The interrogator reception sensitivity setting method, wherein the reception circuit includes a low noise amplification circuit that amplifies a reception signal based on the response radio wave, and an attenuator circuit that attenuates the reception signal based on the response radio wave. ,
Whether the sensitivity setting circuit only amplifies the reception signal based on the response radio wave by the low noise amplification circuit, or passes the reception signal based on the response radio wave only to the attenuator, or the low noise amplification circuit of the reception signal Switch to either state to amplify by the attenuator or to attenuate by the attenuator circuit, and set the receiving sensitivity by controlling the gain of the low noise amplifier circuit and the attenuation amount of the attenuator circuit This is a method for setting the reception sensitivity of the interrogator.

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