JP2001358609A - Interrogator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase communicating distance between an interrogator and a transponder. SOLUTION: A modulation signal, to be input to a modulator 7 of the interrogator 2, is regulated in an amplitude offset regulator, so that a modulation factor of a transmission signal becomes maximum. The communicating distance between the interrogator 2 and the transponder 3 can always be increased by maximizing the modulation factor of a modulated wave, even when the detecting sensitivity of the transponder 3 is the same, by incorporating a circuit configuration at the interrogator 2 side without having to incorporate an additional circuit for raising the detecting sensitivity in the transponder 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving object discriminating apparatus capable of expanding a demodulatable area of a transponder by correcting a modulation degree of a modulated wave in a transmission circuit system of an interrogator.

[0002]

2. Description of the Related Art Conventionally, remote control using microwaves
BACKGROUND ART A moving object identification device is known as a device for identifying a moving object such as a moving object or a person. This mobile unit identification device includes an interrogator installed as a base station and a transponder attached to the mobile unit. When writing a signal to the transponder, the transponder detects and demodulates the signal transmitted from the interrogator, and when the interrogator reads out the information held by the transponder, the interrogator sends out a carrier wave and the transponder transmits an internal signal. According to the information, modulation is performed by reflecting and absorbing the carrier wave, and the modulated signal is transmitted to the interrogator as a modulated signal.

[0003] As a transponder used in the above-described moving object identification device, a configuration described in Japanese Patent Application Laid-Open No. 5-143799 is known.

FIG. 5 shows the configuration of this system. This conventional transponder 20 guides a microwave from an interrogator (not shown) from a composite double-sided microstrip antenna 21 to a microstrip directional coupler 23 through a microwave waveguide 22, and the microstrip directional coupler 23 Microwave modulator 28 as modulation means
The received microwaves are distributed to and processed by the controller 24 as the detecting means.

[0005]

In the prior art, the microstrip directional coupler 23 is used as a means for distributing the received microwave to the detecting means and the modulating means. There is a problem that the received microwave is attenuated, a power loss occurs due to distribution, a detection level of the detection unit is reduced, and as a result, a communication area between the interrogator and the transponder is narrowed. Further, the transponder needs to have a small, low-cost, and low-power-consumption circuit configuration in order to be mounted on a moving body, and a simple modulation / demodulation circuit configuration is required.
Therefore, it is difficult to take a circuit that requires a large amount of power to increase the sensitivity or a complicated circuit configuration.

The signal received by the transponder from the interrogator usually has a burst waveform and depends on the cycle of the burst wave. If the level of the modulation signal to the modulator of the interrogator is not appropriate, the modulation factor Is deteriorated, and as a result, the communication area between the interrogator and the transponder becomes narrow.

Therefore, in order to solve such a problem, instead of increasing the sensitivity of the transponder, the degree of modulation of the modulated wave of the interrogator, which greatly depends on the detection sensitivity of the transponder, is always optimized. An object of the present invention is to increase the communication distance between the interrogator and the transponder by adjusting the level of the modulation signal and compensating for the low detection sensitivity of the transponder.

[0008]

According to the present invention, there is provided a control / memory section for controlling an interrogator and storing data, inputting data from the control / memory section, and applying an amplitude to the data. And an amplitude / offset adjustment unit for setting an offset and an offset, a modulation unit for generating a modulation wave based on a carrier and the amplitude / offset adjustment unit, and a unit for amplifying the modulation wave and sending it as a transmission signal. An interrogator characterized by the following.

According to the present invention, the amplitude and the offset amount of the transmission signal input to the modulator of the interrogator of the mobile object identification device are always adjusted to be optimal, and the modulation of the modulated wave transmitted by the interrogator is performed. By optimizing the degree, it is possible to increase the communication distance.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION
A control / memory unit for storing control and data of the interrogator, an amplitude / offset adjusting unit which receives data from the control / memory unit, and sets an amplitude and an offset to the data, a carrier and the amplitude / offset adjusting unit And a means for amplifying the modulated wave and transmitting the signal as a transmission signal, the transmission signal being input to the modulation unit of the interrogator. The communication distance can be extended by adjusting the amplitude and the offset amount of the interrogator so as to always be optimal and optimizing the degree of modulation of the modulated wave transmitted by the interrogator.

According to a second aspect of the present invention, a memory table storing the amplitude and the offset value of the amplitude / offset adjusting unit of the interrogator is provided in the control / memory unit of the interrogator according to the number of transponders. The mobile object identification device according to claim 1, wherein the amplitude / offset adjustment unit is adjusted. The amplitude and offset amount of a transmission signal input to a modulation unit of an interrogator of the mobile object identification device are adjusted. Adjustment is always made to be optimal, and by optimizing the degree of modulation of the modulated wave transmitted by the interrogator, the communication distance can be extended.

According to a third aspect of the present invention, a part of the output of the modulation unit of the interrogator is branched, a modulation degree detection unit for detecting a modulation degree is provided, and amplitude / offset adjustment is performed using an output value of the modulation degree detection unit. The mobile unit identification apparatus according to claim 1, wherein the amplitude and the offset amount of the transmission signal input to the modulator of the interrogator of the mobile identification apparatus are always optimized. By making adjustments as described above and optimizing the degree of modulation of the modulated wave transmitted by the interrogator, the communication distance can be extended.

According to a fourth aspect of the present invention, there is provided the moving object identification apparatus according to the third aspect, wherein a part of the output of the modulator of the interrogator is branched by a directional coupler.
Adjust the amplitude and offset amount of the transmission signal input to the modulator of the interrogator of the mobile object identification device so that it is always optimal,
By optimizing the degree of modulation of the modulated wave transmitted by the interrogator, the communication distance can be extended.

According to a fifth aspect of the present invention, there is provided the moving object identification apparatus according to the third aspect, wherein a part of the output of the modulator of the interrogator is branched by a branch line. Extending the communication distance by adjusting the amplitude and offset of the transmission signal input to the modulator of the interrogator of the identification device so that they are always optimal, and optimizing the degree of modulation of the modulated wave transmitted by the interrogator Is possible.

According to a sixth aspect of the present invention, there is provided the moving object identification device according to the third aspect, further comprising the modulation degree detecting section that detects a modulation wave by detecting a modulation wave with a diode.
Adjust the amplitude and offset amount of the transmission signal input to the modulator of the interrogator of the mobile object identification device so that it is always optimal,
By optimizing the degree of modulation of the modulated wave transmitted by the interrogator, the communication distance can be extended.

According to a seventh aspect of the present invention, there is provided the moving object identifying apparatus according to the sixth aspect, wherein the diode detection is detected by a half-wave voltage doubler method. By adjusting the amplitude and offset amount of the transmission signal input to the modulation unit to be always optimal and optimizing the degree of modulation of the modulated wave transmitted by the interrogator, the communication distance can be extended. Having.

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

Embodiment 1 Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a configuration of a mobile object identification device, wherein 1 is a mobile object identification device, 2
Is an interrogator, 3 is a responder, 4 is a control / memory unit, 5 is a high-frequency signal generator, 6 is an amplitude / offset adjuster, 7 is a modulator, 8 is a power amplifier, 9 is a transmitting antenna, and 10 is a signal. Processing unit, 11 is a demodulation unit, 12 is a reception amplification unit, 13 is a reception antenna, 14 is a transmission / reception antenna, 15 is a modulation / demodulation unit, 16
Denotes a control / memory unit.

The operation of the above configuration will be described below. The interrogator 2 to the responder 3 in the mobile object identification device 1
When writing data to the high-frequency signal generator, the control / memory unit 4 of the interrogator 2 outputs data for the high-frequency signal generator 5 to generate a high-frequency signal of a desired frequency to the high-frequency signal generator, and modulates the amplitude of the modulation signal. • Output to the offset adjustment unit 6. The amplitude / offset adjustment unit 6 adjusts the amplitude and offset of the amplitude of the modulation signal to an optimum value that maximizes the modulation factor, and inputs the modulation signal to the modulation unit 7. The modulation unit 7 mixes the high-frequency signal output from the high-frequency signal generation unit and the modulation signal output from the amplitude / offset adjustment unit, and modulates the high-frequency signal.

Further, the high frequency signal is amplified to a desired power value in the power amplifier 8 and transmitted from the transmitting antenna 9 to the transponder 3. The transponder 3 receives the high-frequency signal from the interrogator at the transmission / reception antenna 14, demodulates the high-frequency signal at the modulation / demodulation unit 15, and writes the demodulated data to the control / memory unit 16. Also, when the interrogator 2 reads data from the responder 3 in the mobile unit identification device 1, the control / memory unit 4 of the interrogator stores data for the high-frequency signal generator 5 to generate a high-frequency signal of a desired frequency. Is output to the high-frequency signal generator and the modulated signal is output to the amplitude / offset adjuster 6.

Here, the modulation signal is a high or low DC signal only during this read operation. The amplitude / offset adjusting unit 6 sets the amplitude of the modulation signal and the offset of the amplitude to a voltage value such that the modulation unit 7 is always in the operating state. The modulation unit 7 mixes the high-frequency signal output from the high-frequency signal generation unit and the modulation signal output from the amplitude / offset adjustment unit, and outputs an unmodulated high-frequency signal. Further, the power amplifier 8 amplifies the high-frequency signal to a desired power value and transmits the signal from the transmission antenna 9 to the transponder 3. In the transponder 3, the high-frequency signal from the interrogator is transmitted and received by the transmitting / receiving antenna 14.
The modem 15 modulates the high-frequency signal based on the data received by the control and memory unit 16,
The signal is transmitted from the transmitting / receiving antenna 14 to the interrogator 2 again. The receiving antenna 3 of the interrogator 2 receives the modulated signal from the transponder, amplifies the modulated signal in the receiving amplifier 12, and
The signal is demodulated by the demodulation unit 11, the signal is processed by the signal processing unit 10, and the data is stored in the control / memory unit.

As described above, according to the first embodiment, the amplitude and the offset amount of the transmission signal input to the modulator of the interrogator of the mobile object identification device are always adjusted to be optimal, and the transmission of the interrogator is performed. By optimizing the degree of modulation of the modulated wave, the communication distance can be increased.

(Embodiment 2) Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a diagram showing a configuration of a mobile object identification device, wherein 1 is a mobile object identification device, 2
Is an interrogator, 3 is a responder, 4 is a control / memory unit, 5 is a high-frequency signal generator, 6 is an amplitude / offset adjuster, 7 is a modulator, 8 is a power amplifier, 9 is a transmitting antenna, and 10 is a signal. Processing unit, 11 is a demodulation unit, 12 is a reception amplification unit, 13 is a reception antenna, 14 is a transmission / reception antenna, 15 is a modulation / demodulation unit, 16
Denotes a control / memory unit, and 17 denotes a memory table.

The operation of the above configuration will be described below. The interrogator 2 to the responder 3 in the mobile object identification device 1
When writing data to the high-frequency signal generator, the control / memory unit 4 of the interrogator 2 outputs data for the high-frequency signal generator 5 to generate a high-frequency signal of a desired frequency to the high-frequency signal generator, and outputs the modulation signal and the memory. The data in the table 17 is output to the amplitude / offset adjustment unit 6.

Here, in order to communicate simultaneously with a plurality of transponders existing in the communication area, there is a method of dividing a communication frame of a certain length into a plurality of slots and performing time division. Each of the plurality of transponders selects one of the time-divided slots and performs communication. However, when a plurality of transponders respond to one slot and communication with the plurality of transponders cannot be performed efficiently due to interference. There is. Therefore, in order to perform communication with high efficiency, it is necessary to optimize the length of the communication frame and the number of slots for dividing the frame according to the number of transponders. Therefore, the period of the transmission burst signal waveform of the interrogator changes according to the number of transponders, and the average amplitude of the modulation signal changes. Therefore, it is necessary to adjust the modulation degree of the modulation unit each time. Here, in the memory table, the amplitude and the amplitude at which the degree of modulation is optimum are set in accordance with the number of transponders that communicate with the interrogator 2 at a time, which are set in the mobile identification device 1.
Offset value is stored.

Therefore, depending on the system to be applied, by inputting the number of transponders that pass through the communication area at one time by an external terminal or by switching a switch, the optimal transponder stored in the memory table 17 is obtained. The amplitude / offset is selected, and the amplitude / offset adjustment unit 6 adjusts the amplitude and offset of the amplitude of the modulation signal to the optimum values to maximize the modulation degree by using the data from the memory table 17, and modulates the modulation signal. The modulation signal is input to the unit 7. The modulation unit 7 mixes the high-frequency signal output from the high-frequency signal generation unit and the modulation signal output from the amplitude / offset adjustment unit, and modulates the high-frequency signal.

Further, the high frequency signal is amplified to a desired power value in the power amplifier 8 and transmitted from the transmitting antenna 9 to the transponder 3. The transponder 3 receives the high-frequency signal from the interrogator at the transmission / reception antenna 14, demodulates the high-frequency signal at the modulation / demodulation unit 15, and writes the demodulated data to the control / memory unit 16.

The transponder 3 in the mobile unit identification device 1
When the interrogator 2 reads data from the controller, the control / memory unit 4 of the interrogator outputs data for the high-frequency signal generation unit 5 to generate a high-frequency signal of a desired frequency to the high-frequency signal generation unit, The modulation signal is output to the amplitude / offset adjustment unit 6.

Here, the modulation signal is a high or low DC signal only during this read operation. The amplitude / offset adjustment unit 6 sets the amplitude and offset of the amplitude of the modulation signal to a voltage value such that the modulation unit 7 is always in an operating state. The modulation unit 7 mixes the high-frequency signal output from the high-frequency signal generation unit and the modulation signal output from the amplitude / offset adjustment unit, and outputs an unmodulated high-frequency signal.

Further, the power amplifier 8 amplifies the high-frequency signal to a desired power value and transmits the signal from the transmitting antenna 9 to the transponder 3. In the transponder 3, the high-frequency signal from the interrogator is received by the transmission / reception antenna 14, and the modulation / demodulation unit 15 modulates the high-frequency signal based on the data held in the control / memory unit 16 and retransmits the transmission / reception antenna 14 To the interrogator 2. The receiving antenna 3 of the interrogator 2 receives the modulated signal from the transponder, amplifies the modulated signal in the receiving amplifier 12, demodulates the signal in the demodulator 11, performs signal processing in the signal processor 10, control·
The data is stored in the memory unit.

As described above, according to the second embodiment, the amplitude and the offset amount of the transmission signal input to the modulator of the interrogator of the mobile object identification device are always adjusted to be optimal, and the transmission of the interrogator is performed. By optimizing the degree of modulation of the modulated wave, the communication distance can be increased.

(Embodiment 3) Embodiment 3 of the present invention will be described with reference to FIG. FIG. 3 is a diagram showing a configuration of the mobile object identification device 1, where 1 is a mobile object identification device,
2 is an interrogator, 3 is a transponder, 4 is a control / memory section, 5 is a high-frequency signal generation section, 6 is an amplitude / offset adjustment section, 7 is a modulation section, 8 is a power amplification section, 9 is a transmission antenna, and 10 is a transmission antenna. A signal processing unit, 11 a demodulation unit, 12 a reception amplification unit, 13 a reception antenna, 14 a transmission / reception antenna, 15 a modulation / demodulation unit, 1
6 is a control / memory unit, 18 is a modulation degree detecting unit, and 30 is a distributor.

The operation of the above configuration will be described below. The interrogator 2 to the responder 3 in the mobile object identification device 1
When writing data to the high-frequency signal generator, the control / memory unit 4 of the interrogator 2 outputs data for the high-frequency signal generator 5 to generate a high-frequency signal of a desired frequency to the high-frequency signal generator, and modulates the amplitude of the modulation signal. • Output to the offset adjustment unit 6.

The amplitude / offset adjustment section adjusts the amplitude and offset of the modulation signal with the initially set initial value, and outputs the result to the modulation section 7. The modulation unit 7 mixes the high-frequency signal output from the high-frequency signal generation unit and the modulation signal output from the amplitude / offset adjustment unit, and modulates the high-frequency signal. The output of the modulator 7 is supplied to a divider 30
The modulation degree is then distributed to the power amplifying section 8 and the modulation degree detecting section 18. The modulation degree detecting section 18 detects the modulation degree of the output of the modulation section 7 and, if it is out of the desired modulation degree, an amplitude / offset adjusting section. In step 6, the amplitude of the modulation signal and the offset of the amplitude are adjusted to be optimal, and the modulation signal is input to the modulation unit 7.

The power amplifier 8 amplifies the high-frequency signal to a desired power value, and transmits the signal from the transmitting antenna 9 to the transponder 3. The transponder 3 receives the high-frequency signal from the interrogator at the transmission / reception antenna 14, demodulates the high-frequency signal at the modulation / demodulation unit 15, and writes the demodulated data to the control / memory unit 16. Also, when the interrogator 2 reads data from the responder 3 in the mobile unit identification device 1, the control / memory unit 4 of the interrogator stores data for the high-frequency signal generator 5 to generate a high-frequency signal of a desired frequency. Is output to the high-frequency signal generator and the modulated signal is output to the amplitude / offset adjuster 6.

Here, the modulation signal is a high or low DC signal only during this read operation. The amplitude / offset adjustment unit 6 sets the amplitude and offset of the amplitude of the modulation signal to a voltage value such that the modulation unit 7 is always in an operating state. The modulation unit 7 mixes the high-frequency signal output from the high-frequency signal generation unit and the modulation signal output from the amplitude / offset adjustment unit, and outputs an unmodulated high-frequency signal.

Further, the high frequency signal is amplified to a desired power value in the power amplification section 8 and transmitted from the transmission antenna 9 to the transponder 3. In the transponder 3, the high-frequency signal from the interrogator is received by the transmission / reception antenna 14, and the modulation / demodulation unit 15 modulates the high-frequency signal based on the data held in the control / memory unit 16, and retransmits the transmission / reception antenna 14 To the interrogator 2. The receiving antenna 3 of the interrogator 2 receives the modulated signal from the transponder, amplifies the modulated signal in the receiving amplifier 12, demodulates the signal in the demodulator 11, performs signal processing in the signal processor 10, control·
The data is stored in the memory unit.

As described above, according to the third embodiment, the amplitude and the offset amount of the transmission signal input to the modulator of the interrogator of the mobile object identification device are adjusted to always be optimal, and the transmission of the interrogator is performed. By optimizing the degree of modulation of the modulated wave, the communication distance can be increased.

The divider for distributing the output of the modulator 7 may be attacked by a directional coupler or a branch line. Further, the modulation degree detection unit may detect the modulation degree by detecting the modulation wave by a diode or by detecting the diode detection by a half-wave voltage method.

(Embodiment 4) Embodiment 4 of the present invention will be described with reference to FIG. FIG. 4 is a diagram showing a configuration of the mobile object identification device 1, where 1 is a mobile object identification device,
2 is an interrogator, 3 is a transponder, 4 is a control / memory unit, 5 is a high-frequency signal generation unit, 6 is an amplitude / offset adjustment unit, 7 is a modulation unit, 8 is a power amplification unit, 9 is a transmission antenna, and 10 is a transmission antenna. A signal processing unit, 11 a demodulation unit, 12 a reception amplification unit, 13 a reception antenna, 14 a transmission / reception antenna, 15 a modulation / demodulation unit, 1
6 is a control / memory section, and 19 is a modulation degree detecting section.

The operation of the above configuration will be described below. The interrogator 2 to the responder 3
When writing data to the high-frequency signal generator, the control / memory unit 4 of the interrogator 2 outputs data for the high-frequency signal generator 5 to generate a high-frequency signal of a desired frequency to the high-frequency signal generator, and modulates the amplitude of the modulation signal. • Output to the offset adjustment unit 6. The amplitude / offset adjustment unit 6 adjusts the amplitude and offset of the amplitude of the modulation signal to an optimum value that maximizes the modulation factor, and inputs the modulation signal to the modulation unit 7. The modulation unit 7 mixes the high-frequency signal output from the high-frequency signal generation unit and the modulation signal output from the amplitude / offset adjustment unit, and modulates the high-frequency signal.

Further, the power amplifier 8 amplifies the high-frequency signal to a desired power value and transmits it from the transmitting antenna 9 to the transponder 3. In the transponder 3, the high-frequency signal from the interrogator is received by the transmission / reception antenna 14, the high-frequency signal is demodulated by the modulation / demodulation unit 15, and the modulation degree detection unit 19 detects the modulation degree of the modulated wave from the interrogator.

The detected modulation degree is written in the control / memory section 16 together with the demodulated data. Next, when the interrogator 2 reads data from the transponder 3 in the mobile object identification device 1, the control / memory unit 4 of the interrogator is used by the high frequency signal generator 5 to generate a high frequency signal of a desired frequency. The data is output to the high-frequency signal generator and the modulated signal is output to the amplitude / offset adjuster 6.

Here, only at the time of this read operation, the modulation signal is a high or low DC signal. The amplitude / offset adjustment unit 6 sets the amplitude and offset of the amplitude of the modulation signal to a voltage value such that the modulation unit 7 is always in an operating state. The modulation unit 7 mixes the high-frequency signal output from the high-frequency signal generation unit and the modulation signal output from the amplitude / offset adjustment unit, and outputs an unmodulated high-frequency signal.

Further, the power amplifier 8 amplifies the high-frequency signal to a desired power value and transmits it from the transmitting antenna 9 to the transponder 3. In the transponder 3, the high-frequency signal from the interrogator is received by the transmission / reception antenna 14, and the modulation / demodulation unit 15 modulates the high-frequency signal based on the demodulation data and the modulation factor data held in the control / memory unit 16. Are transmitted from the transmitting / receiving antenna 14 to the interrogator 2 again.

The receiving antenna 3 of the interrogator 2 receives the modulated signal from the transponder, amplifies the modulated signal at the receiving amplifier 12, demodulates the signal at the demodulator 11, and performs signal processing at the signal processor 10. Then, the data is stored in the control / memory unit.
Furthermore, if the modulation factor data does not satisfy the desired value based on the modulation factor data from the transponder, the amplitude / offset adjustment unit is adjusted to be optimal.

As described above, according to the fourth embodiment, the amplitude and the offset amount of the transmission signal input to the modulator of the interrogator of the mobile unit identification apparatus are adjusted to always be optimal, and the transmission of the interrogator is performed. By optimizing the degree of modulation of the modulated wave, the communication distance can be increased.

[0048]

As described above, according to the present invention, the amplitude and offset of the transmission signal input to the modulator of the interrogator of the mobile object identification device are adjusted to always be optimal, and the transmission of the interrogator is performed. By optimizing the degree of modulation of the modulated wave, the communication distance can be extended.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a moving object identification device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a moving object identification device according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a moving object identification device according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a moving object identification device according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional moving object identification device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Moving body identification apparatus 2 Interrogator 3 Transponder 4 Control / memory part 5 High frequency signal generation part 6 Amplitude / offset adjustment part 7 Modulation part 8 Power amplification part 9 Transmission antenna 10 Signal processing part 11 Demodulation part 12 Reception amplification part 13 Reception Antenna 14 Transmission / reception antenna 15 Modulation / demodulation unit 16 Control / memory unit 17 Memory table 18 Modulation degree detection unit 19 Modulation degree detection unit 20 Transponder 21 Composite double-sided microstrip antenna 22 Microwave waveguide 23 Microstrip directional coupler 24 Controller 26 Information pulse Generator 27 Microwave waveguide 28 Microwave modulator 29 Card built-in battery 30 Distributor

Claims (8)

[Claims] 1. An interrogator control and data storage control
A memory unit and data of the control / memory unit as inputs,
An amplitude / offset adjusting unit that sets an amplitude and an offset to the data; a modulating unit that generates a modulated wave based on a carrier wave and the amplitude / offset adjusting unit; and amplifies the modulated wave and sends out the signal as a transmission signal. And an interrogator. 2. The method according to claim 1, wherein a memory table storing the amplitude and the offset value of the amplitude / offset adjusting unit is provided in the control / memory unit according to the number of transponders, and the amplitude / offset adjusting unit is adjusted. The interrogator according to item 1. 3. A modulation degree detecting section for branching a part of the output of the modulation section and detecting a modulation degree, and adjusting an amplitude / offset adjusting section using an output value of the modulation degree detecting section. The interrogator according to item 1. 4. The interrogator according to claim 3, wherein a part of the output of the modulator is branched by a directional coupler. 5. The interrogator according to claim 3, wherein a part of the output of the modulator is branched by a branch line. 6. The interrogator according to claim 3, further comprising a modulation degree detecting section for detecting a modulation wave by detecting a modulation wave with a diode. 7. The interrogator according to claim 6, wherein the diode detection is performed by a half-wave voltage multiplication method. 8. A means for receiving modulation degree information detected by a transponder and demodulating the modulation degree information, and a control / memory means for calculating an amplitude and an offset amount of data to be transmitted from an output of the means. And an amplitude / offset adjusting unit for adding the amplitude / offset amount set by the control / memory means to the data.