JPH0836053A - Responder of moving body discriminating device - Google Patents

Abstract

PURPOSE:To make a responder function in two methods, by converting the responder to apply both to the case to use an unmodulated carrier wave from an interrogator, and the case to use a carrier wave generated by the responder. CONSTITUTION:When an unmodulated carrier wave from an interrogator is used, the input impedance of an oscillator 25 is converted to be infinite, and the nonpass and the pass of a diode 23 are switched according to the level of the receiving signal. And in case of the nonpass, the received unmodulated wave is reflected at the input end of the diode 23 and transmitted to the space. And in case of the pass, the wave passes through the diode 23, it is reflected at the input end of the oscillator 25, and the modulated wave having the phase difference pi is transmitted through a transmission passage 24 set at the wavelength lambda. Consequently, the carrier wave is modulated into two conditions having the phase difference pi of the carrier wave. And when the carrier wave generated by the responder is used, the oscillator 25 is made in the line impedance, the carrier wave output by the oscillator 25 is output to the diode 23, and the pass, the cutoff, and the amplitude modulation are applied to an antenna 21 according to the two values of modulation signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transponder in a moving body identifying apparatus. INDUSTRIAL APPLICABILITY The transponder of the present invention is installed in a moving body such as an automobile and can be applied to a system for charging an automobile passing through a toll road without stopping at a gate.

[0002]

2. Description of the Related Art For example, as an automatic charging system for toll roads, there is known a moving body identifying device in which an interrogator is arranged at a toll gate on the toll road and a responder is arranged in an automobile. In this system, an interrogator transmits an interrogation signal in which a carrier wave is ASK or PSK modulated, the interrogator receives the interrogation signal, and in response to the interrogation signal, an identification code of the own vehicle is transmitted from the interrogator to the interrogator. However, the computer that controls the interrogator performs charge management for each vehicle.

In this case, there are two methods of generating a carrier wave when transmitting a response signal from the transponder to the interrogator. One method is that the interrogator inserts an unmodulated carrier into the modulated interrogation signal in a time division manner, and the transponder receives the unmodulated carrier and sends the unmodulated carrier to ASK or PS.
It is a method of K-modulating and retransmitting to the interrogator. This method does not require an oscillator for generating a carrier wave in the transponder, and therefore has a low power loss, and is a desirable method for installation in a mobile unit that cannot freely take power.

In another method, an interrogator does not transmit an unmodulated carrier, but an responder is provided with an oscillator for generating a carrier, and the carrier generated by this oscillator is ASK or PSK.
It is a method of modulating and transmitting to the interrogator. Although this method simplifies the construction of the interrogator, it requires an oscillator for the responder, resulting in a large power loss of the responder.

[0005]

As described above, there are two methods for generating a carrier wave, and which method is adopted is different for each highway. Therefore, the transponder installed in the mobile unit can be used for any method, and the circuit of the method that modulates the unmodulated carrier wave transmitted from the interrogator and the carrier wave generated by its own oscillator are transmitted. It was necessary to have two circuits including a circuit of a system that does.

Therefore, the manufacturing process becomes complicated and the manufacturing cost becomes high, and there is a problem in terms of the efficiency of circuit equipment utilization. Moreover, the detection circuit and the modulation circuit are often shared by a diode or the like. However, in this case, it is necessary to separately adjust the detection circuit and the modulation circuit, and it is difficult to adjust when connecting to a common antenna. The present invention has been made to solve the above problems, and a first object thereof is to enable a transponder to be adapted to the above two methods with a simple structure. The second purpose is to facilitate the adjustment of the transponder.

[0007]

In order to solve the above problems, the structure of the invention of claim 1 is an antenna for receiving an inquiry signal, or an inquiry signal and a first carrier wave, and transmitting a response signal, An oscillator that generates a second carrier wave, a modulator that is arranged between the antenna and the oscillator, and switches between a passing state and a non-passing state according to a binary modulation signal, and the input impedance of the oscillator is infinite with the line impedance. Switching means for switching between high and low, and the first when the modulator is in a non-passing state
The effective line length from the reflection point of the carrier wave to the reflection point of the first carrier wave when the modulated signal is in the passing state and the input impedance of the oscillator is infinite is (2n-1) λ with respect to the line wavelength λ of the first carrier wave. / 4 (n is an integer) and the interrogator transmits the first carrier, the input impedance of the oscillator is set to infinity and the modulator passes and does not pass. Phase-modulates the first carrier wave received by the movement of the reflection point that switches according to
In the case where the interrogator does not transmit the first carrier wave, the input impedance of the oscillator is set to the line impedance and the second carrier wave output from the oscillator passes through the modulator and does not pass through the modulator according to the binary modulation signal. By switching to the state, the second carrier is amplitude-modulated and transmitted.

Further, the invention of claims 2 and 3 is to provide a control means for controlling the switching means by the presence / absence of reception of an unmodulated carrier wave and a command of an inquiry signal.

According to a fourth aspect of the invention, an antenna for receiving the interrogation signal and the unmodulated carrier from the interrogator, a detection circuit for detecting the interrogation signal, and the unmodulated carrier received from the interrogator based on the response signal. A modulation circuit for modulation and a detection circuit and a modulation circuit for the antenna are connected in a state where impedance matching is performed with respect to the line impedance, and one of the detection circuit and the modulation circuit is selected, and the non-selected circuit is The circuit is characterized in that the impedance seen from the connection point to the antenna is infinite, and the selected circuit has a switching circuit whose line impedance is the impedance seen from the connection point to the antenna.

[0010]

[Operation and effect of the invention]

The invention of claim 1 In the case of the first method using an unmodulated carrier transmitted from the interrogator From the interrogator, the ASK or PSK-modulated response signal and the first carrier which is an unmodulated carrier are time-division-based for a fixed time. It is transmitted alternately at intervals. In this system, the transponder is controlled by the switching means so that the input impedance of the oscillator becomes infinite. At this time, a modulation signal of a binary signal is input to the modulator, and the modulator is switched between two states, a passing state and a non-passing state, according to the signal level.

Therefore, when the modulator is in the non-passing state, the unmodulated carrier wave received through the antenna is reflected at the reflection point (first reflection point) on the input side of the modulator, and the space through the antenna. Sent to. On the other hand, when the modulator is in the passing state, the unmodulated carrier wave received via the antenna passes through the modulator and is reflected at the reflection point (second reflection point) on the input side of the oscillator, and the reflected wave is the modulator. And is radiated into space from the antenna. At this time, the effective line length between the first reflection point and the second reflection point in the phase shift means is set to (2n-1) λ / 4 (n is an integer) using the line wavelength λ. The phase shifting means may be composed of a phase shifting circuit instead of a simple line.

Therefore, the phase of the wave reflected at the second reflection point at the first reflection point has a phase difference of π with respect to the phase of the wave reflected at the first reflection point. Therefore, the phase of the carrier wave differs by π depending on the L level and the H level of the modulated signal.
It is possible to modulate into two states. Like this PSK
Modulation is possible.

In the case of the second method in which the carrier generated by the own responder is used without using the unmodulated carrier transmitted from the interrogator, only the response signal which is ASK or PSK modulated is transmitted from the interrogator, and the unmodulated carrier is transmitted. Is not sent. The responder is this second
In the case of the system, the input impedance of the oscillator is the line impedance, and the second carrier wave output from the oscillator is output to the modulator. The modulator performs amplitude modulation (ASK) by transmitting and blocking the second carrier wave to and from the antenna according to the binary modulation signal, and transmits from the antenna.

As described above, the circuit configuration can be made common, and a transponder which can be used in both types can be easily constructed only by controlling by the switching means. Therefore, even when both systems are mixed such as a toll road charging system, it is possible to configure a responder that effectively functions with a simple device configuration.

The invention according to claims 2 and 3 The control means, after decoding the interrogation signal, determines whether or not an unmodulated carrier is received. Then, the switching means is controlled according to the determination result. Further, the control means controls the switching means according to the command of the inquiry signal. In this case, the interrogator incorporates identification data indicating the first system or the second system into the interrogation signal. In this way, regardless of the system adopted by the interrogator, the transponder can be automatically recombined into a circuit adapted to that system to transmit a response signal.

According to the invention of claim 4, at the time of adjusting the transponder, a measuring instrument is connected instead of the antenna. Then, the switching circuit is activated to measure the characteristics of the detection circuit and the modulation circuit independently. At this time, when measuring the characteristics of the detection circuit or the modulation circuit with a measuring instrument, the detection circuit and the modulation circuit have impedance matching with the line in each state, so accurate measurement of the characteristics is possible. Is possible.

[0017]

EXAMPLES The present invention will be described below based on specific examples. FIG. 1 is a block diagram showing the configuration of the transponder 20 of this embodiment. The interrogator 10 is classified into the following two transmission methods according to the signal transmission form of the interrogator 10. That is, as shown in FIG. 2, the interrogator 10 alternately transmits the carrier wave modulated in the period T1 and the unmodulated carrier wave in the period T2, and as shown in FIG. The interrogator 10 transmits the carrier wave modulated in the period T1,
In the period T2, there is a second system in which the response signal from the transponder 20 is only received and the carrier wave is not transmitted alternately.

The interrogator 10 has an antenna 12 and a modulation / control device 11. This modulation / control device 11 carries out ASK or PSK modulation on the carrier wave with a binary modulation signal, and the DSB.
As a signal, it is transmitted to the space from the antenna 12.

The transponder 20 has an antenna 21 for receiving the interrogation signal S1 and the unmodulated carrier S2 or only the interrogation signal S1 and transmitting the modulated response signal S3. The antenna 21 is connected to the anode of the diode 23 via the transmission line 22, and the cathode of the diode 23 is connected to the oscillator 25 via the transmission line 24. The length of the transmission line 24 is λ / with respect to the line wavelength λ of the carrier.
It is set to 4. The anode and cathode of the diode 23 are the coil 28, the resistor 29, and the coil 30, respectively.
And is grounded through a resistor 31. The coil 28 and the capacitor 32, and the coil 30 and the capacitor 33 form a low-pass filter, and together with the diode 23 form an envelope detection circuit for the received signal. The anode of the diode 23 is connected to the power source V via the resistor 34 and the transistor Tr3.
Connected to _DD .

Further, the oscillator 25 is supplied with power from the power supply V _DD through the transistor Tr1, and the connection point between the coil 30 and the resistor 31 is supplied with power from the power supply V _DD through the transistor Tr2. The bases of the transistors Tr1 and Tr2 are C
ROM2 connected to PU26 and connected to CPU26
An identification code peculiar to its own responder is stored in 7.

Next, the operation of the transponder 20 will be described. As shown in FIG. 2, a case will be described in which the interrogator 10 uses the first method in which an unmodulated carrier (first carrier) is transmitted as a carrier for response. The responder 20 is in the reset state,
The transistors Tr1, Tr2, Tr3 are turned off. As a result, the cathode of the diode 23 is grounded via the resistor 31, so that no bias voltage is applied to the diode 23. Therefore, when the inquiry signal S1 shown in the period T1 of FIG. 2 is received from the antenna 21, the inquiry signal S1 is transmitted to the diode 23, the coils 28, 30,
The envelope detection circuit shown by the capacitors 32 and 33 performs envelope detection (that is, the carrier wave is cut off). The demodulated signal S4 (binary level signal) is input to the CPU 26.

This demodulated signal S4 is analyzed by a computer, and when it is determined that it is an interrogation signal, the period T shown in FIG.
The response signal S3 modulated in 2 is transmitted from the antenna 21. The procedure is as follows. When the reception of the inquiry signal S1 ends and the period T2 starts, the demodulation signal S4
Is fixed to the H level, and if it is fixed to the H level, it indicates that the unmodulated carrier S2 is received, and therefore the interrogator 10 is of the first system. Is determined.

In this case, the transistor Tr1 remains off, and the oscillator 25 is not supplied with power. After that, the CPU 26 reads its own identification code from the ROM 27 and generates a response signal S5 ((b) in FIG. 4) of binary data including the identification code. Then, the transistors Tr2 and Tr3 are on / off controlled based on the response signal S5. At this time, transistor Tr2 and transistor Tr3
And are controlled to be turned on and off alternately. When the transistor Tr2 is turned on and the transistor Tr3 is turned off, the power supply voltage V _DD is applied to the cathode of the diode 23, and the diode 23 is reversely biased via the resistor 29. Therefore, the diode 23 is in a non-passing state, the unmodulated carrier wave S2 received by the antenna 21 is reflected by the input terminal (first reflection point) a of the diode 23, and is transmitted to the space as the response signal S3 modulated by the antenna 21. Sent.

When the transistor Tr2 is turned off and the transistor Tr3 is turned on, the diode 23 is in the forward bias state. Therefore, the unmodulated carrier wave S2 is the diode 23
Through the transmission line 24, and is reflected by the input terminal (second reflection point) b of the oscillator 25 having an infinite input impedance. Then, this reflected wave is generated by the diode 2
3 is transmitted in the reverse direction, propagates through the transmission line 22, and is emitted from the antenna 21.

At this time, the effective line length of the transmission line 24 is λ / 4.
Therefore, the phase difference between the wave reflected at the first reflection point a and the wave reflected at the second reflection point b is π. As a result,
(A), the carrier wave is phase-modulated (PSK) by the response signal S5. The modulated response signal S3 is transmitted from the antenna 21 and received by the interrogator 10.

Next, as shown in FIG. 3, a case will be described in which the interrogator 10 uses the second method in which an unmodulated carrier is not transmitted as a carrier for response. The reception of the inquiry signal S1 in the period T1 is as described above. After the demodulated signal S4 is analyzed, if it is determined that the signal is an interrogation signal, FIG.
The response signal S3 modulated in the period T2 shown by is transmitted from the antenna 21. The procedure is as follows. When the reception of the inquiry signal S1 ends and the period T2 starts,
It is determined whether or not the demodulated signal S4 is fixed to the L level. If the demodulated signal S4 is fixed to the L level, it means that the unmodulated carrier wave is not received. It is determined that

In this case, the transistor Tr1 is turned on and power is supplied to the oscillator 25. And oscillator 2
A carrier wave (second carrier wave) is transmitted from 5. Then C
The PU 26 reads its own identification code from the ROM 27 and generates a response signal S5 of binary data containing the identification code. Then, the transistors Tr2 and Tr3 are on / off controlled based on the response signal S5. At this time, the transistors Tr2 and Tr3 are controlled to be turned on and off alternately.

Transistor Tr2 turns on and transistor
When the Tr3 is turned off, the power supply voltage V _DD is applied to the cathode of the diode 23, and the diode 2 passes through the resistor 29.
3 is reverse biased. Therefore, the diode 23
Becomes a non-passage state, and the carrier wave output from the oscillator 25 is blocked by the diode 23.

When the transistor Tr2 is turned off and the transistor Tr3 is turned on, the diode 23 is in a forward bias state. Therefore, the carrier wave generated by the oscillator 25 passes through the diode 23 and is transmitted to the space as a modulated response signal S3 from the antenna 21.

Eventually, the carrier wave is amplitude-modulated (ASK) by the response signal S5. The modulated response signal S3 is transmitted from the antenna 21 and received by the interrogator 10.

In the above embodiment, the first system and the second system are distinguished according to the presence or absence of the unmodulated carrier wave in the period T2. However, the interrogation signal S1 may be transmitted by including the code for identifying the system, and the interrogation signal S1 may be received and decoded to identify the two systems. Also, the transmission from the interrogator of the first type of unmodulated carrier is inserted in time division with respect to the interrogation signal, but by using a carrier of a frequency different from that of the interrogation signal or a carrier having a 90-degree phase difference. , May be transmitted in parallel with the inquiry signal.

In the above embodiment, the modulator is a diode 23, resistors 34, 29 and 31, transistors Tr2 and Tr3.
The switching means is a transistor Tr1, the phase shift means is a transmission line 24, and the control means is a CPU 26 and a ROM 27.

The circuit shown in FIG. 5 can be used as another modulator. That is, PIN diodes 54 and 55 whose directions are opposite to each other are connected in series, the cathode of the diode 54 is the transmission line 22, the card of the diode 55 is the transmission line 24, and the anodes of the diodes 54 and 55 are the coils 5.
8 is connected to the modulation signal output terminal D1 of the CPU 26. The cathodes of the diodes 54 and 55 are grounded via the coils 56 and 57, respectively.

The coils 56 and 57 constitute a low-pass filter for cutting direct current, and the coil 58 is the CPU 2
6 forms a low-pass filter for applying the response signal (modulation signal) S5. A demodulation circuit 60, which is an envelope detection circuit, is connected to the antenna 21, and the demodulation signal S4 is input to the CPU 26.

In the above circuit configuration, when the response signal S5 output from the CPU 26 is at H level, the coil 58
Both diodes 54 and 55 are forward biased via. As a result, the diodes 54 and 55 become conductive, and the unmodulated carrier wave is reflected at the second reflection point b. When the response signal S5 is at L level (earth level), the bias of the diodes 54 and 55 is removed, and the transmission line 22 and the transmission line 24 are separated by the diode 54. As a result, the unmodulated carrier wave is reflected at the first reflection point a. In this way, the CPU 26
The received carrier wave is PSK-modulated based on the binary response signal S5 output from the antenna 21 and transmitted as the response signal S3 from the antenna 21.

Next, the second embodiment will be described. In FIG. 6, the reception and transmission common antenna 41 is connected to a coaxial cable having a line impedance of 50Ω.
The point A is a branch point of the coaxial cable, and is branched into two at the point A, one of which is connected to the modulation circuit 42 and the other of which is connected to the detection circuit 43. Then, the modulation circuit 42 and the detection circuit 43
A switching circuit 44 is provided to supply power to and.

The input impedance of the modulation circuit 42 and the detection circuit 43 is 50Ω when power is supplied, and the input impedance is infinite when power is not supplied. Then, at the point A, the impedance viewed from the circuit side where the input impedance becomes infinite is designed to be 50Ω of the line impedance.

In this circuit, a measuring device is connected instead of the antenna 41. Then, the switching circuit 44 is operated to operate only one circuit. For example, even when power is supplied only to the modulation circuit 42, the impedance seen from the point A at the circuit side is 50Ω of the line impedance, and impedance matching is achieved with a measuring instrument having an input impedance of 50Ω. Therefore, the circuit characteristics of the circuits 42 and 43 can be easily measured.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a transponder according to a specific embodiment of the present invention.

FIG. 2 is a waveform diagram showing a waveform transmitted from an interrogator in the first method.

FIG. 3 is a waveform diagram showing a waveform transmitted from an interrogator in the second method.

FIG. 4 is a waveform diagram showing a modulated response signal transmitted from a transponder.

FIG. 5 is a circuit diagram showing the configuration of another modulator used in the responder.

FIG. 6 is a block diagram showing the configuration of another embodiment.

[Explanation of symbols]

 20 ... Responder 24 ... Transmission line 23 ... Diode 54, 55 ... PIN diode 26 ... CPU

Claims (4)

[Claims] 1. A first carrier, which is an unmodulated carrier received from the interrogator in response to an interrogation signal received from an interrogator which is arranged in a mobile unit and which is a ground station, or a transmission carrier generated by itself. In a transponder that modulates a second carrier wave and transmits it to the interrogator as a response signal, receiving an interrogation signal, or an interrogation signal and the first carrier wave,
An antenna for transmitting the response signal, an oscillator for generating the second carrier wave, and an antenna for transmitting a response signal are provided between the antenna and the oscillator, and a passing state and a non-passing state are set according to a binary modulation signal. A modulator for switching, a switching means for switching the input impedance of the oscillator between a line impedance and infinity, and a modulation signal in a passing state from a reflection point of the first carrier when the modulator is in a non-passing state. Further, the effective line length up to the reflection point of the first carrier when the input impedance of the oscillator is infinite is (2
n-1) λ / 4 (n is an integer) phase shift means, and, in the case of the system in which the interrogator transmits the first carrier, the input impedance of the oscillator is infinite, In a case where the interrogator does not transmit the first carrier wave, the first carrier wave is phase-modulated and transmitted by the movement of the reflection point that is switched according to the passing state and the non-passing state of the modulator. Sets the input impedance of the oscillator to a line impedance, and switches the second carrier wave output from the oscillator between a pass state and a non-pass state of the modulator according to a binary modulation signal. A transponder for a mobile body identification device, characterized in that a carrier wave is amplitude-modulated and transmitted. 2. The transponder, after receiving the interrogation signal,
When the first carrier wave is received, the input impedance of the oscillator is made infinite, and when the first carrier wave is not received, the control means for controlling the switching means so as to make the input impedance of the oscillator the line impedance. The transponder of the mobile body identification device according to claim 1, further comprising. 3. The transponder for a mobile body identification device according to claim 1, wherein the transponder has a control means for controlling the switching means in response to an instruction of the inquiry signal. 4. An unmodulated carrier wave received from said interrogator is modulated in response to an interrogation signal received from an interrogator which is arranged in a mobile station and is a ground station, and is transmitted to said interrogator as a response signal. In the transponder, an antenna that receives the interrogation signal and the non-modulated carrier from the interrogator, a detection circuit that detects the interrogation signal, and modulates the non-modulated carrier received from the interrogator based on the response signal. A modulation circuit and the detection circuit and the modulation circuit are connected to the antenna in a state of being impedance matched to the line impedance, and one of the detection circuit and the modulation circuit is selected and unselected. Circuit makes the impedance seen from the connection point to the antenna infinite, and the selected circuit changes the circuit from the connection point to the antenna. A transponder for a mobile body identification device, comprising: a switching circuit that uses the observed impedance as a line impedance.