JP2001345734A - Onboard transceiver for etc vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive onboard transceiver for ETC vehicle in which the size can be reduced. SOLUTION: A transmitting/receiving antenna 1 is connected alternatively with a receiving circuit 4 for detecting a receiving signal or a transmitting circuit 5 outputting a carrier by means of an antenna switch 3. The antenna 1 is connected with the receiving circuit 4 by means of the antenna switch 3 on upon receiving a signal and connected intermittently with the transmitting circuit 5 by means of the antenna switch 3 when transmitting a signal so that ASK modulation can be effected by means of the antenna switch 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-stop automatic toll collection system (Electronic Toll).
The present invention relates to a vehicle-mounted transceiver for an ETC used in a collection system (hereinafter, referred to as an ETC system).

[0002]

2. Description of the Related Art In an ETC system for a toll road such as an expressway, an ETC transmission / reception terminal installed at a tollgate and an ET mounted on a car by time-division two-way communication.
5.8G ASK-modulated with the on-board transceiver for C
Hz band ASK (Amplitude Shift K)
The transmission and reception are performed using the modulated wave, and a predetermined fee is separately collected by transmitting and receiving the signal. The on-board transceiver for ETC mounted on a car has a transmitting / receiving antenna mounted on a rearview mirror, etc., a transmitter / receiver main body mounted inside a console box, etc., and the antenna and the transmitter / receiver main body are connected by a coaxial cable. You.

FIG. 3 is a block diagram showing an example of a conventional ETC on-board transceiver used in such an ETC system.

The on-board ETC transceiver for ETC can selectively transmit and receive signals, and includes an antenna 31, a dielectric filter 32, and an antenna switch 33.
, A receiving circuit 34, a transmitting circuit 35, and a microcomputer 36.

[0005] The receiving circuit 34 includes a low noise amplifier 37, a mixer 38, an intermediate frequency filter 39, an intermediate frequency amplifier 40, a detector 41 and a demodulated signal amplifier 42.

The transmitting circuit 35 has a phase control loop (PL
L) 43, a local oscillator 44, a multiplier 45, a trap circuit 46, a preamplifier 47, and an ASK modulator 48
And a power amplifier 49.

[0007] The phase control loop 43 is controlled by the microcomputer 36, and stabilizes the oscillation frequency of the local oscillator 44 at 2.9175 GHz. And
The oscillation signal of 2.9175 GHz output from the local oscillator 44 is doubled by the multiplier 45 to be 5.83.
5 GHz. Then, by the trap circuit 46,
4. After attenuating 2.9175 GHz of the original oscillation signal,
The 835 GHz oscillation signal is output to the preamplifier 47 and also to the mixer 38 of the receiving circuit 34.

At the time of receiving the ASK modulated wave, the microcomputer 36 controls the antenna switch 33 to connect the antenna 31 and the receiving circuit 34, and receives the 5.835 GHz oscillation signal from the transmission circuit 35 as a local oscillation signal. The signal is input to the mixer 38 of the circuit 34.

When an ASK modulated wave of 5.795 GHz is transmitted from an antenna (not shown) of an ETC transmitting / receiving terminal installed at a tollgate to a car entering the tollgate, A
The SK modulated wave is received by an antenna 31 mounted on a vehicle, an unnecessary frequency component is removed by a dielectric filter 32, and is input to a receiving circuit 34 through an antenna switch 33.

The ASK modulated wave input to the receiving circuit 34 is amplified by a low noise amplifier 37,
8 is input. The mixer 38 mixes the ASK modulated wave and the local oscillation signal to produce an intermediate frequency signal (frequency of 40 MHz).
z). Then, the intermediate frequency signal passes through the intermediate frequency filter 39, is amplified by the intermediate frequency amplifier 40, and is input to the detector 41.

The intermediate frequency signal is subjected to envelope detection by a detector 41 to become a demodulated signal, which is input to a demodulated signal amplifier 42. The demodulated signal amplifier 42 inputs the amplified demodulated signal to the microcomputer 36, and a CD (Carrier De) indicating that the ASK modulated wave has been received.
Tect) signal is input to the microcomputer 36.

On the other hand, when transmitting an ASK modulated wave, the microcomputer 36 controls the antenna switch 33 to connect the antenna 31 to the transmission circuit 35.

The local oscillator 44 to 2.9175
An oscillation signal of GHz is output, converted to a frequency of 5.835 GHz by the multiplier 45 and the trap circuit 46, and input to the preamplifier 47 as a carrier.

The carrier wave amplified by the preamplifier 47 and the modulation signal (digital signal) output from the microcomputer 36 are input to an ASK modulator 48,
The modulator 48 outputs an ASK modulated wave. The ASK modulated wave is amplified by the power amplifier 49, and the antenna switch 3
3 and the dielectric filter 32, the signal is transmitted to the antenna 31, and transmitted to the antenna of the ETC transmitting / receiving terminal station installed at the tollgate.

[0015]

In recent years, the number of electrical components mounted in the console box of a car has increased, and there has been a strong demand for miniaturization of each electrical component.
There is also a demand for miniaturization of in-vehicle transceivers for TC.

Therefore, the present invention reduces the number of parts,
It is an object of the present invention to provide an in-vehicle transceiver for ETC that can be downsized.

[0017]

In order to solve the above-mentioned problems, an on-vehicle ETC transmitter / receiver according to the present invention is configured such that an antenna for both transmission and reception is selectively connected to a reception circuit and a transmission circuit by an antenna switch. At the time of reception, the antenna and the reception circuit are connected by the antenna switch, and at the time of transmission, the antenna and the transmission circuit are intermittently connected by the antenna switch so that the antenna switch can perform ASK modulation.

The receiving circuit of the on-board ETC transceiver for ETC according to the present invention has a switch which is turned on at the time of reception to pass a demodulated signal and turned off at the time of transmission and does not pass the demodulated signal.

The antenna switch of the ETC on-vehicle transceiver according to the present invention connects the antenna and the transmission circuit via a transmission-side switch diode, and connects the antenna and the reception circuit to each other by a quarter of the wavelength λ of the carrier wave. 1 through a transmission line of a length, a point between the receiving circuit and the transmission line is grounded by a receiving switch diode, and when connecting the antenna and the transmitting circuit, the transmitting switch diode and the receiving switch diode are connected to each other. Are turned on, and when connecting the antenna and the receiving circuit, both the transmitting side switching diode and the receiving side switching diode are turned off.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An on-vehicle transceiver for ETC according to the present invention will be described with reference to FIG.

This on-vehicle transceiver for ETC can selectively perform transmission and reception of a signal. An antenna 1, a dielectric filter 2, an antenna switch 3, a reception circuit 4, a transmission circuit It has a circuit 5 and a microcomputer 6. The connection of the antenna switch 3 is switched by a transmission / reception switching / modulation signal S output from the microcomputer 6, and connects the antenna 1 to the transmission circuit 5 when the transmission / reception switching / modulation signal S is at a high level. When the transmission / reception switching and modulation signal S is at a low level, the antenna 1 and the receiving circuit 4 are connected.

The receiving circuit 4 includes a low noise amplifier 7, a mixer 8, an intermediate frequency filter 9, an intermediate frequency amplifier 10, a detector 11, a demodulation signal amplifier 12, and an AND circuit 13.

The transmission circuit 5 has a phase control loop (PLL)
14, a local oscillator 15, a multiplier 16, a trap circuit 17, a preamplifier 18, and a power amplifier 19.

The phase control loop 14 is controlled by the microcomputer 6 and stabilizes the oscillation frequency of the local oscillator 15 at 2.9175 GHz. The 2.9175 GHz oscillation signal output from the local oscillator 15 is doubled by the multiplier 16 to 5.835.
GHz. Then, after the trap circuit 17 attenuates the 2.9175 GHz of the original oscillation signal, 5.8.
The oscillation signal of 35 GHz is output to the preamplifier 18 and also to the mixer 8 of the receiving circuit 4.

When the ASK modulated wave is received, the transmission / reception switching / modulation signal output from the microcomputer 6 becomes low level, the antenna switch 3 connects the antenna 1 and the receiving circuit 4, and the transmitting circuit 5 to 5.835.
The oscillation signal of GHz is input to the mixer 8 of the receiving circuit 4 as a local oscillation signal.

When an 5.795 GHz ASK modulated wave is transmitted from an antenna (not shown) of an ETC transmitting / receiving terminal installed at a tollgate to a car entering the tollgate, A
The SK modulated wave is received by an antenna 1 mounted on a vehicle, unnecessary frequency components are removed by a dielectric filter 2, and input to a reception circuit 4 as a reception signal through an antenna switch 3.

The received signal input to the receiving circuit 4 is amplified by the low noise amplifier 7 and then input to the mixer 8. In the mixer 8, the ASK modulated wave and the local oscillation signal are mixed and frequency-converted into an intermediate frequency signal (frequency is 40 MHz). The intermediate frequency signal is supplied to the intermediate frequency filter 9.
, And amplified by the intermediate frequency amplifier 10,
1 is input.

The intermediate frequency signal is subjected to envelope detection by a detector 11 to become a demodulated signal, which is input to a demodulated signal amplifier 12. The demodulated signal amplifier 12 inputs the amplified demodulated signal to one input terminal of the AND circuit 13 and
CD (Carrier) indicating that a K modulated wave has been received
(Detect) signal is input to the microcomputer 6. The other input terminal of the AND circuit 13 is connected to the microcomputer 6, to which a high-level voltage is applied during reception and a low-level voltage is applied during transmission. Therefore, the AND circuit 13 operates as a switch that is turned on at the time of reception to pass a demodulated signal and turned off at the time of transmission and does not pass the demodulated signal. Then, the demodulated signal input to the microcomputer 6 is processed as digital data.

On the other hand, when transmitting an ASK modulated wave, a modulation signal (digital signal) is output from the microcomputer 6 as a transmission / reception switching / modulation signal S. When the transmission / reception switching / modulation signal is at a high level, the antenna 1 and the transmission circuit 5 are transmitted. When the transmission / reception switching and modulation signal is at a low level, the antenna 1 and the reception circuit 4 are connected.

At this time, the local oscillators 15 to 2.917
An oscillation signal of 5 GHz is output, converted to a frequency of 5.835 GHz by the multiplier 16 and the trap circuit 17, and input to the preamplifier 18 as a carrier.

The carrier amplified by the preamplifier 18 is amplified by the power amplifier 19 and input to the antenna switch 3. The antenna switch 3 intermittently connects the transmission circuit 5 and the antenna 1 in accordance with the transmission / reception switching and modulation signal S, so that the ASK modulated wave is transmitted from the antenna switch 3 to the antenna 1 through the dielectric filter 2 and sent to the tollgate. It is transmitted to the antenna of the installed ETC transmission / reception terminal station. When transmitting the ASK modulated wave, the receiving circuit 4 is also intermittently connected to the antenna 1, and noise may be input to the receiving circuit 4, but the noise is input to the other input terminal of the AND circuit 13. Level voltage is applied,
The output of the receiving circuit 4 is kept at a low level.

The AND circuit 13 may be provided in the microcomputer 6 or may be processed by software in the microcomputer 6 without physically providing an AND circuit, and the receiving circuit 4 transmits the data to the microcomputer 6 during transmission. The input to the computer 6 may be canceled.

FIG. 2 is a diagram showing an embodiment of the antenna switch 3 used in the present invention. The antenna switch 3 is configured to selectively connect the antenna 1 to the transmission circuit 5 or the reception circuit 4 by using two switch diodes 21 and 20 and a transmission line 22.

The antenna 1 is a quarter of the wavelength λ of the carrier.
Is connected to one end of a transmission line 22 having a length of
Is connected to the receiving circuit 4 and the transmission line 2
The other end of 2 is grounded by the receiving side switch diode 20. The antenna 1 is connected to the transmission circuit 5 via the transmission-side switch diode 21. Since the transmission-side switch diode 21 has a terminal capacitance of about 0.5 pF, a 2.7 mH resonance coil 23 is connected in parallel, parallel resonance is performed at the frequency of the carrier wave, and attenuation between terminals can be obtained. I have. A DC blocking capacitor 24 is connected in series to the resonance coil 23. The transmission / reception switching / modulation signal S is input from the other end of the transmission line 22.

When the ASK modulated wave is received, a low-level voltage is input to the other end of the transmission line 22 as the transmission / reception switching / modulation signal S, so that both the receiving switch diode 20 and the transmitting switch diode 21 are turned off. State. Then, the ASK modulated wave input from the antenna 1 is input to the receiving circuit 4 as it is. Further, since the transmission side switch diode 21 is in the off state,
The carrier output from the transmitting circuit 5 does not reach the antenna 1.

At the time of transmitting the ASK modulation wave, a modulation signal (digital signal) is input to the other end of the transmission line 22 as a transmission / reception switching / modulation signal S. When the modulation signal is at the low level, the transmission side switch diode 21 is in the off state as in the reception, so that the carrier output from the transmission circuit 5 does not propagate to the antenna 1. On the other hand, when the modulation signal is at the high level, both the receiving switch diode 20 and the transmitting switch diode 21 are turned on. Then, the carrier output from the transmission circuit 5 is transmitted to the antenna 1
Sent from Also, the receiving side switching diode 20
Is in the ON state, the other end of the transmission line 22 is grounded, and the transmission line 2 λ / 4 away from the other end of the transmission line 22.
The impedance at one end of the antenna 2 becomes large, and the antenna 1 and the receiving circuit 4 are cut off at a high frequency. Therefore, the carrier is output intermittently according to the modulation signal.

[0037]

As described above, the on-vehicle transceiver for ETC of the present invention selectively connects a transmitting / receiving antenna to a receiving circuit and a transmitting circuit by an antenna switch. The antenna and the receiving circuit are connected, and at the time of transmission, the antenna and the transmitting circuit are intermittently connected by the antenna switch so that ASK modulation can be performed by the antenna switch, eliminating the need for an ASK modulator and reducing the number of parts. Because it is possible, miniaturization becomes possible.

Further, the receiving circuit of the on-board ETC transceiver for ETC of the present invention has a switch which is turned on at the time of reception to pass a demodulated signal and turned off at the time of transmission and does not pass the demodulated signal. When the antenna and the receiving circuit are connected at a high frequency during transmission, even if noise is input to the receiving circuit through the antenna, no noise is output from the receiving circuit, so that the operation is stable.

The antenna switch of the onboard ETC transceiver for ETC according to the present invention connects the antenna and the transmission circuit via the transmission-side switch diode, and connects the antenna and the reception circuit to each other by a quarter of the wavelength λ of the carrier wave. 1 through a transmission line of a length, a point between the receiving circuit and the transmission line is grounded by a receiving switch diode, and when connecting the antenna and the transmitting circuit, the transmitting switch diode and the receiving switch diode are connected to each other. Are turned on, and when the antenna and the receiving circuit are connected, both the transmitting side switching diode and the receiving side switching diode are turned off. Therefore, only the electronic components having a small volume can be used, and the size can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a vehicle-mounted transceiver for ETC of the present invention.

FIG. 2 is a circuit diagram of a switch circuit used in the on-board transceiver for ETC of the present invention.

FIG. 3 is a circuit block diagram of a conventional on-vehicle transceiver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna 2 Dielectric filter 3 Antenna switch 4 Receiving circuit 5 Transmitting circuit 6 Microcomputer 7 Low noise amplifier 8 Mixer 9 Intermediate frequency filter 10 Intermediate frequency amplifier 11 Detector 12 Demodulated signal amplifier 13 AND circuit 14 Phase control loop 15 Local oscillator 16 Multiplier 17 Trap circuit 18 Preamplifier 19 Power amplifier 20 Reception switch diode 21 Transmission switch diode 22 Transmission line 23 Resonant coil 24 DC blocking capacitor

Claims (3)

[Claims] An antenna for both transmission and reception, a transmission circuit for outputting a carrier wave, a reception circuit for detecting a reception signal received by the antenna and outputting a demodulated signal, and the antenna for the transmission circuit or the reception circuit. An antenna switch for selectively connecting the antenna and the receiving circuit by the antenna switch during reception, and intermittently connecting the antenna and the transmission circuit by the antenna switch during transmission. A car-mounted transceiver for ETC, wherein an ASK modulated wave is output from the antenna switch. 2. The receiving circuit according to claim 1, further comprising a switch that is turned on at the time of reception to pass the demodulated signal and is turned off at the time of transmission and does not pass the demodulated signal. The in-vehicle transmitter / receiver for ETC as described. 3. The antenna switch has a transmission-side switch diode, a reception-side switch diode, and a transmission line, the antenna and the transmission circuit being connected via the transmission-side switch diode, and Is a quarter of the wavelength λ of the carrier wave, the antenna and the receiving circuit are connected via the transmission line, and a point between the receiving circuit and the transmission line is The receiving side switch diode is grounded, the receiving side switching diode and the receiving side switching diode are both turned off at the time of reception, and the transmitting side switching diode and the receiving side switch diode are intermittently turned on at the time of transmission. The in-vehicle transceiver for ETC according to claim 1 or 2, wherein: