Registers – Records
Reexamination Certificate
1999-02-19
2001-01-23
Frech, Karl D. (Department: 2876)
Registers
Records
C235S375000
Reexamination Certificate
active
06176432
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a modulating and demodulating device and, more particularly, to a modulating and demodulating device for use in a transmitter-receiver which comprises a modulator-demodulator (circuit) for performing a modulating or demodulating operation in accordance with a bias voltage to be supplied to diodes, transmits a signal at the time of the modulating operation and receives a signal at the time of the demodulating operation.
2. Related Art
At present, an automatic toll collecting (ATC) system has been being developed. According to the system, a roadside device is arranged on a toll facility side as means for collecting a toll of a toll road, an on-vehicle device is mounted on a vehicle, required radio waves are transmitted and received between the roadside device and the on-vehicle device when the vehicle stops at the toll facility, and a toll is collected by wireless means. Various tests are being carried out in order to put the system to practical use.
FIG. 3
is a block diagram showing a construction of an important part of a roadside device for use in the automatic toll collecting system.
FIG. 4
is a block diagram showing a construction of an important part of an on-vehicle device for use in the automatic toll collecting system.
FIG. 5
is a circuit construction diagram showing a specific example of a construction of the on-vehicle device shown in FIG.
4
. In
FIG. 5
, the same component elements as those shown in
FIG. 4
are designated by the same reference numerals.
As shown in
FIG. 3
, the roadside device arranged on the toll facility side comprises an RF receiving filter
31
, an RF receiving amplifier
32
, a frequency converter
33
, an IF (intermediate frequency) amplifier
34
, an IF (intermediate frequency) filter
35
, a local oscillator
36
, first and second buffer amplifiers
37
and
38
, a switch
39
, an FM encoder
40
, an RF transmitting amplifier
41
, an RF transmitting filter
42
, a receiving antenna
43
, a transmitting antenna
44
, a demodulation signal output terminal
45
, and a modulation signal input terminal
46
.
In this case, in the RF receiving filter
31
, the input terminal is connected to the receiving antenna
43
and the output terminal is connected to the input terminal of the RF receiving amplifier
32
. In the frequency converter
33
, a first input terminal is connected to the output terminal of the RF receiving amplifier
32
, a second input terminal is connected to the output terminal of the first buffer amplifier
37
, and the output terminal is connected to the input terminal of the IF amplifier
34
. In the IF filter
35
, the input terminal is connected to the output terminal of the IF amplifier
34
and the output terminal is connected to the demodulation signal output terminal
45
. The local oscillator
36
includes an oscillator, a phase locked loop, a quartz oscillator, a frequency multiplying circuit, and an output buffer amplifier (all of which are not shown in the diagram). The output terminal of the local oscillator
36
is connected to both the input terminal of the first buffer amplifier
37
and the input terminal of the second buffer amplifier
38
. In the switch
39
, the input terminal is connected to the output terminal of the second buffer amplifier
38
, the output terminal is connected to the input terminal of the RF transmitting amplifier
41
, and the control terminal is connected to the output terminal of the FM encoder
40
. The input terminal of the FM encoder
40
is connected to the modulation signal input terminal
46
. The input terminal of the RF transmitting filter
42
is connected to the output terminal of the RF transmitting amplifier
41
and the output terminal is connected to the transmitting antenna
44
.
As shown in
FIG. 4
, the on-vehicle device to be mounted on a vehicle comprises a microstrip line (MSL) network
47
, amodulator-demodulator
48
, a diode
48
D, abias voltage supplying circuit
49
, an FM decoder
50
, a transmitting/receiving antenna
51
, a demodulation signal output terminal
52
, and a change-over signal supplying terminal
53
.
In this case, the input terminal of the microstrip line network
47
is connected to the transmitting/receiving antenna
51
and the output terminal is connected to the input terminal of the modulator-demodulator
48
. In the modulator-demodulator
48
, the diode
48
D is serially connected between the input and output terminals, the output terminal is connected to the input terminal of the FM decoder
50
, and the control terminal is connected to the output terminal of the bias voltage supplying circuit
49
. The input terminal of the bias voltage supplying circuit
49
is connected to the change-over signal supplying terminal
53
. The output terminal of the FM decoder
50
is connected to the demodulation signal output terminal
52
.
Further, as shown in
FIG. 5
, the microstrip line network
47
has first to third microstrip lines
47
A,
47
B, and
47
C. The modulator-demodulator
48
has, besides the diode
48
D, a first inductor
48
A, a second inductor
48
C, a resistor
48
C, and a bias voltage supplying terminal
48
E. The bias voltage supplying circuit
49
has a switch
49
A and a power source
49
B. In
FIG. 5
, a control unit
54
which is not shown in
FIG. 4
is provided.
In the microstrip line network
47
, the first microstrip line
47
A is serially connected between the input and output terminals, the secondmicrostrip line
47
B is connected between the input terminal and the reference potential (ground) point, and the third microstrip line
47
C is connected between the output terminal and the reference potential (ground) point. In the modulator-demodulator
48
, the diode
48
D is serially connected between the input and output terminals, the first inductor
48
A and the resistor
48
C are serially connected between the input terminal and the bias voltage supplying terminal
48
E, and the second inductor
48
C is connected between the output terminal and the ground terminal. In the bias voltage supplying circuit
49
, one terminal of the switch
49
A is connected to the output terminal of the bias voltage supplying circuit
49
, another terminal is connected to the ground terminal via the power source
49
B, and the control terminal is connected to the change-over signal supplying terminal
53
. The control unit
54
is connected to the FM decoder
50
and the change-over signal supplying terminal
53
.
Modes of transmitting and receiving signal waves between the roadside device and the on-vehicle device in the automatic toll collecting system having the above construction will be generally described as follows with reference to
FIGS. 3
to
5
.
First, a first operating mode of transmitting signal waves from the roadside device side to the on-vehicle device side will be described.
In the first operating mode, on the roadside device side, the FM encoder
40
operates in response to a modulation signal supplied to the modulation signal input terminal
46
, and the switch
39
is turned on and off according to a signal encoded by the FM encoder
40
. At this time, a carrier signal generated from the local oscillator
36
is subjected to amplitude shift keying (ASK) modulation by the on-off control by the switch
39
, thereby forming an ASK modulated signal. Subsequently, after the ASK modulated signal is amplified by the RF transmitting amplifier
41
to a required level, unnecessary frequency components are eliminated by the RF transmitting filter
42
, and the resultant signal is transmitted from the transmitting antenna
44
.
In the first operating mode, the on-vehicle device receives the ASK modulated signal transmitted from the roadside device. An un-modulated signal is supplied from the control unit
54
to the change-over signal supplying terminal
53
. By the supply of the un-modulated signal, the switch
49
A of the bias voltage supplying circuit
49
is turned off, an output of the power source
49
B is cut off by the switch
4
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Frech Karl D.
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