JPS59128840A - System for transmitting and receiving signal - Google Patents

Abstract

PURPOSE:To listen to prescribed traffic information by stopping the operation of a switch control circuit while a high-level signal is outputted from a discriminating circuit to a line to stop the scanning of reception of radio broadcast. CONSTITUTION:Voltage setters A1, A2...An are provided in correspondence to carrier frequencies of plural radio broadcasts and each output is outputted to a line 61 connected to a tuner 53 via switches B1, B2...Bn. Further, these switches are controlled by a signal from a switch controlling circuit 91 via stable circuits S1, S2...Sn. Each radio broadcast transmits a decoration signal of a prescribed frequency, a start identification signal, traffic information and an end identification signal in this order during transmission. All the radio broadcasts are received and scanned cyclically during the duration period of the decoration signal and a demodulated output from the tuner 53 is given to an identification circuit 72. Further, while a high-level signal is outputted from the circuit 72, the reception scanning of the radio broadcast is stopped and the traffic information is listened to.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal transmission/reception system that allows a signal having a predetermined frequency to be distinguished from remaining signals and detected accurately.

In radio broadcasts, in order to avoid missing traffic #゛u@ broadcasted at different times, prior to transmitting traffic information, a separate signal with a predetermined frequency is sent out, and this identification is performed. Traffic 1 when a signal is received
・A system has been proposed that allows the N-report to be listened to by converting it into audio.

In such a system, the radio broadcast includes voice and music, and therefore it may be difficult to accurately detect the identification signal tone.

An object of the present invention is to provide a signal transmission and reception system that can accurately detect a signal having a predetermined frequency.

FIG. 1 is a block diagram of a receiving device according to an embodiment of the present invention. Radio broadcast waves from a plurality of radio broadcast stations are received by an antenna 50 and provided from a branching circuit 51 to two tuners 52 and 53. One tuner 52
may be a conventional so-called car radio,
The K readable frequency signal is applied to an individual contact 55 of a changeover switch 54. The tunable frequency signal from the other tuner 53 is applied to another individual contact 56.

The signal from the common contact 57 of the changeover switch 54 is amplified by the amplifier circuit 58 and made into sound by the speaker 59.

The reception frequency of tuner 53 corresponds to the voltage applied via line 61 from frequency setting circuit 60 . In order to set this voltage, voltage settings f++AI, Az, .
is provided. This voltage setting device Al, A2. ..., A
The outputs from switches B1, B2 . . . , are selectively led out to line 61 via Bn. Switch Bl, B2.・
..., En are individually given signals from the switch control circuit 91, and these switches B1 are used for reception scanning.
, B2. ..., Bn is sequentially turned on and off one by one. The switch control circuit 91 has cascade-connected monostables S 1 , S 2 , ..., Sn,
Each of these monostable Sl, S2. . . , the output from Sn is one switch Bl, B2 . ..., are individually given to Bn. The output of the final stage monostable Sn is the first stage monostable S
It is returned to 1. Therefore, only during the period when the output of the monostable s1 is at a high level, the switch B1 becomes conductive, and the voltage corresponding to the carrier frequency of the first radio broadcast from the voltage setting device A1 is applied to the tuner 53 via the line 61. .

Therefore, the tuner 53 receives the first radio broadcast. At this time, the remaining switch B2. ..., B71 is blocked. Next, when the output of the monostable S1 becomes a low level, the output of the monostable S2 becomes a NO level. Therefore, only the switch B2 becomes conductive, and the voltage setting device A2
is applied to tuner 53 from line 61. Therefore, tuning is performed to the carrier frequency of the second radio broadcast corresponding to the voltage set by the voltage setting device A2, and reception of the radio broadcast becomes possible. monostable Sl,
S2. . . , Sn is connected to each monostable Sl only during the period when a high level reset signal is applied via line 62-.

82, . . . , the logic state of Sn is maintained.

Referring to FIG. 2, each radio broadcast includes a decorative signal 63 that uses a predetermined frequency f1 during each radio broadcast transmission, a start identification signal 64, traffic information 65, and an end identification signal 66.
and are sent in this order.

The start identification signal 64 includes a signal 67 having a frequency of 12;
and a signal 68 having a frequency 11if3. for example,
The duration W1 of the decoration signal 63 is 300 ms, and the subsequent pause period W2 is 100 ms. ms, the duration w3 of the signal 67 is 350 ms, the rest period W4 is 100 ms, and the duration W5 of the signal 68 is 350 ms.
It may be 0 ms, and the sum of these periods is selected to be about less than 2 seconds. The termination identification signal 66 includes a signal 69 having the same frequency 13 as the aforementioned signal 68 and a signal 70 having the same frequency f2 as the aforementioned signal 67.

Duration of signal 69°70 W6. For example, W8 is 35
0 ms, and the pause period W7 between them is 100
It is mB. In this embodiment, there are a total of five receivable radio broadcast stations, and in the electrical circuit shown in the first figure, n=5, and the monostable SL of the switch control circuit 91.

S2. ..., Sn are selected to be 60 m5, thereby making it possible to receive and scan all the radio broadcasts in one round during the duration wi of the decoration signal 63.

The demodulated output from the tuner 53 is not only applied to the individual contacts 56 of the changeover switch 54 as described above, but also applied to the identification circuit 72 from the line 71.

When the identification circuit 72 detects the start identification signal 64, it keeps the common contact 57 of the changeover switch 54 connected to the individual contact 56, and derives a high-level signal from the line 73 to the line 62 via the OR gate 74. When the termination identification signal 66 is detected, the selector switch 54 is
The common contact 57 is electrically connected to the individual contact 55, and a low level signal is output to the line 73. In this way, during the period when the high level signal is applied from the identification circuit 72 to the line 73, the monostables Sl, S2 . ...
, Sn are stopped, reception scanning of radio broadcasts remains stopped, and traffic information 65 can be listened to.

The signal from tuner 53 via line 71 is also provided to bandpass filter 75 via demodulation circuits 81 and 82 in that order.

For the decoration signal 63, the radio broadcast station modulates the radio broadcast carrier wave 83 with a first modulated wave 84 having a lower first frequency of 1/1, as shown in FIG. The modulated carrier wave is modulated with a second modulated wave 85 having a second frequency 14 lower than the first frequency 11, and then transmitted. In the receiving apparatus shown in FIG. 1, the signal of the first frequency 1/1 is demodulated and the decoration signal 63 is detected. For this purpose, the tuner 53 performs superhetero gain type reception. This tuner 53 derives an intermediate frequency signal on line 120. This intermediate frequency signal is given to a first demodulation circuit 81, which converts the carrier wave to a second frequency 1.
4 signal 85 is demodulated. The output from the first demodulation circuit 81 is given to the second demodulation circuit 82 and the first frequency 1/
1 signal 84 is demodulated. In this way the second
A signal 84 having a frequency f1, that is, a decorative signal 63 shown in FIG. 2 is obtained from the demodulation circuit 82.

The signal from the second demodulation circuit 82 is given to a bandpass filter 75. The bandpass filter 75 passes only a signal having the same frequency as the frequency f1 of the decoration signal 63, and supplies the signal to the detection circuit 76. The detection circuit 76 derives a signal at a high level only during the period when the signal having the frequency 11 is applied, and outputs a signal at a high level to a monostable circuit 77 (the monostable circuit 77 is supplied from the detection circuit 76). A high level signal is applied to OR gate 74G for a predetermined time W9 from the given time. This time W9 may be, for example, about 1.3 seconds,
After this decorative signal 63 is detected, the reception frequency of the tuner 53 is fixed and reception scanning is stopped so that the identification 1 circuit 72 can receive the start identification signal 64 reliably. A necessary time number is determined, and is, for example, greater than or equal to the sum of the above-mentioned times W1 to W5.

Assume that the common contact 57 of the changeover switch 54 is electrically connected to the individual contact 55, and a radio broadcast selected by the tuner 52 is being listened to.

The tuner 53 receives and scans a plurality of radio broadcasting stations, for example, five stations as described above, at a distance of about 60 m5 per station. This reception scanning signal having a frequency of 11 is
When applied to the detection circuit 76 via the bandpass filter 75, the monostable circuit 77 outputs a high level signal from the line 62 via the OR gate 74 to the switch control circuit 91.
give to As a result, the logic states of the monostables si, s2, . . . , Sn of the switch control circuit 91 are changed to
It is maintained only during the period when a high level signal is derived from 7. Therefore, the tuner 53 continues to receive the radio broadcast from which the signal having the frequency i/1 is derived. While this monostable circuit 77 is deriving a high-level signal, when a subsequent start identification signal 64 is detected by the identification circuit 72, which is the signal-impairing signal 63 having the aforementioned frequency fl, the monostable circuit 77 outputs a high-level signal. Even after the output of the stabilizing circuit 77 becomes low level, a high level signal continues to be derived from the identification circuit 72 to the line 73. At this time, the common contact 57 of the changeover switch 54 is electrically connected to the individual contact 56. In this way, the traffic information 65 is listened to by the tuner 53.

When identification circuit 72 detects termination identification signal 66, a four-level signal is derived on line 73.

As a result, the monostable Sl of the switch control circuit 91.

S2. ..., Sn cycles through the logic states and tuner 5
3 is repeatedly performed, the changeover switch 54 returns to its original state, the common contact 57 becomes conductive to the individual contact 55, and the radio broadcast selected by the tuner 52 can be listened to again. .

The identification circuit 72 receives a signal 57.70 having a frequency f2 included in the start identification signal 64 and the end identification signal 66.
continues for a predetermined time T1 or more, and frequency 1
When the signals 68 and 69 having 3 are longer than the predetermined time T2, and there is a pause period W4 between these signals 67 and 68, and there is a pause period W7 between the signals 69 and 70, The above operation is performed for the first time, thereby preventing false detection. Frequency 11. f2. f3 is selected as an audible frequency similar to the traffic information 65 signal.

Such a decorative signal 63, that is, the signal 8 shown in FIG.
In the radio broadcast transmitting apparatus shown in FIG. A first modulated wave 84 having a frequency f1 is provided from the oscillation circuit 102 to another modulation circuit 103. This modulation circuit 1
03, a second signal having a frequency of 14 is generated from the oscillation circuit 104.
A modulated wave 85 is provided. In the modulation circuit 103, the signal from the oscillation circuit 102 having the frequency f1 is modulated by the signal from the oscillation circuit 104 having the frequency f4, and is applied to the modulation circuit 10'1. Modulation circuit 101 modulates a carrier wave with a signal from modulation circuit 103. In this way, the carrier wave 83 is transmitted to the oscillator circuit 1 having the first frequency 11.
The modulated carrier wave is first amplitude modulated with a first modulated wave 84 from 02, and the modulated carrier wave is transmitted to the oscillation circuit 1 having a first frequency 11.
It will be modulated with the second modulated wave 85 from 04. The output from modulation circuit 101 is applied to antenna 108 through switch 105 and power amplification circuit 107, and is sent out. Signal 67.70 having frequency f2 is applied from oscillation circuit 111 to modulation circuit 113 via switch 112, whereby the carrier wave becomes signal 67.70 having frequency 12.
70. Further, signals 68 and 69 having a frequency f3 are generated by the oscillation circuit 110 and applied to the modulation circuit 113 via the switch 114. This 5 modulates the carrier wave with a signal 68.69 of frequency 13. The signal from modulation circuit 113 is applied to power amplifier circuit 107 via switch 115. This traffic information 65 and other sounds, music, etc. are provided from circuit 116 to modulation circuit 113 via switch 117. Switches 105, 114, 115, 1
By switching 17, a decorative signal 63, a start identification signal 64, and an end identification signal 66 are generated, and traffic information 65 and other signals such as voice and music are switched and sent.

FIG. 5 is a block diagram showing a specific configuration of the identification circuit 72. The output from the tuner 53 is sent to the filter 130.
, 1.31 and the level setting circuit 153. Filter 130, l31Li, frequency &f2.
Each identification signal having f3 is selected and derived. The outputs from the filters 130, 131 are sent to the detection circuits 132,
133.

The detection circuit 132 includes a coupling capacitor 151,
It includes a detection diode 152 and an integrating capacitor 136. The detection circuit 133 has the same structure as the detection circuit 132. The outputs from the detection circuits 132 and 133 are given to one input of a comparison circuit 134.13'5. The level setting circuit 1 is connected to the other input of the comparison circuits 134 and 135.
53 and a signal via a detection circuit 154 is applied. The detection circuit 154 has the same structure as the detection circuits 1, 32 and 133. Outputs from comparison circuits 134 and 135 are provided to time determination circuits 137.1'38, respectively.

The time determination circuit 137 includes a resistor 139, an integrating capacitor 140, a comparator circuit 141, and a diode 142 connected in parallel to the resistor 139. One input of the comparator circuit 141 receives the output from the integrating capacitor 140. Given. A signal at a predetermined level is applied to the other input of the comparison circuit 141 from the terminal 143. The other time determination circuit 138 has the same structure as the time determination circuit 137.

The output of the time determination circuit 137 is applied to one input of an AND gate 145 via a monostable circuit 144, and directly to one input of an AND gate 146. The output from time determination circuit 138 is applied to the other input of AND gate 146 via monostable circuit 147 and directly to the other input of AND gate 145. The output of the AND gate 145 sets the flip 70 knob 148 and outputs the AND gate 146.
The output from resets flip-flop 148.

Transistor 21 is turned on by the set output from flip-flop 148. Therefore, the relay coil 22 of the relay 61 is energized, and the common contact 57 of the changeover switch 54 is electrically connected to the individual contact 56 only during the energization period.

For example, as shown in FIG. 6, the monostable circuit 144 includes a diode 110, an integrating capacitor 111, a resistor 112 that forms a time constant circuit together with the et capacitor 111, and a transistor 113 that forcibly and instantaneously discharges the integrating capacitor 111. The output of the integrating capacitor 111 is level-discriminated by the threshold value of the AND gate 145.

Referring to FIG. 7, assume that the signal shown in FIG. 7(1) is derived from the tuner 53 when receiving the signal. The filter 130 selects only the identification signal 67 having the audible frequency f2 and transmits it to the detection circuit 1.
Give to 32. As a result, the output of the integrating capacitor 136, ie, the output of the detection circuit 132, becomes as shown in FIG. 7(2). The identification signal 67 having an audible frequency of 12 is
The signal is applied from the level setting circuit 153 to the detection circuit 154 to determine the discrimination level of the comparison circuit 134. audible frequency f2
When only the identification signal 67 having
The output from the detection circuit 154 and therefore the discrimination level of the comparison circuit 134 is low. Therefore, when the identification signal 67 of the audible frequency f2 exceeding this discrimination level is given from the detection circuit 132, the comparison circuit 134 derives the waveform shown in FIG. 7(3). The output from this comparison circuit 134 is connected to the resistor 139.
is integrated by an integrating capacitor 140 via an integral capacitor 140. The output waveform of the integrating capacitor 140 is shown in FIG. 7(4). When the output of the integrating capacitor 140 exceeds the discrimination level applied to the terminal 143 after a time TIM,
Comparison circuit 141 derives a signal having the waveform shown in FIG. 7(5). In this way, only when the identification signal 67 of the audible frequency f2 is received for more than the time T1,
Comparison circuit 141 derives the output. The monostable circuit 144 derives a pulse having a predetermined pulse width W17 as shown in FIG. 7(9). During this period of pulse width W17, an identification signal having an audible frequency of 12 is received and detected as described below.

When the identification signal having the audible frequency f3 is output from the tuner 53, the identification signal 68 is selected by the filter 131 and detected by the detection circuit 133. The output from the detection circuit 133 is shown in FIG. 7(6). The output from the comparison circuit 135 is shown in FIG. 7 (7), and the output from the time determination circuit 138 is shown in FIG. 7 (8). The output from the time determination circuit 138 is an audio frequency @f
When the identification signal 68 having a value of 3 continues for a time T2 or more, the appearance is derived. In this way, the AND gate 145 obtains the waveform shown in FIG. 7 Oo. Therefore, the flip-flop 148 is set and the traffic information from the tuner 53 is outputted from the speaker 59 via the changeover switch 54 and the amplifier circuit 58.

When the traffic information radio broadcast ends, the audio frequency 13. An identification signal having f2 is derived from one tuner 53 in this order. When an identification signal having an audible frequency f3 is detected, a signal having a predetermined pulse width w18 is derived from the monostable circuit 147. Pulse width W
18 may be equal to the pulse width W7. During the period in which the output is being derived from this monostable circuit 147, if an identification signal having an audible frequency f2 is detected, the output from the AND gate 146 causes the seven limp flop 148 to be reset. Therefore, the changeover switch 54 is
The signal from the tuner 2 is guided to the amplifier circuit 58, and the radio broadcast being received by the tuner 52 can be heard again from the speaker 59.

In the embodiment described above, the audio frequency 12. When a signal having a frequency spectrum over a wide frequency band including f3 is derived from the tuner 53, the level setting circuit 13
2 through the detection circuit 154, that is, the discrimination level of the comparison circuits 134 and 135 is high. Therefore, the outputs of the comparison circuits 134 and 135 remain at low level. In this way, the audible frequency 12. Only when the identification signal having only the frequency spectrum of f3 is received by tuner 53, high level outputs are obtained from comparator circuits 134 and 135 as described above. This prevents erroneous detection of traffic information.

Also, in the time determination circuits 137 and 138, the audible frequency 12
．． Outputs are obtained from the time determination circuits 137 and 138 only when f3 lasts longer than the time TI (see FIG. 7(5)) and longer than the time T2 (see FIG. 7(8)), respectively. Therefore, it is possible to more reliably prevent erroneous detection of traffic information. Furthermore, monostable circuit 1.44, 147
Due to the action of the audible frequency 12. The flip-flop 148 operates only when the identification signal having f3 is continuously generated within a predetermined time W7, ws. This also further reliably prevents erroneous detection of traffic information.

A diode 142 included in the time determination circuit 137 serves to discharge the charge in the capacitor 140 as soon as the output of the comparison circuit 134 becomes low level. Therefore, the next input output of the comparison circuit 134 can be reliably integrated by the capacitor 140 via the resistor 139.
Accurate time T1 can be obtained.

Audible frequency of occupational signals 12. f3 may be selected to have a chord relationship that satisfies the first equation to obtain good hearing.

/3=1.5·f2 (1) f2 is, for example, 900 H2, and f3 is 1.35 QHz.

Duration w3 in start identification signal 64. In order to detect that there is a pause period W4 between the signals of w5 and thereby more reliably avoid false detection, the following configuration is adopted. The output from the detection circuit 154 is given to one input of the comparison circuit 156.

The other input of this comparison circuit 156 is given a voltage Vrl that determines a predetermined discrimination level. Comparison circuit 156
gives a high level signal to the AND gate 157 when the output from the detection circuit 154 exceeds the discrimination level corresponding to the voltage Vrl.

The output from time determination circuit 137 is given to differentiation circuit 158. The output of the differentiating circuit 158 is given to one of the comparators 159 . A voltage vrz that determines the discrimination level is applied to the other input of the comparison circuit 159. The comparison circuit 159 is configured so that the output from the differentiating circuit 158 is the voltage Vr.
2, a high level signal is output to the AND gate 157. The aforementioned differentiation circuit 158 derives high-level and low-level differential pulses when the time determination circuit 137 rises and falls, respectively. In this way, a high level pulse is derived from the comparison circuit 159 at the time of the fall of the time determination circuit 137. The output of the AND gate 157 is applied to a pulse shaping circuit 160, where the pulse width is shaped to a predetermined value and applied to the transistor 113 (see FIG. 6) of the monostable circuit 144. The lucid stabilizing circuit 144 is reset in response to the output from the pulse shaping circuit 160, and sets its output to a low level.

Assume that a start identification signal having a normal waveform shown in FIG. 8(1) is derived from the tuner 53 on the line 71. In this case, from the -1 detection circuit 154 to the comparison circuit 1
56 is given the signal shown in FIG. 8(2). The output of the comparison circuit 156 is shown in FIG. 8(3). The time determination circuit 137 derives the signal shown in FIG.

The output of the differentiating circuit 158 is shown in FIG. 8(5).

Due to the functions of the differentiating circuit 158 and the comparing circuit 159,
The comparator circuit 159 and the AND gate 157 are connected to each other as shown in FIG.
A pulse is derived at the falling edge of the pulse shown in 4). The output of the AND game) 157 remains low level, so the output from the pulse shaping circuit 160 is the 81f.
No pulse is derived as shown by fl(7). Therefore, the transistor 113 of the monostable circuit 144 is cut off, and its output is at a high level for a period w7, as shown in FIG. 8(8). The output of the time determination circuit 138 is shown in FIG. 8(6). Therefore, the pulse shown in FIG. 8(9) is derived from the AND game 145, and the flip 70 knob 148 is set.

In the pause period w4 included in the start identification signal, the 9th ff
Assume a case where signals are mixed as shown in JQ). The output j of the detection circuit 154 is shown in 9th til(2), the output of the comparison circuit 134 is as shown in FIG. 9(3), and the output of the one-hour judgment circuit 137 is as shown in FIG. 9(4). be. The output of the differentiating circuit 158 is as shown in FIG. 9(5). AND game) 157 is comparison circuit 1
The signal from 56 remains at a high level and the comparison circuit 15
A high level pulse is derived in response to the pulse from 9. The pulse shaping circuit 160 derives the pulse shown in FIG. 9(7) to interrogate the transistor 11.3 of the monostable circuit 144. Therefore, the capacitor 111 is discharged and the output of the monostable circuit 144 becomes high level for a very short time as shown in FIG. 9(8), and then is forced to low level. The output of the time determination circuit 138 is
This is shown in FIG. 9(6). The output of the AND gate 145 remains at a low level as shown in FIG. 9 (9),
Flip-flop 148 is not set. In this manner, the flip-flop 148 is not set when there is a frequency signal during the pause period w4, and erroneous detection of the start identification signal is prevented.

In the embodiment described above, the frequency f1 of the decoration signal 63 may be chosen equal to one of the frequencies 12° f3 of the signal 67.70768.69. The duration W1 of the decorative signal 63 is, for example, 300 m5 as described above, which is relatively long and is unpleasant to the ear.

In order to solve this problem, the 10th
As shown in the figure, the signal having frequency 11 is maintained for a relatively long period W9 during the transmission of each radio broadcast during reception scanning, and then the signal having frequency 11 is suspended for an extremely short period Wl□. The period W1 is 60 as mentioned above.
m5, W9 is 50 ms, and Wlo is 10
It may be m5. In this way, the decorative signal 63 can be heard intermittently, eliminating unpleasantness.

It is particularly pointed out that the invention is not only implemented in connection with traffic information transmission and reception schemes, but also broadly in connection with other signal transmission and reception schemes. Frequency fl, /2
Instead of amplitude modulation of the carrier wave, frequency modulation or other types of modulation may be used.

As described above, according to the present invention, signals can be detected without error by performing demodulation twice.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an electric circuit of a receiving device according to an embodiment of the present invention, FIG. 2 is a diagram showing a modulated waveform of a radio broadcast, and FIG. 3 is a radio broadcast for sending out a decorative signal 63. FIG. 4 is a block diagram schematically showing a radio broadcasting station, FIG. 5 is a block diagram showing the specific configuration of the identification circuit 72, and FIG. An electric circuit diagram showing a specific configuration of the stabilizing circuit 144, FIGS. 7 to 9 are waveform diagrams for explaining the operation of the identification circuit 72, and FIG. 6 is a waveform diagram of a decoration signal 63. FIG. 50... Antenna, 51... Branching circuit, 52.53
... tuner, 58 ... amplifier circuit, 59 ... speaker, 60 ... frequency setting circuit, 72 ... identification circuit, 75 ... band pass filter, 76 ... detection circuit, 77. 144.147... Monostable circuit, 81 reason 1st
Demodulation circuit, 82... Second demodulation circuit, 91... Switch control circuit, 100... Carrier wave oscillation circuit, 102...
・First frequency multiplier oscillation circuit, 104...Second frequency signal oscillation circuit Agent Patent attorney Kei Nishi Part 7 (10) ”” (7)□ (9) (7) (9)□ No. Figure 10

Claims (1)

[Claims] modulating the carrier wave with a first modulated wave having a first frequency lower than that of the carrier wave, modulating the modulated carrier wave with a second modulating wave having a second frequency lower than the first modulating wave, and transmitting the modulated wave;
On the receiving side, the transmitted carrier wave is received and the second
A signal transmission/reception system characterized by demodulating frequency double code and then demodulating first frequency double code.