JPH0685550U - Receiving machine - Google Patents

Abstract

(57) [Summary] [Purpose] A receiver that can have one microcomputer port for inputting a detection signal for determining the presence or absence of a station and whether the selected station is a stereo broadcast. I will provide a. [Structure] A station detection signal SD from a station detector 11 and a stereo detection signal ST from an AM stereo demodulation circuit 7 are supplied to a detection signal synthesizing circuit 15, and the synthesizing circuit 15 determines the presence / absence of a station and the selected station. A combined detection signal VD is formed by distinguishing whether or not it is a stereo broadcast by a voltage value. The controller 5 including a microcomputer determines the presence or absence of a station and whether or not the selected station is a stereo broadcast based on the voltage value of the composite detection signal VD. The controller 5 needs only one port for inputting the detection signal, which can contribute to elimination of the shortage of the number of ports.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a receiver such as an AM stereo radio receiver capable of receiving stereo broadcasting in addition to monaural broadcasting.

[0002]

[Prior art]

 FIG. 4 is a block diagram showing the configuration of an example of a conventional AM stereo radio receiver.

In the figure, a high frequency signal which is a broadcast signal received by an antenna 1 is amplified by a high frequency amplifier circuit 2 and supplied to a mixing circuit 3. The local oscillation signal is supplied from the PLL circuit 4 to the mixing circuit 3 and mixed with the above-mentioned high frequency signal to form the intermediate frequency signal SIF. The frequency of the local oscillation signal output from the PLL circuit 4 is controlled by the controller 5 composed of a microcomputer to perform tuning.

The intermediate frequency signal SIF output from the mixing circuit 3 is amplified by the intermediate frequency amplifier circuit 6 and then supplied to the input terminal 7i of the AM stereo demodulation circuit 7. At the output terminals 7oL and 7oR of the demodulation circuit 7, the left audio signal L and the right audio signal R are respectively obtained when the selected station is for stereo broadcasting, while the selected station is for monaural broadcasting. If it is a monophonic audio signal, both are obtained. The audio signals obtained at the output terminals 7oL and 7oR of the demodulation circuit 7 are supplied to the speakers 10L and 10R via the muting circuit 8 and the low frequency amplification circuits 9L and 9R.

Further, the intermediate frequency signal SIF amplified by the intermediate frequency amplifier circuit 6 is supplied to the station detector 11. The station detector 11 determines that there is a station when the level of the intermediate frequency signal exceeds a predetermined value. The station detector 11 outputs a station detection signal SD which is at a high level "H" when no station is detected and at a low level "L" when a station is detected. The station detection signal SD is supplied to the controller 5. A display device (indicator) 12 is connected to the controller 5, and the presence or absence of a station is displayed on the display device 12 based on the station detection signal SD.

Further, a stereo detection signal ST is supplied from the demodulation circuit 7 to the controller 5, and the station selected for the display unit 12 based on the stereo detection signal ST is a stereo broadcast or a monaural broadcast. Is displayed.

Reference numeral 13 is a key panel provided with various operation keys connected to the controller 5. When automatic tuning is instructed by the key panel 13, the frequency of the local oscillation signal output from the PLL circuit 4 is sequentially changed by the control of the controller 5. Then, when the station detection signal SD from the station detector 11 becomes low level "L" to indicate station detection, the change of the frequency of the local oscillation signal is stopped, whereby the channel selection is automatically performed. Done.

FIG. 5 shows a specific configuration example of the AM stereo demodulation circuit 7, which corresponds to the well-known C-QUAM system. In the figure, the intermediate frequency signal SIF supplied to the input terminal 7i is supplied to the envelope detector 71, and the output signal of the envelope short line detector 71 is supplied to the matrix circuit 72.

Further, the intermediate frequency signal SIF supplied to the input terminal 7i is supplied to the in-phase synchronous detector 74 and the quadrature synchronous detector 75 via the gain control amplifier 73. Reference numeral 76 is a voltage controlled oscillator (VCO) having a center frequency of an intermediate frequency (450 KHz). The 0 ° phase frequency signal output from the oscillator 76 is supplied to the synchronous detector 74, and the oscillator 76 outputs the frequency signal. The output 90 ° phase frequency signal is supplied to the synchronous detector 75. In this case, the output signal of the synchronous detector 75 is supplied to the voltage controlled oscillator 76 as a control signal, and a PLL type synchronous detection circuit is configured.

The output signal of the synchronous detector 74 and the output signal of the envelope detector 71 are supplied to the error amplifier 77, and the output signal of this error amplifier 77 is supplied to the gain control amplifier 73 as a control signal. The output signal of the synchronous detector 75 is supplied to the matrix circuit 72.

When the intermediate frequency signal SIF is for stereo broadcasting, the envelope detector 71 outputs a sum signal (L + R). Further, the synchronous detector 74 outputs a signal of (L + R) cos θ. cos θ is a correction value on the transmission side. A signal of cos θ is output from the error amplifier 77, the gain of the gain control amplifier 73 is feedback-controlled by the signal, and the cos θ component is removed from the intermediate frequency signal SIF. As a result, the differential signal (LR) is output from the synchronous detector 75, the left audio signal L and the right audio signal R are separated by the matrix circuit 72, and the left audio signal L and the right audio signal are output to the output terminals 7oL and 7oR, respectively. An audio signal R is obtained.

When the intermediate frequency signal SIF is for monaural broadcasting, the envelope detector 71 outputs a monaural audio signal and the synchronous detector 75 does not output a difference signal (LR). A monaural audio signal can be obtained at both the output terminals 7oL and 7oR.

Further, the output signal of the synchronous detector 75 is supplied to the pilot signal detection circuit 78. In the detection circuit 78, the 25 Hz pilot signal added to the difference signal LR is detected on the transmission side. When the intermediate frequency signal SIF is for stereo broadcasting, the differential signal (LR) is output from the synchronous detection circuit 75, and the pilot signal is detected by the detection circuit 78. Therefore, the stereo detection signal ST has a high level. The "H" signal is output. On the other hand, when the intermediate frequency signal SIF is for monaural broadcasting, the differential signal (LR) is not output from the synchronous detection circuit 75 and the pilot signal is not detected by the detection circuit 78, so the stereo detection signal ST As a result, a low level “L” signal is output.

By the way, in the AM stereo radio receiver as shown in the example of FIG. 4, the intermediate frequency signal SIF and the output signal of the voltage control oscillator 76 of the demodulation circuit 7 are automatically selected, for example, when the frequency of the local oscillation signal is sequentially changed. There is a problem that a beat sound is generated from the speakers 10L and 10R due to the interference with.

Since this beat sound continues to be generated for a predetermined period, for example, 1 second or more, even after the time t1 when the station is detected by the station detector 11, in the example of FIG. The muting circuit 8 is operated until the time t2 after the elapse, and the muting of the voice is performed.

FIG. 6B shows the muting control signal MU supplied from the controller 5 to the muting circuit 8. When the control signal MU is at the high level “H”, the muting operation is performed and the muting operation is performed at the low level. When L ", the muting operation is not performed. 6A shows the station detection signal SD output from the station detector 11, FIG. 6C shows the stereo detection signal ST output from the pilot signal detection circuit 78 of the demodulation circuit 7, and FIG. 6D shows the speaker detection signals from the speakers 10L and 10R. The audio output is shown.

[0017]

[Problems to be solved by the device]

 In the AM stereo radio receiver as in the example of FIG. 4, the station detection signal SD output from the station detector 11 and the stereo detection signal ST output from the pilot signal detection circuit 78 of the demodulation circuit 7 are respectively supplied to the controller 5 The controller 5 determines from the detection signals SD and ST whether or not there is a station and whether or not the selected station is a stereo broadcast. Two ports are required for inputting the signals SD and ST, which is a hindrance when the audio system is configured by using one microcomputer.

Therefore, in this invention, one port of the microcomputer can be used for inputting a detection signal for determining the presence or absence of a station and whether or not the selected station is for stereo broadcasting. The purpose is to provide a machine.

[0019]

[Means for Solving the Problems]

 This invention is based on a station detecting means for detecting the presence / absence of a station, a stereo detecting means for detecting whether or not a selected station is for stereo broadcasting, a detection signal of the station detecting means and a stereo detecting means. A detection signal synthesizing means for synthesizing the detection signal to obtain a synthesized detection signal in which presence / absence of a station and whether or not the selected station is for stereo broadcasting are distinguished by voltage value, and the detection signal synthesizing means outputs the synthesized signal. Based on the voltage value of the combined detection signal, a discriminating means for discriminating whether or not there is a station and whether or not the selected station is a stereo broadcast is provided.

[0020]

[Action]

 In this invention, since the discriminating means can discriminate the presence or absence of a station and whether or not the selected station is a stereo broadcast based on the voltage value of the combined detection signal, the discriminating means is composed of a microcomputer. It is possible to have only one port for inputting the detection signal.

[0021]

【Example】

 An embodiment of the present invention will be described below with reference to FIG. This example is an example applied to an AM stereo radio receiver. In FIG. 1, parts corresponding to those in FIG. 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this example, the station detection signal SD output from the station detector 11 and the stereo detection signal ST output from the pilot signal detection circuit 78 (see FIG. 5) of the AM stereo demodulation circuit 7 are detection signal synthesis signals. The combined detection signal VD supplied to the circuit 15 and output from the combining circuit 15 is supplied to the controller 5.

FIG. 2 shows a specific configuration of the detection signal synthesis circuit 15. In the figure, a power supply terminal 21 to which a positive direct current voltage + B is supplied is grounded via a resistor 22 and a collector-emitter series circuit of an NPN transistor 23. The connection point of the collectors of the resistor 22 and the transistor 23 is connected to a power supply terminal 27 to which a positive DC voltage + 5V is supplied via a series circuit of a resistor 24, a cathode / anode of a diode 25 and a resistor 26. .

The stereo detection signal ST is supplied to the base of the transistor 23, and the station detection signal S D is supplied to the connection point between the resistor 24 and the cathode of the diode 25 via the resistor 28. Then, the signal obtained at the connection point between the anode of the diode 25 and the resistor 26 is output as the combined detection signal VD.

Here, the voltage value of the combined detection signal VD is as follows. When no station is detected, the station detection signal SD is at the high level "H", the diode 25 becomes an inverse bias and is turned off, and the voltage value of the combined detection signal VD becomes + 5V. When a station is detected and the station is for monaural broadcasting, the diode 25 is forward biased and turned on because the station detection signal S D is at low level “L”, and the stereo signal is turned on. Since the detection signal ST is at the low level “L”, the transistor 23 is turned off, and the voltage value of the combined detection signal VD becomes V1 (V1 <+ 5V).

When a station is detected and the station is for stereo broadcasting, the diode 25 is forward biased and turned on because the station detection signal SD is at the low level “L”, and Since the stereo detection signal ST is at the high level "H", the transistor 23 is turned on and the voltage value of the composite detection signal VD becomes V2 (V2 <V1). In this example, the resistance values of the resistors 22, 24, 26, 28 and the voltage value of + B are set so that V1 = + 3V and V2 = + 2V.

Returning to FIG. 1, the controller 5 determines the presence or absence of a station and whether or not the selected station is a stereo broadcast based on the voltage value of the synthesized detection signal VD from the detection signal synthesis circuit 15. It That is, when the combined detection signal VD is + 5V, it is determined that there is no station. When the combined detection signal VD is + 3V, it is determined that there is a station and that the station is for monaural broadcasting. When the synthesized signal VD is + 2V, it is determined that there is a station and that the station is for stereo broadcasting.

Then, the presence / absence of a station is displayed on the display unit 12 according to the determination result of the presence / absence of a station, and the display unit 12 is selected according to the determination result of whether or not the selected station is a stereo broadcast. Displays whether the station is for stereo broadcasting or monaural broadcasting. If it is determined that there is a station during automatic tuning, the change in the frequency of the local oscillation signal is stopped according to the result of the determination, and tuning is automatically performed.

Further, in this example, the controller 5 supplies the forced monaural control signal MN to the voltage controlled oscillator 76 of the AM stereo demodulation circuit 7 (see the broken line in FIG. 5), and the time t 1 when the station detector 11 detects the station. The operation of the voltage controlled oscillator 76 is stopped until time t3 immediately after (for example, a time within 100 msec from time t1) and the forced monaural state is set. In this forced monaural state, even if the selected station is for stereo broadcasting, the differential signal (LR) is not output from the synchronous detector 75, and both the output terminals 7oL and 7oR are output from the matrix circuit 72. A sum signal (L + R) is output to each.

FIG. 3B shows the forced monaural control signal MN, in which the voltage controlled oscillator 76 operates when the control signal MN is at the low level “L”, while the control signal MN is at the high level “H”. When the operation is controlled to stop.

In the present example, the muting circuit 8 mutes the voice until a time point t4 immediately after the time point t3 (for example, a time point 250 msec after the time point t1) t4. FIG. 3C shows the muting control signal MU. In the muting circuit 8, the muting operation is performed when the control signal MU is at the high level “H”, and the muting operation is performed when the control signal MU is at the low level “L”. Is not done. The broken line in FIG. 3C indicates the muting control signal MU in the conventional example.

3A is a station detection signal SD output from the station detector 11, FIG. 3D is a stereo detection signal ST output from the pilot signal detection circuit 78 of the demodulation circuit 7, and FIG. 3E is a speaker 10L. , 10R is a voice output, and FIG. 7F shows a combined detection signal VD output from the detection signal combining circuit 15.

The present example is configured as described above, and the others are configured similarly to the example of FIG.

In the present example, the detection signal synthesizing circuit 15 synthesizes the detection signal SD from the station detector 11 and the stereo detection signal ST from the pilot signal detecting circuit 78 of the demodulation circuit 7 to determine the presence or absence of a station and the channel selection. A combined detection signal VD is formed by discriminating whether or not the selected station is a stereo broadcast by a voltage value, and the controller 5 determines whether or not there is a station and the selected station is a stereo broadcast by the voltage value of the combined detection signal VD. It is determined whether or not

Therefore, the controller 5 composed of a microcomputer requires only one port for inputting a detection signal. Therefore, according to this example, it is possible to contribute to the elimination of the shortage of input ports when the audio system is configured by using one microcomputer.

Further, in this example, the operation of the voltage controlled oscillator 76 of the demodulation circuit 7 is stopped until the time point t3 immediately after the time point t1 when the station detector 11 detects the station. It is possible to prevent beat noise from being generated by the interference between the intermediate frequency signal SIF and the output signal of the voltage controlled oscillator 76 during the automatic tuning in which the frequencies are sequentially changed and the tuning is automatically performed. Therefore, the muting period of the voice after the station detection in the muting circuit 8 can be shortened as compared with the conventional case, the silent state after the station detection can be shortened, and the voice can be output after the station detection display is performed on the display unit 12. Unnaturalness due to the longer period until output can be eliminated.

Further, in this example, since the muting of the sound in the muting circuit 8 is canceled at the time point t4 after the time point t3 when the forced monaural state is released, the operation of the voltage controlled oscillator 76 is stopped at the time point t3. It is possible to prevent the noise generated at the start, that is, a so-called clicking sound, from being output from the speakers 10L and 10R.

In the above embodiment, the DC voltage supplied to the power supply terminal 27 of the detection signal synthesizing circuit 15 is set to +5 V (see FIG. 2), and V1 = + 3 V and V2 = + 2 V are set. However, the respective voltage values are not limited to those in the embodiment, and may be set to other voltage values capable of distinguishing the presence / absence of a station and whether or not the selected station is for stereo broadcasting. Good.

In the above embodiment, the presence / absence of a station is detected by the station detector 11 based on the level of the intermediate frequency signal SIF. However, the station detecting means is not limited to this, and It is also possible to have a configuration of.

Further, although the above-mentioned embodiment is applied to the AM stereo radio receiver, the present invention can be similarly applied to other receivers capable of receiving stereo broadcast in addition to monaural broadcast. is there.

[0041]

[Effect of device]

 According to this invention, the discriminating means can discriminate the presence or absence of a station and whether or not the selected station is a stereo broadcast based on the voltage value of the combined detection signal. In this case, the number of ports for inputting the detection signal can be set to one, which has the effect of contributing to elimination of port shortage and the like in the case of forming an audio system using one microcomputer.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a receiver according to the present invention.

FIG. 2 is a connection diagram showing a detection signal combining circuit according to an embodiment.

FIG. 3 is a time chart for explaining the operation of the embodiment.

FIG. 4 is a block diagram showing an example of a conventional AM stereo radio receiver.

FIG. 5 is a block diagram showing an example of an AM stereo demodulation circuit.

FIG. 6 is a time chart for explaining the operation of the conventional example.

[Explanation of symbols]

 3 Mixing circuit 4 PLL circuit 5 Controller 6 Intermediate frequency amplification circuit 7 AM stereo demodulation circuit 8 Muting circuit 10L, 10R Speaker 11 Station detector 12 Display 15 Detection signal synthesis circuit

Claims (1)

[Scope of utility model registration request] 1. A station detecting means for detecting the presence or absence of a station, a stereo detecting means for detecting whether or not the selected station is for stereo broadcasting, a detection signal of the station detecting means and the stereo detection. A detection signal synthesizing means for synthesizing the detection signal of the means to obtain a synthesized detection signal in which presence / absence of a station and whether the selected station is a stereo broadcast are distinguished by a voltage value; A receiver comprising: a determination unit that determines the presence or absence of a station and whether or not the selected station is a stereo broadcast based on the voltage value of the combined detection signal output from the receiver.