JP2594740B2 - Receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television set installed in an FM tuner, a cassette tape recorder, a tape player or the like.
The present invention relates to a receiving device used for receiving an audio multiplex broadcast such as an audio multiplex signal.

[0002]

2. Description of the Related Art In various broadcastings, for example, FM broadcasting includes monaural broadcasting and stereo broadcasting.
Broadcast audio multiplex broadcasting includes dual audio broadcasting such as bilingual broadcasting in which main audio is broadcast in Japanese and sub audio is broadcast in a foreign language, and stereo broadcasting using main audio and sub audio.

FIG. 2 shows a frequency spectrum of audio multiplex broadcasting. S ₁ is a main channel signal, S ₂₀ is a sub-carrier, S ₂₁ is a sub-channel signal at the time of dual audio broadcasting, S ₂₂
The sub-channel signal during stereo broadcast, S ₃ the control channel signal, S ₃₀ the control signal subcarrier, S _31, S ₃₂ is a control signal sideband. In this case, in a stereo broadcast, the main channel signal includes the sum signal (L + R) of the left and right signals L and R,
The difference signal (LR) is set in the sub-channel signal. The horizontal synchronizing signal f _H of the television is about 1
5.75 kHz and the sub-carrier S ₂₀ is 2f _H (= 31.5 kHz
z), the control signal sub-carrier S ₃₀ is 3.5 f _H (= 55.125kH
z) The relationship is set.

FIG. 3 shows a frequency spectrum of FM stereo broadcast. _Sa is the main channel signal (L
+ R), S _b is a pilot signal, the S _C is a sub-channel signal (L-R). In this case, the pilot signal _Sb is
19 kHz and the subcarrier are set to 38 kHz.

Conventionally, a receiving apparatus for receiving both an audio multiplex broadcast and an FM stereo broadcast having such a frequency spectrum is configured as shown in FIG. The TV radio wave or the FM radio wave received by the antenna 2 is converted into an intermediate frequency through a channel selection and high frequency amplification by the front end 4, is amplified by an intermediate frequency (IF) amplifier circuit 6, and is then transmitted to an FM demodulation circuit 8. Added. The FM stereo composite signal or the multiplex composite signal demodulated by the FM demodulation circuit 8 is applied to the FM stereo demodulation circuit 12 or the audio multiplex demodulation circuit 14 via the switch 10A.

The FM stereo demodulation circuit 12 demodulates the left and right signals L and R from the FM stereo composite signal, and the audio multiplex demodulation circuit 14 generates the stereo left and right signals L and R from the multiplex composite signal or the main audio from the double audio broadcast. And the secondary audio. On the output side of the FM stereo demodulation circuit 12, variable resistors 16 and 18 for adjusting the level of the demodulated signal are provided for each channel, and on the output side of the audio multiplex demodulation circuit 14, variable resistors 20 and 22 are provided. Have been.

[0007] The demodulated outputs of the FM stereo demodulation circuit 12 and the audio multiplex demodulation circuit 14 are applied to an output amplifier 24 via a switch 10B and to an output amplifier 26 via a switch 10C. The amplified outputs of 24 and 26 are individually applied to speakers 28 and 30 and reproduced.

Further, each of the switches 10A, 10B, 10C
Is simultaneously closed to the contact a side or the contact b side, and when closed to the contact a side, the demodulation mode of FM stereo broadcast,
When closed to the contact b side, the mode is switched to the demodulation mode of the audio multiplex broadcasting.

[0009]

By the way, in such a receiving apparatus, the audio multiplexed signal and the FM stereo demodulated signal obtained from the FM stereo demodulation system are individually processed by the F-mode.
Since the signals are added to the M stereo demodulation circuit 12 and the audio multiplex demodulation circuit 14, switches 10B and 1B for extracting each demodulated output together with a switch 10A for selecting and adding each signal are provided.
0C is required, and installing such a large number of switches has disadvantages such as complicating the circuit configuration and requiring an installation space in the receiving device.

In addition, the audio multiplex demodulation system and the F
If the M stereo demodulation system is set separately, each demodulation level must be adjusted by the variable resistors 16, 18, 20, and 22, respectively. If the demodulation levels of each demodulation system are not equal, the demodulation mode is switched. In such a case, the level of the reproduced sound changes, so that the level of the reproduced sound must be adjusted according to the switching of the demodulation mode.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a receiving apparatus in which the mode switching is simplified and the demodulation level in the demodulation mode is made uniform.

[0012]

[0013]

As shown in FIG. 1, a receiving apparatus according to the present invention is a receiving apparatus for receiving an audio multiplex broadcast and an FM stereo broadcast, and comprises an audio multiplex signal and an FM stereo broadcast.
Receiving a stereo signal, the passed through the sound multiplex signals, demodulating means for demodulating the FM stereo signal, the presence or absence of sub-carriers of the sound multiplex signal which has passed through the demodulation means
A discriminating circuit for discriminating whether the received broadcast is in the audio multiplex mode, and when the discriminating circuit discriminates the audio multiplex mode,
A switching circuit that generates a switching output representing the voice multiplex mode, and a switch input from the outside,
In the audio multiplex demodulation mode, the dual audio demodulation mode
Switching circuit for generating a switching output indicating whether the mode is a rheo demodulation mode
Receiving the switching output of the switching circuit,
Demodulation mode according to audio multiplex mode or FM stereo mode
Mode, and the switching circuit
Receiving the switching output, the audio multiplex demodulation mode
Mode, switch between dual sound demodulation mode and stereo demodulation mode.
And a matrix circuit for performing a demodulation process on the output of the demodulation means in accordance with the demodulation mode switched and switched .

[0014]

[0015]

In this receiver, the FM stereo demodulation signal obtained from the FM stereo demodulation system is discriminated as to whether or not it is in the voice multiplex mode based on the presence or absence of a subcarrier of the voice multiplex signal in the voice multiplex demodulation circuit. Based on this, demodulation processing corresponding to the TV audio multiplex mode or the FM stereo mode is performed to reproduce each demodulated signal, so that it is not necessary to selectively switch each demodulated signal.

A switching circuit for generating a switching output indicating whether the mode is the dual voice demodulation mode or the stereo demodulation mode in the voice multiplex demodulation mode by an external switch input;
The matrix circuit is switched to the demodulation mode by receiving the output signal, the switching output or the switching output from the demodulation means, receives the output signal of the FM stereo demodulation system, and performs demodulation processing corresponding to the set demodulation mode from the output signal. If so, the demodulation process can be performed by setting a desired demodulation mode by an external switch input to the switching circuit.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments shown in the drawings.

FIG. 1 shows an embodiment of a receiving apparatus according to the present invention, and the same parts as those of the receiving apparatus for receiving the audio multiplex broadcast shown in FIG. On the output side of the FM demodulation circuit 8, an FM stereo demodulation circuit 12 is provided as demodulation means for demodulating the FM stereo signal from the FM stereo composite signal and passing an audio multiplex signal. The stereo composite signal and the multiplex composite signal are input to an input terminal 3 of an audio multiplex demodulation circuit 32 composed of, for example, a one-chip semiconductor integrated circuit.
4, 36.

A buffer circuit 38 is provided at an input section of the audio multiplex demodulation circuit 32. Each signal passing through the buffer circuit 38 is applied to a matrix circuit 40 via a low-pass filter 42 and a terminal 44 , 46 to a buffer circuit 50 via a high pass filter 48. That is, the audio multiplexed composite signal applied to the input terminal 34 is applied to the matrix circuit 40 as a main channel signal (L + R) via the buffer circuit 38 and the low-pass filter 42, while the audio applied to the input terminal 36 is The multiplexed composite signal is applied to a high-pass filter 48 via a buffer circuit 38. The FM stereo composite signal is applied from the buffer circuit 38 to the low-pass filter 42, passes through the matrix circuit 40, and is output from the output terminals 102, 1
04.

The audio multiplexed composite signal is demodulated via a buffer circuit 50 into a demodulation circuit 52 for demodulating a sub-channel signal.
And a voice multiplexing mode discriminating circuit 54
(Hereinafter referred to as a determination circuit 54).

The demodulation circuit 52 includes a voltage controlled oscillation circuit (VC
O) A phase-locked loop (PLL) including a waveform shaping circuit 58, a phase comparator 60, and a low-pass filter 62, a capacitor 64 for determining a reference oscillation frequency at a terminal 64, and a resistor at a terminal 66 70 and a terminal 72 are connected to a smoothing capacitor 74, respectively.
A variable resistor 76 as a feedback element is connected between 72. The sub-channel signal (LR) extracted from the output side of the low-pass filter 62 is supplied to the buffer amplifier 7.
8 to the matrix circuit 40.

The discriminating circuit 54 comprises a phase comparator 80 and a low-pass filter 82. The phase comparison signal having the frequency of the subcarrier obtained by shifting the phase by 90 ° with respect to the subcarrier obtained from the waveform shaping circuit 58 is output from the phase comparator 8.
In addition, a subcarrier synchronized with the audio multiplex composite signal is detected. The demodulated output of this sub-carrier is smoothed by a capacitor 86 connected to a terminal 84 and then applied to a switching circuit 88. The determination circuit 54 determines the voice multiplex mode based on the presence or absence of the subcarrier of the voice multiplex composite signal. The switching circuit 88 generates a switching signal corresponding to the sound multiplexing mode based on the discrimination output and applies the switching signal to the matrix circuit 40, and also includes a light emitting diode 94 connected between a terminal 90 and a power supply line via a resistor 92.
Drive.

The matrix circuit 40 is adapted to selectively switch between the audio multiplex demodulation mode and the FM stereo demodulation mode in accordance with the switching signal from the switching circuit 88, and to perform two modes in the audio multiplex demodulation mode. That is, the dual sound demodulation mode and the stereo demodulation mode are switched by the switching signal from the switching circuit (SW) 96. In this case, the switching signal for the switching circuit 96 is formed based on the switching input to the terminals 98 and 100. Therefore, the matrix circuit 40
Is switched between an audio multiplex demodulation mode and an FM stereo demodulation mode in response to a switching signal from a switching circuit 88. In the audio multiplex demodulation mode, a double audio demodulation mode or a stereo demodulation is performed based on a switching signal from the switching circuit 96. Mode.

The left and right signals L and R of the FM stereo demodulated signal passed through the matrix circuit 40 and the matrix circuit 40
The left and right left and right audio signals L and R of the audio multiplexed demodulated signal demodulated in the steps (1) and (2) are extracted from output terminals (102, 104) and individually applied to speakers (28, 30) via amplifiers (24, 26).

As described above, the FM stereo demodulation system is installed in the stage preceding the audio multiplex demodulation circuit 32, and the FM stereo demodulation system
The left and right signals L and R, which are stereo demodulated signals, and the multiplexed composite signal are added to the audio multiplex demodulation circuit 32, and the left and right signals L, R of the FM stereo demodulated signal simply pass through the buffer circuit 38, the low-pass filter 42, and the matrix circuit 40. And output from the output terminals 102 and 104.
Main channel signal (L + R) via low-pass filter 42
And demodulation of the sub-channel signal (LR) by the demodulation circuit 52 of the audio multiplex demodulation circuit 32 to demodulate the double audio or stereo signal and output the output terminal 10
2, 104.

In this case, the demodulation mode of the matrix circuit 40 is switched based on the output of the discrimination circuit 54,
At the time of M stereo demodulation and FM monaural demodulation, the matrix circuit 40 is simply made to pass a signal, and is switched to the demodulation mode in the audio multiplex mode. Then, in the audio multiplex demodulation mode, it can be determined by the lighting of the light emitting diode 94.

In this case, the levels of the FM stereo demodulated signal and the audio multiplexed demodulated signal are set to a common matrix circuit 4.
Since it passes through 0, it is adjusted to the same level.

[0028]

As described above, according to the present invention,
The following effects are obtained. a. F obtained from demodulation means for performing FM stereo demodulation
The M stereo composite signal can be extracted through the audio multiplex demodulation circuit, and the double audio or stereo signal can be demodulated from the multiplex composite signal, so that the switching of each demodulation process can be simplified and the demodulation levels can be made uniform. This eliminates the need for level adjustment. b. Since a double sound or a stereo signal can be demodulated and extracted from the multiplex composite signal, a switch conventionally required for selection switching of each demodulated signal becomes unnecessary,
The circuit configuration can be simplified, and the space for installing the switch can be reduced. c. A desired demodulation mode can be switched by an external input applied to the switching circuit, and together with automatic switching of the demodulation mode depending on the presence or absence of a subcarrier included in the audio multiplex signal, the degree of freedom in selecting the demodulation mode is increased, and the reception electric field strength is increased. It is also possible to cope with switching of the demodulation mode according to the above.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a receiving apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a frequency spectrum of an audio multiplex composite signal.

FIG. 3 is an explanatory diagram showing a frequency spectrum of an FM stereo composite signal.

FIG. 4 is a block diagram showing a conventional audio multiplex broadcast receiving apparatus.

[Explanation of symbols]

 12 FM stereo demodulation circuit (demodulation means) 32 audio multiplex demodulation circuit 40 matrix circuit 54 discrimination circuit 88 switching circuit 96 switching circuit

Continuation of the front page (56) References JP-A-58-187083 (JP, A) JP-A-57-14262 (JP, A) JP-A-56-167656 (JP, U) JP-A-58-147363 (JP, A) , U) Actually open 58-71270 (JP, U)

Claims (1)

(57) [Claims] 1. A receiving device for receiving an audio multiplex broadcast and an FM stereo broadcast , comprising: a demodulation means for receiving an audio multiplex signal and an FM stereo signal, passing the audio multiplex signal, and demodulating the FM stereo signal. The sub-carrier of the audio multiplex signal passed through the demodulation means
The presence or absence, and discrimination circuit receiving broadcast determines whether the sound multiplex mode, when the determination circuit has determined the sound multiplex mode, a switching circuit for generating a switching output representing the sound multiplex mode, switching from external In the above-mentioned voice multiplex demodulation mode upon receiving input
Indicates whether the mode is dual sound demodulation mode or stereo demodulation mode.
A switching circuit for generating a switching output, receiving a switching output of the switching circuit,
Demodulation mode according to multiplex mode or FM stereo mode
And before the switching circuit occurs.
By receiving the switching output, the voice multiplex demodulation mode
Time, switch between dual sound demodulation mode and stereo demodulation mode.
And a matrix circuit for performing demodulation processing on the output of the demodulation means in accordance with the demodulated mode that has been switched .