JPS61117933A - Receiver - Google Patents

Abstract

PURPOSE:To simplify the circuit constitution and cost-down by detecting the absence of a 19kHz stereo pilot signal, presence of subcarrier and locking of an FM detection circuit of a PLL system and regarding the said detection as the reception of a television sound multiplex signal. CONSTITUTION:Since the 19kHz stereo pilot signal does not exist, the sub carrier exists and the FM detection circuit 27 of the PLL system is in locking state at the reception of a television sound multiplex signal, all inputs to an AND gate 35 are logical H and an output of the AND gate 35 is logical H. Thus, a bias is applied to a buffer transistor (TR)28 and a polarity inverting TR29 and an output of the FM detection circuit 27 is given to a base of the polarity inverting TR29 via the buffer TR28, a de-emphasis circuit 49 and a low passfilter 50. Since the output of logical H of the AND gate 35 is fed to the 1st switch 40 as an operating power supply, the 1st-4th switch circuits 25-34 are switched depending on the state of the 1st switch 40.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a receiving device capable of receiving an FM stereo signal and a television audio multiplex signal, and in particular, to a receiving device capable of receiving an FM stereo signal and a television audio multiplex signal. The present invention relates to a receiving device capable of demodulating the television audio multiplexed signal without detection.

(b) Prior Art At present, receiving devices capable of receiving FM stereo broadcasts and television audio multiplex broadcasts are known.

The FM stereo signal used in the FM stereo broadcasting consists of a main channel signal consisting of a stereo sum signal (L+R) and a stereo difference signal (L-R) using a 38KHz subcarrier.
A sub-channel signal AM-modulated by 19KH
It is created by FM modulating the main carrier wave with the z stereo pilot signal. The TV audio multiplex signal used in the TV audio multiplex broadcast is composed of a main channel signal consisting of a stereo sum signal (L+R) or a first audio signal (Japanese) and a stereo difference signal (L- R) or second audio signal (foreign language)
a sub-channel signal FM-modulated by 55.1
25 KHz control subcarrier to 982°5Hz 1i
It is created by FM modulating the main carrier wave with a control channel signal that is AM-modulated with a separate signal or a second identification signal of 922.5 Hz. However, since the FM stereo signal and the TV audio multiplexed signal have different modulation methods as mentioned above, they cannot be demodulated using the same demodulation circuit, and independent demodulation circuits are required in the receiving device. had to be placed.

On the other hand, when comparing FM stereo broadcasting and TV audio multiplex broadcasting, we focused on the fact that the structure of the main channel signal is the same, and there is a technology that uses an FM stereo demodulation circuit as a circuit to separate the main channel signal. Japanese Unexamined Patent Publication No. 1983-
It is disclosed in the 38084 newsletter. As shown in FIG. 2, the receiving device described in FIG. 3 of the publication includes a stereo multiplex circuit (stereo demodulator including 11) and an FM detection circuit for FM detecting a sub-channel signal of a TV audio multiplex signal. (Sub-channel signal demodulation unit including 31 (
4), a control channel signal demodulator including a λM detection circuit (5) for performing AM detection on the control channel signal and an identification circuit +61 for determining the type of identification signal included in the AM detected control channel signal; When receiving a stereo signal of a television audio multiplexed signal (hereinafter referred to as a television stereo signal), a stereo sum signal (L+R) obtained from a stereo demodulator (4)) and a stereo difference signal (L+R) obtained from a sub-channel signal demodulator (4)) are A matrix circuit (8) for matrixing LR).

Now, if an F, M" stereo signal is received, an FM stereo composite signal is applied to the input terminal (9), and the signal is separated into left and right stereo signals 0 and [yes] by the stereo multiplex circuit (1). Then, the left stereo signal υ is outputted to the left output terminal (2) via the de-emphasis circuit al and the low-pass filter (111), and the right stereo signal ■ is outputted to the left output terminal (2) via the de-emphasis circuit αj and the low-pass filter α. At that time, since there is no identification signal in the FM stereo signal, the output of the switch circuit ae (to the control channel demodulator) is in the first state (for example, rHJ) K, and the The first and second switches αD and α& are in the illustrated state.

Next, if a TV stereo signal is received, a TV stereo composite signal is applied to the input terminal (9),
It is applied to the stereo multiplex circuit (11). At the same time, the sub-channel signal signal in the TV stereo composite signal is applied to the FM detection circuit (3) through a band pass filter α9 having a band of 15 to 47 KHz.
and the control channel signal is applied to 55.1
The signal is applied to the AM detection circuit (5) via a bandpass filter (2) having a center frequency of 25 KfIz. Thus, the control channel signal applied to the AM detection circuit (5) is AM-detected and then identified by the identification circuit (6), indicating that it is a TV stereo signal at 982.5Hz.
A first identification signal is applied to the switch circuit (16).

In that case, the output of the switch circuit αe maintains the first state, and the first and second switches a also maintain the first state.

Further, the sub-channel signal applied to the FM detection circuit (3) is subjected to FM detection and then sent to the de-emphasis circuit +211.
and a matrix circuit (81
is applied to Furthermore, a stereo multiplex circuit (
The TV stereo composite signal applied to 1) is
Since there is no 19KHz stereo pilot signal, the stereo multiplex circuit (1) is just a back 7.
Since it operates as an amplifier circuit, it passes through the M stereo multiplex circuit (1) as it is, and then the de-emphasis circuit CI[)031 and the low-pass filter (1).
11 (141), and stereo sum signals (L
+R). Then, the stereo sum signal and the stereo difference signal (L-R) from the sub-channel demodulated signal are matrixed in a matrix circuit (8), and the left stereo signal ■ is sent to the left output terminal α2, and the left stereo signal ■ is sent to the right output terminal α2. Terminal αSK right stereo signal ■ is generated respectively.

Furthermore, if two audio signals of the TV audio multiplexed signal are received, the two audio signals are applied to the input terminal (9), which are applied to the stereo multiplex circuit (1), and the two audio signals are applied to the stereo multiplex circuit (1). The sub-channel signal is applied to the FM detection circuit (3) via the band-pass filter a9, and the control channel signal is applied to the AM detection circuit (51) via the band-pass filter (2).

Therefore, a second m-separate signal of 922.5 Hz is generated from the identification circuit (61), and the output of the switch circuit αe is in the second state (
For example, rLJ)K, the first and second switches (171
and 6 seconds, the situation is opposite to that shown in the diagram. Said first switch α
When n is switched to the opposite state as shown, the output signal of the sub-channel signal demodulator (4) is generated at the right output terminal αS via the first switch a. In addition, the second switch (
When 1g+ is switched to the opposite state as shown, the input terminal of the matrix circuit (8) is grounded, so the matrix circuit (8) stops operating. Therefore, the two audio signals applied to the stereo multiplex circuit (11) pass through the stereo multiplex circuit (1), which operates as a buffer amplifier circuit, and are passed through the left output terminal α2 through the de-emphasis circuit αl and the low-pass filter αB. occurred in
FM detection circuit (3) through bandpass filter (19)
The sub-channel signal applied to the de-emphasis circuit +211. after being subjected to FM detection. It is generated at the right output terminal a via the low-pass filter and the fJIc1 switch aη. Therefore, the signal obtained at the left output terminal az is the first
The signal obtained at the right output terminal α9 becomes the audio signal (Japanese), and the signal obtained at the right output terminal α9 becomes the second audio signal (foreign language).

As mentioned above, by using the circuit shown in Fig. 2, it is possible to correctly demodulate the FM stereo signal and the TV audio multiplex signal, and moreover, the FM stereo demodulator (1) can be used to reproduce the main channel signal of the TV audio multiplex signal. Since it is shared by the circuits, the single circuit configuration becomes simple.

e→ Problem to be Solved by the Invention However, the circuit shown in FIG. 2 performs circuit switching by detecting the identification signal included in the TV audio multiplexed signal, and the main carrier wave is not controlled by the control channel signal. Due to the fact that the degree of modulation is low at 2 KHz, the frequency of the control channel signal is relatively high at 55 KHz, and the frequencies of 982.5 K and 922.5 Hz of the first and second identification signals are close to each other, etc. After the control channel signal to detect the signal, y4s becomes very complicated,
It also had the disadvantage of being expensive.

In addition, in the case of the circuit shown in Fig. 2, when two audio signals of the TV audio multiplex signal are received, the first audio signal is generated at the left output terminal a, and the second audio signal is generated at the right output terminal a9. When the amplifier circuit and left and right speakers are connected to the left and right output terminals tlz and (l191c), it is not possible to listen to only the first audio signal or the second audio signal, so a separate switch circuit is provided to listen to the first audio signal or the second audio signal. This method has the disadvantage that it is necessary to select between two audio signals.

B) Means for Solving the Problems The present invention has been made in view of the above-mentioned points.
z The first means for detecting the absence of the stereo pilot signal, the second means for detecting the subcarrier of the television audio multiplex signal, and the PLL type FM detection circuit for FM detecting the subcarrier are in a locked state. The present invention is characterized in that it comprises a third means for detecting, and a fourth means for generating a control signal according to the output signals of the first to third means and correctly demodulating the television audio multiplexed signal.

(E) Effect According to the present invention, it is possible to determine whether the signal currently being received is an FM stereo signal or a TV audio multiplex signal by only the first to fourth means, and depending on the signal currently being received. It is possible to perform circuit switching.

(f) Embodiment Figure 1 is a circuit diagram showing an embodiment of the present invention.
An input terminal to which the detected FM stereo signal and TV audio multiplexed signal are applied, @ is a stereo multiplex circuit for separating the FM stereo signal into left and right stereo signals, (C) is the input terminal (C) and the above. The first switch circuit inserted between the input terminal of the stereo multiplex circuit @, ■ is a bandpass filter with a bandwidth of 15 to 47 KHz, and @ is a PLL system that performs FM detection on the subcarrier of the TV audio multiplex signal. FM detection circuit, ■ is a buffer transistor, 4 is a polarity inversion transistor that generates an FM detected sub-channel signal at the emitter and an inverted signal of the sub-channel signal at the collector, (to) is the first subtraction circuit, 0υ is a second subtraction circuit; (to) a second switch circuit inserted between the collector of the polarity inversion transistor and the first subtraction circuit; (to) a second switch circuit inserted between the emitter of the polarity inversion transistor and the first subtraction circuit; 1 subtraction transistor (7
), and (b) a third switch circuit inserted between the right output terminal of the stereo multiplex circuit □□□ and the input terminal of the second subtraction circuit GIJ. 4-switch circuit, (to) becomes KrLJ when receiving an FM stereo signal, and becomes KrHJ when receiving other signals.The first switch to which the lighting signal of the stereo indicator (to) is applied.
The human power, the second human power to which the rHJ compensation signal generated at one end of the capacitor (b) is applied when a subcarrier is present, and the lock signal generation end +K that indicates that the PLL type FM detection circuit @ is locked are connected. 33 and a driving transistor for driving the TV audio multiplexing indicator according to the output signal of the AND gate. Incidentally, the first to fourth switch circuits (c) to the example are configured to be in a conductive state when the rHJ signal is applied to the control terminal.

Now, if an FM stereo signal is applied to the input terminal (to), the FM stereo signal is applied to the stereo multiplex circuit (2) via the first switch circuit (c), and the left and right stereo signals are output as before. Separated into [F] and ■. At this time, since the FM stereo signal includes a 19 KHz stereo pilot signal, the cathode of the stereo indicator (to) becomes rLJ, and the stereo indicator (to) lights up to indicate FM stereo reception. At the same time, the rL441 is applied to the first power of the AND gate (to), so the rL441 is applied to the first power of the AND gate (to).
The output of (to) becomes rLJ, and the bias of the buffer transistor (c) and the polarity inversion transistor (to) is cut off. Therefore, no signal is generated at the collector and emitter of the polarity inversion transistor 4, regardless of the state of the first and second switches and I. Therefore, the left stereo signal generated at the output end of the stereo multiplex circuit @ [
F] is applied to the first subtraction circuit (to) k via a de-emphasis circuit and a Hiropass filter.

In addition, the right stereo signal generated at the output end of the stereo multiplex circuit (goods) is de-emphasized by the de-emphasis circuit.
It is applied to the second subtraction circuit Gυ via a low-pass filter and a fourth switch circuit, G4). Then, the signals obtained at the collector and emitter of the polarity inversion transistor 4 become zero, and the left and right stereo signal colors and 2 are output as they are to the left and right output terminals 2 and Qη, thereby achieving FM stereo reception. Incidentally, when receiving an FM stereo signal, the output of the AND gate becomes rLJ, so the first switch status becomes irrelevant to the operation.

Next, FM monaural signal or TV monaural signal (
When a monaural signal (hereinafter referred to as a monaural signal) is applied to the input terminal (c), the monaural signal is applied to the stereo multiplex circuit (2) via the first switch circuit 4. At that time, since there is no 19 KHz stereo pilot signal, the stereo multiplex circuit (2) operates as a mere buffer amplifier circuit, and equal monaural signals are generated at both output ends. Then, the monaural signal is processed through a tie-emphasis circuit (42, ()), a low-pass filter (43, (c), and a first and second subtraction circuit (to)).
, C3υ to the left and right output terminals -, (4'rI, so monaural reception is achieved. In that case, 19
Since there is no KHz stereo pilot signal, the stereo indicator (To) is turned off and the rHJ compensation signal is applied to the first input of the AND gate (To). On the other hand, since the monaural signal does not include components of 15 KHz or higher, there is no signal that passes through the bandpass filter@. Therefore, the capacitor (9) is not charged and the second
Human power becomes rLJ. Further, since the above-mentioned 15 KHz or higher component is not included, the PLL type FM detection circuit does not lock, and the third human power of the AND gate (to) becomes rLJ. Therefore, like when receiving an FM stereo signal, the output of the AND gate becomes rLJ, and the buffer transistor @
The polarity reversing transistor (support) is turned off, and the signals at the collector and emitter of the polarity reversing transistor become zero.

Furthermore, when a television audio multiplex signal is applied to the input terminal t23VC, the television audio multiplex signal is applied to the stereo multiplex circuit 0 through the first switch circuit, and the sub-channel signal of the television audio multiplex signal is applied to the stereo multiplex circuit 0 through the first switch circuit. PLL through bandpass filter country and amplifier circuit decoy
It is applied to the FM detection circuit of the method. Since the stereo multiplex circuit (24) operates as a buffer amplifier circuit in this case as well as when receiving a monaural signal, the positive input terminals of the first and second subtraction circuits (7) and 131 are connected to the main A channel signal is applied. Further, the sub-channel signal applied to the FM detection circuit is applied to the base of the buffer transistor after being subjected to FM detection. However, when receiving a TV audio multiplex signal, 19
Since there is no KIIz stereo pilot signal, there is a subcarrier, and the PLL type FM detection circuit is in a locked state, all inputs of the AND gate are r.
HJ, and the output of the AND gate becomes rHJK. Therefore, a bias is applied to the buffer transistor (to) and the polarity inversion transistor 4, and the output of the FM detection circuit (2) is polarity inverted via the buffer transistor (to), the assist circuit Kl, and the pass filter. Applied to the base of the transistor wire. Furthermore, since the output rHJ of the AND gate Kasumi is supplied to the first switch as an operating power source, the first to fourth switch circuits (
C) to (B) can be switched depending on the state of the first switch.

Here, if the received TV audio multiplexed signal is a TV stereo signal, the first switch is manually switched to the stereo position (BL).Then, the second switch circuit becomes conductive, and the polarity inverting transistor 4 becomes conductive. The inverted stereo difference signal -(L-R) obtained at the collector is applied to the first subtraction circuit (TO) via the second switch circuit Q, and is applied from the low-pass filter to the first subtraction circuit (TO). is subtracted from the stereo sum signal (L+R), and a left stereo signal ■ is generated at the left and right power terminals. Also, the stereo difference signal (L-
R) is directly applied to the second subtraction circuit Gυ, and is subtracted from the stereo sum signal (L+R) applied from the fourth switch circuit (2) to the second subtraction circuit Cl1)K, and the right stereo signal is output to the right output terminal. ■ occurs.

Next, assume that the received television audio multiplex signal is a two-audio signal, and move the first switch to the main channel position (a) shown in the figure.
If the switch is switched to l, the interlocking second switch will also switch to the main channel position shown in the figure (all), and the base of the buffer transistor will be grounded. Therefore, the generation of the sub-channel signal will stop, and the stereo A first audio signal is derived from the multiplex circuit (2) to the left output terminal via a de-emphasis circuit, a low-pass filter, and a first subtraction circuit (to); c), 4th switch vr04
, the right output terminal Q? via the second subtraction circuit 6υ. ) is also the first
An audio signal is derived. Furthermore, when the first switch decoy is switched to the sub-channel position (d), the first switch circuit (to) is cut off, the main channel signal is no longer applied to the stereo multiplex circuit L24), and the third switch circuit Q is Since it is in a conductive state, the second audio signal obtained at the emitter of the polarity inversion transistor 翰 is applied to the fourth subtraction circuit (to) via the third switch circuit and is also directly applied to the second subtraction circuit Gυ. A second audio signal is generated equally at the left and right output terminals - and Cη. Furthermore,
When the first switch μQ is switched to the mixing position (cl) of the main channel signal and the sub-channel signal, @4 switch circuit - is cut off, and the first subtraction circuit (to) is connected to the first audio signal from the low-pass filter (c). Since the second audio signal is applied to the second subtraction circuit 01) from the polarity inversion transistor wire, the first audio signal is applied to the left output terminal, and the second audio signal is applied to the right output terminal 17). Each occurs. Note that when the output of the AND gate (to) becomes rHJ, the drive transistor (to) turns on, so the audio multiplex indicator (to) lights up, indicating that the TV audio multiplex signal is being received.

(G) Effects of the Invention As described above, according to the present invention, the absence of a 19KHz stereo pilot signal, the presence of a subcarrier, and the PLL
Since it is assumed that the TV audio multiplex signal has been received by detecting the lock of the FM detection circuit of the system, the TV audio multiplex signal can be accurately received without detecting the identification signal in the TV audio multiplex signal. I can recognize it. In particular, since the three signals are detected, it is possible to prevent malfunctions due to noise and malfunctions when the PLL detection circuit is abnormally turned on, and the recognition can be performed with high accuracy. Furthermore, according to the present invention, there is no need to detect an identification signal, so it is possible to significantly simplify the circuit and reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional receiving device. Explanation of main books (2)...Stereo multiplex circuit, ■, Zeng, (To), (Goods)...Switch circuit, (To)...
Bandpass filter, ■...FM detection circuit, (To), 0υ...Subtraction circuit, (To)...And gate. Applicant Sanyo Electric Co., Ltd. and one other agent Patent attorney Shizuo Sano Figure 1

Claims (1)

[Claims] (1) In a receiving device capable of receiving an FM stereo signal and a television audio multiplex signal, a first means for detecting the absence of a 19 KHz stereo pilot signal, a second means for detecting a subcarrier of the television audio multiplex signal, The subcarrier is F
It consists of a third means for detecting that a PLL type FM detection circuit for performing M detection is in a locked state, and a fourth means for generating a control signal in accordance with the output signals of the first to third means. A receiving device characterized in that a television audio multiplex signal is recognized in accordance with a control signal obtained from the fourth means.