JPS5841032B2 - Audio multiplex receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for receiving audio multiplexed signals of television broadcasting.

Generally, in an audio multiplex receiver that is combined with a television receiver, it is not possible to ensure sufficient speaker spacing, and it is difficult to obtain a sufficient stereo reproduction effect even when receiving a stereo broadcast mode.

Furthermore, when receiving monaural signals in monaural broadcasting mode or different type of broadcasting mode, the sound image is localized to the center, so even if a two-speaker system is prepared as a device, the sound image will be zero.
It was an unsatisfying struggle as there was no sense of expansion.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an audio multiplex reception device that can provide a sufficient stereo sound or pseudo-stereophonic sound even with a small speaker interval when receiving audio multiplex broadcasts. .

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

First, FIG. 1 shows the form of the received signal.

This is a tuner that receives a television signal and demodulates the audio signal.

The signal includes a main channel signal, a sub channel signal, and a control signal.When in stereo broadcast mode, the main channel signal is used as the main audio signal (L+R) signal power 1\\sub channel signal is used as the sub audio signal. The (L-R) signal is transmitted as the control signal, and the 982.5H2O) signal is transmitted as the control signal.
In the different broadcast mode, the main channel signal is a Japanese main audio signal, the sub channel signal is an English sub audio signal, and the control signal is a 9225H2 signal.

In monaural broadcast mode, only the main channel signal is transmitted.

Next, FIG. 2 shows a block diagram of the entire receiving apparatus and will be explained.

Here, 1 is an input terminal to which a multiplex audio signal as shown in FIG. 1 demodulated by the audio demodulation circuit of the television receiver is supplied, and 2 is a multiplex demodulation circuit that demodulates the main and sub audio signals from the input signal. , 3 is a broadcast mode detection circuit that detects the broadcast mode by identifying the presence or absence of a control signal from the input signal, and 4 is a reception mode switching circuit that inputs the desired reception mode using a switch or the like. It is similar to that of the receiving device.

The multiplex demodulation circuit 2 connects the broadcast mode detection circuit 3 to terminals 5 and 6.
demodulates the input signal according to the stereo detection signal and the different type detection signal output to the receiver, switches the output based on the instruction from the reception mode switching circuit 4, and outputs main and sub audio signals to the output terminals 7 and 8. do.

In the case of stereo broadcast reception, an L signal is output to the output terminal 7 and an R signal is output to the output terminal 8.

In the case of receiving a different type of broadcast, either the main audio signal is output to both output terminals 7 and 8 (main audio reception), or the output terminals 7,
8 (sub-audio reception), or the main audio signal is output to the output terminal 7 and the sub-audio signal is output to the output terminal 8 (main-sub simultaneous reception).

When receiving monaural broadcasting, the same audio is output to both output terminals 7 and 8.

9.10 is an output circuit that amplifies and outputs each audio signal, and 11.12 is a pair of left and right speakers that emit audio.

The speakers 11, 12 may be built into the television receiver.

The present device is characterized in that an indirect sound adding circuit 13 is provided in such a receiving device.

Q) The indirect sound addition circuit 13 includes an indirect sound switching circuit 14 that switches the indirect sound signal to be added at the time of stereo reception and at other times according to the stereo detection output of the broadcast mode detection circuit 3, and A delay circuit 15 that delays the indirect sound signal by a predetermined time, a defeat circuit 16 that switches whether or not to add the indirect sound signal depending on the reception mode, an inversion circuit 17 that inverts the indirect sound signal, and a forward and reverse indirect sound signal. Synthesizing circuits 18 and 19 are provided to add the two original audio signals respectively.

Further, in order to be able to switch the indirect sound signal delay time between stereo reception and other reception, a digital delay element 20 such as a BBD element is used as a delay circuit 15, and a clock generation circuit 21 for driving the digital delay element 20 is used as a delay circuit 15. The clock frequency is switched by the stereo detection output from the broadcast mode detection circuit 3.

22 and 23 are filters for input and output thereof.

FIG. 3 shows a specific circuit example of the indirect sound switching circuit 40), FIG. 4 shows a specific circuit example of the clock generation circuit Q), and FIG. 5 shows a specific circuit example of the default circuit.

In such a configuration, the operation during stereo reception will first be described.

At this time, the L audio signal is output to the output terminal 7 of the multiplex demodulation circuit 2, and the R signal is output to the output terminal 8.
Moreover, a stereo detection output is generated at the output terminal 5 of the broadcast mode detection circuit 3.

Therefore, at this time, the indirect sound switching circuit 14 switches to stereo based on its detection output, and creates an (LR) signal as an indirect sound signal.

In other words, since the stereo detection output is at a low level, the third
The transistor 24 in the figure is cut off, and the L signal and the R signal taken out from the collector of the transistor 25 are transferred to the resistor 26.
28, it is successfully output as an LR)' signal.

This (LR)' signal is then added to the delay circuit 15 and delayed.

The optimum delay time for stereo reception is about 0.15 mse, and if 128 BBD elements are used as the delay element 20, the clock frequency is switched to about 450 KHz.

Here, the above optimal delay time (approximately 0.15 m5ec)
is determined as follows.

First, the relationship between a television receiver with built-in left and right speakers and a viewer is as shown in FIG. 4, for example.

Here, the position of the left speaker is A1, the position of the right speaker is B1, the position of the viewer's left ear is C1, and the position of the right ear is D.

The sound coming from speaker A and the sound coming from speaker B are both C and D.
However, the time required for the sound emitted from A to reach D's ear (this is set as τ1) is the time required for the sound emitted from B to reach D's ear (this is set as τ2). ) is slightly longer than

Therefore, from the left speaker A, L+(L-R) "L is the original left audio output R is the original Q right audio output (L-R)" is the delayed signal of (L-R). When speaker B outputs the sound R+(R-L), D's ear (Hi hears R+(R-L)h).
The sound is heard earlier than the sound of L+(LR)'' by (τ1-τ2).

At this time, if the delay time for creating (R-L) is equal to (τ1-τ2), it will reach D's ear and +(L-R)". Sound and R+(R-L)
The Rel (-L) component contained in the ``Rel (-L)'' component cancels each other out, so that more of the R sound reaches D's ear, and less of the L sound reaches the ear of D.

As a result, an effect of improving the stereo feeling such that the B speaker is located further to the right and the A speaker is located further to the left is produced.

Assuming that the positional relationship between speakers A and B and the listener's ears C and D is as shown in the general figure 4, the distance between AD = 15
8.11cr/L Distance between BD = 152.97 (11771) If the sound speed is 340m/SeC, (τ1-τ2) is (158,11-152,97)÷34000=0.1
5 m5ec.

In other words, if the delay time is set to 0.15 m5ec, the sound on the left will arrive at the right ear 0.15 m5ec later than the sound on the right, and the sound from the right of the opposite polarity will be delayed by 0.15 m5ec. It cancels out the sound and improves the stereo feeling.

Based on this, the optimal delay time is 0, 15 m5
It is called ec.

In other words, the transistor 29 in FIG.
Increase the oscillation frequency of the oscillation circuit consisting of 3°34 etc.

The delayed indirect sound signal (L-R) is taken out via the defeat circuit 16 and added to the L audio signal in the synthesis circuit 18 to form an L+(L-R) signal, which is emitted from the speaker 11.

Further, the inverting circuit 17 inverts the polarity to create a (R-L) signal, and the synthesizing circuit 19 adds it to the R audio signal and adds it to the R+(R-
L) “signal and is generated from the speaker 12.

In this way, when the difference signal between the L signal and the R signal is synthesized with the voice emitted from the speaker lL12 with the delayed (L-R) signals having opposite polarities, the sound is output from the two speakers 11 and 12 to the left and right ears of the listener. It is possible to cancel the crosstalk components from the speakers on the opposite side that reach the speakers on the opposite side.

In other words, it is possible to make it possible for only the L sound to reach the left ear and only the R sound to reach the right ear, so that the two speakers 1L12 can be placed at a narrow interval such as in a television receiver 0) Cow Yabinet. Even if the sound is set at the listener's ear, the separation between the L and R sounds can be improved.
This makes it possible to significantly expand the sound field of stereo audio.

Next, the case where only one of the main audio or the sub audio is received during reception of different types (during selective reception of different types) and the time of non-multiplex reception will be described.

At this time, the multiplex demodulation circuit 2 (/, J output terminals 7, 8
Both generate the same output signal (M signal), which is either the main audio signal, the auxiliary audio signal or a non-multiplexed single signal.

Therefore, in either case, a monaural reception state is achieved.

In this case, since there is no low-level stereo detection output from the output terminal 5 of the broadcast mode detection circuit 3, the transistor 24 of the indirect sound switching circuit 14 becomes conductive and cuts off the output of the transistor 25, and the indirect sound signal is As a result, the M signal is output as is (0) as the M' signal.

On the other hand, since the optimum delay time of the M' signal for sound field expansion Φ during monaural reception is about 4 m5ec, which is longer than that during stereo reception, the transistor 29 in the clock generation circuit 21 is conductive. The capacitor 30 is coupled in parallel with the capacitor 33, and the frequency of the clock applied to the delay element 20 consisting of 128 stages of BBD elements is set to 15.
．． Lower it to about 7KHz.

This optimum delay time (approximately 4771 SeC) was determined as follows.

When monaural, originally left and right Q) speakers A and B
The same sound can be heard from

However, when the (M + M') ov signal is output from the left and the (M-V) ov signal is output from the right as in this method Q, the signal of (M+M") is generated because the phase of the delayed signal M" of M is opposite to that of M. The amplitude becomes small at a frequency where the phase of M" matches that of M, and the amplitude becomes large at a frequency where the phase of M" coincides with M.

0) As a result, the amplitude of the left and right outputs changes depending on the frequency of the sound.

The larger the change in the left and right output amplitudes, the more the sound spreads left and right. On the other hand, the longer the delay time, the narrower the frequency interval between the peaks and troughs of the amplitude change, improving the audibility.

For this reason, the delay time is longer in monaural mode than in stereo mode, but due to design and manufacturing issues, approximately 4 m5ec is appropriate.

In other words, when using digital delay elements as delay elements, it is better to have as few stages as possible, and
The frequency of the clock for driving one delay element is also limited by the relationship with the transmission band and the horizontal and vertical frequencies of the television set, so it was set to 47FLSeC.

The M" signal of the indirect sound signal delayed in this way is taken out via the defeat circuit 16, and synthesized with the M signal in the synthesis circuit 18, and is emitted from the speaker 11 as an M+M" signal.

On the other hand, after the polarity is inverted in the inverting circuit 17, it is combined with the M signal in the combining circuit 19, and is generated from the speaker 12 as the MM'' signal.

In this way, the sound field is expanded even though it is monaural by synthesizing the M "sound" and -M "sound, which are delayed and have opposite polarities to the M sound emitted from speakers 11 and 12 during monaural reception. It is a conflict that can play pseudo-stereo audio.

Now, during stereo reception, heterogeneous selective reception, and non-multiplex reception as described above, in each case, the effective effect of sound field expansion is achieved by creating and synthesizing indirect sound signals. However, in the case of simultaneous main and sub-reception in which both the main audio and sub-audio are received during heterogeneous reception, for example, when the main audio is generated by the speaker 11 and the sub-audio is generated by the speaker 12. (Actually, one of them often uses earphones)
If indirect sounds are synthesized as described above, unnecessary loss talk will occur between the main sound and the sub-sound, which are completely different.

Therefore, in the case of warping, the default circuit 16 is switched to cut off the indirect sound so as not to extract it.

That is, in FIG. 6, the transistors 35 and 360 connected in parallel are connected to the base of the first transistor 35, a low level foreign detection output 43 is applied from the output terminal of the broadcast mode detection circuit 3, and the base of the other transistor 36 is applied. When a low-level instruction output indicating that simultaneous main and sub-reception is being applied from the reception mode switching circuit 4 to the receiver, a high-level output is taken from its collector and added to the base of the transistor 37. By making it conductive, the transmission path of the indirect sound signal is grounded and its transmission is cut off.

In this way, crosstalk between the main audio and the sub audio can be eliminated during simultaneous main and sub audio reception, and each can be reproduced separately with good separation.

As described in detail above, according to the present invention, in an apparatus for receiving audio multiplexed signals, it is possible to improve the stereo effect during stereo reception, and to improve the sound field by creating a pseudo-stereo effect during heterogeneous selection reception and non-multiplex reception. It is possible to expand the scope of the project.

[Brief explanation of the drawing]

FIG. 1 is a spectrum diagram of an audio multiplex signal, and FIG. 2 is a block diagram of an audio multiplex receiver according to an embodiment of the present invention.
3, 4, and 5 are specific circuit diagrams of a portion of the apparatus, and FIG. 6 is a plan view illustrating the positional relationship between the speaker and the viewer. 2...Multiple demodulation circuit, 3...Broadcasting mode detection circuit, 4...Reception mode detection circuit, 9,
10... Output circuit, 11, 12... Speaker, 13... Indirect sound addition circuit, 14...
... Indirect sound switching circuit, 15 ... Delay circuit, 1
6... Defeat circuit, 17... Inversion circuit, 18, 19... Synthesis circuit, 20...
...Delay element, 21...Clock generation circuit.

Claims (1)

[Scope of Claims] 1. A multiplex demodulation circuit that demodulates an audio multiplexed signal and outputs at least one of a left audio signal and a right audio signal of a stereo broadcast, and a main audio signal and a sub audio signal of a different type of broadcasting from two output terminals. , an indirect sound switching circuit that extracts the difference signal between the left audio signal and the right audio signal or one of the main audio signal and the sub audio signal as an indirect sound signal; a delay circuit that delays the indirect sound signal; and a delay circuit that delays the indirect sound signal. a synthesizing circuit that synthesizes the indirect sound signal with the output signals of the two output terminals of the multiplex demodulation circuit with opposite polarities, two speakers that respectively emit voices based on the two synthesized output signals, and the above-mentioned audio. The broadcast mode detection circuit detects a control signal in a multiplexed signal and switches the demodulation method in the multiplex demodulation circuit, the indirect sound signal in the indirect sound switching circuit, and the delay time in the delay circuit, respectively. audio multiplex receiver. 2. The audio multiplex reception device according to claim 1, characterized in that the supply of indirect sound is cut off when receiving different types of broadcasts simultaneously.