JPS5916478B2 - Multi-channel record demodulation method - Google Patents

Description

Detailed Description of the Invention The present invention provides a method for demodulating an angle modulated wave signal reproduced from a multi-channel record in which a direct wave signal and an angle modulated wave signal are multiplexed, and for demodulating an angle modulated wave signal. In the middle and low frequencies of the angle-modulated wave signal, the phase head nok droop (hereinafter referred to as P) has a relatively wide lock range.
(abbreviated as LL) demodulates a modulated signal with a large frequency shift with low distortion '0, and the PLL, which has a relatively narrow lock range, reduces distortion due to interference waves from the direct wave signal band to the angle modulated wave signal band. The abnormal sound (including distortion) is caused by the fact that the frequency deviation of the modulated signal, which is demodulated so that it is small and has a lot of energy distributed in the middle and low frequencies, is 15 times larger than the lock range. Since this cannot occur in PLLs with a wide range, the demodulated outputs of multiple PLLs are switched depending on the presence or absence of abnormal sounds in the demodulated outputs, and compared to the 20 PLLs with the widest range. Multi-channel record demodulation that sequentially turns on and off the demodulated outputs of PLLs having narrow lock ranges using the switching circuit, and selects one of the demodulated outputs of the plurality of PLLs to obtain a demodulated signal from which abnormal sounds have been removed. Method 25 is proposed.

When a PLL is used to demodulate an angle-modulated wave signal played from a multi-channel record in which a direct wave signal and an angle-modulated wave signal are multiplexed and recorded, the signal changes from the direct wave signal band to the angle-modulated wave signal band 30. interference waves may occur,
When the frequency deviation of the modulation signal, which has a lot of energy distributed in the middle and low frequencies, is larger than the lock range of the PLL, the PLL may deviate from the lock state and generate harsh abnormal sounds in the reproduced sound. be.

35 Conventionally, for abnormal sounds caused by the former, for example, P
A method has been proposed in which the abnormal sound detection signal of the synchronous detector connected to the LL is used to increase the loop gain of the PLL and control the ROTU 17-clean range to reduce the abnormal sound in the demodulated output. However, this method was vulnerable to abnormal noises caused by the latter.

In order to remove both of the above abnormal sounds, the applicant has
We previously proposed a demodulation method using L. However, even though the time rate in which the abnormal sound is present in the demodulated output is small, in the normal state where the time rate is large, the PLL has a wide lock range with high Hi-Fi characteristics. The demodulated output of a PLL with a narrow lock range cannot be Hi-Fi due to the delay in tracking high frequencies, etc., and it is necessary to maintain the Hi-Fi nature of the added demodulated output. However, there were disadvantages such as the need to add a delay circuit and a high frequency correction circuit. The present invention eliminates the above-mentioned problems, and the present invention will be explained below with reference to the drawings.

FIG. 1 is a block diagram for explaining the demodulation method according to the present invention, in which the angle-modulated wave signal supplied from the input terminal 1 is applied to a plurality of PLLs 2a, 2b, 2c, . . . and demodulated. Ru.

The plurality of PLL2a, 2b, 2c,... are PLL2
PIJ.a has the widest lock range, PLL2b has a narrower lock range, and PIJ.a has the widest lock range. 2
PLL c has a narrower lock range than PLL 2b, and is arranged in order from a wide lock range to a narrow lock range. PLL・
The demodulated signals from the switching circuits 2a, 2b, 2c, . . . are supplied to the switching circuits 3a, 3b, 3c, . The outputs of the switching circuits 3a, 4b, 4c, . . . are taken out from the output terminal 5 as demodulated outputs.

Switching circuits 3a and 4b, 3b and 4c, 3c and 4d
... are connected in a reciprocal manner to each other. For example, if the switching circuit 3a is 0N, the switching circuit 4
b is 0FF, and when the switching circuit 3a is 0FF, the switching circuit 4b is set to 0N. The switching circuits 3a, 3b, 3c, . . . are configured to turn 0FF when an abnormal sound occurs in the demodulated signals of the connected PLLs 2a, 2b, 2c, . Switching circuits 4b, 4c
,... are switching circuits 3a, 3b, 3c,...
Since they are connected reciprocally, PLL2a, 2b, 2
When no abnormal sound occurs in the demodulated signals of c, . . ., the switching circuits 3a, 3b, 3c, . . . are all 0N.
Therefore, all the switching circuits 4b, 4c, .

The out-of-lock state that causes abnormal noise in the demodulated signals of PLLs 2a, 2b, 2c, etc. is caused by interference waves from the direct wave signal band to the angle modulated wave signal band, and by interference waves in the middle and low frequencies. 2) This is due to an apparent overmodulation phenomenon due to the modulation signal of the angle-modulated wave signal having a frequency deviation larger than the lock range in which much energy is distributed.
There are two types: the former is likely to occur in PLLs with a wide lock range, and the latter is likely to occur in PLLs with a relatively narrow lock range.

In the configuration shown in Figure 1, PL with a wide rotary range
When abnormal sound occurs in L due to interference waves from the direct wave signal band to the angle modulated wave signal band, for example, PLL2a, 2
An abnormal sound is generated in PLL b, but no abnormal sound is generated in a PLL with a relatively narrow lock range, for example, PLL 2c or lower, switching circuits 3a and 3b are 0FF, and switching circuits 3c and lower are 0N, so the switching Since the circuits 4b and 4c are set to 0N and the switching circuits 4d and below are set to 0FF, only the demodulated signal of the PLL 2c is supplied to the output terminal 5 and taken out as a demodulated output.

Furthermore, due to the apparent overmodulation phenomenon caused by the modulation signal of the angle-modulated wave signal, which has a larger frequency deviation than the lock range in which much energy is distributed in the middle and low ranges, for example, the PLL has a relatively narrow lock range below 2c. When an abnormal sound occurs, switching circuits 3a and 3b switch to O'.
becomes N, and switching circuits below 3c become 0FF.
Therefore, the switching circuits 4b and 4c become 0FF, the switching circuits 4d and below become 0N, and only the demodulated signal of the PLL 2a is supplied to the output terminal 5 and taken out as a demodulated output.

As described above, according to the configuration shown in FIG. 1, the demodulated signal of the PLL having the widest lock range among the PLLs in which abnormal noise is not generated can be taken out as the demodulated output.

FIG. 2 shows one embodiment of the present invention.

In this embodiment, to simplify the explanation, a case is shown in which two PlJs are used. That is, the angle-modulated wave signal input from the input terminal 6 is applied to the two PLLs 7 and 8.

The PLL 7 has a locking range that is equal to or wider than the maximum deviation frequency range of the modulated signal of the angle-modulated wave signal, and is suitable for modulating signals with a large amount of energy distributed in the middle and low frequencies, such as trumpet sounds. On the other hand, demodulation with less distortion is performed, but it is not possible to prevent abnormal sounds caused by interference waves from the direct wave signal band to the angle modulated band. PLL
PLL 8 has a narrow lock range compared to PLL 7, and for modulated signals such as cymbal sounds in which a lot of energy is distributed especially in high frequencies, the narrow lock range causes a delay in high frequency tracking. Although it reduces apparent distortion and at the same time reduces the occurrence of abnormal sounds caused by interference waves from the direct wave signal band to the angle modulated wave signal band, the lock range has a large amount of energy distributed in the middle and low frequencies. When demodulating an angle-modulated wave signal having a frequency shift larger than the above, abnormal noise is generated. The demodulated output of PLL 7 is applied to switching element 9. The switching element 9 is switched from 0N to 0FF depending on the presence or absence of abnormal sound in the demodulated output of the PLL 7 by the output signal of a synchronous detector connected to the PLL 7, and at the same time, the demodulated output of the PLL 8 is applied by the inverter 10. Element 11
The switching element 9 is also turned ON-OFF by the operation opposite to that of the switching element 9. The demodulated output of the PLL 8 is applied to the switching element 12 and then to the switching element 11 described above. The switching element 12 is turned ON-OFF depending on the presence or absence of an abnormal sound in the demodulated output of the PLL 8 using an output signal from a synchronous detector or the like connected to the PLL 8. As the switching elements 9 and 11 turn ON-OFF in reverse operation, one of the demodulated outputs of the PLLs 7 and 8 is taken out from the output terminal 13 as a reproduced angle-modulated wave signal. If no abnormal sound is generated in the demodulated outputs of PLLs 7 and 8, the switching element 9 is in the 0N state, and therefore the switching element 11 is in the 0N state.
becomes 0FF, that is, the demodulated output of PLL 8 is suddenly cut off, and the demodulated output of PLL 7 is taken out from output terminal 13. When an abnormal sound occurs in the demodulated output of the PLL 7 due to an interference wave from the direct wave signal band to the angle modulated wave signal band, the abnormal sound detection signal of the PLL 7 immediately turns the switching element 9 into the 0FF state, and at the same time the switching element 9 11 becomes 0N state.

That is, the demodulated output of PLL 7 is suddenly cut off. At this time, PLL8 has a narrow locking range, so high frequency follow-up is slow, and therefore the interfering sound often disappears before the output of the PLL's voltage controlled oscillator locks onto the interfering wave. In other words, abnormal noise is heard during the demodulated output of PLL8. The probability of this occurring is extremely low. Therefore, the switching element 12 is in the ON state, and the demodulated output of the PLL 8 is taken out from the output terminal 13. When an abnormal sound is generated in the demodulated output of PLL 3 due to a modulation signal having a frequency deviation larger than the lock range in which energy is distributed more in the middle and low frequencies, the switching element 12 is immediately turned 0FF by the abnormal sound detection signal of PLL 8. becomes the state of

That is, the demodulated output of the PLL 8 is immediately cut off. At this time,
Since the PLL 7 has a maximum shift frequency range equal to the maximum deviation frequency range of the modulation signal of the angle-modulated wave signal, or has a wide lock range, no abnormal sound is generated in its demodulated output. Therefore, the switching element 9 is in the ON state, and the demodulated output of the PLL 7 is taken out from the output terminal 13. The demodulated output of PLL7 has an abnormal sound due to interference waves from the direct wave signal band to the angle-modulated wave signal band, and the demodulated output of PLL8 has a frequency deviation larger than the lock range where a lot of energy is distributed in the middle and low frequencies. When an abnormal sound is generated simultaneously with a modulated signal, the switching element 9 immediately becomes 0FF, and at the same time, the switching element 11 becomes 0N, but the switching element 12 also immediately becomes 0FF, emphasizing sound quality. From this point of view, no demodulated output appears at the output terminal 13. That is, except for the second and fourth cases, Hi-F
The demodulated output of the PLL 7 with high i-characteristics becomes the demodulated signal of the angle-modulated wave signal.

In FIG. 2, it is also possible to add a high frequency correction circuit to improve the demodulated output of the PLL 8. Also, if two or more PLLs are used, a similar circuit configuration can be made.
Depending on the number, it is possible to respond more precisely to abnormal sounds, and at the same time, it is possible to improve Hi-Fi performance. Figure 1,
Figure 2 shows a block diagram of the demodulation method of the present invention.
The present invention is not limited to this, but the demodulated signals from a plurality of PLLs with different lock ranges are demodulated by the PLL having the widest lock range among those that do not contain abnormal sounds. It is sufficient to generate the signal as a demodulated signal of the angle-modulated wave signal.

The present invention uses a PLL having a wide lock range and a PLL having a relatively narrow lock range when demodulating an angle modulated wave signal reproduced from a multi-channel record in which a direct wave signal and an angle modulated wave signal are multiplexed and recorded.
The demodulated output of the PLL is switched depending on the presence or absence of abnormal sound generated in the demodulated output, and the demodulated output of the PLL having the widest lock range is determined by the demodulated output that does not contain abnormal sound. Since it is obtained as a demodulated signal of the angle-modulated wave signal, abnormal sounds can be removed without impairing the Hi-Fi characteristics of the demodulated output in the normal state. When playing channel records, the playback sound is always maintained in good condition.

[Brief explanation of drawings]

FIG. 1 is a block system diagram for explaining the demodulation system according to the present invention, and FIG. 2 is a block system diagram for one embodiment of the demodulation system according to the present invention. 1, 6... Input terminal, 2a, 2b, 2c...
...7,8...PLLl3a, 3b, 3c,
...... 4b, 4c... Switching circuit, 5, 13... Output terminal, 9, 11, 12...
...Switching element, 10...Inverter circuit.

Claims (1)

[Claims] 1. When demodulating the angle modulated wave signal reproduced from a multi-channel record in which a direct wave signal and an angle modulated wave signal are multiplexed and recorded, a phase-locked loop with a relatively wide lock range characteristic and a relatively wide lock range characteristic are used. At least one phase-locked loop with narrow lock range characteristics.
The angle modulated wave signal to be demodulated is added to these phase-locked loops for demodulation, and the demodulated outputs from these phase-locked loops are added to switching elements corresponding to each phase-locked loop. , the ON/OFF of these switching elements is controlled according to the abnormal sounds in these demodulated outputs, and the phase-locked switch which has the widest lock range characteristic among the demodulated outputs that do not include abnormal sounds is selected from these demodulated outputs. A multi-channel record demodulation method characterized in that a demodulated signal of the angle-modulated wave signal from which abnormal sounds are removed is obtained by selecting a demodulated output demodulated by a loop.