JPS6024640B2 - Demodulator for angle modulated wave signals reproduced from multi-channel disc records - Google Patents

Description

[Detailed description of the invention] Frequency modulated wave signals (FM wave signals) and phase modulated wave signals (P
It is well known that a phase-locked loop (hereinafter abbreviated as PLL) can be used as a demodulation circuit for angle modulated wave signals such as M signal (M signal). A PLL may also be used to demodulate the angle modulated wave signal in a signal reproduced from a multi-channel disc record in which the angle modulated wave signal is frequency-multiplexed and recorded.

Now, as is well known, the above-mentioned PLL has a locking range that changes over a wide range depending on the signal level of the input angle modulated wave signal.
Since the frequency band range of the demodulated signal from the angle modulated wave signal demodulation circuit configured by is determined depending on the lock range of the PLL, if the signal level of the angle modulated wave signal input to the PLL is sufficiently high, The occupied frequency band of the demodulated signal from the PLL is sufficiently wide, and contrary to the above case, when the signal level of the input angle modulated wave signal to the PLL is low, the occupied frequency band of the demodulated signal from the PLL is wide enough. becomes narrow. In other words, the PLL's lock range automatically changes depending on the signal level of the angle modulated wave signal input to it, and the occupied frequency band of the demodulated signal automatically changes to widen or narrow accordingly. Therefore, PLLs with such characteristics generally have the following characteristics:
Multi-channel disc record, for example, so-called CD-4
This method is considered to be advantageous as means for demodulating the angle modulated wave signal in the signal reproduced from the disc record of the system. By the way, the baseband signal recorded in the frequency multiplexed format of the so-called CD-4 multi-channel disc record and the sub-channel signal formed by the angle modulated wave signal are located extremely close to each other on the frequency axis. Therefore, in the case of a program source where the baseband signal contains a large signal component in the high frequency part, for example, the sound of the s, such as s, s, s, c, s, or cymbal sound. In the case of a program source that contains a large signal component in the high pitched part of the baseband signal, such as in It appears as having a large amount of energy within the frequency band of the channel signal, and when it is vectorially added to the angle modulated wave signal that constitutes the sub-channel signal, it causes the angle modulated wave signal to disappear, or Something happens that causes the angle modulated wave signal to become extremely distorted.

Therefore, when the angle modulated wave signal in the signal reproduced from a CD-4 disc record is demodulated by a PLu-based demodulation circuit, the PLL may become out of lock or distorted when the angle modulated wave signal disappears. P to the angle modulated wave signal
This has caused a problem in that the LL may become locked, resulting in abnormal pulse-like noise occurring in the demodulated signal. As one means for solving the above problems, conventionally, a synchronous detector is used in which the oscillation frequency from a voltage controlled oscillator provided in the loop of a PLL for demodulating an angle modulated wave signal is given as a reference wave. By supplying the angle modulated wave signal to be demodulated to the synchronous detector, P
When the LL performs an operation that causes abnormal noise in its demodulated signal, the rapid change in phase that appears in the oscillation wave of the voltage controlled oscillator in the PLL loop is extracted from the synchronous detector as its output signal, and the Attempts have been made to use the output signal to remove or reduce abnormal noise in the demodulated signal from the PLL. FIG. 1 is a block diagram showing a schematic configuration of a conventional example for explaining the above-mentioned conventional solution means.
In the figure, 1 is the input terminal of the angle modulated wave signal to be demodulated, 2 is the output terminal of the demodulated signal, and the block PLL is a phase comparator 3, a loop filter 4, an amplifier. 5. A PLL composed of a voltage controlled oscillator 6, etc., in which the oscillation frequency value when the voltage controlled oscillator 6 is performing free-running oscillation is angularly modulated to be demodulated. The frequency value of the carrier wave in the wave signal is approximately equal to the frequency value of the carrier wave, and the PLL exhibits demodulation characteristics such that the angle modulated wave signal to be demodulated can be successfully demodulated. So its loop gain is set.

In FIG. 1, 7 is a synchronous detector that synchronously detects the angle modulated wave signal supplied to the input terminal 1, and this synchronous detector 7 is connected to the voltage controlled oscillator 6 in the PLL described above. The oscillation wave of is given as a reference wave.

P when the PLL is performing normal demodulation operation
Since the phase difference between the oscillation wave from the voltage controlled oscillator 6 in the LL and the input angle modulated wave signal is 900 degrees, when the PLL is in such an operating state, an output signal is sent from the synchronous detector 7. However, when the PLL deviates from the locked state, the phase of the oscillation wave from the voltage controlled oscillator 6 in the PLL may be in phase with (or out of phase with) the input angle modulated wave signal. Then, an output signal appears from the synchronous detector 7.

The output signal from the above-mentioned synchronous detector 7 is converted into a control signal by a control signal generation circuit 8 comprising, for example, a time constant circuit and an amplifier.

In the conventional circuit shown in FIG. 1, the abnormal noise in the PLL demodulated signal is removed or removed by controlling the gain of the gain control circuit 9 provided in the transmission path of the PLL demodulated signal, for example, using the control signal. This makes it possible to reduce the However, in the conventional example circuit shown in FIG.
The output signal is not output from the synchronous detector 7 only when abnormal noise occurs in the demodulated signal from the PLL, such as when L is locked to a distorted angle modulated wave signal, but the PLL demodulation Even if there is no abnormal noise in the signal, if there is a sudden large phase change in the angle modulated wave signal to be demodulated, the output signal of the synchronous detector 7 In such cases, the circuit arrangement shown in the first diagram has the disadvantage of causing malfunctions.

In other words, the carrier wave is angularly modulated using a signal wave, such as a trumpet sound, which has a repetition frequency in the middle to low frequency range, has a pulse train shape with a steep rise, and has a large peak value. If the obtained angle modulated wave signal is to be demodulated, the angle modulated wave signal to be demodulated will be in a state where a large phase change has suddenly occurred. ing.

On the other hand, the PLL used for demodulating the angle modulated wave signal that is the target of demodulation has its loop gain etc. set so that it can also output a demodulated signal corresponding to a signal wave having the above signal form. Of course, if the PLL loop gain is set large,
As mentioned above, there are disadvantages such as an expansion of the lock range and a decrease in noise resistance. Therefore, as a PLL for demodulation, the occupied frequency band of the angle modulated wave signal to be demodulated is Although the loop gain is within the lock range, the loop gain is set relatively small so as not to indicate a lock range that is significantly wider than the frequency band occupied by the angle modulated wave signal to be demodulated. Therefore, when a normal angle modulated wave signal with a large phase change suddenly occurring is supplied to the demodulating PLL, the oscillation from the voltage controlled oscillator 6 in the PLL The phase of the wave shifts greatly at that moment, and the output signal is sent out from the synchronous detector 7. In addition,
Even in the above state, the PLL does not go out of lock due to the so-called flywheel effect in the PL, and the PLL continues normal demodulation operation, so a normal demodulation signal can be obtained from the PLL. As described above, in the conventional solution described with reference to FIG. 1, the synchronous detector 7 provided to obtain an output signal when abnormal noise occurs in the demodulated signal from the PLL
Depending on the program source, the PLL may malfunction by sending out an output signal even when it is performing normal demodulation operation.

The present invention provides a signal reproduced from a multi-channel disc record in which an angle-modulated wave signal in a signal reproduced from a multi-channel disc record is demodulated by an angle-modulated wave demodulation circuit configured with a phase-locked loop. In a demodulating device for an angle modulated wave signal, the angle modulated wave signal in a signal reproduced from a multi-channel disc record is free-running oscillated at a frequency value near the frequency value of a carrier wave in the angle modulated wave signal. a first phase-locked loop that includes a voltage-controlled oscillator and is configured to obtain a demodulated signal from an input angle-modulated wave signal by setting an appropriate loop gain; It includes a voltage controlled oscillator that performs running oscillation at a free running oscillation frequency value different from that of the voltage controlled oscillator in the locked loop, and has a loop gain greater than the loop gain in the first phase locked loop. a second phase-locked loop configured to have a loop gain so that the occupied frequency band of the input angle modulated wave signal is included within a monolock range; It is configured to be supplied as an input signal to a synchronous detector, etc., in which the number of oscillations from the voltage controlled oscillator in the loop is given as a reference wave, and is generated based on the output signal of the synchronous detector. A demodulating device for an angle modulated wave signal reproduced from a multi-channel disc record is provided, the loop gain of a first phase-locked loop being controlled by a control signal obtained by controlling the loop gain of a first phase locked loop.
This solution solves the drawbacks of the conventional solutions mentioned above, and the details thereof will be explained below in detail with reference to the attached drawings.

FIG. 2 is a block diagram showing a schematic configuration of one embodiment of the demodulating device for angle modulated wave signals reproduced from a multi-channel disc record of the present invention. In FIG. input terminal for the angle modulated wave signal,
2 is the output terminal of the demodulated signal, and the block PLL
The part indicated by , is a first circuit which is composed of a phase comparator 3, a loop filter (low frequency filter) 4, an amplifier 5, a voltage controlled oscillator 6, and a loop gain control circuit 14 provided as necessary. phase-locked loop (first PL
L), and the part indicated by flock PLL2 includes a phase comparator 10, a loop filter (low-pass wave filter) 1
1, an amplifier 12, a voltage controlled oscillator 13, and the like.

Further, 7 is the voltage controlled oscillator 1 in the second PLL described above.
The oscillation wave of No. 3 is given as a reference wave and is a synchronous detector that synchronously detects the input angle modulated wave signal.The output signal of this synchronous detector 7 is given to a control signal generation circuit 8.
The control signal generated by the control signal generation circuit 8 is given as a gain control signal to a loop gain control circuit 14 and a demodulation signal gain control circuit 9 provided in the first PLL in the illustrated example. In addition, 15 in the figure is a low frequency monkey wave generator, and this monkey wave reducer 15 is the first PLL.
The function is to remove the carrier wave component from the output signal.

In the illustrated example, the gain control circuit, loop gain control circuit, etc. indicated by drawing symbols 9 and 14 in FIG. 2 include a resistor R inserted and connected in series with the signal transmission path, A variable resistor VR inserted and connected in parallel to the transmission line (the figure shows an example of using a variable resistor VR whose collector-emitter resistance of a transistor is varied by the base input voltage) )
Although a variable attenuation network type circuit is shown as being used, it is obvious that other types of gain control circuits may be used in implementation.

The angle modulated wave signal to be demodulated supplied to the input terminal 1 is transmitted to the first PLL described above, the second PLL 2,
When simultaneously applied as an input signal to the synchronous detector 7, etc., the first PLL operates to send the demodulated signal to the subsequent circuit, and the second PLL 2 operates to send the demodulated signal to the subsequent circuit, and the second PLL 2 operates to output the demodulated signal to the voltage controlled oscillator provided in its loop. The synchronous detector 7 operates to provide the oscillation wave of P.13 as a reference wave to the synchronous detector 7, and furthermore, the synchronous detector 7 converts the angle modulated wave signal input thereto into the second P.
A synchronous detection operation is performed using the oscillation wave from the voltage controlled oscillator 13 provided in the LL as a reference wave.

Now, here, the above-mentioned first PLL and second PLL
how each is structured,
The following description will be made with reference to FIGS. 3a to 3e. First, Fig. 3a is a diagram showing the arrangement of occupied frequency bands A and B of the baseband signal Sb and the angle modulated wave signal Sa in the multiplexed signal reproduced from a multi-channel disc record.
f in the figure indicates the frequency of the carrier wave of the angle modulated wave signal Sa (center frequency of the angle modulated wave signal).

The multiplexed signal reproduced from a multi-channel disc record is passed through a Takagi wave transducer or an Obishiro wave transducer to produce an angle modulated wave signal Sa in the occupied frequency band B as shown in Figure 3b. This signal is separated and supplied to the input terminal 1 as an angle modulated wave signal Sa to be demodulated. The PPL used to demodulate the angle-modulated wave signal Sa to be demodulated, which occupies the frequency band B mentioned above, has a free-running oscillation frequency as a voltage-controlled oscillator 6 provided in its loop. An angle modulated wave signal whose lock range is the frequency f of the carrier wave in the angle modulated wave signal Sa to be demodulated, or a frequency near the frequency f of the carrier wave, and whose lock range is the target of demodulation. The loop gain is set to be approximately the same as or slightly wider than the occupied frequency band B in Sa.

As a result, if the input angle modulated wave signal supplied to the first PLL is in a normal state,
A demodulating operation is performed to send a normal demodulated signal to a subsequent circuit regardless of the program source.

FIG. 3c is an example diagram showing the relationship between a change in the signal level of the input angle modulated wave signal of the first PLL and a change in the lock range of the first PLL. In addition, the second PLL2
is a voltage controlled oscillator 13 provided in the loop, which has a target running oscillation frequency f different from the free running oscillation frequency f of the voltage controlled oscillator 6 in the first PLL.
2 is used, and the loop gain is set to be large so that the lock range can include the occupied frequency band B in the angle modulated wave signal Sa to be demodulated. There is.

FIGS. 3d and 3e are exemplary diagrams showing the relationship between the signal level of the input angle modulated wave signal of the second PLL 2 and the change in the lock range of the second PLL 2. The second PLL2 mentioned above
The target running frequency f2 of the voltage controlled oscillator 13 at
Even if the free-running oscillation frequency of the voltage controlled oscillator 6 in the first PLL is set lower than the above, as illustrated in FIG. 1st
The free-running oscillation frequency f of the voltage-controlled oscillator 6 in the PLL may be set higher than the free-running oscillation frequency f.

Furthermore, the free-running oscillation frequency f of the voltage-controlled oscillator 13 described above
2 is desirably selected to have a frequency value that is somewhat distant from the frequency value of f, rather than to select a frequency value that is close to the frequency value of f.

When the free-running oscillation frequency f of the voltage-controlled oscillator 6 in the first PLL is 30 KHz, the target running oscillation frequency of the voltage-controlled oscillator 13 in the second PLL is, for example, 1
Appropriate frequency within the range of song HZ ~ 2 class day 2, or,
Selecting an appropriate frequency within the range of 3 to 4 HZ is an example of how to select the free-running oscillation frequency f2 of the voltage controlled oscillator 13, and in fact, the first P
When the target running oscillation frequency f of the voltage controlled oscillator 6 in the LL is 30 KHz, when the free running oscillation frequency f2 of the voltage controlled oscillator 13 in the second PLL is selected to be 1 HZ and the device of the present invention is implemented, , good results have been obtained. As mentioned above, the second PLL 2 uses the frequency f of the carrier wave in the angle modulated wave signal Sa given as an input signal to the second PLL 2.
．． It is equipped with a voltage controlled oscillator 13 configured to perform free-running oscillation at a frequency f2 different from Because of this setting, the phase of the oscillation wave of the voltage controlled oscillator 13 follows the phase of the input angle modulated wave signal even when the program source is a trumpet sound signal, for example. Therefore, in such a case, no output signal is generated from the synchronous detector 7 to which the oscillation wave of the voltage controlled oscillator 13 in the second PLLI is supplied as a reference wave.

However, due to various causes, the wave of the angle modulated wave signal to be demodulated is missing, and therefore the second PLL
2 may be out of lock, or the angle modulated wave signal to be demodulated is distorted by interference waves mixed into it, and the second PLL is applied to the distorted angle modulated wave signal.
When the PLL is locked, a large output signal is reliably sent out from the synchronous detector 7 which receives the reference wave from the voltage controlled oscillator 13 in the second PLL.

The output signal sent from the synchronous detector 7 is converted into a control signal in the control signal generation circuit 8, and is passed through the first PLL, the loop gain control circuit 14, and the demodulation signal gain control circuit 9. etc., the loop gain control circuit 14 in the first PLL reduces the loop gain of the first PLL by its operation, narrows the lock range of the first PLL, and The gain control circuit 9 for the demodulated signal attenuates the demodulated signal through its operation, and therefore, abnormal noise occurring in the demodulated signal is effectively removed or reduced by the gain control operation by the gain control circuits 9 and 14 described above. be. As described above, in the demodulating device for the angle modulated signal reproduced from the multi-channel disc record of the present invention, in order to demodulate the angle modulated wave signal to be demodulated with good noise resistance characteristics, In addition to the free-running oscillation frequency f of the voltage-controlled oscillator 6 provided in the first PLL, and the first PLL in which the loop gain and the like are set, the free-running oscillation frequency f of the voltage-controlled oscillator 6 in the first PLL described above , and has a voltage controlled oscillator 13 having a free-running oscillation frequency different from that of , and has a lock range that includes the occupied frequency band of the angle modulated wave signal to be demodulated. A second PLL2 with a large gain is provided,
By giving the oscillation wave from the voltage controlled oscillator 13 in the second PLL 2 as a reference wave to the synchronous detector 7, the first PLL takes an operating state that causes abnormal noise in the demodulated signal from it. The output signal is obtained from the synchronous detector 7 only when the signal is in the form of a pulse train with a repetitive frequency in the middle and low frequency band, a sudden rise, and a large peak value, such as the sound of a trumpet. When the angle-modulated wave signal obtained by angle-modulating the carrier wave using a signal as shown in FIG. The device of the present invention does not cause any malfunctions that were a problem with the conventional device as shown in the first figure, and the control signal generated based on the output signal of the synchronous detector 7 allows the first PLL to The lock range is narrowed by controlling the loop gain in the demodulated signal, and the gain control circuit of the demodulated signal is controlled by the control signal to cut off or reduce the demodulated signal, thereby removing abnormal noise appearing in the demodulated signal. can be reduced.

Brief description of the box Fig. 1 is a block diagram of an example of a follower device, and Fig. 2 is a block diagram of an embodiment of a demodulating device for angle modulated wave signals reproduced from a multi-channel disc record of the present invention. , and FIGS. 3A to 3E are characteristic curve diagrams for explanation.

1...Input terminal, 2...Output terminal, PLL, PLL
, PLL2...phase locked loop, 3,1
0... Phase comparator, 4, 11... Loop filter, 5, 12... Amplifier, 6, 13... Voltage controlled oscillator, 7... Synchronous detector, 8... Control signal generation circuit,
9...Gain control circuit, 14...Loop gain control circuit, 15...Low band passer.

Mug 1 Plan 2 Plan 3

Claims (1)

[Claims] 1. A multi-channel disc record in which an angle-modulated wave signal in a signal reproduced from a multi-channel disc record is demodulated by an angle-modulated wave demodulation circuit composed of a phase locked loop. In a demodulating device for an angle modulated wave signal reproduced from a record, the angle modulated wave signal in the signal reproduced from a multi-channel disc record is subjected to free-running oscillation at a frequency value near the frequency value of a carrier wave in the angle modulated wave signal. comprising a voltage controlled oscillator adapted to perform
Further, the first phase locked loop is configured such that the occupied frequency band of the input angle modulated wave signal is included within its lock range by setting an appropriate loop gain; It is equipped with a voltage controlled oscillator that performs free-running oscillation at a free-running oscillation frequency value different from that of the voltage controlled oscillator in the locked loop, and has a loop gain greater than the loop gain in the first phase locked loop. a second phase locked loop configured to include the occupied frequency band of the input angle modulated wave signal within its lock range by setting the loop gain; The oscillation wave from the voltage controlled oscillator is configured to be supplied as an input signal to a synchronous detector or the like which is provided as a reference wave,
Furthermore, the loop gain of the first phase locked loop is controlled by a control signal generated based on the output signal of the synchronous detector described above. Signal demodulator. 2. The angle reproduced from a multi-channel disc record in which the angle-modulated wave signal in the signal reproduced from the multi-channel disc record is demodulated by an angle-modulated wave demodulation circuit composed of a phase-locked loop. In a demodulating device for a modulated wave signal, a voltage configured to cause an angle modulated wave signal in a signal reproduced from a multi-channel disc record to undergo free-running oscillation at a frequency value near the frequency value of a carrier wave in the angle modulated wave signal. Equipped with a controlled oscillator,
The first phase locked loop is configured such that the occupied frequency band of the input angle modulated wave signal is included in its lock range by setting an appropriate loop gain.
a voltage controlled oscillator configured to perform free-running oscillation at a free-running oscillation frequency value different from that of the voltage controlled oscillator in the first phase locked loop; a second phase locked loop configured such that the occupied frequency band of the input angle modulated wave signal is included within the locked range by setting the loop gain to be larger than the loop gain in the locked loop; The oscillation frequency from the voltage controlled oscillator in the second phase locked loop is configured to be supplied as an input signal to a synchronous detector or the like in which the number of oscillations from the voltage controlled oscillator is given as a reference wave, and further, the output of the synchronous detector is A demodulating device for an angle modulated wave signal reproduced from a multi-channel disc record, wherein the amplitude of a demodulated signal from a first phase locked loop is controlled by a control signal generated based on the signal.