JPS5975402A - Reproducing device - Google Patents

Abstract

PURPOSE:To prevent incidence of step-difference noises with a simple constitution by demodulating two different sound signals which are frequency-modulated by plural frequencies and supplying their difference frequency signal to a frequency converting circuit, and then, converting and reproducing one side signal to the other side signal. CONSTITUTION:Sound output signals of limiter circuits 421 and 423 are switched to outputs of limiter circuits 422 and 424 outputted through multiplying circuits 70L and 70R by switching circuits 72L and 72R and supplied to demodulators 43L and 43R through BPFs 73L and 73R. On the other hand, a signal from the BPF 73L is supplied to a phase comparison circuit 76 through a frequency dividing circuit 75 of 1/N1 and the output of the circuit 76 is supplied to a voltage controlling oscillator 78 through an LPF 77. The output of the oscillator 78 is supplied to multipiers 70L and 70R and, at the same time, to the comparator 76 through a frequency dividing circuit 79 of 1/N2. If a phase error occurs with the output of the oscillator 78 when sound FM waves ALF1 and ALF2 are reproduced, the oscillator 78 is controlled so as to minimize the error and incidence of step- difference noises after demodulation is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a video tape recorder (V) that reproduces a recorded signal in which an audio signal is frequency-modified (δIM) (FM modulated) and frequency-multiplexed with a video signal. The present invention relates to a reproduction device suitable for application to i'R).

BACKGROUND TECHNOLOGY AND PROBLEMS The luminance signal in the video signal is FM modulated on the western side, and the chroma signal is frequency-interleaved between adjacent tracks to perform low frequency conversion, and two rotating heads with different azimuth angles are used. Recording is performed without placing a guard pan I on the second slope 1 rank of the ``ζ tape''.

In such a VTR, audio signals have conventionally been recorded using a fixed head on continuous tracks in the tape transport direction in a manner similar to what is known as an audio tape recorder.

However, in the case of the above-mentioned V1''R, when the recording density has been increased, the tape transport speed has been made extremely slow, currently up to, for example, 1.33 cm/sec. ζ The relative speed between the fixed head and the tape became slow, making it impossible to record good audio signals.

Therefore, it has been proposed to FM-modulate the audio signal in a band between the FM-modulated luminance signal and the low-frequency converted chroma signal, superimpose it on the video signal, and record it on a tilted track.

That is, in FIG. 1, +11 is a tuner,
The video signal from this tuner fJ) is transmitted to the AGC amplifier (2
), an emphasis circuit (3), and a clamp circuit (4) to the FM modulator (5) so that, for example, the sync chip 4. OMllz, Whitebeak is 5.2 MH
FM luminance signal J+=l−Y that is FM modulated so that z
F? -1 is formed. In addition, the video signal from tuner +11 is passed through a bandpass filter (6), an ACC circuit (7),
Immediately connect the frequency converter (8) to the low-pass filter (
9) and the subcarrier +7fl wave number is 61H311y
, a low frequency converted chroma signal JF+Co is formed.

Furthermore, the first audio signal JF# (for stereo, f signal, main signal for dual audio) AL from the tuner (1), and the second audio signal (right signal for stereo, sub signal for dual audio) A
R and AGC amplifier (IOL), respectively (101n)
, noise canceller (IIL), (IIR), pre-emphasis circuit (12L), (12R) through FM modulator (141), (142) and (14i), (14
4), each with a carrier frequency of 1.3, for example.
25 MI4z Sl, 475 MH'z, '1.6
25 MHz and 1.775 MHz so that the frequency deviation width is a constant 150 kHz, and the respective levels are as shown in Figure 2, ALFl < ALF2 < ARF3 < ARF4.
FM audio signal A LF 1, A adjusted so that
LF 2 , A RF 3 and A RF 4 are formed. Of these, FM audio signals ALFI and ARF3 are supplied to the mixing amplifier (16o) through bandpass filters (151) and (153), respectively, and FM audio signals ΔLF2 and ARF4 are supplied to the mixing amplifier (16o) through bandpass filters (152) and (154), respectively. Through °ζ mixing amplifier (16e
). This mixing amplifier (16o), (16e
) are sent to the adder circuits (17o) and (17e), respectively.
) is supplied to the adder circuit (17o), (17
e) are commonly supplied with the above-mentioned FM luminance signal YFtl and low frequency converted chroma signal C. Then, the added signals are sent to the rotary heads (19o) and (19e) with different azimuth angles through the recording amplifiers (18o) and (lee), respectively.
).

Also, the first and second audio signals ΔA from the top (1)
R through recording circuits (2OL) and (2OR), respectively.
(It is also supplied to conventional fixed heads (21L) and (21R).

In this apparatus, the spectrum of the recorded signal is as shown in FIG. Among these, the head (19o) has an F
M# voice signal Api2, ARF4 removed signal, navel l
” (19e) shows the ALFI% of the FM audio signal.
The ARF3 removed signal is provided.

Then, as shown in FIG. 4, inclined tracks to and te having different recording azimuths are alternately formed on the tape 'F] by the respective heads (19o) and <19e), and each of them receives a signal (YH+CD+ALFl). “ARyi
) or signal (Y-→-CI) + ALF2 10AR
F4J is recorded. Incidentally, the inclined tracks to and te are each longer than one field, and are formed so that signal overlap is provided between the respective tracks. In addition, continuous tracks LL and 1R in the tape transport direction are provided with heads (21L) and (21R).
Audio signals AL and AR are recorded in the same manner as before. Further, a control signal/CTL from a servo system (not shown) is recorded in the continuous track tc.

In this way, video signals and audio signals are recorded.

To reproduce the signal recorded in this manner, for example, the following procedure is performed.

That is, in FIG. 5, the rotating head (19o), (1
The reproduction signal of 9e) is output to the amplifier (40o) and (40o), respectively.
e). The signal from this amplifier (40o) has a center frequency of 1.325 MHz and 1.
The signals from the amplifier (40e) are fed to bandpass filters (41t) and (413) of 625 MHz, and the center frequencies are 1.475 MHz and 1.7 MHz.
75 MHz bandpass filter (412), (41
4). These punt' pass filters (4
Signals from 11) to (414) pass through limiter circuits (42t) to (424), respectively, to an FM demodulator (431).
(434), and the audio signals AL and ζ are demodulated, respectively. These audio signals AL and AR are respectively supplied to ]-pass filters (441) to (444). This low-pass Filter (441), (44
The signal from 2) is supplied to the switch circuit I/8 (451,), and is also supplied to the low-pass filter (44m >, (444)
A signal from the switch circuit (45R) is supplied to the switch circuit (45R).

These switch circuits (45L) and (45R) are connected, for example, to a terminal (45R) from a pulse generator provided in connection with the rotating drum.
46). The signals from these switch circuits (45L) and (45R) are passed through low-pass filters (47L) and (41R), respectively.
Noise canceller (48L), (48R), de-emphasis circuit (49L), (49R), switch circuit (
Audio output terminal (521) through (51L) and (51R)
, ), (52R). Also fixed head (21
The playback signals of L) and (21R) are the playback times WFI, respectively.
The switch circuit (
51L), (5111>).

Further, signals from the amplifiers (40o) and (40e) are supplied to the switch circuit (60).
0) is controlled by the signal from the terminal (46).

The signal from this switch circuit (60) is supplied to a bypass filter (61) to extract an FM luminance signal YFM, which is then sent to a limiter (62) and an FMfjti frequency generator (
63), the luminance signal Y is supplied to an emphasis circuit (64) and reviewed. In addition, the signal from the Sui-Nochi circuit (60) is supplied to a low-pass filter (65) to extract a low-pass converted chroma signal CI>, and this signal is supplied to a west-range conversion circuit (66) and a band-pass filter (67). The signal C is taken out. The luminance signal Y and chroma signal C are mixed in a mixing circuit (68) to form a video signal, which is supplied to a video output terminal (69).

The video signal and the audio signal are played back.

In this case, since the audio signal is FM-modulated and recorded and reproduced together with the video signal by the rotary head, the audio signal will not deteriorate even if the tape transport speed is reduced.

In addition, the recorded FM audio signal has reduced crosstalk from adjacent tracks due to azimuth loss, and
Since the carrier frequencies are different by 150 ktlz between adjacent tracks, the frequency of the beat signal is outside the audible band, allowing good reproduction without interference.

However, in this circuit, ζ, FMf, and
) to (434) have different carrier frequencies, and here the FM demodulation varies depending on the frequency.
Since the level of the output signal changes, the FMfjJ adjustment (4
3t) and (432), (433) and (434), causing fluctuations in the DC components of the output signals. That is, for example, if the original signal shown in FIG.
As shown in Figure C, a level fluctuation a occurs each time the switch is made.
So-called step noise occurs, making it impossible to obtain a good reproduction output.

Therefore, first, for example, the FM demodulator (431), (433)
It was considered to provide an adjustment circuit for DC and vibration @ adjustment on the output side of the . However, in this case, the accuracy of the adjustment circuit is required to be extremely high, and if the frequency of the reproduced FM signal is shifted due to variable speed reproduction or the like, the magnitude of the level fluctuation a changes, making it impossible to perform adjustment.

It has also been proposed to automatically control the amount of adjustment by providing a feedback loop in the two adjustment circuits, but since the response speed of the system is finite, it causes a seating error, and it is impossible to completely eliminate step noise. There wasn't.

On the other hand, as shown in FIG. 7, for example, a multiplier (70'L) is installed on the output side of the limiter circuits (422) and (424).
, (7011), and this IIi calculator (70L), (
FM audio signal A LF from the oscillator (71) to
A signal with a frequency difference between 1 and ALt2 + ARF3 and 8RF4 is supplied, and the Okakoshi transformation is performed so that the carrier frequencies of the FM audio signals ALF2 and ARF4 are respectively equal to ALFl + ARF3, and this multiplier (70L
), (70R) output and limiter times lI! 8C421)
, (423) are switched by the switch circuits (72L) and (72R) controlled by the signal from the terminal (46). ), (43R), demodulating each with one demodulator, and supplying the demodulated signals to low-pass filters (47L), (47I?).

However, in this case, even when recording, the eighth
As shown in the figure, one FM modulation 'A:4 (1
4L), (14R) FM audio signal ALF formed by
1, ARP3 13) Calculator (74L), (74R)
Perform frequency conversion to obtain 8BI7, 8RF4, and perform this frequency conversion using the same oscillator (71) used during playback.
The switch circuit (72L), (7
2R) is completely continuous. However, when playing back a saw tape recorded on another device, one
It is more difficult to match the frequencies of 1)↓, tl)
There is a problem with compatibility. Also, even if you are playing back a tape recorded with your own device, you can use variable speed I#! If I= is performed, the frequency will shift, so there is a risk that step noise will occur.

OBJECTS OF THE INVENTION In view of the above points, the present invention provides a reproducing apparatus which can prevent the occurrence of the level difference noise described in -1-.

SUMMARY OF THE INVENTION The present invention provides a system in which an audio signal is frequency modulated at multiple frequencies;
Overlap periods are sequentially set in different tracks at predetermined intervals. When reproducing the recorded signal, the minus signal of the signal which has been subjected to frequency dispersion at the above plurality of frequencies is directly supplied to the demodulation circuit, and the above-mentioned plurality of The other signals of the frequency dispersion 11 at the frequency of 1. The signals of -1-1 and the signals related to the signals of -1- are compared in phase, and the comparison output is converted into a variable frequency sporadic signal. 1, the signal is supplied to the frequency conversion circuit ζ, which forms a signal with a frequency that is the difference between the frequency of the signal described above and the frequency of other signals, and the signals 1 and 2 are supplied to the frequency conversion circuit ζ, This is a reproducing device which frequency-converts the signal of 1 to the frequency of the signal of -, and is designed to prevent step noise generation 1 with a simple configuration.

In FIG. 9 of the embodiment, limiter times WR (422), (424
) are provided with multipliers (70L) and (70R) on the output side of
3) are switched by the switch circuits (72L) and (72R), and the (?
3R) to 1ffJ C'-CF M i, i adjuster (43
L ), (43R) When supplied with 2? The signal from the band pass filter (73L) is supplied to one input terminal of the phase comparator circuit (76) through a 1/N1 frequency dividing circuit (75). The signal from this comparator circuit (76) is supplied to the ζ voltage controlled oscillator (78) through a locus filter (77). The signal from this oscillator (78) is supplied to the multiplier (70L) and (7 (IR)), and is also passed through the 1/N2 frequency division of 11 blades to the other input terminal of the comparison circuit (76). is supplied to

In each circuit, FM audio signals ALFI, AlF2
If the frequencies of are fl and f2, respectively, nl and r12 are integers between them, and fl<f2, then the above-mentioned procedure is used to set the output frequency of the oscillator (78) to r2 to f1. The frequency division ratios N1 and N2 of the frequency divider circuit 75) and (79) are N1-m °
n l N2-rn (n2ns) However, m is an integer and may deviate from it. Note that m is selected so that the maximum phase deviation of the FM wave of the 1/N1 frequency-divided output is within ±π.

Therefore, in this circuit °(, limiter times lI!8(42
The frequency of the output signal of the limiter circuit (42
2) The frequency of the output signal is set to rb, and the bandpass filter (
73L) fc, the frequency of the output signal of the oscillator (78)
Let fd be the frequency of the output signal of , these are f a
---r I -ns f f b--f2-02 f f c-(rz -nt) ff d -f
+.

For some reason, the output frequency of the oscillator (7B) is ±
If there is a deviation of Δf, then d fd when playing back the audio signal AL71.
=f+, AlF2 When N is generated, a phase error occurs between the FM wave and the output of the oscillator (78), and the oscillator (7B) is controlled in a direction to eliminate this error. .

As a result, this system becomes stable and the sui-nochi circuit (
72L), a continuous FM wave with no phase error is extracted. Then, the FM demodulator (43L) is
It is demodulated in the same way as the M wave.

In this way, the audio signal is demodulated. In this case, the heating frequency of the oscillator (78) is phased and is highly stably locked to the reproduced FM wave by the quadruple loop, so the step noise after demodulation becomes extremely small.

Also, during variable-speed playback, it is shifted and tuned to the third frequency, so accurate conversion can always be performed.

Furthermore, good compatibility with other devices can be obtained.

Regarding FM audio signals ARF3 and ARF4,
Since it is considered that the same fluctuation as LFI and A LF2 is added, the output of the oscillator (78) can be directly supplied to the multiplier (70R), but a similar circuit may be provided independently. .

In addition, the other human power of the comparison circuit (76) is the multiplier (70L
) may be formed from a signal on the input side or output side of the frequency divider circuit (79), in which case the frequency division ratio N2 of the frequency divider circuit (79) can be changed.

Effects of the Invention According to the present invention, generation of step noise can be prevented with a simple configuration.

[Brief explanation of the drawing]

Figures 1 to 4 are diagrams for explaining the recording device, and Figures 5 to 4 are diagrams for explaining the recording device.
FIG. 8 is a diagram for explaining a conventional device, and FIG. 9 is a system diagram of an example of the present invention. (43L), (43k) are FMi summer type circuit 70
L ), (70R) are 1 trigram calculator, (72L), (72R
) is a switch circuit, (75) and (79) are frequency dividing circuits, (
76) is a phase comparison circuit, and (78) is a voltage controlled oscillator. Figure 8-13- Figure 9

Claims (1)

[Claims] When reproducing a signal in which an audio signal is frequency-modulated at a plurality of frequencies and recorded in different tracks sequentially at predetermined intervals with an overramp period, the frequency-modulated signal at the plurality of frequencies is supplying the signal directly to the demodulation circuit, and switching other signals of the signal frequency-modulated at the plurality of frequencies to the above-mentioned signal through a frequency conversion circuit so as to supply the signal to the recording and demodulation circuit; Above-
Compare the phase of the signal with the signal related to the other signals mentioned above,
This comparison output is supplied to a variable frequency oscillator to form a signal having a frequency that is the difference between the frequency of the - signal and the frequency of the other signal, and this signal is supplied to the frequency conversion circuit.
2. A reproducing device which converts the frequency of the other signal to the frequency of the signal mentioned above.