JPH0666082B2 - Magnetic recording / reproducing device - Google Patents

Description

The present invention relates to a magnetic recording / reproducing apparatus, and more particularly to an audio tape recorder (ATR) and a video tape recorder (VTR) for recording FM modulation signals in the longitudinal direction of a magnetic tape. It is suitable for application.

[Conventional technology]

In the ATR and VTR, the audio signal is generally FM-modulated and recorded in the longitudinal direction of the magnetic tape. When the FM-modulated audio signal recorded on the magnetic tape is reproduced, a wow flat is caused by the fluctuation of the tape speed, which causes a frequency fluctuation in the reproduced audio signal from the magnetic tape. Actually, wow flats are 0.05% to 0.15
There exists about [%], and for example, when the carrier frequency and the frequency shift in FM modulation are 1: 1, the S / N ratio due to this wow-flatter is about 60 [dB]. Therefore, even if the S / N ratio is improved due to the wow flat, the limit is 60 [dB].

Conventional to this problem, as shown in FIG. 2, at the same time the magnetic narrowband pilot signal S _P around the frequency f _P outside the occupied frequency band B _FM of the FM modulated wave S _AFM of audio signals A method of recording on a tape and removing the FM modulation noise component due to the wow flat from the reproduced audio signal based on the frequency fluctuation component due to the wow flat appearing in the reproduced signal of the pilot signal S _P is used.

[Problems to be solved by the invention]

However, the recording level of the pilot signal S _P is smaller than the recording level of the audio signal S _AFM so that it does not affect the central audio signal S _AFM , and the frequency band is narrow outside the band B _FM of the audio signal S _AFM. It was selected in the range. Further, since each circuit is designed in accordance with the band B _FM of the audio signal S _AFM, the pilot signal S _P is recorded and reproduced under bad conditions. Therefore, even if the FM modulation noise component due to the wow-flatter is removed from the reproduced audio signal based on the frequency fluctuation component due to the wow-flatter detected from now on, the S / N ratio is still low because the pilot signal S _P has a low level.
The ratio is not sufficiently improved, and the band of the frequency fluctuation component due to the detected wow flatter is narrowed because the band is narrow. In such a state, the removal of the FM modulation noise component by the wow flat with a relatively high frequency component in the reproduced audio signal becomes insufficient, and the S / N ratio after the removal of the FM modulation noise component by the wow flat is actually improved. It wasn't enough.

The present invention has been made in view of the above points, and provides a magnetic recording / reproducing apparatus capable of significantly improving the S / N ratio by canceling the FM modulation noise component due to the wow flat included in the reproduction audio signal. It is what

[Means for solving problems]

Since the present invention is to solve the problems described above, the first recording system 20 for recording by modulating an input signal A _IN to the first track on the magnetic tape 10, inverts the phase of the input signal A _IN A second recording system 30 for modulating the obtained phase-inverted signal A _IN to record it on a second track close to the first track, and a second recording system 30 for reproducing and demodulating the signal recorded on the first track. 1 reproduction system 40, 2nd reproduction system 50 for reproducing and demodulating the signal recorded in the 2nd track, 1st demodulation signal A _OUT1 and 2nd output from the 1st reproduction system 40 Second demodulation signal output from the reproduction system 50 of And an output circuit 62, 63, 64 for inputting the inverted demodulated signal A _OUT2 whose phase is inverted and outputting a combined output OUT of the first demodulated signal A _OUT1 and / or the inverted demodulated signal A _OUT2 , and Dropout detection circuits 46, 56 for detecting dropouts from the respective reproduced signals reproduced from the second track and controlling the output circuits 62, 63, 64 based on the detected signals.
And the dropout detection circuits 46 and 56 are provided with the first and second demodulated signals A _OUT1 output from the first and second reproduction systems 40 and 50, respectively. In the first case where no dropout occurs in any of the first and second demodulated signals A _OUT1 , The output signals 62, 63, 64 of the combined output of the first demodulation signal A _OUT1 and the inverted demodulation signal A _OUT2 so that the FM modulation noise components due to the wow-flatter included in
In the second case where the dropout occurs only in the first demodulated signal A _OUT1 output from the first reproduction system 40, the signal is demodulated by the second reproduction system 50 in which the dropout does not occur. Second demodulated signal The inverted demodulated signal A _OUT2 having the inverted phase of the output circuit 62, 63, with the same level amplitude as the amplitude of the combined output in the first case.
The second demodulated signal output from the second reproduction system 50, which is output from the second reproduction system 50. In the third case where the dropout occurs only in the first case, the first demodulation signal A _OUT1 demodulated by the first reproduction system 40 in which the dropout does not occur has the same level as the amplitude of the combined output in the first case. The amplitude is output from the output circuits 62, 63, 64.

[Action]

The magnetic tape 10 is the first for recording the output signal A _IN in the longitudinal direction.
And a second track. The first recording system 10 modulates the input signal A _IN and records it on the first track of the magnetic tape 10, and the second recording system 20 a phase inversion signal of the input signal A _IN. Is modulated and recorded in the second track. First reproduction system 40
Reproduces and demodulates the recorded signal of the first track and supplies the demodulated signal A _OUT 1 to the output circuit 60. The second reproduction system 50 is the second
Playback demodulation of the track recorded signal of To the output circuit 60. The output circuit 60 outputs the demodulated signal from A _OUT 1 To output the output signal OUT. As a result, the output signal OUT
The signal component in can be doubled, and FM by wow flat
The modulation noise component can be canceled. Further, when the dropout is detected, the demodulated signal A _OUT reproduced and demodulated from the first reproducing system 40 or the second reproducing system 50 is output as the output signal OUT. As a result, it is possible to reduce the chances of quality loss due to dropout.

〔Example〕

Hereinafter, a first embodiment of a magnetic recording / reproducing apparatus according to the present invention will be described.
The figure will be described in detail. In FIG. 1, reference numeral 1 denotes a magnetic recording / reproducing apparatus as a whole, which has two series of recording systems 20, 30 and reproducing systems 40, 50.

In the audio signal recording system 20, the FM modulation circuit 22 inputs the carrier of the frequency f ₁ to the FM according to the input audio signal A _IN.
After being modulated, the modulated signal S22 is amplified by the recording / amplifying circuit 23 and then recorded on the first track TR1 formed along the longitudinal direction on the magnetic tape 10 by the recording head 24.

Further, in the inverted audio signal recording system 30, the inverter 31 inverts the phase of the audio signal A _IN to invert the audio signal A _IN. To the FM modulation circuit 32. The FM modulation circuit 32 inverts the carrier of frequency f _{2 to} an audio signal. FM modulation is performed according to the
Is amplified and then recorded on the second track TR2 of the magnetic tape 10 by the recording head 34.

Here, the second track TR2 is formed along the longitudinal direction of the magnetic tape at a position close to the first track TR1 so that the wow fratters are substantially equal. In this case, since the tracks TR1 and TR2 are close to each other, a beat due to crosstalk occurs. Therefore, selecting the difference as not help hearing the beat component as sound the carrier frequency f ₁ of the audio signal recording system 20 and the carrier frequency f ₂ of the inverted audio signal recording system 30 over the band of the audio signal A _IN.

On the other hand, in the audio signal reproducing system 40, the reproducing head 41 picks up the recording signal from the first track TR1 of the magnetic tape 10 and supplies it to the reproducing amplifier circuit 42, and the reproducing amplifier circuit 42 amplifies the recorded signal. After that equalizer 43
Give to. The equalizer 43 frequency-compensates the reproduction signal S42 and then supplies it to the FM demodulation circuit 44.The demodulation circuit 44 demodulates the audio signal A _OUT 1 and then the audio signal A _OUT 1 via the level adjustment circuit 45. It is given to the output circuit 60.

The reverse audio signal reproduction system 50 is also the audio signal reproduction system 40.
It has the same configuration as. That is, the reproduction head circuit 51 amplifies the recording signal picked up from the second track TR2 of the magnetic tape 10 by the reproduction amplifier circuit 52 and supplies it to the equalizer 53. Circuit 54 has inverted audio signal Demodulate. However, no level adjusting circuit is provided in the inverted audio signal reproducing system 50. The level adjusting circuit 45 outputs the wow-flatter component of the audio signal A _OUT 1 and the inverted audio signal. Reproduction system that matches the level of wow and fructose components of
It is provided on one of 40 and 50.

Audio signal reproduction system 40 and inverted audio signal reproduction system
50 also includes dropout detection circuits 46 and 56, respectively. The dropout detection circuit 46 receives the output signal from the equalizer 43 and detects the dropout. When the dropout is detected, the demodulation circuit 44 gives a command signal MUT1 to cause the audio signal A _OUT 1 to be muted. Similarly, when the dropout detection circuit 56 detects the dropout based on the signal from the equalizer 53, it gives a command signal MUT2 to the demodulation circuit 54 to invert the audio signal. To make a job.

The output circuit 60 outputs the demodulated signal from A _OUT 1 To form the output signal OUT. An inverter that inverts to form the audio signal A _OUT 2
1 and an adder circuit 62 for adding the demodulated signal A _OUT 1 and the audio signal A _OUT 2.

In addition to this, the output circuit 60 is provided with switch circuits 63 and 64 for switching the input signal to the adder circuit 62 when a dropout is detected.
Equipped with. Switch circuit 63 receives a first input terminal 63a audio signal A _OUT 1, audio signal A _OUT to the second input terminal 63b
2 and further receives the dropout detection signal DO1 of the dropout detection circuit 46 as a switching control signal, and is connected to the second input terminal 63b when the dropout is detected, and is connected to the first input terminal 63a otherwise. On the other hand, switch circuit 6
4 receives the audio signal A _OUT 2 at the first input terminal 64a,
The other audio signal A _OUT 1 is received at the input terminal 64b, and the dropout detection signal DO2 of the dropout detection circuit 56 is received.
As a switching control signal, and is connected to the second input terminal 64b when the dropout is detected, and is connected to the first input terminal 64a when the dropout is not detected.

In the configuration of FIG. 1, the input audio signal is input to the input terminal.
When A _IN is given, the audio signal A _IN is modulated in the audio signal recording system 20 and then the first signal of the magnetic tape 10.
The audio signal A _IN recorded in the track TR1 is first phase-inverted in the inverted audio signal recording system 30, and then the inverted audio signal A _IN is inverted. Is modulated and recorded on the second track TR2 of the magnetic tape 10.

The recorded signal of the first track TR1 is the audio signal reproducing system 40.
Reproduced and demodulated at, and the demodulated audio signal A _OUT
1 is provided to the output circuit 60. The recorded signal of the second track TR2 is reproduced and demodulated in the inverted audio signal reproducing system 50, and the inverted audio signal is reproduced. Are provided to the output circuit 60.

When no dropout occurs in the reproduction signals S42 and S52, the audio signal A _OUT 1 is given to the adding circuit 62 via the switch circuit 63, and the inverted audio signal is output by the inverter 61. The audio signal A _OUT 2 formed by inverting is supplied to the adder circuit 62 via the switch circuit 64, and is added in the adder circuit 62 to become the output signal OUT.

Here, the input signal A _IN is given to the adding circuit 62 via the audio signal recording system 20 and the audio signal reproducing system 40,
The inverted audio signal recording system 30 inverts the signal all over, and then the inverted audio signal reproduction system 50 inverts it again to add it.
Is given to 62. Therefore, the signal component of the output signal OUT is 2
Doubled.

On the other hand, since the first and second tracks TR1 and TR2 are in close proximity to each other, the FM modulation noise component due to the wow flatter which changes in the same manner causes the reproduced signals S42 and S52 of the audio signal reproduction system 40 and the inverted audio signal reproduction system 50. include. However, the FM modulation noise component due to the wow-flatter in the inverted audio signal reproduction system 50 is phase-inverted and the addition circuit 62
Therefore, the FM modulation noise component due to the wow-flatter is canceled in the adding circuit 62. If the cancel is insufficient, the level of the level adjusting circuit 45 is adjusted so that the cancel is completely performed.

Since noises other than the FM modulation noise component due to the wow-flatter are random noises, even if they are added in the adder circuit 62, they do not have a simple sum size but a square root size of the sum of squares.

Therefore, when dropout does not occur, the signal level of the signal component in the output signal OUT is doubled (6 [dB]) as compared to the case where the recording / reproducing system is a single system, and the FM modulation noise component due to wow and flatter. Is canceled, other noise increases the square root of the sum of squares (3 [dB]), and the overall S / N ratio improves.

On the other hand, when a dropout occurs in the reproduction signal S42, the dropout detection circuit 46 detects it, and the switching control signal DO1 is given to the switch circuit 63 to be switched to the second input terminal 63b. Therefore, the adder circuit 62 has a switch circuit.
63 audio signals A _OUT 2 is given through, also the same audio signal A _OUT 2 is supplied via a switch circuit 64, are audio signals A _OUT 2 twice unrelated to dropout from the adding circuit 62 outputs To be done. In this way, the FM modulation noise component due to the wow-flatter cannot be canceled, but it is possible to prevent a sudden change in the level of the output signal OUT, and prevent a significant loss in hearing.

On the other hand, when a dropout occurs in the reproduction signal S52, the switch circuit 64 is switched and the adder circuit 62 outputs the output signal OUT which is twice the audio signal A _OUT 1 in which the dropout has not occurred.

Audio signal reproduction system 40 and inverted audio signal reproduction system
When a dropout occurs in both the reproduced signals S42 and S52 of 50, both the switch circuits 63 and 64 are switched to the second input terminals 63b and 64b, and accordingly, the audio signals A _OUT 1 and A _OUT 2 are output from the adder circuit 62. The addition output OUT of is output. At this time, the audio signal A _OUT 1 is output to the dropout detection circuit 4
6 is being muted because the muting command MUT1 is sent to the FM demodulation circuit 44, and the audio signal A _OUT 2 is also output from the dropout detection circuit 56 to the FM demodulation circuit 5
4 The miutering command MUT2 has been sent, so it is being muted. Therefore, the audio signals A _OUT 1 and A
_The output signal OUT due to the addition of _OUT 2 is also the one that is muted. As described above, in the apparatus of FIG. 1, the sound is interrupted only when the two reproduction signals S42 and S52 both drop out.

As described above, according to the embodiment of FIG. 1, since the FM modulation noise component due to the wow flatter obtained from the two tracks is added in the opposite phase and the signal component is added in the same phase, the FM modulation noise due to the wow flatter in the output signal is added. The components can be significantly reduced. In addition, the signal component is increased by 6 [dB] as compared with the case of one recording / reproduction system, while the noise component other than the FM modulation noise component due to wow and flatter is increased by only 3 [dB], so the S / N ratio is increased. Can be improved.

According to the embodiment shown in FIG. 1, when a dropout occurs in one reproduction signal, the other reproduction signal can be used to perform the interpolation process, so that an opportunity to drop the hearing by the dropout is provided as compared with the conventional apparatus. It can be reduced.

〔The invention's effect〕

As described above, according to the present invention, when the input signal and its inverted signal are recorded in the adjacent tracks on the same magnetic tape, and the dropout does not occur in any of the reproduced signals reproduced from both tracks, First and second output from the first and second reproduction systems corresponding to the respective tracks
Of the demodulated signal of wow-flatter included in both demodulated signals
The noise components in the output signal can be remarkably reduced by combining and outputting the FM modulation noise components so that the FM modulation noise components are in opposite phases to each other and are canceled. As a result, the S / N ratio of the output signal can be remarkably improved as compared with the conventional case. On the other hand, when a dropout occurs in the reproduction signal reproduced from one of the two tracks, the demodulation signal output from the reproduction system in which the dropout does not occur or the inverted demodulation signal that is the phase inversion signal thereof is By outputting the amplitude of the same level as the amplitude of the output signal that is output when there is no dropout in the reproduced signal that is reproduced from both tracks, it is possible to prevent sudden changes in the amplitude of the output signal. The risk of damage can be effectively prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a magnetic recording / reproducing apparatus according to the present invention, and FIG. 2 is a schematic diagram used for explaining a cancel method of an FM modulation noise component due to a wow-flatter in a conventional magnetic recording / reproducing apparatus. 10 ... Magnetic tape, 20 ... Audio signal recording system, 30 ...
… Inverted audio signal recording system, 40 …… Audio signal playback system, 50 …… Inverted audio signal playback system, 60 …… Output circuit, A _IN …… Input audio signal, A _OUT 1, …… Demodulation audio signal, OUT …… Output signal.

Claims (1)

[Claims] 1. A first recording system for modulating an input signal to record it on a first track on a magnetic tape, and a phase inversion signal obtained by inverting the phase of the input signal for modulating the first signal. A second recording system for recording on a second track close to the first track; a first reproducing system for reproducing and demodulating the signal recorded on the first track; and recording on the second track. A second reproduction system that reproduces and demodulates the generated signal, a phase of the first demodulation signal that is output from the first reproduction system, and a phase of the second demodulation signal that is output from the second reproduction system. An output circuit which inputs the inverted inverted demodulated signal and outputs a combined output of the first demodulated signal and / or the inverted demodulated signal, and a dropout from the respective reproduced signals reproduced from the first and second tracks. Output and output based on the detection signal A drop-out detection circuit for controlling the path, wherein the drop-out detection circuit is a first drop-out detection circuit in which no drop-out occurs in any of the first and second demodulated signals output from the first and second reproduction systems. In the case of, the output circuit outputs a combined output obtained by combining the first demodulated signal and the inverted demodulated signal so as to cancel the FM modulation noise components due to wow flatter contained in the first and second demodulated signals. In the second case where the dropout occurs only in the first demodulated signal output from the first reproduction system, the second demodulated by the second reproduction system in which the dropout does not occur. The inverted demodulated signal obtained by inverting the phase of the demodulated signal is output from the output circuit as an amplitude of the same level as the amplitude of the combined output in the first case, In the third case where dropout occurs only in the second demodulated signal output from the second reproduction system, the first demodulated signal demodulated by the first reproduction system in which no dropout occurs A magnetic recording / reproducing apparatus, wherein the output circuit outputs an amplitude of the same level as the amplitude of the combined output in the first case.