JPH04182903A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To allow optimum correction so as to minimize the error rate of a PCM signal by switching the output signal from a D/A converter and zero value by inputted recording/reproducing signals and outputting the same as a control signal to a transversal filter. CONSTITUTION:Two pieces of band-pass filters(BPE) 95 and level detectors 96 are used at the time of reproduction and the voltage proportional to the pass band component of the reproduced PCM signal through a filter 102 is detected. The detected two signals are corrected of the error by the fluctuation in the BPF 95 and the level detector 96 from the value of the level detector 96 at the time of recording recorded in a memory 98. The characteristics of the variable transversal filter 73 are determined from the result of the subtraction of the resulted two signals after the correction. Even if the PCM signal having the attenuation rate of any high frequency component is inputted, the frequency characteristics of the variable transversal filter are so controlled as to minimize the error rate and the deterioration by the inadequateness of the correction characteristic of an equalizer is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus that records digital audio signals and video signals simultaneously.

BACKGROUND OF THE INVENTION In recent years, video tape recorders (hereinafter referred to as VTRs) have been developed.
There is a trend toward higher image quality. Regarding audio signals, the development of systems capable of recording pulse code modulated signals, such as compact discs and digital tape recorders, is progressing. Additionally, systems have been developed that can record digital audio signals simultaneously with video signals. For example, JP-A-61
There is a magnetic recording/reproducing device disclosed in Japanese Patent No.-294663.

A conventional magnetic recording/reproducing device will be explained below.

FIG. 3 is a block diagram of a conventional magnetic recording/reproducing device.

Figure 4 is an explanatory diagram of the signal processing format, Figure 5 is a PC
The frequency spectrum diagram of the M signal, and FIG. 6 is a recording signal track diagram of the tape.

In FIG. 3, 1 is a first input terminal into which a video signal is input, 2 is a modulator that modulates the video signal input to the first input terminal 1 into a signal that can be recorded on tape, and 3 is a modulator. 2
A first output signal attached to the cylinder 6 is amplified via a first switch 4 and a first rotary transformer 5.
8 is a second input terminal to which an audio signal is input; 9 is an amplifier for digitizing the audio signal input to the second input terminal 8; , a first signal processor that processes various signals; 10 is a first signal processor;
0-Q for performing offset four-phase differential phase modulation (hereinafter referred to as 0-QDPSK) on the output signal of the signal processor 9 of
A DPSK modulator 11 amplifies the output signal of the 0-QDPSK modulator 10 and amplifies the output signal of the 0-QDPSK modulator 10 and a second
15 is a tape, 16a, 16b are guide posts, 17 is a second amplifier for supplying magnetic head groups 14a and 14b to the magnetic head groups 14a and 14b;
This is a control device that controls the running of No. 5. 18 is a third amplifier that amplifies the signal reproduced by the first magnetic head group 7 al 7 b; 19 demodulates the output signal of the third amplifier 18 into a video signal and outputs it to the first output terminal 20; a demodulator 21 for amplifying the PCM signal reproduced by the second magnetic head group 14a, 14b;
22 is an equalizer, 23 is a 0-QDPSK demodulator, 24
is a second signal processor that performs various signal processing on the output signal of the 0-QDPSK demodulator 23, returns it to the original audio signal, and outputs it to the second output terminal 25.

The operation of the conventional magnetic recording/reproducing apparatus configured as described above will be described below.

First, the operation during recording will be explained.

A video signal input to the first input terminal 1 is separated into a luminance signal and a color signal by a modulator 2, and then subjected to frequency modulation and frequency conversion, respectively. The frequency-modulated luminance signal and the frequency-converted chrominance signal are added and supplied to the first amplifier 3. The signal amplified by the first amplifier 3 is transmitted through the first switch 4 switched to the R side and the first rotary transformer 5 at an azimuth angle ±
6'' magnetic head group 7 al 7 b.

At the same time, the audio signal input to the second input terminal 8 is
After being digitized (converted into a digital audio signal) by the signal processor 9, signal processing such as addition of an error correction code and formatting is performed. Then, it is output to the 0-QDPSK modulator 10 as a 2.8 MbpS digital signal.

An example of formatting in the first signal processor 9 is shown in the fourth example.
As shown in the figure. The digitized digital audio signal is converted into a data length synchronized with the length of one field of the video signal. Then, an ID signal, a synchronization signal, and an address signal are added to this digital audio signal.

A header composed of parity and error correction codes C1 and C2 generated from the digital audio signal are added,
One data block is constructed. The signal of one field is divided into 150 data blocks by the 0-QDPSK demodulator 2.
The most optimal pattern is added to the clock generation phase-locked loop (hereinafter referred to as PLL) circuit in the third and second signal processors 24. For example 90H
It's a pattern. The 0-QDPSK modulator 10 performs 0-QDPSK modulation on the output signal of the first signal processor 9 using a 3.0 MHz carrier wave into the RE spectrum band shown in FIG. 5, and supplies the modulated signal to the second amplifier 11. The signal amplified by the second amplifier 11 is transferred to the second switch 12 which is switched to the R side.
and a magnetic head group 14 with an azimuth angle of ±30' attached to the cylinder 6 via a second rotary transformer 13.
a, added to 14b.

Tape 1 is attached to cylinder 6 using guide pins 16a and 16b.
5 is wound diagonally and runs in the direction of arrow B.

At the same time, the cylinder 6 is controlled by the control device 17 and rotates in the direction of arrow A. second magnetic head group 14a,
14b are attached to cylinders at different heights so that signals can be recorded on the tape 15 before the first magnetic head group 7 al 7 b. Therefore, the first magnetic head groups 7a, 7b record signals on the tracks on which the second magnetic head groups 14a, 14b have recorded signals. The situation is shown in FIG. Here, A1°A2.
A3 is the track recorded by the second magnetic head group 14a, 14b, Vl, V2 . V3 is the first magnetic head group 7
These are the tracks recorded in a and 7b.

Next, the operation during playback will be described.

The signal reproduced by the first magnetic head 7 al 7 b is applied to the third amplifier 18 via the first rotary transformer 5 and the first switch 4 switched to the P side. The signal amplified by the third amplifier 18 is demodulated into a video signal by the demodulator 19 and output to the first output terminal 20.

At the same time, the signals reproduced by the second magnetic head group 14a, 14b are applied to the fourth amplifier 21 via the second rotary transformer 13 and the second switch 12 switched to the P side, and are amplified. . The signal (PCM signal) output from the fourth amplifier 21 is transmitted to the first magnetic head group 7a.
, 7b from above, the high-frequency components are attenuated (see PB in FIG. 5).

The output signal (PCM signal) of the fourth amplifier 21 is input to an equalizer 22, the high-frequency characteristics attenuated in the recording/reproduction system are corrected, and the output signal is output to the 0-QDPSK demodulator 23. 0-
The PCM signal input to the QDPSK demodulator 23 is demodulated into a digital signal and output to the second signal processor 24. The second signal processor 24 demodulates this signal into the original audio signal and outputs it to the second output terminal 25.

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, the attenuation rate of the high frequency component of the PCM signal depends on the material of the tape, the first . It depends on the gap length of the second magnetic head group 7a, 7b, 14a, 14b, recording current, etc. Therefore, this PC
If the equalizer for correcting the frequency characteristics of the M signal is a circuit with fixed frequency characteristics, the error rate may increase due to mismatching of the correction characteristics in the equalizer. Particularly when playing back a tape recorded on another VTR (when tapes are compatible), C/N deterioration due to off-track also increases the error rate, reducing the C/N margin of the PCM signal, which in turn causes the difference in the quality of the audio signal being played. This had the problem of causing quality deterioration.

The present invention solves the above-mentioned conventional problems, and no matter what attenuation rate of high frequency components a PCM signal is input,
It is an object of the present invention to provide a magnetic recording and reproducing device that controls the frequency characteristics of a variable transversal filter so that the error rate is minimized and eliminates deterioration due to mismatching of the correction characteristics of an equalizer.

Means for Solving the Problems To achieve this object, the magnetic recording and reproducing apparatus of the present invention comprises:
a modulating means for performing offset four-phase differential phase modulation on a digitized audio signal; a recording/reproducing means for recording and reproducing an output signal of the modulating means on a recording medium; and an input recording/reproducing means.
a first switch for switching and outputting an output signal from the modulation means and an offset four-phase differential phase modulation signal reproduced from the recording medium as a reproduction signal; and an offset four-phase differential phase modulation output from the first switch. a transversal filter that receives the signal as input and determines frequency characteristics based on the control signal; and a first filter that limits the pass band of the offset four-phase differential phase modulation signal output from the transversal filter. a second bandpass filter; a first bandpass filter;
The first one detects the level of the output signal of the second band pass filter. a second level detector; and a second level detector; a first and second analog/digital converter that converts the output signal of the second level detector into a digital signal;
．． a memory that records the output signal of the second analog/digital converter; an error calculator that calculates an error voltage from the output signal of the memory and a predetermined reference value;
During reproduction, the first and second analog/digital converters calculate the difference between the output signals of the first and second analog/digital converters and the output signals of the error calculator. a second subtractor; a first subtractor; a third subtracter that calculates the difference between the output signals of the second subtractor; a filter that processes the output signal of the third subtractor; and a digital/analog converter that converts the output signal of the filter into an analog signal. a second switch that determines whether the control signal input to the transversal filter is an output signal from the digital/analog converter or a "zero" value according to the input recording/playback signal, and outputs the control signal; and demodulation means for demodulating the four-phase differential phase modulation signal output from the transversal filter into a digital audio signal.

Operation With the above-described configuration, the present invention performs offset four-phase differential phase modulation (PCM signal) on a digitized audio signal and records it on a recording medium at the time of recording. At the same time, two bandpass filters and a level detector are used, each having a passband symmetrical to the carrier frequency of the PCM signal, and the passband of the filter for the PCM signal having an energy distribution symmetrical to the carrier frequency during recording. Detect the voltage proportional to the component and record it in memory.

During reproduction, two bandpass filters and a level detector are used to detect a voltage proportional to the filter passband component of the reproduced PCM signal. The detected two signals are recorded in memory, and errors due to variations in the bandpass filter and level detector are corrected from the level detector values at the time of recording. Then, the characteristics of the variable transversal filter are determined from the result of subtraction of the two signals after correction.

As a result of the above, no matter what high-frequency component attenuation rate a PCM signal is input, the frequency characteristics of the variable transversal filter can be controlled to minimize the error rate, and deterioration due to mismatching of the equalizer's correction characteristics can be avoided. It is possible to eliminate it.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a magnetic recording/reproducing apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram of a variable transversal filter and a detector.

In FIG. 1, 50 is a first input terminal into which a video signal is input, 51 is a modulator that modulates the video signal input to the first input terminal 5o into a signal that can be recorded on tape, and 52 is a modulator. A first magnetic head group 56a, 56 is attached to a cylinder 55 via a first switch 53 and a first rotary transformer 54.
b. 57 is a second input terminal into which an audio signal is input; 58 is a first signal processor that processes various signals after digitizing the audio signal input to the second input terminal 57; 59 is a first signal processor; A 0-QDPSK modulator 6o amplifies the output signal of the O-QDPSK modulator 62, and a second switch 61 and a second rotation Second magnetic head/F group 63 a, 63 attached to cylinder 55 via transformer 62
b. 64 is a tape, 65a, 65b are guide posts, 66 is a cylinder 55
This is a control device that controls the rotation of the tape 64 and the running of the tape 64. 67 is a third amplifier that amplifies the signal reproduced by the first magnetic head group 56a, 56b, and 68 demodulates the output signal of the third amplifier 67 into a video signal and outputs it to the first output terminal 69. It is a demodulator. 70 is the 0-QDP reproduced by the second magnetic head group Et3a, 63b.
A fourth amplifier 71 that amplifies the SK signal (PCM signal)
72 is an automatic gain control circuit (hereinafter referred to as A).
Abbreviated as GC. ). 73 is a variable transversal filter whose frequency characteristics can be varied by an externally applied control signal CO; 74 is a detector that detects the spectrum shape of the PCM signal output from the variable transversal filter 73 and calculates the control voltage CO; 75 is 0-QDPS
The K demodulator 76 is a second signal processor that processes the output signal of the 0-QDPSK demodulator 75 in various ways, returns it to the original audio signal, and outputs it to the second output terminal 77. Reference numeral 78 denotes a third signal to which a high level signal (recording/playback signal) is input during recording.
This is the input terminal of

The first amplifier 52 . First switch 53. First rotary transformer 54. The first magnetic head group 56a, 56b, the third amplifier 67, and the demodulator 68 constitute a second recording/reproducing means that frequency modulates the video signal and records/reproduces it over the track of the offset 4-phase differential phase modulation signal. are doing. Also, a second amplifier 60. Second switch 61. Second rotating transformer 62+ second magnetic head group 63 al 63
b.

The fourth amplifier 70 constitutes a first recording/reproducing means for recording/reproducing offset four-phase differential phase modulation onto a recording medium.

In FIG. 2, 90 is an input terminal, 73 is a delay device 91a, 91b with a delay time T, adders 92, 93, and a multiplier 94.
This is a variable transversal filter consisting of.

95a and 95b are the first. The second band-limiting filter (hereinafter referred to as BPF), 96a, 96b, outputs a DC voltage proportional to the input signal level. The second level detectors 97a, 97b are connected to the first level detectors 97a, 97b. A second analog/digital converter (hereinafter abbreviated as A/D converter), 98 is a third
When a high level recording/playback signal is input to the input terminal of the first. Second A/D converter 97a.

This is a memory for recording the output signal value of 97b. 99 is the first one from the output signal of the memory 98. Second BPF95a, 9
5b and 1st. This is an error calculator that calculates the dispersion value of the second level detectors 96a and 96b. 100 a,
100 b is the first. Second A/D converter 97a, 97b
and the output signal of the error calculator 99. The second subtractor 101 is the first subtractor. second subtractor 100a,
This is a third subtractor that calculates the difference between the 100 b output signals. 102 is a filter, and the output signal of the filter 102 is amplified by an amplifier 103 and then converted to analog by a digital/analog converter (hereinafter abbreviated as a D/A converter). 105 is a fourth switch;
The output signal of the switch 105 becomes the control signal CO of the variable transversal filter 73. 106 is an output terminal. In addition, 1. Second B P F 95 a,
95b to the fourth switch 105 constitute a detector 74.

The operation of the magnetic recording/reproducing apparatus in the embodiment configured as above will be explained below.

First, the operation during recording will be explained.

The video signal input to the first input terminal 50 is transmitted to the modulator 51
After the signal is separated into a luminance signal and a color signal, each signal is frequency modulated and frequency converted. The frequency-modulated luminance signal and the frequency-converted chrominance signal are added, and the first amplifier 52
supplied to The signal amplified by the first amplifier 52 is
A group of magnetic heads 56a, 56 with an azimuth angle of ±6° are attached to the cylinder 55 via the first switch 53 switched to the R side and the first rotary transformer 54.
added to b. At the same time, the audio signal input to the second input terminal 57 is digitized (converted into a digital audio signal) by the first signal processor 58, and then subjected to signal processing such as adding an error correction code and formatting. -QD
The PSK modulator 59 has a frequency of 2.6 Mbps (f sMHz
shall be. ) is output as a digital signal. An example of the format of the digital signal is shown in FIG.

2.6MBPS input to 0-QDPSK modulator 59
The digital signal is 0-QDPSK modulated with a 3.0 MHz (fcMHz) carrier wave,
0 and the third switch 71. The signal amplified by the second amplifier 60 is transferred to the second amplifier 60 which is switched to the R side.
is applied to the magnetic head group Ei3a, 63b with an azimuth angle of ±30' attached to the cylinder 55 via the switch 61 and the second rotary transformer 62. A tape 64 is wound diagonally around the cylinder 55 by guide pins 65a and 85b, and runs in the direction of arrow B. At the same time, the cylinder 55 is controlled by the control device 66 and rotates in the six directions of arrows.

The second magnetic head group 83a, 63b is attached to the cylinder 55 at different heights so that signals can be recorded on the tape 64 before the first magnetic head group 56a, 58b. Therefore, the second magnetic head group 63a, 6
3b, the first magnetic head group 5
6a and 56b will record signals.

Although the tracks recorded on the tape 64 overlap, the azimuth angles of the magnetic heads are different, so
Signals recorded by magnetic heads with different azimuth angles are attenuated due to azimuth loss during reproduction. Furthermore, the carrier wave frequency is selected so that portions of high signal energy do not overlap in the frequency band of signals recorded by each magnetic head group. As a result, mutual interference can be reduced, and even if recording tracks overlap, the degree of attenuation of previously recorded signals can be reduced.

Since a high level recording/reproduction signal is input to the third input terminal 78, the third switch 71 and the fourth switch 105 (see FIG. 2) are switched to the R side. Therefore,
The output signal of the 0-QDPSK modulator 59 passes through the switch 71, and after the amplitude value is changed to a predetermined value by the AGC 72, it is input to the variable transversal filter 73.

Figure 2 shows the variable transversal filter 73 and the detector 7.
4 is shown. Variable transformer 1 < -The frequency characteristic G(w) of the monkey filter 73 is G(w)" 201
111i++@(1+2 ・CO-aswT)w=2π
f f: Frequency (H2) T: Delay time of delay device (seconds). Here, CO is the control voltage value output from the detector 75. During recording, the fourth switch 105 is grounded, so C0=O, and the frequency characteristic of the variable transversal filter 73 becomes flat. Therefore, the 0-QDPSK signal that passes through the variable transversal filter 73 and is input to the detector 74 has a carrier frequency of 3.
．． The energy distribution is symmetrical with respect to 0MH2.

The detector 74 has a first BPF 95a (pass band fc-5
f s/18MHz±100KHz) and the second BPF9
5b (passband fc+5fs/18MH2±100K
Hz) for the carrier frequency fcMHz.
To extract high-frequency components and low-frequency components of a PCM signal in frequency-separated bands. 1st. 2nd B P F 95 a, 9
The signal extracted in step 5b is sent to the first and second level detectors 9.
8a, 98b, a DC voltage LVI proportional to the input signal level.

Convert to L V 1 . The voltage values LVI and LV2 are the first
゜The second A/D converters 97a and 97b convert the signal into a digital signal and record it in the memory 98. Here, the first. Variations in the bands of the second BPFs 95a and 95b and the first
．． If there is no variation in the frequency characteristics of the second level detectors 96a and +96b, the two A/D converters 97a,
Both output signals of 97b match the design value LVO. However, the actual value will vary depending on the above factors.

Next, the playback operation will be described.

The signals reproduced by the first magnetic heads 56a and 56b are transferred to the first rotary transformer S4 and the first magnetic head switched to the P side.
The signal is applied to the third amplifier 67 via the switch 53 . The signal amplified by the third amplifier 67 is demodulated into a video signal by a demodulator 68 and output to a first output terminal 69.

At the same time, the signals reproduced by the second magnetic head group 63a, 83b are applied to the fourth amplifier 70 via the second rotary transformer 62 and the second switch 61 switched to the P side, and are amplified. . The signal (PCM signal) output from the fourth amplifier 70 is transmitted to the first magnetic head group 56.
Since it was overridden from above by a, 58b,
It has a characteristic in which high-frequency components are attenuated (see PB in Fig. 5).

The reproduced PCM signal is corrected for high-frequency characteristics attenuated in the recording/reproducing system by a variable transversal filter 73, and is output to a detector 74 and a 0-QDPSK demodulator 75.

The detector 74 extracts the input PCM signal from the first BPF 9.
5a (pass band fc+5fs/18MH2±100K
Hz), second BPF95b (passband f c-
5f s/16MHz±100KHz) and 11th
Using the second level detectors 96a and 98b, the PC in the same frequency band with respect to the carrier frequency fcMHz is detected.
DC voltage LV3 proportional to the high frequency component and low frequency component of the M signal
．． Find LV4.

At this time, the error calculator 99 records the first . Second A/D converter 97a.

97b output signal value LVI, error value LVl- from LV2
Find LVO, LV2-LVO. Then, the correction value LV5 is added and subtracted from this error voltage to obtain the first and second
LVI-LVO+LV5 in the subtracters 100a and 100b
．． Output LV2-LVO-LV5. 1st. The second subtracters 100a, 100b are connected to the first subtracters 100a, 100b. Second A/D converter 9
The difference between 7a, 97b and the output signal of the error calculator 99 is calculated.

As a result, variations in the BPF and level detector can be corrected without any adjustment. The third subtractor 101
．． The difference between the output signals of the second subtracters 100a and 100b is calculated, and the calculation result (LV3+LV2-LV1-LV4-
2 LV5) is output to the filter 102. The output signal of the third subtracter 101 is smoothed by the filter 102 and then amplified by A times (A>O) by the amplifier 103. Then, it is converted into an analog signal by the D/A converter 104, and the fourth
is output to the switch 105. Fourth switch 105
is the record of the low level input to the third input terminal 78/
It has been switched to the P side due to the reproduction signal. Therefore, D/
The output signal of the A converter 104 is the control signal CO1 of the variable transversal filter 73.
V2-LVl-LV4-2LV5).

The variable transversal filter 73 has a characteristic of attenuating high frequencies when CO increases, and amplifying high frequencies when CO decreases. In other words, the variable transversal filter 73 and the detector 74 form a feedback system, and the frequency characteristics of the variable transversal filter 73 converge to a pre-designed characteristic. Here, when LV5=O, the characteristic of the variable transversal filter 73 converges with the characteristic that the spectrum shape of the reproduced PCM signal is symmetrical with respect to the carrier frequency. However, this characteristic is not one that minimizes the error rate of the PCM signal to be demodulated. The minimum error rate during demodulation of PCM signals is 3.5MHz/2.
This is when 5 MHz has a characteristic of approximately -3 dB. This is because if the high frequency range is amplified too much, the C/N will deteriorate. Therefore,
The error calculator 99 adds and subtracts the correction value LV5, and provides an offset so that the variable transversal filter 73 converges with a characteristic that minimizes the error rate. As a result of the above, the PCM signal input to the variable transversal filter 73 is optimally corrected.

The 0-QDPSK demodulator 75 demodulates the input PCM signal into a digital signal and outputs it to the second signal processor 76. The second signal processor 76 uses an error correction code to correct errors in the digital audio signal generated in the recording/reproducing system,
Convert digital audio signal to original audio signal. Then, it is output to the second output terminal 77.

As described above, according to this embodiment, there is provided a modulating means for performing offset four-phase differential phase modulation on a digitized audio signal, a recording/reproducing means for recording and reproducing an output signal of the modulating means on a recording medium, and a recording/reproducing means for recording and reproducing an output signal of the modulating means on a recording medium, /a first switch for switching and outputting an output signal from the modulation means and an offset four-phase differential phase modulation signal reproduced from a recording medium using a reproduction signal;
A transversal filter receives the offset 4-phase differential phase modulation signal output from the switch and determines the frequency characteristics based on the control signal, and limits the passband of the offset 4-phase differential phase modulation signal output from the transversal filter. First thing to do. a second bandpass filter;
1st. The first one detects the level of the output signal of the second band pass filter. a second level detector; a first level detector; The first level detector converts the output signal of the second level detector into a digital signal.
a second analog-to-digital converter and, when recording, a first;
a memory for recording the output signal of the second analog/digital converter; an error calculator for calculating an error voltage from the output signal of the memory and a predetermined reference value; The first one calculates the difference between the output signal of the second analog/digital converter and the output signal of the error calculator. a second subtractor; a first subtractor; a third subtracter that calculates the difference between the output signals of the second subtractor; a filter that processes the output signal of the third subtractor; and a digital/analog converter that converts the output signal of the filter into an analog signal. , input record/
By providing a second switch that determines whether the control signal input to the transversal filter based on the playback signal is an output signal from the digital/analog converter or a "zero" value, and outputs the control signal, the control signal is digitized during recording. The audio signal is recorded on a recording medium using offset/nodal 4-phase differential phase modulation (PCM signal). At the same time, using two bandpass filters and a level detector, a voltage proportional to the filter passband component of the PCM signal is recorded in the detection 17 memory.

During regeneration, two bandpass filters and a level detector are used to detect a voltage proportional to the filter passband component of the regenerated worn-out PCM signal. The detected two signals are recorded in a memory, and errors due to variations in the bandpass filter and level detector are corrected from the level detector value at the time of recording. Then, the characteristics of the transversal filter are determined from the result of subtraction of the two signals after correction.

As a result, the material of the tape, 1. Second magnetic head group 5
Gears 6a, 56b, 66a, 66b.

Even if the frequency characteristics of the PCM system change due to factors such as length and recording current, it is possible to perform optimal correction so that the error rate during demodulation is minimized.

In addition, in this embodiment, the passband of the first BPF 95a is f c-5f s/16MHz±100KH2N
Passband fc+5fs/1 of second BPF95b
Although it is set to 6 MHz±100 KHz, it may be set to any band as long as it is a pass band symmetrical to the carrier wave frequency and within the band of the PCM signal.

Effects of the Invention As described above, the present invention includes a modulation means for performing offset four-phase differential phase modulation on a digitized audio signal, a recording/reproducing means for recording and reproducing the output signal of the modulation means on a recording medium,
a first switch that switches and outputs an output signal from the modulation means and an offset 4-phase differential phase modulation signal reproduced from the recording medium based on the input recording/reproduction signal; and an offset 4-phase differential output signal output from the first switch. A transversal filter that receives a phase modulation signal as input and determines frequency characteristics based on a control signal, and a first filter that limits the passband of the offset four-phase differential phase modulation signal output from the transversal filter. a second bandpass filter; a first bandpass filter; The first one detects the level of the output signal of the second band pass filter. a second level detector; a first level detector; The first level detector converts the output signal of the second level detector into a digital signal. a second analog-to-digital converter; when recording, a first analog-to-digital converter; a memory for recording the output signal of the second analog/digital converter; an error calculator for calculating an error voltage from the output signal of the memory and a predetermined reference value;
The first one calculates the difference between the output signal of the second analog/digital converter and the output signal of the error calculator. a second subtractor; a first subtractor; a third arithmetic unit that calculates the difference between the output signals of the second subtracter; a filter that processes the third output signal; and a digital/digital processor that converts the output signal of the filter into an analog signal.
By providing an analog converter and a second switch that switches between the output signal from the digital/analog converter and a zero value based on the input recording/playback signal and outputs it as a control signal to the transversal filter, it is possible to solve any conditions. Even if you play back the tape recorded below, it will stably return zero without any adjustment.
-QDPSK demodulation becomes possible. In other words, even if the frequency characteristics of the PCM system change due to factors such as the material of the tape, the gap length of the magnetic head group, and the recording current, it is possible to optimally correct the error rate of the PCM signal to minimize it.

This method converts digitized audio signals into 0-QDPSK
Since the spectral shape of the modulated signal is detected, there is no need to record a pilot signal to newly determine the characteristics of the equalizer section, thereby reducing recording efficiency. Furthermore, when recording the energy distribution is equal to the carrier frequency, 0-
By inputting the QDPSK modulated signal to the detector as a reference signal, variations in the bandpass filter and level detector can be detected and frequency correction can be performed completely without adjustment, which has a great practical effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a magnetic recording and reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram showing the internal configuration of the variable transversal filter 73 and detector 74 in FIG. 1, and FIG. 4 is a format diagram showing an example of the format of a digital audio signal, FIG. 5 is a frequency spectrum diagram for explaining the frequency band of a PCM signal, and FIG. The figure is a track pattern diagram of a magnetic tape. 50.57.78...Input terminal, 51...Modulator, 52.60.67.70...Amplifier, 53,
61゜71...Switch, 54.62...Rotating transformer, 55-...Cylinder, 56a, 56
b, 63a, 63b...magnetic head, 5
8.76...Signal processor, 59...0-QDPSK
Modulator, 64...Tape, 6t5a, 65b...
・Guide post, 66...control device, 68・
...Demodulator, 69.77...Output terminal, 72...
・AGCl 73...Variable transversal filter, 74...Detector, 75...0-QDP
SK demodulator.

Claims (1)

[Claims] Modulating means for performing offset four-phase differential phase modulation on a digitized audio signal; first recording and reproducing means for recording and reproducing the output signal of the modulating means on a recording medium; a second recording/reproducing means for modulating, recording and reproducing the offset four-phase differential phase modulation signal over a track; and reproducing from the output signal from the modulating means and the recording medium using the input recording/reproducing signal. a first switch that switches and outputs the offset four-phase differential phase modulation signal output from the first switch; and a transversal switch that inputs the offset four-phase differential phase modulation signal output from the first switch and determines frequency characteristics based on the control signal. a filter; first and second bandpass filters that limit the passband of the offset four-phase differential phase modulation signal output from the transversal filter; and levels of output signals of the first and second bandpass filters. first and second level detectors that detect the first and second level detectors, and first and second analog/digital converters that convert the output signals of the first and second level detectors into digital signals; a memory for recording output signals of the first and second analog/digital converters; an error calculator for calculating an error voltage from the output signals of the memory and a predetermined reference value; , first and second circuits that calculate the difference between the output signal of the second analog/digital converter and the output signal of the error calculator.
a subtracter, and a third subtracter that calculates the difference between the output signals of the first and second subtracters.
a subtracter; a filter that processes the output signal of the third subtractor; a digital/analog converter that converts the output signal of the filter into an analog signal; a second switch that determines whether the control signal input to the filter is an output signal from the digital/analog converter or a "zero" value, and outputs the control signal; and an offset four-phase differential phase modulation output from the transversal filter. A magnetic recording and reproducing device comprising demodulating means for demodulating a signal into a digital audio signal.