JPS5975415A - Record and reproduction compensating circuit of pcm sound recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the error rate at the time of reproduction and improve the reliability, by providing a delay element corresponding to less than the detection window width of digital signals, coefficient instrument which changes the output gain of the delay element, a circuit for inverting the polarity of a signal, and their adder. CONSTITUTION:The high level and low level of input signals 61 are dependently detected by using two detecting circuits 83 through an inverter 84. The detecting circuit 83 for data width at a high level of the input signal 61 is constituted with a set of 2T- pulse detecting circuit 79 and coefficient instrument 81 and another set of 1.5T-pulse detecting circuit 80 and coefficient instrument 82 and, when 2T- and 1.5T-pulses of the input signal 61 are detected, the 2T-pulse output is intensified to a prescribed level as compared with the 1.5T-pulse, and then, outputted. This processing is also made in the case of an low level input. A synchronizing circuit 78 outputs the synchronizing circuit output signal 85 of input signals synchronizing to the 2T- and 1.5T-pulses detected by the detecting circuit 83 and a record compensating circuit output 91 is obtained by adding the signals 85-89 to each other at an adder circuit 90. Therefore, the error rate at the time of reproduction can be reduced and the reliability as a PCM sound recording and reproducing device can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a recording and reproducing compensation circuit for a PCM recording and reproducing machine that minimizes the number of code errors when recording and reproducing signals on a magnetic tape.

[Prior art]

The configuration of a conventional PCM recording tfFj raw machine, the configuration of a recording/reproducing compensation circuit, and the problems thereof will be explained with reference to FIGS. 1 to 4. FIG. 1 is a schematic block diagram of a modulation/demodulation circuit system including a magnetic head and tape of a conventional fixed head type PCM recording/reproducing machine.

In the figure, a digital input signal 1 is transmitted to a modulation circuit 2,
Through the recording amplifier 3, the recording head 4l magnetic tape 5
recorded in During playback, the signal read from the magnetic tape by the playback head 6 is amplified by the playback amplifier 7, and after equalizing one waveform distortion of the transmission system by the playback compensation circuit 8,
It is input to the integrating circuit 9. The signal whose waveform has been shaped by the integrating circuit 9 is converted into a square wave by the comparator 10, and then the clock is recovered by the demodulating circuit 11, and the demodulated output signal 1 is output.
It becomes 2. FIG. 2 shows a recording waveform 13 and a reproduction waveform 14. The Wagyu beef waveform differentially detected by the reproducing head 6 generally has an insufficient band of the magnetic tape, the head, and the recording h raw silk with the spacing between them, and the base of the differential output waveform of the single step input signal is widened. It's coming. Due to the characteristics of the magnetic tape and head system, this waveform has a pulse width (normally half width W5) at the maximum amplitude point A as shown in the figure.
0) or 1<0 such as t>0, an imbalance occurs.

Using a system in which the frequency characteristics of the nails and Wagyu thread are insufficient and non-linear, an acoustic signal or an analog signal is converted into a digital signal, and the signal shown in Fig. 2 is converted into a digital signal, for example. When transmitting data bit change points every t = T, the quality of the reproduced signal deteriorates due to code amount interference between the recorded data pits, the data pit interval during recording changes during reproduction, and the digital number 13 identification becomes difficult, and code errors increase. Therefore, in a conventional compensation circuit that performs waveform equalization to correctly identify the transmitted signal, the recording amplifier 3 is configured with a constant current amplifier, and a constant current is recorded in the recording/rad 4, and the reproducing head 6 A system was used in which the differentially detected signal was compensated for only by the reproduction system 0), and the configuration was as shown in FIG. 3. FIG. 3 shows a conventional example using two delay elements.

In FIG. 3C, 14 is a reproduced signal, 15 is a delay element that adjusts to the same length as the data pit interval T, 16 and 18 are coefficient units that change the gain, 19 is a polarity inversion circuit, 23 is an adder, and 24 is the output of the regeneration compensation circuit. A method of waveform equalization in this figure will be explained using FIG. 4.

Generally, in order to identify the signal transmitted at every data bit interval T, it is necessary to identify the signal transmitted at every data bit interval T (t = nT) except for the one pulse peak point (t = 0 point) shown in Figure 4. Basically, it can be identified as long as it becomes zero. Therefore, in the conventional circuit shown in FIG. 3, the reproduced signal 14 is delayed by the data bit interval T by the delay element 15, and the gain is changed by the coefficient multiplier 17.
After changing the gain through the polarity inverting circuit 19, the signal 21 whose polarity has been inverted by the polarity inverting circuit 19, and the signal which has been further delayed from the signal 20 by T delay element 15 are similarly sent to the coefficient multiplier 18,
The signal 22 obtained through the polarity inversion circuit 19 is sent to the adder 231.
By inputting and setting the values of the coefficient multipliers 16 to 18, the amplitude of the reproduction compensation circuit output 241 is made zero at least at the adjacent data change points (1=±T) as shown. In this case, assuming that the amplitude values at the pulse peak point of the reproduced signal 14 and the data change points t=-T and T before and after the peak point are 1, 0.3, and 0.7, respectively, the coefficient multipliers 16, 17. The 18 coefficients ~+, ko, and kx are uniquely determined by the following equation based on the conditions of the reproduction compensation circuit output 24. That is, in Fig. 4, A direct at t=-T...k-1+0.3ko = □t
= A straight line at Q...0.7 to -x +ko + 0.3
kt = 1t=value at T...0.7kO+kl
= 0 so -1= -0,52, ko -1,7
2, 1 = -1,21 is found, and the reproduction compensation circuit output 2
You can get 4. However, even if a reproduced signal with an insufficient recording/reproducing band and nonlinear characteristics is waveform-equalized using a conventional compensation circuit, the half-width W50 +< A value of 0, 10>0 is unbalanced. Therefore, the output signal 26 of the reproduction compensation circuit when the signal 25 with the data bit interval T as shown in FIG. ，
24', 24''), there has been a problem in which the recording/reproducing thread changes significantly by dr 1.
When the output signal 26 is waveform-shaped by the integrating circuit 9, converted into a square wave by the comparator 10, and then demodulated by the demodulating circuit 11, the margin for data identification is significantly reduced due to the above-mentioned change in the data bit interval during recording and reproduction. This caused an increase in the number of data errors. Furthermore, conventional P
A CM recording/reproducing machine performs constant current recording by setting the recording current of the recording head near the recording current value at which the reproduction output level from the magnetic head is maximum at the maximum recording frequency of the digital signal to be transmitted. However, generally magnetic tape,
In a magnetic recording system using a magnetic head, in addition to deterioration of frequency characteristics in high frequency components when performing constant current recording, there is a problem in that it is difficult to transmit a band from direct current to low frequency components. Therefore, this lack of low-frequency component bandwidth causes DC level fluctuations in the reproduced signal, which further reduces the margin for data identification/belt, and the lack of low-frequency components can be compared to high-frequency components. If the entire band is corrected by lowering it with a reproduction compensation circuit, S,/N deteriorates and the number of data errors increases.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a recording/playback compensation circuit for a PCM recording/playback machine that eliminates the drawbacks of the prior art, corrects distortion of transmission waveforms due to magnetic tape and magnetic heads, and makes it possible to correctly identify data. be.

[Summary of the invention]

The present invention focuses on the fact that the conventional drawback is that waveform equalization is performed only by a reproduction compensation circuit, and that this occurs because the configuration of the reproduction compensation circuit corrects it with a delay element corresponding to the data bit interval Tζ. The compensation circuit has a plurality of data points for correction/second correction within the data bit interval to improve the accuracy of phase correction and expand the control range.

Further, the recording compensation circuit increases the recording current of the low frequency component without changing the phase characteristics.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. M6
The figure shows an example of a regeneration compensation circuit. ■
4 is a reproduced signal manually; 27 is a delay element corresponding to the value obtained by dividing the data bit interval T into two; 28 to 32 are coefficient units that change the gain of each delay element output; 19 is a polarity inversion circuit;
23 is an adder, and 38 is a reproduction compensation circuit output. Here, for the reproduction signal [manual power] 4 that causes waveform distortion,
It is necessary to correctly identify the signal transmitted every data bit interval T. For this reason, in the present embodiment shown in FIG. 6, if the amplitude at the pulse peak point in the reproduction compensation circuit output 38 is fi-1, the amplitude is made zero at the adjacent data bit point t=±T excluding the pulse peak point. With,
A delay element 27 corresponding to half the data bit interval 'r is provided, and the amplitude value at t:10.5T is set to 05 to eliminate phase distortion. That is, when the reproduced signal 14 has the same waveform as the conventional example and the pulse peak point 1t=Q, t
=-T, -0,5'I", 0.0.5T, TnioFJ
The amplitude values for each channel are set to 0.3, 0.8, 1, 0.
9, 0.7, the coefficients 1-1, 1-0, .
5, 10, 10, 5, 11 are reproduction compensation circuit output 3
It can be determined as follows from the conditions of 8. If the pulse peak point of the reproduction compensation circuit output 38 is tI+:+0, then the straight line at t=-T...l-z 10.81-o, a
-4-0,3io = 0t=-0,5'l'...0
．． 91-1 +1-0.5+0.81o-4-Q, 31
o,s =0.51=0...0.71-1+0.91
-0.5+IO+0.810.5+0.311=1t=
o, 5'l"...0.71-0.5+0.91o+1
0.5+Q, 811 =0.5t=1゛...0.71
From the four equations of 0 +0.9io, s +11 = Q, I-1 = 1.9, l -o, s = -1,5,
l Q=-2,3, lo, s = 7.1, l 1
=-4,7.

The operation of this embodiment shown in FIG. 6 will be explained using FIG. 7. In FIG. 7, when the reproduced signal input 14 described above in FIG.
T.

The above coefficient 1- is applied to the signal delayed by x, s'f', 2T.
1=1.9.1-〇, 5=-1.6, 1o=-2,3
,10,5=7.1. The input signals 33 to 37 of the adder 23 are obtained by passing through the coefficient multipliers 28 to 32 with I+=-4 and 7 and the polarity inversion circuit, respectively. By adding these signals in the adder 23, a reproduction compensation circuit output 38 is obtained. This output 38 has zero amplitude at adjacent bit points t=±T excluding the pulse peak point, and the amplitude values at ±0.5T are both half of the pulse peak value, and the nonlinear characteristics can be greatly increased.

FIG. 8 is a diagram showing the effect of the present embodiment shown in FIG.
The mail differentially detected by the square head is equalized by the reproduction compensation circuit shown in FIG. When the input signal 25 with the data bit interval 'r is recorded p+, the reproduction compensation circuit output is the output 38 when t==Q and the output 38 when t=-'1'.
The signal is the sum of the output 39 at t=T and the output 40 at t=T. This addition signal becomes 41, and there is almost no change in the data bit point during recording and playback. Shi, Ig
It is possible to obtain a sophisticated PCM recording/playback device.

In the present embodiments shown in FIGS. 6 to 68, the delay elements are arranged by pressing inward at equal intervals within the data hit interval T, or the delay elements are arranged at unequal intervals and the pulse peak point is Even when the excluded data bit points are excluded, the same effect as in this embodiment can be obtained.

Figure 9 shows how to convert an analog signal into a digital signal and convert the M
This is an example of a reproduction compensation circuit when recording and reproduction is performed with FM modulation. In MFM modulation recording, the data bit length is T, 1.5T, 2T, as is well known.
In order to eliminate waveform interference and correctly identify data, it is necessary to make the amplitude of the differential output waveform zero at intervals of 0.5T. In FIG. 9, data with a data bit length T of approximately 8.3 μs is transmitted to the delay element 42 every 1 μs.
-\, and the waveform distortion of the reproduced signal input is equalized by adding them in the adder circuit 23 through the coefficient multipliers 43 to 53 and the polarity inversion circuit 19. The amplitude characteristics and group delay characteristics of the reproduction compensation circuit shown in FIG. 9 in this case are shown at 55 and 56 in FIG. 10, respectively.

Next, one embodiment of the recording compensation circuit according to the present invention will be described in the eleventh embodiment.
This will be explained using figures. In FIG. 11, a recording compensation circuit 60 is connected to the output of the modulation circuit 2 to enhance the low frequency band without changing the phase characteristics from the digital input signal 1, and then input to the recording amplifier 3 and output to the recording head 4. The information is recorded on the magnetic tape 5 at the same time. One embodiment of the recording compensation circuit 60 will be described with reference to FIGS. 12 and 13.

The embodiment shown in FIG. 12 uses a delay element to compensate for the lack of a low frequency band caused by the magnetic tape and magnetic head when recording an MFM modulated signal on a magnetic tape. Here, the data bit length T of the MFM adverbial signal is approximately 8.3
In the case of μs, ten 1 μs delay elements are connected in cascade, and the gain of each delay element output is changed by coefficient multipliers 63 to 73 and added by an adder 74 7, and the output signal 61 of the modulation circuit 2 is amplified in the low frequency range. Then, a recording compensation list output signal 75 of 1 is obtained. In FIG. 13, 76 is the obtained amplitude characteristic, and 77 is the group delay characteristic. In general, in magnetic recording, low frequency characteristics may vary significantly depending on the material of the magnetic tape (for example, -Fez-03 type, metal type, etc.) and the performance of the recording head used. Even in such a case, in the embodiment shown in FIG. 12, by adjusting only the coefficient of the coefficient multiplier 68 of the output of the central delay element of the plurality of delay elements, the result as shown in FIG. 13 76 can be obtained. Since low frequency characteristics can be easily achieved, the control range regarding the performance of the magnetic tape and head can be widened, and the performance 2 and reliability of the PCM recording/reproducing machine can be improved. In FIG. 12, the coefficients other than the coefficient multiplier 68 are symmetrical with respect to the coefficient multiplier 68, that is, the coefficient multiplier 6
These coefficients are the same, such as 7 and 69.66 and 70.

FIG. 14 shows another embodiment of the recording compensation circuit when performing MFM modulation. In FIG. 14, 78 is a synchronization circuit;
79 is a 2T pulse detection circuit, 80 is a 15'r pulse detection circuit, 81.82 is a coefficient unit, 83 is a data width detection control circuit, 84 is an inverter circuit, 85 is a synchronization circuit output,
86 is a high level 2T pulse output of the modulation circuit output signal, 87 is a 1.5T pulse output, 88 is a low level 2T pulse output of the modulation circuit output signal, and 89 is a 1.5T pulse output.
90 is an adder, and 91 is a recording compensation circuit output.

The operation of this embodiment will be explained using FIG. 15.

The data width detection circuit 83 detects the modulator output signal 11t.
4 FM input signal 610) 2 'L'j6yoU;1
．． 5'J'U) It detects the pulse width, and there are two data width detection times w! 83 is used to independently detect the high level and low level of the input signal 61 via the inverter 84.

The data width detection circuit 83 at the It i g b level of the input 1g+f61 is composed of a 2T pulse detection circuit 79 and a coefficient multiplier 81.
When 1.5T pulse is detected, 2T pulse output 86
Compared to the 1.5T pulse output 87, the PJ1 constant amplitude level is enhanced and output. The data width detection circuit at the l and ow levels of the input signal 61 also operates in a similar manner.
T pulse output 88.1.5T pulse output 89 is output. The synchronization circuit 78 outputs a synchronization circuit output signal 85 of a human input signal synchronized with the 2T pulse and the 1.5T pulse detected by the data width detection circuit 83,
By adding the signals 85 to 89 described above, a recording compensation circuit output 91 is obtained.

According to this embodiment, it is possible to enhance the low frequency band with a simple configuration without changing the phase characteristics of the digital signal of the modulation circuit 2, thereby reducing the deterioration of S/N during reproduction and the loss of data. A reliable recording compensation circuit can be realized without reducing the identification margin.

Although this embodiment has been described with respect to the input of the MFM modulation signal, the same effect can be obtained with other modulation signals such as 3PM and FMfl.

When an MFM modulated signal with a data bit length ']' = 8.3 μs is recorded and reproduced using the recording compensation circuit and reproduction compensation circuit according to this embodiment, the error L--1- of the conventional method is
However, compared to JO-1, an error rate of 10-3 was obtained using this method, and the reliability was significantly improved.

〔Effect of the invention〕

According to the present invention, the error rate when recording and reproducing a digital signal f on a 4B tape is from 10-1 to 10
The reliability of the PCM recording/playback device was greatly improved.

[Brief explanation of the drawing]

Figure 1 shows the configuration of the PCM recording/playback machine, Figure 2 shows the recording and playback waveforms, Figure 3 shows the playback compensation circuit, Figure 4 shows the waveform equalization waveform, Figure 5 shows the waveform interference waveform, and Figure 6 shows the invention. Figure 7 shows the waveform equalization waveform, Figure 8 shows the waveform interference waveform, Figure 9 shows the reproduction compensation circuit, Figure 10 shows the reproduction compensation characteristics, and Figure 11 shows the reproduction compensation circuit.
The figures are I) CM recording system professional diagram; FIG. 12 is a recording compensation circuit; FIG. 13 is a recording compensation equality; FIG. 14 is a recording compensation circuit; and FIG. 15 is a recording compensation operation diagram. 8...Reproduction compensation circuit 15.27, 42.62...Delay element 16-18.28-32.43-53, 63-73.
・・Coefficient unit 23.74.90・・Adder 60・・
- Recording compensation circuit 78...Synchronization circuit 79...2T pulse detection circuit 80...1.5T pulse detection circuits 81-82...Coefficient unit 83...Data width detection circuit 84...Inverter Representative Patent Attorney Usui 1) Tori Yukidai l Figure 2 Figure 3 Figure 7 is a port d Figure O 7 is $? Shout-27-TI=OT 2T Fig. 70 Frequency (m) Chi/2 Mouth Fig. 11

Claims (1)

[Claims] 1. In a PCM recording/playback machine that converts analog signals into digital signals and records and plays them on a magnetic recording medium, a delay element whose width is equal to or less than the detection window width of the recorded digital signal and an output of the delay element are provided. a coefficient multiplier that changes the gain of the signal, a polarity inversion circuit that inverts the polarity of the signal, and an adder that adds the output of the coefficient multiplier or the output of the polarity inversion circuit, N delay elements are connected in series, and the first The input of the delay element and the output of each delay element are input to the coefficient multiplier corresponding to each delay element.The outputs of the coefficient multipliers of (N+1) are input to the adder directly or via a polarity inverting circuit to generate N+1) signals. A playback compensation circuit for a PCM recording/playback device characterized by addition. 2. The reproduction compensation circuit of the patented product, characterized in that, among the N delay elements, N delay elements in which at least one delay element has a different delay amount are connected in series. 3. In a PCM recording/playback machine that converts an analog signal into a digital signal and records and reproduces it on a magnetic recording medium, a delay element corresponding to a detection window width of the recording digital signal or less and a coefficient that changes the gain of the output of the delay element. a polarity inversion circuit that inverts the polarity of a signal, and an adder that adds the output of the coefficient multiplier or the output of the polarity inversion circuit, N delay elements are connected in series, and the first delay element input and The outputs of each delay element are input to the coefficient multiplier corresponding to each delay element.The outputs of the (N+1) coefficient multipliers are input directly or through a polarity inverting circuit to an adder, and the (N+1) signals are added. It is equipped with a coefficient multiplier that changes the gains of the outputs of the elements and delay elements, and an adder that adds the outputs of a plurality of coefficient multipliers, and N delay elements are connected in series, and the first delay element input and each delay element output is input to the coefficient multiplier corresponding to each delay element, and the outputs of (N+1) coefficient multipliers with varying gains are input to the adder and summed.
Recording compensation circuit for recording/playback equipment. 4. Among the coefficient multipliers connected to the N delay elements, the coefficients of the coefficient multipliers connected to the delay element corresponding to the center of all delay values obtained by connecting N delay elements in series are each given an equal advance. 3. A recording compensation circuit for a PCM recording/reproducing machine according to claim 3 of the patent scope, characterized in that the coefficients of the coefficient multipliers connected to the delay elements and the delay elements are made equal. 5. I) as set forth in claim 3, characterized in that, among the N delay elements, N delay elements in which at least one delay element has a different delay amount are connected in series. Recording compensation circuit for commercial recording and playback equipment. 6. In the PCM recording/playback device described in the above item 3, a data width detection circuit detects the data pit length of the recorded digital signal and changes a predetermined amplitude level in accordance with the detected bit length; A record of a PCM recording/playback device, characterized in that it is equipped with a synchronization circuit that synchronizes a digital input signal with a signal detected by a detection circuit, and an adder that adds the output of the synchronization circuit and the output of the data width detection circuit. Compensation circuit.