JPS58182110A - Pcm sound recorder - Google Patents

Abstract

PURPOSE:To detect and set the amount of correction for obtaining a minimum data error rate automatically by varying the amount of correction of a playback frequency and storing data error rates at several points within a variation range. CONSTITUTION:A playback signal amplified by a regenerative amplifier 6 is passed through a frequency correcting circuit 7 for high band correction and converted into digital data by a comparator 9. This digital data is processed by an error detecting circuit 10, whose error detection signal is transferred to a microcomputer 11 for control. The microcomputer 11 counts the frequency of error detection per unit time and the result is stored in an external memory while corresponding to the amount of frequency correction. Then, the control microcomputer 11 sends a control signal 13 for the amount of correction to the frequency correcting circuit 7 and the frequency of error detection is counted again with the varied amount of correction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a PCM recorder having a function of automatically setting the frequency correction amount of a reproduction circuit so that the number of data errors is minimized.

The configuration of a conventional PCM recorder and its problems will be explained with reference to FIGS. 1 to 3. Figure 7 shows the conventional fixed head type P.
FIG. 2 is a block diagram of the CM recorder head and its surroundings.

In the figure, a digital signal l is recorded on a magnetic tape by a recording head 3 via a recording amplifier. When playing, play head! The signal read by
The signal is amplified by the reproduction amplifier, and high frequency correction is performed by the frequency correction circuit 7 to produce a reproduction output signal. Thereafter, the reproduced output signal g enters a comparator and is converted into a digital signal, where it is subjected to processing such as error detection, correction, and correction of digital data. At this time, the number of data errors is determined by the so-called aperture ratio of the eye pattern. The aperture ratio of the eye pattern is determined by the frequency characteristics of the recording/reproducing system.

For this reason, the frequency correction circuit 7 performs high frequency correction as shown in FIG. 1, and sets the correction amount to the maximum aperture ratio of the eye pattern, that is, the minimum number of data errors. The relationship between this correction amount and the number of data errors per unit time (data error rate) is generally as shown in the 1lcJ diagram. That is, once the tape-head transmission system is determined, the optimum correction amount is uniquely determined.

Conventionally, the above-mentioned optimum correction amount has been set by changing the circuit constants of the frequency correction circuit. However, the optimum amount of correction varies depending on variations in heads between tracks and the tape used, and adjusting the amount of correction in accordance with these factors requires an extremely large amount of time. Furthermore, this will be a major impediment to the widespread use of fixed head type PCM recorders.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a PCM recorder having a function of automatically setting the reproduction frequency correction amount to a value that minimizes the data error rate.

It is now possible to automatically change the frequency correction amount, memorize the data error rate at several points within the range of change, and automatically detect and set the correction amount that gives the minimum data error rate from the results. At the point.

Embodiments of the present invention will be described below based on the drawings.

FIG. 3 shows an embodiment of the present invention, in which a function for automatically detecting and setting the optimal value of the reproduction frequency correction amount is added to the conventional system shown in FIG.

In the figure, 9 is a level comparator, /.

I/ is a control microcomputer, l is an external memory, and /3 is a correction amount control signal. Further, the symbols other than these indicate the same meaning as in FIG.

First, the basic operation will be explained with reference to Fig. q. The reproduced signal amplified by the reproduction amplifier is high-frequency corrected by a frequency correction circuit, and then converted into digital data by a converter. This digital data is processed by the error detection circuit 10, and the error detection signal is sent to the control microcomputer//
will be forwarded to. The control microcomputer //l-1 counts the number of error detections per unit time, and stores the result in an external memory in correspondence with the frequency correction amount. Subsequently, the control microcomputer // outputs the correction amount control signal /3
is sent to the frequency correction circuit 7, and the number of error detections is counted again with the correction amount changed. By repeating the above operations, the correction amount that minimizes the data error rate is detected from the correspondence between the frequency correction lid and the data #% rate, and is set to the optimum correction amount. - Next, an example of a reproduction frequency correction circuit is shown in FIG. In the figure, /q is an input terminal for the reproduced output signal, 15 is a cascade connection of a delay line with a delay time τ, and /6#'i
Coefficient circuit group (however, only the real part with coefficient Fikt), 17#: is an addition circuit, and lza is an output terminal. Chapter S
The reproduction frequency correction circuit having the configuration shown in the figure is called a transversal filter, and is characterized in that the group delay is θ and arbitrary frequency characteristics can be obtained.

#! FIG. 6 shows the response when the input terminal /4tK impulse of FIG. 5 is input. As shown in the figure, the amplitude is determined according to the coefficient &4 for each time τ. Generally, the impulse response of a transmission system corresponds to the Fourier transform of the frequency domain transfer function of the transmission system. That is, by controlling the behavior (impulse response) of a system in the time domain, it is possible to control the frequency characteristics of that system. For example, when 1″tk; is closed in FIG. 6, the frequency correction amount in FIG. 5 corresponds to CI
to C:. That is, by controlling the coefficients of the coefficient circuit group shown in FIG. S, an arbitrary frequency correction amount can be obtained.

FIG. 2 is an example of a coefficient circuit that can be controlled by an external signal. In the same figure, /f#i input terminal, -〇 is an operational amplifier, 21 is an output terminal, 2- is a feedback resistor, ko3 is a fixed resistor, con is a resistor group, koj is a control transistor, 2
6 is a dabit data input terminal. In Figure 7,
The degree of increase from the input terminal 1 to the output terminal 20''& is determined by R6 and the resistance here when the davit data is all 0. Also, depending on the state of the davit data, for example (''
In the case of t he '+ d) = (/, 0. /, 0), the resistances α and 2 da C are connected in parallel with Ro, so the amplification of the circuit in Figure 7 is adjusted accordingly. is determined. By using such a coefficient circuit as the coefficient kl in Fig. 6, the frequency correction amount can be changed as shown in Fig. S.
It becomes possible to control from the outside according to the value of 1.

FIG. 9 is a flowchart for detecting and setting the optimum correction amount when using a q-bit microcomputer and external memory. Moreover, FIG. 7θ shows changes in the amount of correction and the data error rate according to the test time. First, in step / in FIG. 9, the initial value of the correction amount is set (FIG.
, corresponding to the amount of correction). Next, in StepCo, the memory address α is set to O, and in Step 3, 7 is added to α. Subsequently, davit data is output to the correction circuit in order to set the correction amount. Next, the number of data errors with the above correction amount is stored in memory. Subsequently, the values of a and le are compared (le is 2'=/& times in davit),
If a<ru, return to step J. Then, af - further / is added, and the correction amount is set to be /R steps larger than the previous correction amount. Changes in various quantities when this operation is repeated t
It will look like the atixio diagram.

When α≧ru in step 6, from the memorized result,
The correction amount that minimizes the data error rate is detected and set to the correction amount using the dabit signal.

As described above, according to the present invention, the correction t of the reproduction frequency correction circuit is detected at the point where the data error rate p is minimized, regardless of variations in characteristics of the tape used or variations between tracks of the reproduction head. -Can be set. Therefore, there is a great effect that digital data can always be reproduced with the best frequency correction amount even when the reproduction frequency characteristics vary.

[Brief explanation of drawings]

Figure 1 is a block diagram of the area around the tape head of a conventional PCM recorder, Figure 1 is a characteristic diagram showing an example of the frequency characteristics of the reproduction frequency correction circuit, and Figure 3 is an example of the relationship between the amount of correction and data error rate. FIG. 9 is a block diagram of an optimum correction amount automatic detection circuit using a data error detection circuit and a control microcomputer according to an embodiment of the present invention, and FIG. 5 is a diagram of the frequency correction circuit in FIG. Figure 6 is a diagram showing an impulse response of the circuit in Figure S, Figure 7 is a diagram showing an example of the coefficient circuit in Figure 5, Figure S is a diagram showing the frequency that changes depending on the coefficient. A graph showing an example of the correction amount, FIG. 9 is a flowchart showing the operation of the frequency correction amount automatic detection setting circuit, and FIG.
FIGS. 3A and 2B are diagrams illustrating changes in the correction amount and data error rate according to the flowcharts in FIGS. <Explanation of symbols> l...digital input signal c...recording amplifier 3...
・8 self-enabled head Da... Magnetic tape S... Playback head 6... Playback amplifier 7... Playback frequency correction circuit t... Playback output signal 9... Level comparator 10... Data error Detection circuit /...control microcomputer /co...external memory/
3...Correction amount control signal /Tei...Correction circuit input terminal/j...Delay element /6...Coefficient circuit group/7...Addition circuit 7g...Correction circuit output terminal/9. ...Coefficient circuit input terminal, 20...Operation amplifier circuit/...Coefficient (b) circuit output terminal, 2...Feedback resistor 3...Fixed resistor 21I...Resistor group, 25... Control transistor roller...davit data input terminal 7 city correct amount t1t2 ------ Zt test day)

Claims (2)

[Claims] (1) A magnetic head for recording and reproducing digital signals;
A reproduction frequency correction circuit that amplifies the output of the reproduction head and can control the reproduction frequency characteristics within a predetermined band, detects errors in reproduced data for each reproduction frequency correction amount, and detects errors in the reproduction frequency. comprising means for counting the number of times, storage means for storing the counting results of the nucleon stage in correspondence with the correction amount, and means for determining the magnitude relationship of the counting results stored in the storage means, A PCM recorder, characterized in that the frequency characteristics of the correction circuit are controlled according to the minimum count result. (2) The PCM recorder according to claim 1, wherein a transversal filter using a delay circuit is used as the reproduction frequency correction circuit.