JPS63209005A - Reproduced waveform equalization circuit - Google Patents

Abstract

PURPOSE:To make a pulse in a waveform asymmetric to a peak point into a waveform symmetric to a peak point by subtracting an output signal from an attenuator from a result obtained by adding an output signal from a delay circuit with a reproduced signal set in a specified amplitude. CONSTITUTION:A resistance 4 is provided and the reproduced signal (a) is adjusted in terms of amplitude in the resistance 5 and supplied to a differential amplifier 7 as a non-inverse input. The amplitude of a composite signal (e) is decided by setting the quantity of attenuation of the attenuator 6 in order that the amplitude of a point obtained delaying from the peak point of a delay signal (b) by a pulse transmission interval T becomes zero. Thus, the amplitude of the point obtained by forwarding from the peak point of the delay signal (b) by the pulse transmission interval T becomes negative by the subtraction of the peak value before the composite signal (e). Therefore, by adding a signal (f) through the resistance 4, the amplitude of the point where the delay signal (b) is negative is corrected to become zero. Thus, a phase strain by a recording and reproducing system is removed and the pulse (g) whose first transition and last transition are sharp and the front and rear of the peak point is symmetric waveform can be obtained in an output terminal 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reproduced waveform equalization circuit suitable for use in a magnetic recording/reproducing apparatus such as a rotary head type digital audio tape recorder.

[Conventional technology]

- Generally, the high frequencies of the reproduced signal obtained from a recording medium are attenuated, and in magnetic recording and reproducing devices that record and reproduce digital signals such as digital audio signals, each pulse of the reproduced signal has a gradual rise and fall. It has a waveform with a wide hem. For this reason, in a digital signal, the amplitude of each pulse should originally be zero before and after the pulse transmission interval (the center-to-center distance between two adjacent pulses) apart from its center; Since the pulses have a wide base, the pulses interfere with each other, making it impossible to perform pulse transmission without causing errors in the detection of each pulse.

Therefore, the magnetic recording/reproducing device is provided with a reproduction waveform equalization circuit that enhances the high frequency range of the reproduction signal and sharpens its rise and fall.

FIG. 6 is a block diagram showing the recording and reproducing system of a rotary head type digital audio tape recorder (R-DAT), in which 50 is an audio signal input terminal, 51 is an A/D
converter, 52 a recording signal processing circuit, 53 a recording amplifier, 54 a rotary head, 55 a magnetic tape, 56 a reproduction amplifier, 57 a reproduction waveform equalization circuit, 58 a data identification circuit, 59 a reproduction signal processing circuit, 60 is a D/A converter, and 61 is an audio signal output terminal.

In the figure, first, when the R-DAT is in a recording state, an audio signal input from an audio input terminal 50 is converted into digital data by an A/D converter 51. Next, the digital data is converted by the recording signal processing circuit 52 into recording data according to the recording format, and after being amplified by the recording amplifier 53,
The information is recorded on a magnetic tape 55 by a rotating head 54. Next, when the R-DAT is in the reproduction state, the rotary head 54 scans the magnetic tape 55 to read recorded data. After the read data is amplified by a reproducing amplifier 56, interference between pulses is removed by a waveform equalization circuit 57. Furthermore, the clock in the data is extracted by the data identification circuit 58, and the “
0" and "1" are discriminated.Furthermore, this read data is input to the reproduced signal processing circuit 59, and after error detection and correction are performed, the data is processed by the D/A converter 60.
It becomes an audio signal again and is output to the output terminal 61.

Conventionally, as such a reproduced waveform equalization circuit, a transversal filter using a delay line is often used, as disclosed in Japanese Patent Publication No. 54-3603, for example.

That is, a reproduced signal from a recording medium is supplied to a delay line having a delay time τ approximately equal to the pulse transmission interval T, and a reproduced signal delayed only at the output terminal of this delay line is obtained. reflected at the output terminal of 2τ
A reflected reproduced signal delayed by 1 is obtained at the input terminal of this delay i, and the input reproduced signal of this delay line and this reflected reproduced signal are combined, and this combined signal is subtracted from the output signal of the delay line. be. This is the angular frequency ω at which maximum gain is obtained. is a transversal filter where is π/τ. Therefore, if the delay time τ of the delay line is made almost equal to the pulse transmission time T of the reproduced signal, the time before and after the peak point of the output signal of the delay line will be significantly subtracted, and therefore, the rising and falling edges of the reproduced signal from the recording medium will be significantly subtracted. Even if the pulses are made up of gentle, wide-tailed pulses, they will be delayed by approximately the pulse transmission time T compared to this reproduced signal, but these pulses will have steep rises and falls. That is, even if the pulse is attenuated in the high frequency range due to magnetic recording and reproduction, the reproduction waveform equalization circuit restores the original waveform by adjusting the strength of the high frequency range.

This conventional technology is configured to minimize the number of delay lines and the delay time of each delay line, and has excellent features such as a small circuit scale and low cost. In addition, in this prior art, the relationship between frequency and phase (hereinafter referred to as phase frequency characteristics) is linear, and when the phase frequency characteristics between the recording medium and the head are linear, the phase of the waveform of the reproduced signal is Another advantage is that only amplitude harmonics can be performed without changing the amplitude.

According to this, the pulse transmission interval of the digital signal does not change due to waveform equalization, and there is no need to reduce the data recording density.

However, in a digital signal recording/reproducing apparatus, the phase frequency characteristics of the recording medium and the head are non-linear, and a peak shift I. occurs in the reproduction pulse depending on the pulse interval and the pulse repetition frequency. A reproduced waveform equalization circuit designed to eliminate such a peak shift is disclosed in, for example, Japanese Patent Laid-Open No. 58-3117.

[Problem that the invention seeks to solve]

By the way, in order to detect data from the reproduced digital signal without error, it is necessary to
The waveform must be symmetrical. However, the reproduced digital signal obtained from the recording medium often has phase distortion, and its pulse waveform is asymmetrical around the peak point at which the amplitude is maximum on the time axis. That is, the amplitudes at two points separated by the pulse transmission interval from this peak point are different. Particularly in a rotary head type magnetic recording/reproducing device, due to the recording process, the amplitude at a time point delayed by the pulse transmission interval from the peak point becomes larger than the amplitude at a time point advanced by that time. Even if such a reproduced digital signal is subjected to waveform equalization processing by the reproduced waveform equalization circuit disclosed in the above-mentioned Japanese Patent Publication No. 54-3603,
Since this phase frequency characteristic is linear, the pulse waveform remains asymmetrical about the peak point, and interference between pulses is not eliminated, making data detection prone to errors.

Furthermore, the reproduced waveform equalization circuit disclosed in Japanese Patent Application Laid-Open No. 58-3117 eliminates the peak shift by improving the rising edge of the reproduced signal. Satisfactory waveform equalization cannot be performed on a reproduced signal with a distorted waveform.

In order to compensate for pulse asymmetry using a transversal filter using a delay line, it is necessary to subtract the rising and falling edges of the reproduced signal delayed by τ, which is approximately equal to the pulse transmission interval T, to make the input signal steeper. There must be a level difference between the outgoing signal and the reproduced signal delayed by 2τ, in particular, the level of the latter must be greater than that of the former. However, it is impossible to obtain such a signal using the means disclosed in Japanese Patent Publication No. 54-3603, which utilizes the reflection of a delay line, and two delay lines are required in the case of the square type. When the number of delay lines increases in this way, there are problems in terms of circuit scale, cost, etc.

An object of the present invention is to solve these problems, minimize the number of delay lines used, and reproduce pulses that are asymmetrical with respect to the peak point to a waveform that is symmetrical with respect to the peak point. The object of the present invention is to provide a waveform equalization circuit.

[Means for solving problems]

To achieve the above object, the present invention includes a delay circuit that delays a portion of a reproduced signal by approximately its pulse transmission time, and a delay circuit that delays a portion of the reproduced signal by approximately twice the delay time of the delay circuit. and a subtraction circuit that subtracts the output signal of the attenuator from the output signal of the delay circuit. is supplied to the subtraction circuit with a predetermined amplitude, and the output signal of the attenuator is subtracted from the addition result of the output signal of the delay circuit and the reproduction signal set to the predetermined amplitude.

[For production]

If the pulse of the reproduced signal has an asymmetric waveform with respect to the peak point, even if the output signal of the attenuator is subtracted from the output signal of the delay circuit, the resulting pulse waveform will not be symmetrical with respect to the peak point. The reproduced signal of the predetermined amplitude corrects this asymmetry, and by adding it to the subtracter, the signal obtained by subtracting the output signal of the attenuator from the output signal of the delay circuit is reproduced before the peak point of the signal. Make the waveform symmetrical with the waveform behind the peak point.

[Example〕 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the reproduced waveform equalization circuit according to the present invention, where ■ is a signal source such as a tape head system, 2 is a delay line, 3, 4, 5 is a resistor, and 6 is a signal source such as a tape head system. 7 is a differential amplifier, 8 is a resistor, and 9 is an output terminal. The reproduction waveform equalization circuit is also provided with an integration circuit for removing differential characteristics generated during the magnetic recording and reproduction process, but this is omitted here.

Further, FIG. 2 is a waveform diagram showing signals of each part in FIG. 1, and signals corresponding to those in FIG. 1 are given the same symbols.

1 and 2, a reproduced signal a from a signal source 1 has a characteristic impedance Z of a delay line 2.

Through an impedance matching resistor 3 with a resistance value equal to
The signal is supplied to the t delay line 2 whose amplitude is 1/2 due to the impedance matching resistor 3 and the characteristic impedance of the delay line 2. A delayed signal having the same waveform as the reproduced signal a but delayed by a time τ is obtained from the delay line 2, and is supplied to the differential amplifier 7 as an inverting input via a resistor 5. This resistor 5 determines the degree of amplification of the delayed signal S, and is set sufficiently larger than the characteristic impedance z0 of the delay line 2. For this reason, the delay line 2 and the differential amplifier 7 are in a non-matching state, and a portion of the delayed signal is reflected by the resistor 5 and passes through the delay line 2 again. This reflected signal d is obtained at the input terminal of the delay line 2 with a time delay of 2τ after the reproduced signal a, and this is the reproduced signal a that has passed through the impedance matching resistor 3, that is, the amplitude is the reproduced signal output from the signal source 1. It is combined with input signal C, which is 1/2 of signal a. This composite signal e is suitably attenuated by an attenuator 6 and is supplied to a differential amplifier 7 as a non-inverting input. The above configuration constitutes a transversal filter in the same manner as the above-mentioned conventional technology.

In this embodiment, in addition to this configuration, a resistor 4 is provided, and the reproduced signal a is amplitude-adjusted by this resistor 5 and is supplied to a differential amplifier 7 as a non-inverting input.

The operation of this embodiment is to subtract the synthesized signal e whose amplitude has been adjusted by the attenuator 6 from the delayed signal, and further add the signal f which has passed through the resistor 4. When the reproduced signal a consists of pulses with a waveform that is symmetrical with respect to the peak point, by subtracting the composite signal e from the delayed signal, a sufficiently symmetrical pulse with respect to the peak point can be obtained at the output terminal 9. . However, as explained earlier, R-D
In the case of AT, the pulse waveform is asymmetrical with the amplitude larger after the peak point than before. In such a case, the two peaks of the composite signal e is at least smaller than the previous amplitude.

For this reason, an asymmetric pulse waveform cannot be made symmetrical.

Therefore, in this embodiment, first, the attenuation amount of the attenuator 6 is set so that the amplitude of the composite signal e is set so that the amplitude at a point delayed by the pulse transmission interval T from the peak point of the delayed signal S becomes zero. decide. As a result, the amplitude at a point that is ahead of the peak point of the delayed signal by the pulse transmission time T becomes negative due to the subtraction of the previous peak value of the composite signal e. Therefore, resistance 4
By adding the signal f which has passed through , the amplitude at this point where the delayed signal S becomes negative is corrected to zero. As a result, phase distortion caused by the recording/reproducing system is removed, and the output terminal 9 receives
A pulse g with a waveform that has steep rises and falls and is symmetrical about the peak point is obtained.

Now, if the delay time τ of the delay line 2 is approximately equal to the pulse transmission interval T, the peak point of the pulse g obtained at the output terminal 9 will be delayed by the time T than the peak point of the reproduced signal a. Then, the peak value of the reproduced signal a is co, and the amplitude at the time T before and after the peak point is C-1n and CI, respectively.
, and the amplitudes at times separated by time 2T are respectively C-
,,C, since the waveform of the reproduced signal a is asymmetrical about the peak point, these amplitudes c-tt
c-++ Cl102 is not zero and C-! #C
m, C-1#C1. Further, the pulse g obtained at the output terminal 9 has a peak value C0', and an amplitude C-1' at the time T apart from this peak point, respectively.
+C, /, these amplitudes C-1' + Cl'
The resistance value RI of resistor 4 + resistor 5 so that both become zero
The resistance value R2 and the attenuation amount A of the attenuator 6 are set.

These are determined by the following equations (1) to (3).

That is, assuming that the peak point of the pulse g obtained at the output terminal 9 is the reference time 0, first, since the amplitude c-+' of the pulse g at time T is zero, and the amplitude c-+' of the pulse g at time T is 01. Since ' is also zero, and furthermore, since the amplitude of pulse g at time 0 is C3', it becomes as follows. Note that these two (11, +21. The amplification degree, G, is the amplification degree at which the composite signal e is amplified by the differential amplifier 7 via the attenuator 6,
Each is expressed as the following formula.

In this way, by appropriately setting the resistance values of the resistors 4 and 5 and the amount of attenuation of the attenuator 6, the rise and fall of the reproduced signal can be made steep (that is, the amplitude frequency characteristics are compensated for), and the pulse waveform can be changed. The amplitude becomes zero at the previous and subsequent pulse transmission points, and the asymmetry of the pulse waveform is improved (that is, the phase frequency characteristic is compensated).

FIG. 3 is a circuit diagram showing a part of the reproducing system of the magnetic recording and reproducing apparatus including the embodiment shown in FIG. 1 is a transformer, 14 is a reproducing amplifier, and 15 is an integrating circuit. Parts corresponding to those in FIG. 1 are given the same reference numerals and redundant explanations will be omitted.

In the figure, a reproduction signal read out from a magnetic tape 11 by a rotary head 12 is supplied to a reproduction amplifier 14 via a rotary transformer 13. The reproduction signal amplified by the reproduction amplifier 14 is supplied to the integrating circuit 15, and the reproduction signal is amplified by the reproduction amplifier 14.
The differential characteristics that occur during the magnetic recording and reproducing process are removed.

Delay line 2. Resistance 3-5. M display device 6. The differential amplifier 7 and the resistor 8 constitute a circuit similar to that shown in FIG. 1, and together with the integrating circuit 15, form a reproduced waveform equalization circuit.

Therefore, the output signal of the integrating circuit 15 is processed as explained in FIGS. 1 and 2, and the output signal rises at the output terminal 9.
A pulse signal g with a waveform that has a steep fall and is symmetrical in front and behind the peak point is obtained.

Note that here, a variable resistor 10 is connected to the output terminal of delay vA2.
By adjusting this, the reflectance at the output terminal of the delay line 2 changes, and the amplitude ratio between the input signal C of the delay line 2 and the reflected signal d (Fig. 2) changes. It is possible to change the amplitudes of the two peaks of the composite signal e (FIG. 2). If such adjustment is possible, contrary to the waveform shown in FIG. 2, the amplitude of the reproduced signal at the point where it advances by the pulse transmission interval T from the peak point lags the peak point by the pulse transmission interval T. Even in the case where the pulse g has an asymmetrical waveform larger than the amplitude at the point in time, it is possible to obtain a pulse g at the output terminal 9 having a steep rise and fall and a waveform that is symmetrical with respect to the peak point.

According to this embodiment, the reproduced waveform equalization circuit of the R-DAT can be realized with a simple circuit configuration, and it is possible to reduce the cost of the circuit, improve reliability, and simplify adjustment.

In addition, in FIG. 3, the integrating circuit 1 is installed immediately after the reproducing amplifier 14.
5 is connected, and a circuit for compensating the amplitude frequency characteristic 1 phase frequency characteristic is connected in the subsequent stage, or a circuit for this compensation is connected immediately after the regenerative amplifier 14, and a circuit for compensating for the amplitude frequency characteristic 1 phase frequency characteristic is connected in the subsequent stage. A circuit configuration in which the integrating circuit 15 is connected may also be used. Further, the circuit configuration of the integrating circuit 15 is the third one.
As shown in the figure, instead of connecting a capacitor in parallel to the feedback resistor of the differential amplifier, a first-order low-pass filter made of a capacitor and a resistor is connected to the output terminal of the regenerative amplifier 14, and a buffer amplifier is connected at the subsequent stage. Good too.

Furthermore, instead of separating the integrating circuit 15 and the compensation circuit as in the circuit configuration shown in FIG. 3, a single differential amplifier may be provided with an integrating characteristic and a high frequency emphasis characteristic. As for the specific circuit configuration, in FIG. 3, the integrating circuit 15 is deleted, the output terminal of the regenerative amplifier 14 is directly connected to the matching resistor 3, and the feedback resistor 8 of the differential amplifier 7 is given an integral characteristic. Simply connect the capacitors in parallel.

In addition, in FIG. 3, the differential amplifier 7 is used as a subtraction means for the signal obtained by the delay line 2, but the reproduced signal and the signal obtained at the non-matching terminal of the delay line 2 are added at one end,
After further inversion amplification, the signal obtained from the matching terminal of the delay line 2 may be added and amplified. Furthermore, although the integrating circuit 15 and the differential amplifier 7 are constructed from operational amplifiers in FIG. 3, they may also be constructed from a combination of transistors.

Further, the resistor 4 may be a variable resistor for phase adjustment, and the attenuator 6 may be a fixed resistor having a constant amount of attenuation.

By the way, when the pulse transmission interval T of the reproduced signal a is constant, the delay time τ of the delay line 2 may be fixed. However, some magnetic recording and reproducing devices have multiple different readout speeds, and if the pulse recording strategy on the magnetic tape is always constant, if the readout speed is different, the pulse transmission interval of the playback signal will also be different. become.

FIG. 4 is a circuit diagram showing another embodiment of the reproduced waveform equalization circuit according to the present invention for this purpose, in which 3a+3b are resistors for impedance matching, 16 to 19 are switching transistors, and 20a to 20c are capacitors. , 21 are input terminals for control signals, and parts corresponding to those in FIGS. 1 and 3 are given the same reference numerals.

Here, the magnetic recording/reproducing device has two readout speeds vr
+ Vl (however, Vl < Vl), the pulse transmission interval when the reading speed is V is 71, and the pulse transmission interval when the reading speed is V□ is Tt (however, Tt > Tz). .

In FIG. 4, the delay line 2 is composed of an LC low-pass filter, and when switching transistors 17 to 19 are turned on and off by a control signal from an input terminal 21, capacitors 20a to 20c are added to the delay line 2. The delay time of the delay line 2 is changed by adding or removing the delay line 2.

At present, the read speed of magnetic recording and reproducing devices is relatively high.
1, the pulse transmission interval of the repeating signal output from the integrating circuit 15 is a relatively narrow TI. At this time,
Due to the low level control signal from the input terminal 21, the switching transistors 16-19 are turned off, and the capacitors 20a-20c are not added to the delay line 2. The delay time τ8 of the delay vA2 at this time is the pulse transmission interval T
t, and the resistance value of the resistor 3a for mi' impedance matching is set equal to the input impedance 20g of the delay line 2 at this delay time τ2.

Therefore, the reproduced signal output from the integrating circuit 15 passes through the core of this resistor 3a and is supplied to the delay line 2, etc., and the embodiment shown in FIG. 1 when the delay time of the delay line 2 is τ2. A similar processing operation is performed to obtain a pulse having a waveform that has steep rises and falls at the output terminal 9 and is symmetrical in front and back with respect to the peak point.

When the read speed of the magnetic recording/reproducing device is relatively slow vl, the pulse transmission interval of the reproduction signal output from the integrating circuit 15 is relatively wide T.

At this time, switching transistors 16 to 19 are turned on by a high level control signal from input terminal 21, impedance matching resistor 3b is connected in parallel to impedance matching resistor 3a, and capacitors 20a to 20c are connected to delay line 2. added to.

As a result, the delay time of delay line 2 is the pulse transmission time T,
τ1 is almost equal to τ1, and the impedance matching resistor 3
The parallel combined resistance value of a and 3b is equal to the input impedance 201 of the delay line 2 when the delay time is τ.

Therefore, the reproduced signal output from the integrating circuit 15 passes through these resistors 3a and 3b and is supplied to the delay line 2, etc., and the embodiment shown in FIG. 1 when the delay time of the delay line 2 is τ1. A similar processing operation is performed, and output terminal 9 rises,
A pulse with a waveform that has a steep fall and is symmetrical around the peak point can be obtained.

Incidentally, delay lines are generally very expensive and have large external dimensions, which tends to increase the cost of the circuit. However, according to this embodiment, by using only one delay line, it is possible to support magnetic recording/reproducing devices having two different read speeds, and it is possible to realize lower cost and space saving of the circuit.

In this example, the magnetic recording/reproducing device has two different readout speeds, but even if it has three or more readout speeds, the impedance matching resistor and delay line 2 should be added accordingly. It is only necessary to provide a capacitor with a constant value and switch these capacitors according to the reading speed.

FIG. 5 is a circuit diagram showing still another embodiment of the reproduction waveform equalization circuit according to the present invention for a magnetic recording and reproduction apparatus having two different read speeds, in which 2a and 2b are delay lines, 3a', 3b' is an impedance matching resistor, 5a,
5b is a resistor, 22a and 22b are switching transistors, 23a and 23b are resistors, 24 is an inverter,
25 is an input terminal for a control signal, and parts corresponding to those in FIG. 4 are given the same reference numerals.

In Fig. 5, delay line 2a + resistor 3a' + 4i5
a, 23a, fi attenuator 6. The differential amplifier 7 and the feedback resistor 8 have a circuit configuration similar to that shown in FIG. 1, and the delay time τ1 of the delay line 2a is made approximately equal to the pulse transmission interval T when the read speed of the magnetic recording/reproducing device is 1. By this,
A circuit (hereinafter referred to as a first characteristic compensation circuit) that compensates for the amplitude frequency characteristics and phase frequency characteristics of the reproduced signal of the pulse transmission interval T outputted from the integrating circuit 15 is configured. Also, a delay line 2b, a resistor 3b', 4. 5b
, 23b.

Attenuator6. The differential amplifier 7 and the feedback resistor 8 also have the same circuit configuration as shown in FIG. By making it approximately equal to (≠T1), the pulse transmission interval T! output from the integrating circuit 15! A circuit (hereinafter referred to as a second characteristic compensation circuit) for compensating the amplitude frequency characteristics and phase frequency characteristics of the reproduced signal is configured. These first. The second compensation circuit includes a resistor 4. for removing phase distortion. Attenuator6. The differential amplifier 7 and the feedback resistor 8 are shared, and the other parts are in a parallel relationship between the integrating circuit 15 and the differential amplifier 7.

Note that the resistors 23a and 23b are for amplitude adjustment, and together with the attenuator 6, set the amplitude of the composite signal (FIG. 2e) obtained at the input terminal of the delay line 2a+2b+ to a predetermined magnitude.

These first. Either one of the second characteristic compensation circuits connects the switching transistor 22 with a control signal from the input terminal 25.
It is selected by turning on and off a and 22b.

That is, now the read speed of the magnetic recording/reproducing device is v
When it is 1, the control signal input to the input terminal 25 is at a low level, the switching transistor 22a is turned off, and the first characteristic compensation circuit is in an operating state. On the other hand, the switching transistor 22b is supplied with a control signal whose level has been inverted by the inverter 24, so that it is in an on state, the resistor 3b' is grounded, and the second characteristic compensation circuit is in an inactive state.

Therefore, the first characteristic compensation circuit processes the reproduced signal with the pulse transmission interval T1 outputted from the integrating circuit 15 in the same manner as in the embodiment shown in FIG. As a result, a pulse having a waveform that rises and falls steeply at the output terminal 9 and is symmetrical around the peak point can be obtained.

On the other hand, the read speed of the magnetic recording/reproducing device is v2
At this time, the control signal input to the input terminal 25 is at a high level, the switching transistor 22b is turned off, and the second characteristic compensation circuit is in an operating state. On the other hand, the switching transistor 22a is in the on state,
The resistor 3a' is grounded and the first characteristic compensation circuit is in an inactive state.

Therefore, the second characteristic compensation circuit processes the reproduced signal with the pulse transmission interval T2 outputted from the integrating circuit 15 in the same manner as in the embodiment shown in FIG. As a result, a pulse having a waveform that has steep rises and falls and is symmetrical around the peak point can be obtained from the output terminal 9.

In the above operation, when the first characteristic compensation circuit is in the operating state, the resistor 3b' is grounded via the switching transistor 22b, so that the output signal of the integrating circuit 15 is connected to the output resistor of the integrating circuit 15 and the resistor. 3b', and when the second characteristic compensation circuit is in operation, the resistor 3a' is grounded via the switching transistor 22a, so that the integrating circuit 15
The output signal of the integrating circuit 15 and the resistor 3a1
However, since the resistance value of the output resistor of the integrating circuit 15 is sufficiently small compared to the resistors 3a' and 3b', the first . The amplitude of the reproduced signal input to the second characteristic compensation circuit is not reduced by these factors.

According to this embodiment, the number of switching transistors can be reduced compared to the embodiment shown in FIG. Further, since dedicated delay lines are used for two different read speeds, it is easy to optimize each one. Further, in this embodiment as well, by providing a predetermined number of characteristic compensation circuits in the same manner as described above, it is possible to support a magnetic recording/reproducing apparatus having a read speed of three or more.

Note that in FIGS. 4 and 5, the arrangement order of the integrating circuit 15 and the characteristic compensation circuit may be changed.

Further, it goes without saying that the differential amplifier may be constructed by combining transistors, and a mechanical open/close switch may be used instead of a switching transistor.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to compensate the amplitude frequency characteristics and phase frequency characteristics of the reproduced signal,
A pulse with an asymmetrical waveform that has a gentle rise and fall and is centered around the peak point.

The pulse can have a steep fall and a symmetrical waveform around the peak point, making it possible to perform pulse transmission and data detection from the pulse signal without error, and also to reduce the number of delay lines used. It is possible to minimize the amount of noise, simplify the circuit configuration, and significantly simplify adjustment, thereby reducing costs and improving reliability.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a reproduced waveform equalization circuit according to the present invention, FIG. 2 is a waveform diagram showing signals of each part of FIG. 1,
FIG. 3 is a circuit diagram showing a reproduction system of a magnetic recording and reproducing apparatus using the embodiment shown in FIG. 1, and FIGS. 4 and 5 show other embodiments of the reproduction waveform equalization circuit according to the present invention. FIG. 6 is a block diagram showing a recording and reproducing system of a rotary head type digital audio tape recorder. 2.2a, 2b...Delay circuit゛, 3.3a, 3b
. 3aZ ab'... Impedance matching resistor, 4
... Phase distortion removal resistor, 5... Resistor, 6... Attenuator, 7... Differential amplifier, 8... Feedback resistor. Figure 1 ρ Figure 2 - T OT - 1 - HLtl - Ward 3 Figure 4 Figure 6, Figure 5 Figure 6 Procedure Ne

Claims (1)

[Claims] 1. A delay circuit into which a reproduced signal from a recording medium is input via an impedance matching resistor and whose delay time is approximately equal to the pulse transmission interval of the reproduced signal, and a delay circuit at an input terminal of the delay circuit. an attenuator for adjusting the amplitude of a composite signal of the reproduced signal and a reflected signal that is reflected at the output terminal of the delay circuit and output to the input terminal of the delay circuit; and an output of the delay circuit. A reproduced waveform equalization circuit including a subtraction circuit that performs subtraction processing between a signal and an output signal of the attenuator,
A means for removing phase distortion of a reproduced signal from the recording medium is provided, and an output signal of the means is also supplied to the subtraction circuit, so that amplitude frequency characteristics and phase frequency characteristics of the reproduced signal can be compensated. A reproduced waveform equalization circuit characterized by: 2. In claim 1, the delay circuit is capable of selectively setting a plurality of delay times, and has amplitude frequency characteristics and phase frequency characteristics for each of the reproduced signals having different pulse transmission intervals. A reproduced waveform equalization circuit characterized in that it is configured to be capable of compensation. 3. In claim 1, the delay circuit has a plurality of delay lines having different delay times, and by selecting one of the delay lines according to the pulse transmission interval of the reproduced signal, A reproduced waveform equalization circuit characterized in that it is configured to be able to compensate amplitude frequency characteristics and phase frequency characteristics for each reproduced signal.