JPH01128204A - Reproduction equalizer circuit - Google Patents

Abstract

PURPOSE:To obtain an objective equalizer characteristic with simple circuit constitution by using an inductance element and combining one operation amplifier and plural resistances and capacities. CONSTITUTION:A reproduction signal input terminal 55 is connected to the inverted input terminal of the operation amplifier 58 through a capacity 56 and a resistance 57, and grounds a non-inverted input terminal. One of equalizer characteristic alteration capacities 60 is connected to the input terminal 57 in parallel through a second input resistance 59 by a switch 61. Feedback capacities 62 and 63 are connected in serial between the output terminal and the inverted input terminal of the operation amplifier 58, and a feedback resistance 64 is connected. One of characteristic alteration resistances 65 is connected in parallel with the capacity 63 through a switch 66. The switches 61 and 66 are set to interlock and they are also set to interlock with a tape speed control circuit, whereby they are switched according to the switching of a speed. The switches 61 and 66 respectively select a capacity C and a resistance R, and the objective equalizer characteristic can be obtained if CR=1/n<2> is set when a tape speed scale factor shows (n).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reproduction equalizer circuit for a magnetic tape direct recording/reproducing machine or the like.

[Prior Art] The frequency characteristics of the output voltage of the reproducing head of a magnetic tape recording/reproducing machine are not flat, and as shown in Fig. 4, the frequency characteristic is 6 dB/
It shows an octave drop and shows a loss-based drop in the high range. Also, due to changes in tape running speed, the frequency characteristics change to B.
It changes like 1, B2, B3. Therefore, the frequency characteristics of the reproduction equalizer circuit of the magnetic tape recording/reproducing machine are set as shown in the characteristic lines AI, A2, and A3 in FIG.
The frequency characteristics of the head output voltage shown in the figure must be compensated to make the overall frequency characteristics of recording and reproduction flat as shown in FIG.

FIG. 7 shows a typical reproduction equalizer circuit for a conventional multi-speed data recorder. This reproduction equalizer circuit consists of a combination of an integrating circuit 1 and a high frequency compensation circuit 2. The integrating circuit 1 has an integration characteristic in the low frequency range, and includes an operational amplifier 3, a resistor 6 connected via a pay capacitor 5 between the inverting input terminal and the reproduced signal input terminal, and the operational amplifier 3. a variable resistor 11a connected in series to the capacitor 9 via an analog switch 10 whose switching is controlled according to the tape speed; Consists of llb. Note that the non-inverting input terminal of the operational amplifier 3 is connected to ground.

High frequency compensation port F! @2 is an operational amplifier 12, a resistor 14 connected via a coupling capacitor 13 between this inverting input terminal and the output terminal of the preceding operational amplifier 3, and a resistor 14 connected between the output terminal of the operational amplifier 12 and the inverting input terminal. Capacitor 15 and resistor 16.17 connected between the capacitor 15 and resistor 16.17, inductance 19a, 19b selectively connected via analog switch 18 between the middle of resistor 16.17 and ground, capacitor 20a, 20b, variable Resistors 21a, 21b
It consists of Note that the non-inverting input terminal of the operational amplifier 12 is connected to ground.

Switch 10.18 is linked to the tape speed switching operation,
Set the playback equalizer characteristics corresponding to the speed. For convenience of illustration, only two switching contacts are shown in the switch 10.18 in FIG. 7, but in reality, the switch 10.18 is designed to switch the reproduction equalizer characteristics in eight stages.
are configured, and six further equivalent to variable resistors 11a and llb are provided, and inductances 19a and 19b are provided.
, capacitors 20a, 20b, variable resistors 21a, 21b
There are also six equivalents.

The resistors 11a, 11b, 21a, and 21b are constructed of variable resistors to finely adjust the characteristics.

The integrating circuit 1 has the frequency characteristics shown in FIG.
It has the effect of increasing the rate of dB/octave. The high frequency compensation circuit 2 has the function of increasing the high frequency gain as shown in FIG.

The composite frequency characteristic of the integrating circuit 1 and the high-frequency compensation circuit 2 is the first
0, and it becomes possible to compensate for the frequency characteristics of the head shown in FIG. Note that the characteristic lines indicated by dotted lines in FIGS. 8, 9, and 10 show the characteristics when the switch 10.18 is switched.

, -6- [Problems to be Solved by the Invention However, the conventional reproduction equalizer circuit has the following problems.

(1) High-frequency compensation inductances 19a and 1b are required, and two operational amplifiers 3.12 are required, resulting in high cost.

(2) The values of the inductances 19a and 19b must be increased as the tape speed becomes lower. Therefore,
It is difficult to downsize the inductances 19a and 19b,
It is also difficult to miniaturize the reproduction equalizer circuit.

(3) Since the inductances 1.9a and 19b are composed of coils, they are generally inferior in vibration resistance, temperature characteristics, failure rate, change in characteristics over time, etc., compared to resistors and capacitors.

(4) Since it is configured by a combination of the integrating circuit 1 and the high-frequency compensation circuit 2, it is difficult to obtain the target frequency characteristics.

(5) Two variable resistors 11 for one tape speed
a, 21a or 111), 21t1, etc., not only the configuration becomes complicated but also the number of adjustment points increases.

Although the multi-speed data recorder has been described above, similar problems exist in other magnetic recording and reproducing apparatuses having a similar configuration.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a reproduction equalizer circuit having a relatively simple configuration.

[Means for Solving the Problems] In order to solve the above problems and achieve the above objects, the present invention compensates for the frequency of a signal obtained by a relative scanning motion between a magnetic recording medium and a reproducing head. It is related to a regenerative equalizer circuit consisting of an operational amplifier and a plurality of resistors and capacitors having constants such that they perform Miller integral operation in a low frequency band and perform differential operation in a high frequency band. .

[Function] According to the above invention, desired equalizer characteristics are obtained by a combination of one operational amplifier and a plurality of resistors and capacitors without using an inductance element, so the circuit can be simplified, miniaturized, and lowered in cost. become.

[Embodiment] Next, a multi-speed data recorder according to an embodiment of the present invention will be explained with reference to FIGS. 1 to 5.

As shown in FIG. 3, this multi-speed data recorder includes a capstan 34, a pinch roller 35, a capstan motor 36, and a pair of glue motors 37, 38 for running the tape 33 mounted on a pair of reels 31, 32. and a travel control circuit 39. Tape 33 is control circuit 3
76 cm/s, 38 am/
s, 19 am/s, 9°5 cm/s,
4.8cm/s, 2.4cm/s, 1.2cm/s
, 0, 6 am/s.

Between the analog recording signal input terminal 40 and the recording head 41, there is an input level adjuster 42, an input amplifier 43, a high-frequency compensation port 144, and a constant current characteristic (characteristic for keeping the current constant regardless of changes in head impedance). a recording amplifier 45 which supplies a head current, and a bias trap circuit 4.
6 are connected in sequence. A bias oscillator 48 is also connected to the recording head 41 via a capacitor 47.

At the output stage of the playback head 49, a head amplifier 50 and a playback equalizer F! ? 151, a reproduction level adjuster 52, an output amplifier 53, and an output terminal 54 are connected in sequence.

FIG. 1 shows the reproduction equalizer circuit 51 of FIG. 2 in detail. A reproduced signal input terminal 55 connected to the head amplifier 50 of FIG. 3 is connected to a 1 μF input capacitor 56 and a 1. It is connected to an inverting input terminal of an operational amplifier (op-amp) 58 via a first input resistor 57 of OkΩ. operational amplifier 5
The non-inverting input terminal of 8 is connected to ground. 1st
An equalizer characteristic changing capacitor 60a is connected in parallel to the input resistor 57 of
, 60b, 60c is the first switch 6
1. A series circuit of a first feedback capacitor 62 of 1200 pF' and a second feedback capacitor 63 of 220 pF is connected between the output terminal and the inverting input terminal of the operational amplifier 58, and a feedback resistor of 3.3 MΩ is further connected. has been done. Equalizer characteristic changing resistors 65a, 65b, 65 are connected in parallel to the second feedback capacitor 63.
c is connected via the second switch 66. An output terminal 67 of the reproduction equalizer circuit 51 is connected to an operational amplifier 58.

The first and second switches 61, 66 are interlocked with each other and the speed control circuit f! of FIG. It is an analog switch linked to @39. That is, it is a switch that is switched in accordance with the switching of the running speed of the tape 33.

First, second, and third characteristic changing capacitors 6°a, 60
b, 60C have values of 100PF, 180pF, and 360PF, and the first, second, and third characteristic changing resistors 65a,
65b and 65c are 2.4Ω, 5.1Ω, 10Ω
has the value of

In FIG. 1, there are three capacitors 60a to 60c and three resistors 65a corresponding to three tape speeds = 11.
- Only 65c is shown, but in reality there are 5 more
Five capacitors and five resistors are provided corresponding to the tape speeds of the steps. First and second switches 61.
Contact a of 66 is turned on when the tape speed is 76 mm/s, contact S is turned on when the tape speed is 38 am/s, and contact C is turned on when the tape speed is 19 am/s. The relationship between other tape speeds and characteristic changing capacitors and resistors is as follows.

Tape speed capacitor resistance 9.5 a
m/s 750 pF 20 kΩ
4, 8am/s 1500pF
39 kΩ2.4cn/s 3300pF
75Ω1.2cn/s 6800pF 15
0 to Ω0.6cn/s 12000pF 300
The capacitors and resistors corresponding to the above tape speed of 9.5 to 0.6 an/s are arranged in parallel to the characteristic changing capacitors 60a to 60c and the resistors 65a to 65c shown in FIG. 1, and the switches 61. It is selectively connected at 66.

Note that the characteristic changing resistors 65a to 65c are connected to the reproducing head 4.
In order to adjust the variation in the characteristics of 9, the resistor is configured as a variable resistor.

When the contacts a of the first and second switches 61 and 66 of the reproduction equalizer circuit 51 in FIG. 1 are turned on, the frequency characteristics of A1 in FIG. When the contact C is turned on, the frequency characteristic of A3 is obtained.

A second input resistor 59 of 2.0 Ω and a second feedback capacitor 63 of 220 PF have the function of limiting the high-frequency gain in order to determine the band of the reproduced signal.

1μF input capacitor 56 and 3.3MΩ feedback resistor 6
4 is for making the gain of direct current and its vicinity zero times.

The input resistor 57 of 10Ω and the first feedback capacitor 62 of 1200 pF are used to determine the low-frequency integral characteristic.

In the circuit shown in FIG. 1, if the second switch 66 is fixed to an arbitrary contact point and the first switch 61 is switched in the order of a, b, and c, the peak of the high-frequency compensation shown in FIG. Move upward along the octave line. Also, when the first switch 61 is fixed to any contact point and the second switch 66 is switched to contacts a, b, and c in order, the peak of the high frequency compensation in FIG. 2 becomes the 16 dB/octave line. Move upward along! In order to set the frequency characteristics to match the tape speed, for example, each constant is set so that an ideal frequency characteristic is obtained at a tape speed of 76/S. The constants of each part of the circuit shown in FIG. 1 are the values when the bias current is set to a -3 dB overbias state and a Maxell video cassette HGX GOLD 120 is used as the tape 33.

Next, the frequency characteristics of each tape speed are set as follows.

Now, the capacitor 60a selected by the first switch 61
If the capacitance value of the resistors 65a to 65c etc. selected by the second switch 66 is R, and the tape speed multiplier is n, then when the tape speed is increased by n times, the values of C and R are Set the product (CR) to (1/n) twice. At this time, C is multiplied by 1/n and R is multiplied by 1. / Of course, there is no problem even if it is multiplied by n, and there is no problem even if the ratio of C and R is changed.

AI, A2, and A3 in Figure 2 are tape speeds of 76 x 15
．． It shows the frequency characteristics of 38 am/s and 19 an/s, which results in B1, B2, and B3 in Fig. 4.
The frequency characteristics of the head can be compensated for.

This embodiment has the following advantages.

(1) Since high-frequency compensation characteristics can be obtained without using an interface element, miniaturization, cost reduction, and improved reliability can be achieved.

(2) Once C and R at a certain tape speed are determined, the values of C and R at other tape speeds can be calculated. Therefore, desired frequency characteristics for multiple tape speeds can be easily set. Note that in order to correct variations in the characteristics of the head 49, the resistors 65a to 65c are variable resistors, but since the frequency characteristics shift along the -6 dB/octave line according to the CR product, only one of the CRs is changed. Just change it. In the conventional example shown in FIG. 7, one resistor 11a
, 11. b and the other resistors 21a and 21b = 15
- Adjustment was troublesome as both had to be changed, but
In this embodiment, since only one side is used, adjustment is easy.

(3) Since a single operational amplifier 58 is used to obtain low-frequency integral characteristics and high-frequency compensation characteristics, the circuit is simplified and mid-range characteristics are also improved.

[Modifications] The present invention is not limited to the above-described embodiments, and, for example, the following modifications are possible.

(1) Replace the capacitor C and resistor R in Figure 1 with the 6th
As shown in the figure, a variable capacitor 6o and a variable resistor 65 may be used to change the values of C and R in conjunction with the tape speed. Furthermore, in the case of a single tape speed, the variable capacitor 6o and the variable resistor 65 may be replaced by a fixed capacitor and a fixed resistor.

(2) The connection points between the resistor 59 and the capacitors 60a to 60c may be replaced, and the connection points between the capacitors 62 and 63 may be replaced.

(3) It can also be applied to audio cheap recorders.

(4) The first and second switches 61 and 66 may be analog switches such as transistors whose number corresponds to the capacitors 60a to 60C and the resistors 65a to 65c.

[Effects of the Invention] As is clear from the above, according to the present invention, desired frequency characteristics can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a reproduction equalizer circuit according to an embodiment of the present invention, FIG. 2 is a frequency characteristic diagram of the reproduction equalizer circuit of FIG. 1, and FIG. 3 is a diagram showing a data recorder according to an embodiment of the present invention. 4 is a diagram showing the frequency characteristics of the playback head shown in FIG. 3, FIG. 5 is a diagram showing the overall frequency characteristics of the data record shown in FIG. 3, and FIG. 6 is a diagram showing a modified example of the playback equalizer circuit. Circuit diagram: Figure 7 is a circuit diagram showing a conventional reproduction equalizer circuit; Figure 8 is a diagram showing the frequency characteristics of the integrating circuit in Figure 7; Figure 9 is a diagram showing the frequency characteristics of the high-frequency compensation circuit in Figure 7. FIG. 10 is a diagram showing the frequency characteristics of the reproduction equalizer circuit of FIG. 7. 49... Playback head, 51... Playback equalizer circuit, 56... Input capacitor, 57... First input resistor, 58... Operational amplifier, 59... Second input resistor, 60a , 60b, 60c... Characteristic changing capacitor, 61... First switch, 62... First feedback capacitor, 63... Second feedback capacitor, 64
...Feedback resistor, 65a, 65b, 65c...Resistance for changing characteristics.

Claims (1)

[Claims] [1] A device for frequency compensation of a signal obtained by relative scanning motion between a magnetic recording medium and a reproducing head, comprising an operational amplifier and a mirror integral operation in a low frequency band. None, a regenerative equalizer circuit consisting of a plurality of resistors and capacitors having constants that perform differential operation in a high frequency band. [2] The plurality of resistors and capacitors include an input capacitor (56) whose one end is connected to the input terminal (55) of the regenerative equalizer circuit, and the other end of the input capacitor (56) and the operational amplifier (58). a first input resistor (57) connected between one input terminal of the input resistor (57); and a second input resistor (59) connected to the first input resistor (57).
and means for connecting the other input terminal of the operational amplifier (58) to ground; a feedback resistor (64) connected between the one input terminal and a first feedback capacitor (62) connected between the output terminal of the operational amplifier (58) and the one input terminal; A series circuit with a second feedback capacitor (63), and equalizer characteristic changing resistors (65a to 65c) connected in parallel to the second feedback capacitor (63). The reproduction equalizer circuit according to item 1. [3] The magnetic recording medium can change the relative scanning speed with respect to the reproducing head, and the equalizer characteristic changing capacitors (60a to 60c)
) is the capacitance value C, and the equalizer characteristic changing resistor (65
If the resistance value of a to 65c) is R and the change magnification of the scanning speed is n, then when the scanning speed is increased by n times, the C
The equalizer characteristic changing capacitor (6) is used to change the value of the product of
3. The reproduction equalizer circuit according to claim 2, characterized in that the equalizer characteristic changing resistors (65a to 65c) are configured. [4] The magnetic recording medium is capable of changing a relative scanning speed with respect to the reproducing head, and the equalizer characteristic changing capacitor changes a capacitance value in inverse proportion to a change in the scanning speed. The equalizer characteristic changing resistor is composed of one or more resistors whose resistance value is changed in inverse proportion to the change in the scanning speed. The reproduction equalizer circuit described in item 2.