JPH04243003A - Magnetic recording circuit - Google Patents

Abstract

PURPOSE:To obtain a wide frequency range for a recording circuit by providing a frequency compensator circuit and damping resistor. CONSTITUTION:The recording current compensated by a frequency compensator circuit 1 to have flat frequency characteristics to high frequencies is supplied through an amplifier 2 and a rotary transformer 4 to a magnetic head 5. A damping resistor 3 is provided parallel to the head 5 and the transformer 4 at the output stage of the amplifier 2 so that the resonance caused by the inductance of the magnetic head, etc., and the output capacitance of the amplifier is damped and that the phase distorsion is decreased. Thereby, the obtd. circuit for magnetic recording has a wider frequency range over the resonance frequency.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording/reproducing apparatus, and more particularly to a digital signal recording circuit.

0002

2. Description of the Related Art FIG. 10 is a block diagram of a conventional magnetic recording circuit. A digital recording signal inputted from an input terminal is amplified by a recording signal amplifier 2, and sent to a magnetic head 5 via a rotary transformer 4. Apply recording current. Note that the magnetic head 5 is normally mounted on a rotating head (not shown), and the rotary transformer 4 exchanges signals with a fixed part. The equivalent circuit in this case is shown in Figure 11.
It can be expressed as That is, the recording signal amplifier 2
are the recording signal generation source, output resistance Ri, and output capacitance Ci, and the rotary transformer 4 has three coils L1 as shown in the figure.
, L2, L3, and the magnetic head 5 also becomes one coil L4. If the frequency is even higher, coil L
Since the inductance of L3 among 1 to L4 is large, the rotary transformer 4 can be represented by one coil connected in series. If the inductance of is L, it can be expressed as shown in FIG.

In this case, if the combined capacitance of the output capacitance Ci and the stray capacitance Cd of the amplifier is C, then this circuit resonates at a frequency f0 expressed by the following equation. (pp. 13-14), etc. And based on the description in this document,

0004

[Math 1]

[0005] Therefore, the frequency characteristics and phase characteristics of the conventional digital recording circuit shown in FIG. 10 are as shown in FIGS. 13 and 14, respectively. In this way, the resonant frequency f
In the vicinity of 0, the amplitude increases due to resonance and the phase rotates, that is, the phase difference differs depending on the frequency f. Conventionally, it is possible to record up to a sufficiently low frequency (f1 in the figure) where the influence of this resonance is small. It was used as a circuit band.

However, it is known that when recording a digital signal on a magnetic recording medium, the band of the signal to be recorded is generally about seven times that of analog recording using the FM modulation recording method. ing. Therefore, digital magnetic recording devices require wideband recording circuits.

Broadband recording circuits have been achieved by setting the resonant frequency f0, which limits the band in conventional magnetic recording devices, to a high frequency. As is clear from equation (1), this can be achieved by reducing the combined inductance L of the magnetic head and rotary transformer, or by reducing the combined inductance C of the recording amplifier's output capacitance and the stray capacitance of the transmission line.
All you have to do is make it smaller. Specifically, the number of turns of the magnetic head or rotary transformer is reduced. Alternatively, they used transistors with low output capacitance in the output stage of the recording amplifier, or made the wiring as short as possible to reduce the stray capacitance of the power transmission lines. but,
Considering the recording efficiency of the magnetic head and the transmission loss when the rotary transformer is shared with the playback system, the number of turns cannot be reduced unnecessarily, and there are limits to reducing the output capacity and stray capacitance. There was a problem.

[0008]

[Problems to be Solved by the Invention] As mentioned above, in conventional magnetic recording circuits, even if an attempt is made to widen the band, the combined inductance L of the magnetic head and rotary transformer
, or the combined capacitance C of the output capacitance of the recording amplifier and the stray capacitance of the transmission line could not be arbitrarily reduced. For this reason, there was a problem in that it was not possible to widen the band of the recording circuit. The present invention has been made to solve the above-mentioned problems, and its purpose is to provide a magnetic recording circuit with broadband frequency characteristics. [Structure of the invention]

[0009]

[Means for Solving the Problems] In order to achieve the above-mentioned object, a magnetic recording circuit of the present invention includes a recording signal amplifier and a low-speed recording signal amplifier for amplifying recording signals to be recorded on a magnetic recording medium.
A magnetic recording circuit consisting of a rotary transformer and a magnetic head includes a frequency compensation circuit for compensating the frequency characteristics of the recording signal before the recording signal amplifier, and a frequency compensation circuit for compensating the frequency characteristics of the recording signal at the output end of the recording signal amplifier. It is characterized by providing a resistor arranged in parallel with the transformer. Furthermore, the present invention is characterized in that a phase compensation circuit is provided between the frequency characteristic compensation circuit and the recording signal amplifier.

0010

[Operation] According to the magnetic recording circuit of the present invention having the above-described structure, the conventional magnetic recording circuit is provided with a frequency characteristic compensation circuit for compensating the frequency characteristics of a recording signal, and an inductance of a magnetic head and a rotary transformer. By providing a resistor for damping resonance due to the output capacitance of the recording signal amplifier and the stray capacitance of the electric transmission path, the frequency band of the magnetic recording circuit can be expanded beyond the resonance frequency.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a circuit block diagram of an embodiment according to the present invention. 1 is a frequency characteristic compensation circuit. Although various circuits can be applied to this circuit, a cosine equalizer is used in this embodiment. This will be explained later. 2 is a digital recording signal amplifier. 3 is a damping resistor, 4 is a rotary transformer, and 5 is a magnetic head. What characterizes the present invention compared to the conventional example shown in FIG. 8 is the frequency characteristic compensation circuit 1 and the damping resistor 3.

As in the case of explaining the conventional example, the equalization circuit after the amplifier of this embodiment is shown in FIG. Here, Ri and Ci are the output resistance and output capacitance of the amplifier. In addition, Rd is the resistance value of the damping resistor 3, L is the combined inductance of the magnetic head and rotary transformer,
Cd is the stray capacitance of the transmission line.

At this time, if the combined capacitance of the output capacitance Ci and the stray capacitance Cd of the amplifier 2 is C, then the formula 1 holds true as is, and it resonates at the frequency f0 expressed by the formula 1. But Q
The value is expressed as follows. Q=kRi(C/L)
... (3) However, K=Rd/(Rd+Ri)<1 ...
(4)

Therefore, compared to the conventional recording circuit, the Q value is reduced and the resonance is damped. FIG. 3 shows the frequency characteristics of the digital recording circuit according to the embodiment. In this way, the frequency characteristic becomes a gentle downward-sloping curve. Further, as shown in FIG. 4, the phase characteristics become closer to a straight line because the Q value is lowered, so that the phase rotation becomes smaller.

FIG. 5 shows a cosine equalizer used as the frequency compensation circuit 1 of this embodiment. In this cosine equalizer, an input signal is passed through a resistor 501 to prevent reflection at a high impedance input amplifier 503 and to perform impedance matching, and then to a delay line 502 composed of a coil and a capacitor, for example, and a high impedance input amplifier 503. input amplifier 504. Also,
The high impedance input amplifier 504 includes a delay line 5
02, and the signal reflected by the high impedance input amplifier 503 with 100% in phase is also added. A high impedance input amplifier 504 amplifies these signals and adjusts the amplitude thereof with a variable attenuator such as a variable resistor 505. This amplitude-adjusted signal and the signal amplified by the high impedance input amplifier 503 are applied to a differential amplifier 506. As a result, the frequency characteristics of the frequency compensation circuit 1 as shown in FIG. 6 can be obtained. And this circuit is "VTR technology" edited by Japan Broadcasting Corporation (47)
p. From 50p. ), it has a frequency characteristic that is a cosine curve, and there is no phase distortion at all.

By providing this frequency compensation circuit 1 before the digital signal amplifier, the frequency characteristics of the recording current flowing in the digital recording circuit according to this embodiment are as shown in FIG.
As shown in , the characteristics are flat up to a frequency f2 that is much higher than the resonance frequency f0. This is because the frequency characteristic a obtained by damping the resonance shown in FIG. 3 is compensated by the frequency compensation circuit 1 as shown in FIG. Further, the phase characteristics are maintained as shown in FIG. 4 since there is no phase distortion of the frequency compensation circuit 1. Therefore, the recording circuit can be made to have a dramatically wider band without being limited by the resonance frequency f0.

Furthermore, as shown in FIG. 8, a phase compensation circuit 8 for compensating for some phase distortion in the high frequency range may be provided at the front stage of the recording amplifier. Note that this phase compensation circuit 8 is realized, for example, by a series resonant circuit as shown in FIG. Then, by setting the resonance frequency determined by L and C to a frequency f2 or higher and adjusting the Q using a variable resistor R, it is possible to compensate for phase distortion at a frequency f2 or higher. This makes it possible to record even wider band digital signals. Further, by using a variable resistor R, the above-mentioned Q can be easily adjusted.

[0019]

As described in detail above, according to the magnetic signal recording circuit of the present invention, the inductance of the magnetic head and rotary bounce, which conventionally limited the frequency band of recording signals, and the output of the recording signal amplifier can be eliminated. Regardless of resonance due to capacitance and stray capacitance of electrical transmission lines, etc., it can have broadband frequency characteristics, so even high-frequency digital signals can be easily recorded, for example.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment according to the present invention.

FIG. 2 is an equivalent circuit diagram of an embodiment according to the present invention.

FIG. 3: Frequency characteristics after the recording signal amplifier of the embodiment according to the present invention.

FIG. 4 shows phase characteristics after the recording signal amplifier of the embodiment according to the present invention.

FIG. 5 A frequency characteristic compensation circuit used in an embodiment according to the present invention.

FIG. 6 shows the frequency characteristics of the frequency characteristic compensation circuit used in the embodiment according to the present invention.

FIG. 7: Frequency characteristics of an embodiment according to the present invention.

FIG. 8 is a block diagram in which a phase compensation circuit is provided in an embodiment according to the present invention.

FIG. 9 is a circuit diagram of the phase compensation circuit of FIG. 8.

FIG. 10 is a block diagram of a conventional recording circuit.

FIG. 11: Equivalent circuit of a conventional recording circuit.

FIG. 12: Equivalent circuit for high frequencies of a conventional recording circuit.

FIG. 13: Frequency characteristics of a conventional recording circuit.

FIG. 14: Phase characteristics of a conventional recording circuit.

[Explanation of symbols]

1... Frequency characteristic compensation circuit 2... Recording signal amplifier 3... Damping resistor 4... Rotary transformer 5... Magnetic head 6... Combined inductance of rotary transformer and magnetic head 7... Stray capacitance of electric transmission path 8... Phase compensation circuit

Claims (2)

[Claims] 1. A recording signal amplifier for amplifying a recording signal to be recorded on a magnetic recording medium, and transmitting the output of the recording signal amplifier to a magnetic head for recording the recording signal mounted on a rotating member. In a magnetic recording circuit equipped with a rotary transformer for recording the recording signal, a resistor is arranged at the output end of the signal amplifier in parallel with the rotary transformer, and a resistor is disposed at the output end of the signal amplifier in parallel with the rotary transformer, and A magnetic recording circuit comprising a frequency compensation circuit for compensating frequency characteristics. 2. The magnetic recording circuit according to claim 1, further comprising a phase compensation circuit provided between the frequency characteristic compensation circuit and the recording signal amplifier.