JPS5857801B2 - Jikiki Rokusai Seisouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording/reproducing apparatus which eliminates troubles caused by leakage of erase signals to a recording head.

Conventional rotary head type VTRs use a fixed head as the erasing head, and employ a full width erasing method for erasing the entire surface of the tape, as shown in FIG.

1 is a magnetic tape, A is a track that has already been erased by the fixed magnetic head at position B, and C is a rotating recording head 2.
shows the track recorded by.

With this full-width erasing method, it is not possible to erase track by track, so if, for example, a new video signal is recorded in the middle of a tape that has already been recorded, blank areas can be avoided in the playback output. This will cause playback problems.

Therefore, as shown in FIG. 2, a method has recently been attempted in which a rotating erasing head 3 is mounted on the same rotating drum as the recording head 2, and only the track to be recorded is erased.

In the case of this method, the distance between the recording head 2 and the erasing head 3 must be very narrow, for example, about 5 mm or less.

Therefore, a part of the erase signal supplied to the erase head 3 leaks to the recording head 2 due to electromagnetic induction.

In this case, if the erasure signal frequency is as low as 50 kHz as in the case of the full-width erasure method, it will not be much of a problem, but in the case of the above-mentioned track erasure method, the erasure signal frequency should be about 10 MHz. Therefore, if this leaks to the recording head 2, it will appear as an interference signal in the reproduced video signal band, resulting in deterioration of S/H and increase in distortion.

Now, suppose that the reproduced output signal is expressed by the following equation, taking into account the distortion of the input/output characteristics of the recording system.

y=x+ax+bx2 ・・・・・・・・・・・・-
... (1) Then, the carrier of the video signal, which is the recording signal, is expressed as x1=sin 27r ft + As1n6πft 10 songs - (2) Furthermore, the erase signal is expressed as x=Bsin2πfot...・・・・・・・・・
Suppose that it is expressed as (3).

Here, if it is assumed that Xl and X2 flow to the recording head 2 at the same time due to the erasure signal leaking to the recording head 2, they become a reproduced output signal.

As a result, the reproduced output signal contains, as shown in Figure 3,
As spurious signals due to secondary distortion, fo±f, 3f+
fo,..., 2f+fo 4f±f as a spurious signal due to third-order distortion.

Gf±fo, 2fo±f, 2fo±3 f, -...
Beat components such as the following will be generated.

Due to the demand for smaller VTRs, the distance between the recording head and the erasing head tends to become narrower, regardless of whether or not the track erasing method described above is adopted. It is clear that similar problems arise as the signal current increases and the frequency increases.

The present invention has been made in view of the above points, and when the distance between the recording head and the erasing head, which are electrically independently provided, is narrow and the erasing signal frequency is relatively high, the erasing signal from the erasing head is Even if the erase signal current is induced in the recording head due to magnetic coupling, the circuit prevents the erase signal current from flowing to the recording head, thereby eliminating problems caused by leakage of the erase signal to the recording head. It is an object of the present invention to provide a magnetic recording/reproducing device as described above.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a circuit diagram of a recording section of a magnetic recording and reproducing apparatus showing an embodiment of the present invention, which includes a recording head 2 and a recording amplifier 4 that supplies a recording signal, for example, a video signal consisting of a frequency modulated wave, to the head 2. As an erase signal blocking circuit,
Parallel resonant circuit 5 consisting of inductor L and capacitor C
is inserted.

The resonant frequency fo' of this resonant circuit 5 is expressed by , and the impedance is maximum at this frequency fo'.

Therefore, this resonant frequency fo/ is set equal to the erase signal frequency fo supplied to the erase head 3.

In this way, even if an erase signal component is magnetically induced to the recording head 2 by the electrically independent erase head 3 provided close to the recording head 2, the resonance index 5 will be at the erase signal frequency. f.

Since the erase signal component exhibits a high impedance to the recording head 2, the erase signal component hardly flows as a current in the recording head 2.

Here, the erasure signal frequency is, for example, f o = 10MH
Selected by z.

On the other hand, the carrier frequency of a video signal, which is a recording signal, is usually about f=4 MHz.

Therefore, since the resonant circuit 5 has a low impedance with respect to the carrier frequency, the recording signal is supplied to the recording head 2 with almost no attenuation.

Therefore, not only the erase signal component but also the beat component between this and the recorded signal hardly appear in the reproduced output signal.

Figure 5 shows the frequency spectrum of the reproduced output signal when the resonance index 5 is provided, and shows the recording signal carrier frequency and its harmonic components as seen in Figure 3, and the erase signal frequency. Spurious signals consisting of beat components and their harmonic components are sufficiently suppressed, and f
, 2f, . . . are extracted as the reproduced output signal.

As described above, according to the present invention, by providing the erase signal blocking circuit between the recording signal supply list and the recording head,
It is possible to prevent the generation of spurious signals in the playback output signal due to leakage of the erase signal to the recording head, resulting in less distortion and
A playback output with good S/N can be obtained.

In the above embodiment, an LC parallel resonant circuit was used as the erase signal blocking circuit, but in some cases, a series resonant circuit whose resonant frequency is set equal to the recording signal frequency may be used. Any circuit may be used as long as it has a low impedance and a high impedance with respect to the erasure signal frequency.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing erasing and recording patterns on a magnetic tape to explain the full-width erasing method in a VTR.
2a and 2b are a side view and a plan view for explaining the configuration of the head section of a track erasing VTR, FIG. 3 is a frequency spectrum diagram of a reproduced output signal in a conventional magnetic recording and reproducing device, and FIG. 4 5 is a circuit diagram of the main part of a magnetic recording/reproducing apparatus for explaining an embodiment of the present invention, and FIG. 5 is a frequency spectrum diagram of a reproduced output signal according to the embodiment. Erasing head, 4... Song recording amplifier (recording signal supply circuit)
, 5...LC parallel resonant circuit (erasing signal blocking circuit).

Claims (1)

[Claims] 1. In a magnetic recording/reproducing device having a recording head and an erasing head arranged close to each other and electrically driven independently, a recording signal is transmitted between the recording head and a recording signal supply circuit that supplies recording signals to the recording head. an erase signal blocking circuit that exhibits a low impedance with respect to the frequency of the erase signal and exhibits a high impedance with respect to the frequency of the erase signal leaking from the erase head to the recording head to prevent the erase signal current from flowing into the recording head. A magnetic recording/reproducing device characterized by being inserted.