JPS6273401A - System of reproducing signal recorded to depth of tape - Google Patents

Abstract

PURPOSE:To exclude an AM component from a signal reproduced from a signal recorded to the depth of a tape by changing an amplification factor or an attenuation factor in reproducing a signal recorded to the depth of the tape in response to the frequency and recording current of a video signal recorded to the upper layer of the tape. CONSTITUTION:An amplifier 11, while the gain is changed by using an inputted gain control signal thereto, amplifies a reproduced AFM signal inputted from a head 2. That is, the amplification factor of the amplifier 11 is changed by using the gain control signal having a characteristic opposite to that from the rate where an AFM signal recorded to the depth of the tape 1 is erased by the video signal recorded to the upper part B of the tape 1, and when the level of the AFM signal reproduced by the head 2 is small, the amplification factor of the amplifier 11 is increased and when the amplification factor of the amplifier 11 is decreased to output the reproduced AFM signal whose amplitude level is nearly constant to a band-pass filter 4.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention provides video signals in the upper layer of the tape and AFM in the deeper layer.
The present invention relates to a tape depth M recording signal reproduction method for a video tape recorder that records a (FM modulated audio signal) signal.

[Technical background of the invention]

Conventionally, in this type of tape recorder, when an AFM signal is recorded in the deep part of the tape by changing the azimuth angle of the head, etc., it is then recorded in the deep part by the frequency and recording current of the video signal recorded in the upper part of the tape. The percentage of erased signals differs. Therefore, if the AFM signal recorded in the deep layer is reproduced as it is,
The playback envelope has sharp changes in amplitude level, that is, A
This results in a large amount of M component. Therefore, in order to remove this AM component, a method has conventionally been used in which the AFM signal recorded in the deep layer is reproduced using the method shown in FIGS. 5 to 7.

In the method shown in FIG.
The FM signal is reproduced by head 2, and this reproduced signal is sent to the AGC.
It is amplified by an amplifier (automatic gain control amplifier) 3. At this time, the reproduced AFM signal is converted into a reproduced signal with a constant amplitude by an AGC amplifier. This reproduced signal having a constant amplitude is inputted to a demodulator 5 after unnecessary components are removed by a bandpass filter 4.

In the method shown in FIG. 6, the AF reproduced by the head 2
After the M signal is amplified by a preamplifier 6, unnecessary components are removed by a bandpass filter 4, and the signal is input to a limiter 7. Playback A that includes AM components input to limiter 7
The amplitude level of the FM signal is limited to a constant amplitude signal, which is input to the demodulator 5.

In the method shown in Fig. 7, the AFMi signal reproduced from the head 2 is converted into a signal with a constant amplitude level by the AGC amplifier 3, and then
Furthermore, after limiting the amplitude level with a limiter 7, a reproduced APM signal with a constant amplitude and a constant level is input to a demodulator 5.

[Problems with V-scenery technology]

In this way, in the conventional reproduction method described above, the AM component is removed from the reproduced AFM signal by the AGC amplifier 3, limiter 7, etc. However, if the response speed of the AGc amplifier is increased too much, when a dropout occurs, the amplitude of the signal part (often noise) whose level has decreased will be almost completely corrected, and the dropout detection circuit (not shown) will cause the dropout to occur. The response speed cannot be increased very much because the problem arises that it cannot be detected even though it is occurring. Therefore, there is a problem in that the AM component cannot be completely removed using the AGC amplifier 3 alone. In addition, normally, when the demodulator 5 is implemented as an IC, a limiter is built in at the first stage, but this limiter alone cannot completely remove the AM component.
There is a drawback that the AM component has an adverse effect on the output after demodulation. Furthermore, in the case of a home video tape recorder, there are carriers for the left channel and right channel in an extremely narrow band, and there is a cross-modulation JA component for these channels.
The cutoff of the bandpass filter 4 must be made steep, which tends to cause fluctuations in frequency characteristics and group delay. When such a rampage occurs, part of the AM component of the reproduced AFM signal is replaced by the FM acid component, which cannot be removed by a limiter or the like, which has the drawback of adversely affecting the signal after demodulation.

[Purpose of the invention]

In view of the above-mentioned drawbacks, it is an object of the present invention to provide a tape deep recording signal capable of removing AM components from a reproduced signal of a signal recorded in the deep part of the tape without causing any negative effects on the signal after demodulation. The purpose is to provide a reproduction method.

[Summary of the invention]

The present invention achieves the above object by changing the amplification factor or attenuation factor when reproducing the signal recorded in the deep layer of the tape according to the frequency and recording current of the video signal recorded in the upper layer of the tape. be.

[Embodiments of the invention]

Hereinafter, an embodiment of the present invention will be described with reference to the drawings, in which the same parts as those of the conventional example are denoted by the same reference numerals. As shown in FIG. 1, a video signal (first signal) recorded on the upper opening of the tape 1 is reproduced by a head 8 and inputted to an amplifier 9. The reproduced video signal amplified by the amplifier 9 is demodulated by the demodulator 1o and then output to the next stage. The APΔ (signal (second signal)) recorded in the deep layer A of the tape L is reproduced by the head 2, delayed for a certain period of time by the 1-delay circuit 13, and then input to the amplifier 11. The amplified reproduced AFM signal is passed through a bandpass filter 4.
After removing unnecessary parts, the signal is input to a demodulator 5 and demodulated. Reference numeral 12 denotes a gain control circuit of the amplifier 11, which takes in the pre-demodulated playback video signal output from the amplifier 9 or the demodulated playback video signal output from the demodulator 1o, and generates a control signal based on this playback video signal. . A control signal output from the gain control circuit 12 is input to the amplifier 11 and controls the gain of the amplifier 11.

Next, the operation of this embodiment will be explained. First, the characteristics of the gain control circuit 12 will be described below. Generally, the erasure rate of the signals recorded on the tapes f, i4, LM, f5B changes depending on the frequency of the signal recorded on the upper layer and the recording current, as shown in FIG. 2 (5) and ◎ in FIG. That is, when the characteristics of the head are constant, the higher the frequency of the signal to be recorded, the more shallowly the signal is recorded. Therefore, as shown in FIG. 2 (5), the higher the frequency of the signal recorded in the upper layer, the more the signal recorded in the deeper layer remains without being erased, and the output of the reproduced signal becomes larger. Generally, when the recording current for a signal recorded on the upper layer of the tape is increased, a magnetic field is applied to a deeper portion, and the signal is recorded deeper. Therefore, as shown in FIG. 2 (5), as the recording current of the signal recorded in the upper layer increases, the erasure rate of the signal recorded in the deeper layer of the tape increases, and the erase rate of the signal recorded in the deeper layer increases. Level decreases. After all, there is a predetermined relationship between the reproduction output Y of the signal recorded in the deep layer and the frequency f and recording current i of the signal recorded in the upper layer. - (1).

Generally, when recording on and reproducing from a tape using a magnetic head with the same characteristics, the reproduction output during reproduction is determined by the frequency and level (recording current) of the signal during recording. Therefore, the gain control circuit 12 calculates the erasure rate of the AFM signal recorded in the deep layer A from the frequency f of the video signal recorded by the head 8 and the recording current i, and then creates a signal with inverse characteristics. , which is output to the amplifier 11 as a gain control control signal. Delay circuit 13
Then, the reproduced AFM signal is delayed by a delay time based on the distance between the heads 8 and 2, and is input to the amplifier 11. The amplifier 11 amplifies the reproduced AFM signal input from the head 2 while changing its gain in accordance with the input gain control signal. That is, in the amplifier 11, the A recorded in the deep part A of the tape 1 is
The rate at which the FM signal is erased by the video signal recorded on the upper layer of the tape 1 is different from that of the AFM signal reproduced by the head 2 because the amplification factor is changed by a gain control signal having the opposite characteristics. By increasing the amplification factor of the amplifier 11 when the level is small and decreasing the amplification factor of the amplifier 11 when the level is large, it is possible to output a reproduced AFM signal with a substantially constant amplitude level to the bandpass filter 4.

FIG. 3(8) shows the envelope of the AFM signal reproduced by the head 2, and 0 in FIG. 3 shows the envelope of the output signal of the amplifier 11, and the amplitude of the output signal envelope of the amplifier 11 is approximately constant.

According to this embodiment, the frequency f of the video signal recorded in the upper layer and the recording current i cause the AF
By changing the amplification factor during reproduction of the M signal, the AM component of the reproduced AFM signal can be substantially removed, resulting in a high-quality demodulated FM reproduction signal that almost eliminates the generation of FM acid components due to the AM component generated after demodulation. You can get the video signal with or without it.

In addition, in the above embodiment, if the reproduced video signal itself is similar to the gain control control signal outputted by the gain control circuit @path 12, the gain of the amplifier 11 may be controlled using this reproduced video signal. . or,
Delay circuit 13 includes gain control circuit 12 and amplifier 1
1 so that the gain control control signal is delayed, or if there is a temporal correlation between the reproduction signals of the heads 2 and 8, the delay circuit 13 itself may be omitted.

FIG. 4 is a block diagram showing another embodiment of the present invention. In this example, the AFM signal reproduced by the head 2 is amplified/depressed by the preamplifier 6 and then delayed by the delay circuit 13.
The signal is output to the bandpass filter 4 via the attenuator 14. Therefore, the gain control control signal from the gain control circuit 12 is input to the attenuator 14, and by changing the attenuation amount of the attenuator 14 in the same way as the circuit shown in FIG. A substantially constant reproduction AFM signal is input. Therefore, this embodiment also has the same effects as the previous embodiment.

〔Effect of the invention〕

As described above, according to the tape deep recording signal reproducing method of the present invention, the amplification factor or attenuation when reproducing the signal recorded in the tape deep layer is determined according to the frequency and recording current of the video signal recorded in the upper layer of the tape. By changing the ratio, AM
The components can be removed without adversely affecting the demodulated signal.

[Brief explanation of drawings]

Fig. 1 is a book diagram showing an embodiment of a head reproduction signal processing circuit to which the tape deep recording signal reproduction method of the present invention is applied, and Fig. 2 shows the frequency and recording current of No. 4ij recorded on the upper layer of the tape. A characteristic diagram showing the relationship between the signal recorded in the deep part of the tape and the playback output level, Figure 3 is similar to Figure 1.
FIG. 4 is a block diagram showing another embodiment of the present invention; FIG. 5 is a block diagram showing an example of a conventional head reproduction signal processing circuit; FIG. 6 is a block diagram showing another example of the conventional head reproduction signal processing circuit, and FIG. 7 is a block diagram showing still another example of the conventional head reproduction signal processing circuit. 2.8...-head 4... bandpass filter 5,
lO...Demodulation circuit 12...Gain control) a-le circuit 13...Delay circuit Agent Patent attorney Rule Chika Ban Yudo
Hiromu Uji (A) 7 CB) -1 to 11 to 11 Figure 3

Claims (1)

[Claims] In a video tape recorder that records and plays back a first signal into the upper layer of the tape and a second signal into the deeper layer of the tape, the amplification factor of the playback circuit that plays back the second signal is set to A tape deep recording signal reproduction method characterized by changing the recording frequency and recording current.