JP2002074821A - Magnetic recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent noise from being caused to an FM audio signal even if a mechanical part of a deck is nor properly adjusted. SOLUTION: This magnetic recording and reproducing device is fundamentally comprised of a Hi-Fi integrated circuit 30 which is a circuit part for generating FM audio signals AUDIO R, AUDIO L, respectively, based on the Hi-Fi signals HFA, HFB outputted from Hi-Fi heads 11A, 11B and a head changeover pulse signal PG outputted from a head changeover pulse generator 12 of a cylinder 10, and which detects generation of demodulated noise and also has a function to output the detection result as a noise detection signal ND, and a head changeover pulse signal phase adjusting part 41 which is a circuit arranged between the head changeover pulse generator 12 and the Hi-Fi integrated circuit 40, and which adjusts the phase of a head changeover pulse signal PG' to be inputted to the Hi-Fi integrated circuit 40 so that a time difference is eliminated between a demodulated noise generating point α presented by the noise detection signal ND and a head changeover point β presented by the head changeover pulse signal PG.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-fidelity magnetic recording / reproducing apparatus.

[0002]

2. Description of the Related Art Hi-fi audio units of conventional magnetic recording / reproducing apparatuses often have a basic configuration as shown in FIG. In the figure, 10 is a cylinder, 21 _A and 21 _B are A and Bch
Reference numerals 22 _{A and} 22 _B denote AGC circuits for A and B channels, and reference numeral 30 denotes an integrated circuit for hi-fi.

[0003] The cylinder 10 has hi-fi heads 21 _{A and} 21 _B for reproducing the hi-fi signals HF _{A and H B B} recorded on the magnetic tape, and a head switching pulse for generating a head switching pulse signal PG synchronized with the rotation of the cylinder 10. A generator 12 and the like are provided.

[0004] hi-fi signal HF _A, HF _B is, A, Bc
After being amplified by h preamplifier 11 _A, 11 _{B, A,}
The Bch AGC circuits 22 _{A and} 22 _B hold the signals at a fixed level, and input to the Hi-Fi integrated circuit 30.
The head switching pulse signal PG is similarly input to the integrated circuit 30 for high fidelity.

[0005] HiFi integrated circuit 30, high-fidelity signal HF _A, based on HF _B and the head switching pulse signal PG R, FM audio signal for Lch AUDIO _R, A
Each of the circuits generates a UDIO _L, and a PLL (Phase Lock Loop) is used as a demodulation circuit.
The operation is briefly described as follows.

[0006] First, by switching in accordance with the switch unit 31 to the head switching pulse signal PG, joining the hifi signals HF _A, HF _B, is substantially continuous signal that can be demodulated. And BPF (Band Pass Filter)
32 _R, 32 included in the signal by _L Rch (1.7 M
Hz) and Lch (1.3 MHz) signals.

[0007] hi-fi signal HF _R of Rch PLL3
3 _R , demodulated, and then sequentially passed through a delay unit 34 _R , a sample hold 35 _R , an LPF _R (low-pass filter), a noise reduction circuit 38 _R , and a buffer amplifier 39 _R to produce an FM audio signal AUDIO _R It is output (see FIG. 6).

[0008] The sample hold 35 _R is provided, in order to perform a dropout compensation with dropout detector 36 _R. That is, the hi-fi signal HF
_A, and when the HF _B dropped out, when the voice and the carrier becomes discontinuous by switching the heads, because the demodulation noise is generated, detects that the noise is generated by the dropout detector 36 _R, Hold the part where the noise waveform appears ahead of time with the value without noise immediately before,
A noise pulse is extracted.

The noise reduction circuit 38 _R is provided for reducing so-called triangular noise, which is associated with FM modulation. Incidentally, the above description is exactly the same applies to the hi-fi signal HF _L of Lch.

The magnetic recording / reproducing apparatus is provided with an automatic tracking adjustment circuit (not shown) for automatically adjusting the envelopes of the high-fidelity signal HF and the video signal to be maximum, though not shown. -3625
No. 4, Japanese Patent No. 2854156, etc.).

[0011]

However, in the case of the above-mentioned conventional example, if the mechanical portion of the deck is not properly adjusted, there is a problem that the FM audio signal has a broken envelope and demodulation noise occurs. For example, if the inclination of the loading post of the deck is not appropriate and the contact between the cylinder and the magnetic tape is poor, the FM audio signal becomes as shown in FIG. If the height of the AC head is not properly investigated, the envelope of the FM audio signal is erased by a hi-fi head or a control head.
The M audio signal is as shown in FIG.

That is, since a sufficient envelope level is not output on the entrance side or the exit side of the envelope of the Hi-Fi signal, the Hi-Fi processing cannot be performed.
The envelope of the audio signal is broken, and demodulation noise is generated. Even if the same noise is added to the video signal, this is not a problem because it is not reflected on the TV screen. However, since the audio is output continuously, the demodulation noise generated in the FM audio signal is uncomfortable. Will be played.

The present invention has been made in view of the above circumstances, and has as its object to improve the FM audio signal so that noise is not generated even if the mechanical portion of the deck is not properly adjusted. To provide a magnetic recording and reproducing apparatus.

[0014]

SUMMARY OF THE INVENTION A magnetic recording / reproducing apparatus according to the present invention provides an FM sound based on a hi-fi signal output from a hi-fi head of a cylinder and a head switching pulse signal output from a head switching pulse generator of the cylinder. A circuit section for generating a signal, a hi-fi circuit section having a function of detecting the occurrence of demodulation noise and outputting the detection result as a detection signal, between the head switching pulse generator and the hi-fi circuit. A head switching pulse signal to be input to the hi-fi circuit so that there is no time difference between a demodulation noise generation point indicated by the detection signal and a head switching point indicated by the head switching pulse signal. And a head switching pulse signal phase adjuster for adjusting the phase of It is characterized in that was example.

The high-fidelity circuit includes a comparator for comparing the level of an Rch or Lch signal extracted from the high-fidelity signal with a filter and a reference signal, a detector for detecting an output signal of the comparator, It is preferable to use a hi-fi integrated circuit having a hi-fi / normal detection terminal for outputting the output signal of the detector as the detection signal.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram of a hi-fi audio unit of the magnetic recording / reproducing apparatus, FIG. 2 is a block diagram of a drop-out detector constituting a hi-fi integrated circuit of the hi-fi audio unit, and FIG. 3 is processed by a control circuit of the hi-fi audio unit. FIG. 4 is a timing chart of various signals of the Hi-Fi integrated circuit before the phase of the head switching pulse signal is adjusted by the control circuit. FIG. 5 is a timing chart of the phase of the head switching pulse signal. 6 is a timing chart of various signals of the Hi-Fi integrated circuit in a state after the operation is performed.

The magnetic recording / reproducing apparatus described here is a Hi-Fi / stereo type video tape recorder for recording / reproducing data on / from a magnetic tape, and its Hi-Fi audio section has a configuration as shown in FIG. ing. The same components as those in the conventional example shown in FIG. 6 are denoted by the same part numbers.

The same high-fidelity audio unit, hi-fi signal HF A output from the hi-fi head 11 _A, 11 _B of the cylinder _10, HF _B and a head switching pulse signal PG outputted from the head-switching pulse generator 12 of the cylinder 10 Based on the FM audio signal AUDIO _R , AUDIO
A circuit section for generating O _L , which detects the occurrence of demodulation noise and outputs the detection result to a noise detection signal ND
Hi-Fi integrated circuit 30 having the function of outputting as
(Corresponding to a hi-fi circuit unit) and a circuit unit provided between the head switching pulse generator 12 and the hi-fi integrated circuit 40, and a demodulation noise generation point α (FIG. 4) indicated by the noise detection signal ND. ) And the head switching point β indicated by the head switching pulse signal PG.
A basic configuration including a head switching pulse signal phase adjustment unit 41 that adjusts the phase of the head switching pulse signal PG ′ to be input to the high-fidelity integrated circuit 40 so that the time difference with respect to (see FIG. 4) is eliminated. I have.

FIG. 6 shows a hi-fi integrated circuit section 30.
Is the same Hi-Fi integrated circuit as that shown in the conventional example, specifically, LA72652M manufactured by Mitsubishi Electric Corporation.
The model name is used. The HiFi integrated circuit includes a HiFi / Normal detection terminal 301. The Hi-Fi / Normal detection terminal 301 detects a demodulation blur noise and outputs a primary HPF (fc = 140 kHz).
It is originally used to detect the output through z) with an external capacitor. Here, the signal output from the HiFi / Normal detection terminal 301 is treated as a noise detection signal ND, and is input to the pulse signal phase adjustment unit 41 to perform the above-described processing. The noise detection signal ND is generated by the dropout detector 36 _R (see FIG. 6).

The dropout detector 36 _R has a circuit configuration as shown in FIG. That is, the hi-fi signals HF _{A and} HF are output by the band-pass filter 32 _R (see FIG. 6).
A comparator 361 _R for comparing the level of the hi-fi signal HF _R and the reference signal of the extracted Rch from _B, the comparator 3
And a detector 362 _R for detecting the output signal of 61 _R (dropout detection signal D output to the sample hold 36 _R) and outputting the detected signal to the Hi-Fi / normal detection terminal 301 as a noise detection signal ND. It has a basic configuration.

[0021] Incidentally, if it is not possible to perform high fidelity determination for sufficient Embedded level is not out at the outlet side of the high-fidelity signal HF _A, HF _B as shown in FIG. 4, Embedded FM audio signals AUDIO _R, the AUDIO _L Has occurred and demodulation noise has occurred. This is also true when no out sufficient Embedded level at the inlet side of the high-fidelity signal HF _A, HF _B.

As described above, the FM audio signals AUDIO _R , A
When the envelope is broken in UDIO _L and demodulation noise is generated, the voltage (noise detection signal ND) of the hi-fi / normal detection terminal 301 rapidly changes in a DC manner (within a range of 0 V to 5 V). Therefore, the occurrence of demodulation noise can be detected based on whether or not the voltage of the hi-fi / normal detection terminal 301 has rapidly changed in a DC manner. The point indicating the maximum value of the voltage is the demodulation noise generation point α shown in FIG. With reference to the head switching point β indicated by the head switching pulse signal PG, the time difference between the demodulation noise occurrence point α and the head switching point β is indicated by t in the figure. In addition,
The same applies when no out sufficient Embedded levels in hifi signals HF _A, the inlet side of the HF _B.

In FIG. 1, reference numeral 40 denotes an integrated circuit unit 3 for hi-fi.
This is a control circuit for controlling each part of the apparatus including an automatic tracking circuit (not shown) and an automatic tracking circuit (not shown). Here, a microcomputer is used. A program shown in FIG. 3 is newly added to the built-in memory of the microcomputer, and this program is processed by the built-in CPU.
The control circuit 40 functions as the pulse signal phase adjusting unit 41. Due to this relationship, while the head switching pulse signal PG and the noise detection signal ND are input to the I / O port of the microcomputer,
A head switching pulse signal PG 'is output.

The major difference from the conventional apparatus shown in FIG.
The phase of the head switching pulse signal PG generated by the head switching pulse generator 12 is adjusted by the control circuit 40 (pulse signal phase adjustment unit 41), and the signal is used as the head switching pulse signal PG 'in the high-fidelity integrated circuit unit 30. This is the point that has been entered.

The operation of the magnetic recording / reproducing apparatus configured as described above will be described, and the contents of the program shown in FIG.

When the power switch of the magnetic recording / reproducing apparatus is turned on to start reproduction, an automatic tracking circuit (not shown) is operated to perform automatic tracking adjustment. At this time, a head switching pulse signal PG ′ that is exactly the same as the head switching pulse signal PG is output to the Hi-Fi integrated circuit section 30. Thereafter, the program shown in FIG. 3 is sequentially processed.

First, the noise detection signal ND is inputted, and it is determined whether or not a sudden voltage change has occurred in the noise detection signal ND 30 times or more per second (S1). As a result, when it is determined that demodulation noise has not occurred, it is determined that demodulation noise has not occurred. On the other hand, when it is determined that demodulation noise has occurred, demodulation noise has occurred. Point α and head change point β
Then, it is determined whether or not the time difference t is within the range of -500 (μS) ≦ t <0 (S2).

When it is determined that the time difference t is within the range of -500 (μS) ≦ t <0, the phase of the head switching pulse signal PG is advanced by 0.5H (H: horizontal period), and Is output as a head switching pulse signal PG ′ (S3). Thereafter, the noise detection signal ND is input, and it is determined whether or not the voltage fluctuation of the noise detection signal ND has become 15 times or less per second (S4).
As a result, when the number of times becomes 15 or less, it is determined that the time difference t between the demodulation noise occurrence point α and the head switching point β has disappeared, and the program is terminated.
If the number is not less than 15, the process returns to step 3 and the same processing as described above is repeated. At this time, if the phase of the head switching pulse signal PG 'is advanced by a total of 7H (H: horizontal period) (S5), the phase of the head switching pulse signal PG' is returned to the original state (S6).

Then, the phase of the head switching pulse signal PG is delayed by 0.5H (H: horizontal period) in the reverse of the above, and this is changed to the head switching pulse signal PG '.
(S7). Then, the noise detection signal ND
To determine whether or not the sudden voltage fluctuation in the noise detection signal ND has become 15 times or less per second (S
4). As a result, when the number of times is less than 15 times, it is determined that the time difference t between the demodulation noise occurrence point α and the head switching point β has disappeared, and the program is terminated. Return and repeat the same process as above. At this time, when the phase of the head switching pulse signal PG 'is delayed by a total of 7H (H: horizontal period) (S9), the phase of the head switching pulse signal PG' is returned to the original state (S1).
0), the program is terminated because it is impossible to eliminate the occurrence of demodulation noise only by adjusting the phase of the head switching pulse signal PG.

On the other hand, if the time difference t is -500 (μS) ≦ t <
When it is determined that the difference is not within the range of 0, the time difference t is 0 ≦
It is determined whether or not t is within the range of 500 (μS) (S1
1). As a result, when it is determined that the time difference t is not within the range of 0 ≦ t ≦ 500 (μS), the process returns to step 1 again, and when the time difference t is within the range of 0 ≦ t ≦ 500 (μS), the head The phase of the switching pulse signal PG is delayed by a time corresponding to 0.5H, and this is output as a head switching pulse signal PG '(S12). Subsequent processing is the same as steps 4 to 10 except for the difference between delaying or advancing the phase of the head switching pulse signal PG.

By the above processing, the phase of the head switching pulse signal PG 'to be input to the Hi-Fi integrated circuit 40 is adjusted so that the time difference t between the demodulation noise generation point α and the head switching point β is eliminated.

[0032] For example, adjustment of the mechanical portion of the deck is not appropriate, hifi signal HF A as shown in FIG. _4, H
When the outlet side of the F _B sufficient Embedded level not out, FM audio signals AUDIO _R, torn Embedded occurs AUDIO _L, demodulation noise. However, after the above processing is performed, the head switching point β moves in the direction of the arrow as shown in FIG. As a result, even if the mechanical part of the deck is not readjusted, in most cases, the FM audio signals AUDIO _R , AU
Breaking Embedded in DIO _L is eliminated, demodulated noise is not generated. This is also true when no out sufficient Embedded level at the inlet side of the high-fidelity signal HF _A, HF _B.

As described above, by adjusting the phase of the head switching pulse signal PG 'so that the time difference t between the demodulation noise generation point α and the head switching point β is eliminated, the substantial reason that the demodulation noise does not occur. Is as follows. In other words, the occurrence of noise means that the portion does not have a sufficient level required for reproduction, so that it is based on not reproducing the portion.

In the case of the magnetic recording / reproducing apparatus as described above, even if the mechanical part of the deck is not properly adjusted,
The occurrence of noise in the FM audio signals AUDIO _R and AUDIO _L is reduced. This means that the adjustment of the mechanical part of the deck becomes easier, so that the cost of the adjustment work at the time of product shipment can be reduced. In addition, the existing function of the hi-fi / normal detection terminal 301 of the hi-fi integrated circuit 30 is fully utilized, and only a slight design change is required, which is a significant factor in achieving high performance and low cost of the device. There are benefits.

It should be noted that the magnetic recording / reproducing apparatus according to the present invention is not limited to the above-described embodiment, and the Hi-Fi circuit section outputs the Hi-Fi signal output from the Hi-Fi head of the cylinder and the head switching pulse generator of the cylinder. Any circuit configuration that generates an FM audio signal based on the head switching pulse signal, and has a function of detecting the occurrence of demodulation noise and outputting the detection result as a noise detection signal. It doesn't matter. Also, the same function may be realized by hardware for the head switching pulse signal phase adjustment unit.

[0036]

As described above, in the magnetic recording / reproducing apparatus according to the present invention, the phase of the head switching pulse signal to be input to the Hi-Fi circuit is adjusted so that the time difference between the demodulation noise generation point and the head switching point is eliminated. Therefore, even if the mechanical part of the deck is not properly adjusted, the FM audio signal is broken in the envelope and the occurrence of demodulation noise is reduced. In addition, since the adjustment work of the mechanical part of the deck becomes easy, it is possible to achieve high performance and low cost of the apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention, and is a block diagram of a hi-fi audio unit of a magnetic recording / reproducing apparatus.

FIG. 2 is a block diagram of a dropout detector included in the HiFi integrated circuit of the HiFi audio unit.

FIG. 3 is a flowchart of a program processed by a control circuit of the Hi-Fi audio unit.

FIG. 4 is a timing chart of various signals of the Hi-Fi integrated circuit in a state before the control circuit adjusts the phase of the head switching pulse signal.

FIG. 5 is a timing chart of various signals of the Hi-Fi integrated circuit in a state after adjustment of the phase of the head switching pulse signal.

FIG. 6 is a block diagram of a Hi-Fi audio unit of a conventional magnetic recording / reproducing apparatus.

FIG. 7 is a timing chart of various signals of the Hi-Fi integrated circuit constituting the Hi-Fi audio unit.

FIG. 8 is a waveform diagram of an FM audio signal output from the Hi-Fi integrated circuit.

FIG. 9 is another waveform diagram of the FM audio signal output from the Hi-Fi integrated circuit.

[Explanation of symbols]

Reference Signs List 10 cylinder 11 _A, 11 _B cylinder head 12 Head switching pulse generator 30 Hi-Fi integrated circuit 301 Hi-Fi / Normal detection terminal 40 Control circuit 41 Head switching pulse signal phase adjuster HF _A, HF _B Hi-Fi signal PG Head switching pulse signal AUDIO _R , AUDIO _L FM audio signal α Demodulation noise generation point β Head switching point

Claims (2)

[Claims] 1. A circuit section for generating an FM audio signal based on a hi-fi signal output from a hi-fi head of a cylinder and a head switching pulse signal output from a head switching pulse generator of the cylinder, comprising: A hi-fi circuit unit having a function of detecting occurrence and outputting the detection result as a noise detection signal; and a circuit unit provided between the head switching pulse generator and the hi-fi circuit, wherein the noise detection Head switching pulse signal phase adjustment for adjusting the phase of the head switching pulse signal to be input to the Hi-Fi circuit so that there is no time difference between the demodulation noise generation point indicated by the signal and the head switching point indicated by the head switching pulse signal. Magnetic recording characterized by comprising: Raw devices. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein the high-fidelity circuit unit compares a level of an Rch or Lch signal extracted from the high-fidelity signal with a filter and a reference signal; A magnetic recording / reproducing device comprising: a high-fidelity integrated circuit having a detector for detecting an output signal of a comparator and a hi-fi / normal detection terminal for outputting the output signal of the detector as the detection signal. apparatus.