JPH05128720A - Recording signal amplifying device - Google Patents

Abstract

PURPOSE:To miniaturize the circuit scale and to reduce the man-hour of level adjustment. CONSTITUTION:A video processing circuit 11 performs FM modulation of an analog video signal. An audio processing circuit 12 converts an audio signal to a PCM signal. A changeover switch 13 multiplexes these analog video signal and PCM audio signals in time division. A voltage controlled amplifier 14 amplifies a recording signal multiplexed in time division and supplies it to a magnetic head 17 through an amplifier 15. At this time, adjusting power sources 21 and 22 generate such control voltages that the gain of the voltage controlled amplifier 14 is suitable for recording of the analog video signal and that of the PCM audio signal. The changeover switch 16 selects control voltages from adjusting power sources 21 and 22 synchronously with the switching operation of a changeover switch 13 by switching and supplies them to the voltage controlled amplifier 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording signal amplifying device, and more particularly to a recording signal amplifying device for amplifying a recording signal supplied to a magnetic head in a video tape recorder or the like.

[0002]

2. Description of the Related Art As an apparatus for recording a video signal as an analog signal and an audio signal as a digital signal on a magnetic recording medium, an 8 mm video tape recorder using a magnetic tape of 8 mm width as a magnetic recording medium and a so-called high-definition video signal are used. Time Compressed Integration
) For recording.
Is known).

Such a VTR uses an analog video signal or a time axis compression multiplexed TCI signal (analog signal) as an F signal.
After M-modulation, the FM-modulated analog video signal is amplified so that its level conforms to a predetermined standard. On the other hand, audio signals are converted to so-called PCM (Pulse Code Modulation).
After the conversion, the PCM-converted audio signal (hereinafter referred to as PCM audio signal) is amplified so that its level conforms to a predetermined standard. And these analog video signals and PC
The M audio signal is time-division multiplexed to form a recording signal, the recording signal is amplified again so that the level of the analog video signal is optimum for recording, and then recorded on the magnetic tape by the magnetic head. There is.

Specifically, as shown in FIG. 5, a conventional VTR recording system includes a video processing circuit 62 for performing a predetermined signal processing on an analog video signal and an audio processing for performing a predetermined signal processing on an audio signal. A circuit 64, an amplifier 65 for amplifying the analog video signal from the video processing circuit 62 so that its level becomes a standard value, and a PCM audio signal from the audio processing circuit 64 so that its level becomes a standard value. The amplifier 66 for amplifying, and the amplifiers 65, 66
A selector switch 67 for switching and selecting an analog video signal and a PCM audio signal respectively supplied from, and an amplifier 68 for amplifying the recording signal from the selector switch 67 so that the level of the analog video signal is optimum for recording. It is composed of a magnetic head 69 which generates a modulation magnetic field based on a recording signal from the amplifier 68.

The VTR performs signal processing such as FM modulation on the analog video signal supplied through the terminal 61, and then amplifies it by the amplifier 65 so that the level becomes a standard value, and at the same time, the terminal 63. After the signal processing such as PCM is performed on the audio signal supplied via the amplifier, the signal is amplified by the amplifier 66 so that its level becomes the standard value. Then, the amplified analog video signal and PCM audio signal are switched and selected by the change-over switch 67 and time-division multiplexed, and the obtained recording signal is optimized for recording with the level of the analog video signal included in the recording signal. After being amplified again, the magnetic head 69 records on a magnetic tape (not shown).

By the way, the above-mentioned standard value means the so-called S / S of the reproduced analog video signal with respect to the analog video signal.
N (Signal to Noise Ratio) is the maximum level, and the so-called C / N (Carrier to Noise Ratio) of the reproduced PCM audio signal is maximum with respect to the PCM audio signal, that is, the error rate is the minimum level. Yes, and the adjustment range thereof is, for example, within 0.5 dB. Therefore, it takes time to adjust them. Note that the amplifiers 65 to 68 surrounded by the broken line shown in FIG.
There is also a so-called IC (Integrated Circuit).

[0007]

As described above, the conventional V
In TR, two amplifiers 65 and 66 for amplifying each level of the analog video signal and the PCM audio signal so as to have the respective standard values are required, which is uneconomical. Further, in order to set each level to the standard value, each gain of the amplifiers 65 and 66 (hereinafter referred to as gain) must be adjusted, which requires a lot of test man-hours.

Further, when the impedance of the magnetic head 69 changes due to aging, the gains of the amplifiers 65 and 66 must be readjusted for optimum recording, which is very inconvenient. It was

The present invention has been made in view of the above circumstances, and can reduce the circuit scale and level in comparison with a conventional recording signal amplifying apparatus used in, for example, a VTR. It is an object of the present invention to provide a recording signal amplifier which can reduce the number of adjustment steps.

[0010]

According to the present invention, in order to solve the above problems, when an analog video signal and a digital signal are time-division multiplexed and recorded on a magnetic recording medium by a magnetic head, they are time-division multiplexed. In a recording signal amplifying device for amplifying a recording signal, switching means for switching and selecting an analog video signal and a digital signal for time division multiplexing, and a time division multiplexed recording signal from the switching means for amplifying to the magnetic head. Amplifying means for controlling the gain to be supplied, and control means for controlling the gain of the amplifying means to be suitable for analog video signal recording and digital signal recording respectively in synchronization with the switching operation of the switching means. Is characterized by.

[0011]

In the recording signal amplifying apparatus according to the present invention, the gain of the amplifying means is controlled to be optimum for recording the analog video signal and the digital signal, and the analog video signal is controlled by the amplifying means whose gain is controlled in this way. And a PCM audio signal are time-division-multiplexed and a recording signal is amplified while switching the gain.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a recording signal amplifying apparatus according to the present invention will be described below with reference to the drawings. The first embodiment applies the recording signal amplifying apparatus according to the present invention to a video tape recorder (hereinafter referred to as VTR), and FIG. 1 is a block diagram showing a circuit configuration of a recording system of this VTR.

As shown in FIG. 1, the recording system of this VTR has a video processing circuit 11 for performing a predetermined signal processing on an analog video signal, an audio processing circuit 12 for performing a predetermined signal processing on an audio signal, and the above video. The analog video signal from the processing circuit 11 and P from the audio processing circuit 12
A changeover switch 13 for selecting and selecting a CM audio signal for time division multiplexing, a voltage control amplifier 14 capable of controlling a gain (hereinafter referred to as a gain) for amplifying a time division multiplexed recording signal from the changeover switch 13, Voltage controlled amplifier 14
1 for amplifying the recording signal from the disk and generating the exciting current
5, the magnetic head 17 for generating a modulation magnetic field based on the exciting current from the amplifier 15, and the gain of the voltage control amplifier 14 in synchronization with the switching operation of the changeover switch 13 for analog video signal recording and PCM audio. It is composed of a control circuit 20 for controlling the signal recording to be optimum.

The VTR is a video processing circuit 1.
1 performs signal processing such as FM modulation on the analog video signal supplied through the terminal 1, and the audio processing circuit 12 converts the audio signal supplied through the terminal 2 into PCM and then converts it into PCM. Audio signal (hereinafter PC
M audio signal) is subjected to signal processing such as data compression processing, and the obtained analog video signal and PCM audio signal are selected by the change-over switch 13 to be time-division multiplexed. Then, the voltage control amplifier 14 amplifies the recording signal from the changeover switch 13 so that each level of the analog video signal and the PCM audio signal included in the recording signal becomes the respective standard values, and the amplified recording signal. Is supplied to the magnetic head 17 via the amplifier 15. That is, in this VTR, an analog video signal and a PCM audio signal are time-division-multiplexed, and then one voltage-controlled amplifier 14 amplifies each signal so that its level becomes a standard value.

Specifically, as shown in FIG. 1, the control circuit 20 includes a first adjusting power supply 21 for generating a control voltage for controlling the gain for the analog video signal, and P.
In synchronization with the switching operation of the second adjusting power source 22 for generating a control voltage for controlling the gain for the CM audio signal and the changeover switch 13, the control voltages from the adjusting power sources 21 and 22 are switched and selected, It is composed of a changeover switch 16 which is supplied to the voltage control amplifier 14. And
At the manufacturing stage, these regulated power supplies 21 and 22 are regulated so that their output voltage (control voltage) becomes a standard value, respectively, and as a result, the gain of the voltage controlled amplifier 14 is regulated.

For example, in the manufacturing stage, the gain of the voltage control amplifier 14 for the analog video signal is so-called maximum S / N (Sign) when the level of the analog video signal is reproduced.
The voltage of the regulated power supply 21 is adjusted so that the gain is such that the al to Noise Ratio) is obtained, and the gain of the voltage controlled amplifier 14 for the PCM audio signal is P
The so-called C / N with which the level of the CM audio signal is maximum during reproduction
(Carrier to Noise Ratio), that is, the voltage of the regulated power supply 22 is adjusted so that the gain is a level at which the minimum error rate is obtained. Each control voltage from the regulated power supplies 21 and 22 thus adjusted is selected by the changeover switch 16 synchronized with the changeover operation of the changeover switch 13, and the voltage control amplifier 1 is selected by the selected control signal.
By controlling the gain of 4 the voltage controlled amplifier 14
It is possible to obtain a recording signal in which the level conforms to each standard and the analog video signal and the PCM audio signal are time-division multiplexed.

Thus, the changeover switch 13 to the amplifier 15
By using the recording signal amplifying device composed of the control circuit 20 and the control circuit 20, that is, by using one voltage control amplifier 14, the gain is switched between the analog video signal and the PCM audio signal, and the analog video signal and the PCM audio signal are obtained. Can be amplified to meet the respective standards. In other words, one amplifier can be reduced compared to the conventional device.

Note that, for example, a so-called microcomputer is used in place of the adjustment power sources 21 and 22, and a D / A converter incorporated in the microcomputer switches the control voltage of the analog video signal and the PCM audio signal to each switch 1.
It may be supplied to the voltage control amplifier 14 via 6. Further, the changeover switches 13 to 16 may be so-called ICs.

Next, a second embodiment of the recording signal amplifying device according to the present invention will be described. This second embodiment also
Similar to the above-described first embodiment, the recording signal amplifying device according to the present invention is applied to a VTR, and FIG.
FIG. 3 is a block diagram showing a circuit configuration of a TR recording system. Therefore, the same circuits as those of the first embodiment are designated by the same reference numerals.

As shown in FIG. 2, the recording system of this VTR has a video processing circuit 11 for performing a predetermined signal processing on an analog video signal, an audio processing circuit 12 for performing a predetermined signal processing on an audio signal, and the above video. The analog video signal from the processing circuit 11 and P from the audio processing circuit 12
From the voltage control amplifier 14, a changeover switch 13 for selecting and selecting a CM audio signal and performing time division multiplexing, a voltage control amplifier 14 capable of controlling a gain for amplifying the time division multiplexed recording signal from the changeover switch 13, and the voltage control amplifier 14. An amplifier 15 for amplifying the recording signal of the above and generating an exciting current, and the amplifier 15
A magnetic head 17 for generating a modulation magnetic field based on the exciting current from the amplifier 1, an amplifier 19 for amplifying a reproduction signal reproduced by the magnetic head 17 during reproduction, and the amplifier 1
5, 19 is synchronized with the changeover switch 18 for changing over the connection between the magnetic head 17 and the magnetic head 17 for recording and reproduction, and the gain of the voltage control amplifier 14 is synchronized with the changeover operation of the changeover switch 13 to record an analog video signal and a PCM audio signal. And a control circuit 30 for controlling each of them to be optimal.

The VTR is a video processing circuit 1
1 performs signal processing such as FM modulation on the analog video signal supplied via the terminal 1, and the audio processing circuit 12 performs signal processing such as PCM on the audio signal supplied via the terminal 2. , The obtained analog video signal and PCM audio signal are selected by the change-over switch 13 and time-division multiplexed. Then, the voltage control amplifier 14 amplifies the recording signal from the changeover switch 13 so that each level of the analog video signal and the PCM audio signal included in the recording signal becomes the respective standard values, and the amplified recording signal. Is supplied to the magnetic head 17 via the amplifier 15 and the changeover switch 18. That is, in this VTR, an analog video signal and a PCM audio signal are time-division-multiplexed, and then one voltage-controlled amplifier 14 amplifies each signal so that its level becomes a standard value.

Further, in the VTR of the second embodiment, when it is necessary to readjust the gain of the voltage control amplifier 14 due to, for example, the impedance of the magnetic head 17 changing due to aging, the gain of the voltage control amplifier 14 is changed. Readjustment is automatically performed.

Specifically, as shown in FIG. 2, the control circuit 30 includes a first level detection circuit 32 for detecting the level of the analog video signal from the reproduction signal from the amplifier 19, and the amplifier 19 as well. Playback signal from PCM
Second level detection circuit 33 for detecting the level of the audio signal
A microcomputer (hereinafter referred to as CPU) 31 that generates a control voltage for controlling each gain for the analog video signal and the PCM audio signal based on the level of each signal detected by the level detection circuits 32 and 33; In synchronization with the switching operation of the change-over switch 13, the change-over switch 16 for changing over and selecting the control voltage from the CPU, and the above-mentioned C in order to obtain the control voltage for the analog video signal.
A switch 34 for supplying an analog video signal of a predetermined level from the PU 31 to the video processing circuit 11, and P
In order to obtain the control voltage for the CM audio signal, the CP
A switch 35 for supplying the audio signal of a predetermined level from U31 to the video processing circuit 11.

When the user turns on the power or sets the recording mode, the CPU 31 operates as follows.
In the test mode, the switches 34 and 35 are controlled to be in an ON state, an analog video signal of a predetermined level is supplied to the video processing circuit 11 via the switch 34, and an audio signal of a predetermined level is audio processed via the switch 35. Supply to the circuit 12. As a result, this analog video signal and a PCM audio signal obtained by converting this audio signal into PCM are time-division multiplexed, and then amplified by the voltage control amplifier 14 and recorded on the magnetic tape. Next, the CPU 31 detects each level of the analog video signal and the PCM audio signal recorded by the level detection circuits 32 and 33 from the reproduction signal obtained by reproducing this magnetic tape, and takes in each detected level. It is like this. When the test mode as described above ends, the CPU 31
Based on these captured levels, the gain of the voltage controlled amplifier 14 is controlled so as to be optimum for analog video signal recording and PCM audio signal recording, respectively. That is, a proper control voltage for the analog video signal and a proper control voltage for the PCM audio signal are supplied from the built-in D / A converter to the voltage control amplifier 14 via the changeover switch 16.

As a result, even if the impedance of the magnetic head 17 changes due to aging, for example, the gain of the voltage control amplifier 14 is adjusted to a value suitable for analog video signal recording and PCM video signal recording, respectively. Can be The VTR of the second embodiment
Needless to say, similarly to the VTR of the first embodiment, one voltage-controlled amplifier 14 can amplify the analog video signal and the PCM video signal to respective levels suitable for recording.

Next, a third embodiment of the recording signal amplifying apparatus according to the present invention will be described. This third embodiment is
Similar to the first embodiment described above, the recording signal amplifying device according to the present invention is applied to a VTR, and FIG.
FIG. 3 is a block diagram showing a circuit configuration of a TR recording system. Therefore, the same circuits as those of the first embodiment are designated by the same reference numerals, and the duplicated description will be omitted.

This VTR is a VTR of the first embodiment that can cope with secular change. Specifically, as shown in FIG. 3, in the same way as in the test mode used in the VTR of the second embodiment, that is, from the CPU 41 via the switch 43, an analog video signal of a predetermined level is supplied to the video processing circuit 11. Is supplied to the magnetic tape to record the analog video signal of a predetermined level on the magnetic tape, the magnetic tape is reproduced, and the level of the analog video signal is detected from the reproduction signal obtained via the change-over switch 18 and the amplifier 19. The control voltage of the voltage control amplifier 14 that adapts to the secular change is detected based on this level, and the change amounts are adjusted by the adders 47 and 48 (adjustment power sources 45 and 46 shown in FIG. 1). (Corresponding to the power supplies 21 and 22), and the added value from the adders 47 and 48 is supplied to the voltage controlled amplifier 14 as a control voltage. You have me.

Therefore, in this VTR as well as in the VTR of the first embodiment, the single voltage control amplifier 14 can amplify the analog video signal and the PCM audio signal respectively so as to be suitable for recording, and Similar to the VTR of the second embodiment, the gain of the voltage controlled amplifier 14 can be controlled by adapting to the change of the impedance of the magnetic head 14 due to the change over time.

Next, a fourth embodiment of the recording signal amplifying apparatus according to the present invention will be described. This fourth embodiment is
Similar to the above-mentioned first embodiment, the recording signal amplifying device according to the present invention is applied to a VTR, and FIG.
FIG. 3 is a block diagram showing a circuit configuration of a TR recording system. Therefore, the same circuits as those of the first embodiment are designated by the same reference numerals, and the duplicated description will be omitted.

This VTR is a VTR of the first embodiment that can cope with aged deterioration. Specifically, as shown in FIG. 4, the impedance detection circuit 51 detects, for example, a voltage applied to the magnetic head 17 when an analog video signal is recorded, so that the impedance of the magnetic head 17 changes with time. Is directly detected, and a voltage adapted to the change in the impedance is added to the voltage from the regulated power supplies 52 and 53 (corresponding to the regulated power supplies 21 and 22 shown in FIG. 1) by the adders 54 and 55, and the adder 54 , 55 is supplied to the voltage controlled amplifier 14 as a control voltage.

Therefore, also in this VTR, as in the VTR of the first embodiment, the analog video signal and the PCM audio signal can be amplified by the single voltage control amplifier 14 so as to be suitable for recording, respectively. Similar to the VTR of the second embodiment, the gain of the voltage controlled amplifier 14 can be controlled by adapting to the change of the impedance of the magnetic head 14 due to the change over time.

[0032]

As is apparent from the above description, according to the present invention, when the analog video signal and the digital signal are time division multiplexed and recorded on the magnetic recording medium by the magnetic head, the time division multiplexed recording signal is used. In a recording signal amplifying device for amplifying, by controlling the gain of the amplifying means so as to be suitable for analog video signal recording and digital signal recording respectively, the levels of the analog video signal and the PCM audio signal can be regulated by a single amplifying means. Therefore, the circuit scale can be reduced as compared with the conventional device.

Further, as described in the embodiments, for example, an analog video signal of a predetermined level is once recorded on a magnetic tape and then reproduced to detect the optimum gain of the voltage controlled amplifier. By directly detecting the impedance of the magnetic head, when the impedance of the magnetic head changes over time, the gain of the voltage controlled amplifier can be changed by adapting to the change.
The analog video signal and the PCM audio signal can be amplified so that they are always compatible with their respective recordings.

[Brief description of drawings]

FIG. 1 is a first example in which a recording signal amplifier according to the present invention is applied.
FIG. 6 is a block diagram showing a circuit configuration of a recording system of the VTR of the example of FIG.

FIG. 2 is a second example to which the recording signal amplifying device according to the present invention is applied.
FIG. 6 is a block diagram showing a circuit configuration of a recording system of the VTR of the example of FIG.

FIG. 3 is a third example to which the recording signal amplifying device according to the present invention is applied.
FIG. 6 is a block diagram showing a circuit configuration of a recording system of the VTR of the example of FIG.

FIG. 4 is a fourth example to which the recording signal amplifying device according to the present invention is applied.
FIG. 6 is a block diagram showing a circuit configuration of a recording system of the VTR of the example of FIG.

FIG. 5 is a block diagram showing a circuit configuration of a recording system of a VTR using a conventional recording signal amplifier.

[Explanation of symbols]

 13, 16 ... Changeover switch 14 ... Voltage control amplifier 17 ... Magnetic head 21, 22 ... Adjusting power supply

Claims (1)

[Claims] 1. A recording signal amplifier for amplifying a time-division multiplexed recording signal when the analog head signal and the digital signal are time-division multiplexed and recorded on a magnetic recording medium by a magnetic head. Switching means for switching and selecting signals for time division multiplexing, amplification means for amplifying the time division multiplexed recording signals from the switching means and controlling the gain to be supplied to the magnetic head, and switching of the switching means A recording signal amplifying apparatus comprising: a control unit that controls the gain of the amplifying unit so as to be suitable for analog video signal recording and digital signal recording, respectively, in synchronization with the operation.