JPH0410280A - Signal regenerating device - Google Patents

Abstract

PURPOSE:To dissolve unbalance of upper and lower sideband waves of a regenerative FM signal in level by selecting a peaking amplifier having a frequency characteristic in response to and corresponding to a regenerative track position and performing the peaking. CONSTITUTION:In the signal reproducing device for regenerating a FM- modulated signal recorded on a recording disk with a head, performing an automatic gain control on this regenerative signal and FM-demodulating the signal, when a regenerative track position is outside the 26th track, a signal '1' is outputted by a system control circuit 19 to change a changeover means 37 to the side of a terminal (a), and a peaking amplifier 36a is selected, and when the regenerative track position is within the 26th-50th tracks, a signal '0' is outputted, and the changeover means 37 is changed to the side of a terminal (b) to select a peaking amplifier 36b. By this method, the peaking can be carried out by the peaking amplifier of its frequency characteristic in response to and corresponding to the regenerative track position, and unbalance of the levels of upper and lower side band waves in each track position on a recording disk can be dissolved.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention reproduces an FM modulated signal recorded on a track of a recording disk of an electronic still camera, etc. using a head, and automatically reproduces it. The present invention relates to a signal reproducing device that performs gain control and then FM demodulation.

(Prior Art) As a type of camera, there is a so-called electronic still camera that records a video signal obtained from an image sensor or the like on a recording disk, for example, a magnetic disk, and reproduces it as needed.

In such electronic still cameras, when recording, the video signal is composed of a luminance signal (hereinafter referred to as the "Y signal") and a color difference line sequential signal (hereinafter referred to as the "C signal"), and each of these is FM modulated to perform frequency multiplexed recording. There is.

The recording/reproducing system of this electronic still camera will be explained in detail below with reference to FIG.

The input Y signal and C signal are signals obtained by processing a video signal obtained from an image sensor, etc., not shown, by a signal processing circuit, also not shown, and an example thereof is shown in FIG.
Shown as a) (C signal) and (b) (Y signal).

These Y signals and C signals are converted into FM signals by corresponding emphasis circuits 11.12 and FM modulation circuits 13.14.
After being modulated and further added by an adder I5, it is applied to the head 18 via the head amplifier 16 and the terminal a side of the changeover switch 17. The spectrum of the FM signal applied to this head 18 is shown in FIG. The changeover switch 17 is controlled by a system control circuit 19 such as a microcomputer so that the terminal a side is turned on during recording, and the terminal a side is turned on during playback.

The head 18 is movable along the radial direction of the magnetic disk 21 by a motor 20 controlled by a system control circuit 19.

Further, the magnetic disk 21 is connected to the system control circuit 1
9 and a spindle motor 23 whose rotation is controlled at a predetermined rotation speed by a servo circuit 22. For this reason, typically 50 concentric tracks are formed on the magnetic disk 21 by the head 18 .

During reproduction, the signal recorded on the magnetic disk 21 as described above is reproduced from the corresponding track by the head 18, and is passed through the terminal side of the changeover switch 17, the reproduction preamplifier 24, and the AGC (automatic gain control) circuit 25. After that, the Y-FM signal and the C-
FM signal.

The signals are then demodulated by the corresponding FM demodulation circuits 28, 29 and de-emphasis circuits 30, 31, and reproduced into Y and C signals equivalent to the input signals shown in FIG. Further, the C signal is transmitted to the color difference synchronization circuit 32 and the encoder 33.
After that, it is added to the Y signal by the adder 34, and the NTS
This becomes a C signal.

By the way, as mentioned above, the magnetic disk 21 usually has 5 discs.
Although zero concentric tracks are formed, in the electronic still camera, the rotation of the magnetic disk 21 is controlled at a constant speed with a constant angular velocity. becomes shorter. On the other hand, since the reproduction gap is constant, the reproduction level of the high frequency becomes lower as the track gets closer to the inner side, according to the principle of magnetic recording and reproduction. This phenomenon is particularly noticeable in the case of Y-FM signals recorded on the high frequency side.

Figure 9 schematically shows the above phenomenon. In the C-FM signal recorded on the low frequency side, the playback level fluctuates slightly due to the difference in track position, but on the high frequency side the Y-F
Regarding the M signal, there is a difference of several dB in reproduction level between the outermost track and the innermost track. Due to such fluctuations, if the reproduced Y-FM signal becomes lower than the minimum input level required for the Y-FM demodulation circuit 28, the FM
Modulation will not be performed correctly, resulting in an unsightly reproduced image.

In order to solve such problems, conventionally, an AGC circuit 25 using peak detection as shown in FIG. 6 is provided, and the input signal level to the Y-FM demodulation circuit 28 is made the same as shown in FIG. 10. It is controlled as follows.

By the way, when a signal is frequency modulated (FM) at a certain frequency (hereinafter referred to as carrier frequency), a frequency spectrum exists in a frequency band higher than the carrier frequency and a frequency band lower than the carrier frequency.
These are generally known as upper sideband waves and lower sideband waves, respectively.

As mentioned above, the conditions for demodulating the FM signal are that the level of the input signal to the FM demodulation circuit is sufficient, and that the levels of the upper and lower sidebands of the input signal are balanced. It is. However, in the recording/playback system of an electronic still camera, the playback level of high frequencies is low on the inner tracks as described above, so it is not possible to simply provide the AGC circuit 25 using peak detection as shown in Fig. 6. It is not possible to balance the upper and lower sideband waves on the side and outer circumferential sides, respectively. Particularly on the inner circumferential side, the balance between the upper and lower side band waves is lost, and a so-called inversion phenomenon tends to occur.

Additionally, in order to improve the balance between the upper and lower sidebands of the reproduced FM signal from a VTR, a tape head FM equalizer equipped with a correction circuit is disclosed in Japanese Patent Application Laid-Open No. 1-296872. When such technology is applied to recording and playback on the disk-shaped media mentioned above, it can be expected to be effective for recording and playback of the disk itself, but when playing back other compatible disks, the frequency characteristics of the FM equalizer are fixed. Therefore, no effect can be expected.

(Problem to be Solved by the Invention) As described above, since the reproduction level of the high frequency signal varies depending on the track position of the recording disk in an electronic still camera, etc., the upper and lower band waves are generated on the inner and outer sides of the disk, respectively. was unable to balance.

The purpose of the present invention is to eliminate the imbalance of upper and lower sideband waves at each track position of a recording disk in an electronic still camera, etc., and to obtain a sufficient reproduction FM signal level to enable good signal reproduction. An object of the present invention is to provide a signal reproducing device.

[Structure of the invention]

(Means for Solving the Problems) A signal reproducing device according to the present invention reproduces an FM modulated signal recorded on a track of a recording disk using a head, performs automatic gain control on the reproduced signal, and then performs FM demodulation. a plurality of peaking amplifiers set to mutually different peaking frequencies and amplification degrees, reproduction track position detection means for detecting the position of the track reproduced by the head of the recording disk, and the reproduction track position. Depending on the track position detected by the detection means, a corresponding peaking amplifier is selected from the plurality of peaking amplifiers, peaking the automatically gain-controlled reproduction signal according to the set frequency characteristics, and outputting it to the FM demodulation side. It is equipped with a switching means.

(Function) In the present invention, a plurality of peaking amplifiers with different peaking frequencies and amplification degrees are provided, and peaking is performed by selecting a peaking amplifier with a corresponding frequency characteristic according to the playback track position. It is possible to eliminate the imbalance between upper and lower sidebands at the track position, and to obtain a sufficient reproduced FM signal level. As a result, it is possible to prevent reversal phenomena caused by imbalance between upper and lower sidebands and perform good signal reproduction.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of a reproducing apparatus according to the present invention, and parts corresponding to the conventional apparatus shown in FIG. 6 are given the same reference numerals.

In FIG. 1, the configuration of the recording side of the recording disk 21 is similar to that of the conventional example shown in FIG. That is, the luminance signal (Y signal) and the color difference line sequential signal (C signal) are sent to the corresponding emphasis circuits 11, 12 and F.
After being FM modulated by M modulation circuits 13 and 14 and further added by an adder 15, it is applied to the head 18 via the head amplifier 16 and the terminal a side of the changeover switch 17. The changeover switch 17 is controlled by a system control circuit 19 such as a microcomputer so that the terminal a side is turned on during recording, and the terminal a side is turned on during playback.

The head I8 is movable along the radial direction of a magnetic disk 21 as a recording disk by a motor 20 controlled by a system control circuit 19 whose function is a reproduction track position detecting means. Further, the magnetic disk 21 is driven by a spindle motor 23 whose rotation is controlled at a rotation speed determined by a system control circuit 19 and a servo circuit 22.

For this reason, typically 50 concentric tracks are formed on the magnetic disk 21 by the head 18 .

During reproduction, the signal recorded on the magnetic disk 21 as described above is reproduced from the corresponding track by the head 18, and is passed through the terminal side of the changeover switch 17, the reproduction preamplifier 24, and the AGC (automatic gain control) circuit 25. After that, the Y-FM signal and the C-
FM signal.

In the present invention, of the reproduced FM signal whose gain is automatically controlled by the AGC circuit 25, the Y-FM signal, which is the high frequency component separated by the HP F 26, is peaked to eliminate the imbalance between the upper and lower sidebands. For this purpose, multiple (in this example, two)
Peaking amplifiers 36a and 36b are provided. These peaking amplifiers 36a and 36b are set to have different frequency characteristics, that is, peaking frequencies and amplification factors, and one of them is selected by a switching means 37 provided between the following FM demodulation circuit 28. It is configured so that it can be done. This switching means 37 switches depending on the reproduction track position on the magnetic disk 21.

That is, the system control circuit 19 has, in addition to the various functions described in FIG. The switching means 37 is controlled to switch according to the detection result.

The signals are then demodulated by the corresponding FM demodulation circuits 28, 29 and de-emphasis circuits 30, 31, and reproduced into Y and C signals equivalent to the input signal. Further, the C signal passes through a color difference synchronization circuit 32 and an encoder 33, and then is added to the Y signal by an adder 34 to become an NTSC signal.

For the peaking amplifiers 36g and 36b, circuits as shown in FIG. 2 are used, respectively. That is, it has a transistor 38, the collector of which is connected to the power supply via a resistor 39. Further, its emitter is connected to the ground via a resistor 40 and also to the ground via a resistor 41, a coil 42, and a capacitor 43. and,
An input signal is applied to the base terminal 381, and an output signal is output from the collector terminal 38°.

The frequency characteristics of these peaking amplifiers 36a and 36b are determined by the capacitor C [F] of the capacitor 43 and the inductor L [H] of the coil 42. And each constant C, L and resistance 4
By continuously changing the value R3 of 1, the gain and peaking frequency of the peaking amplifier 36136b can be continuously changed.

Here, examples of constants of the above circuit are shown below.

For the first peaking amplifier: R3=3.9Ω L=4.7μFI C=36
For pF second peaking amplifier: R3 = 1.5Ω L = 4.7μHC = 47p
F As a result of setting in this way, as shown in Figure 4, the first
The peaking amplifier 368 has, for example, an amplification degree of about 3 dB and a peak of about 3 dB at a frequency of 12 MHI.

Further, the second peaking amplifier 36b has, for example, an amplification degree of about 3 dB and a peak of about 6 dB at a frequency of 11 Mfh.

For example, when the number of tracks on the magnetic disk 21 is 50, the reproduction track position detecting means included in the system control circuit 19 detects that the reproduction track position is the 26th track position.
When it is outside the track, it outputs a signal “1”,
The configuration is such that the analog switch 37, which is the switching means, is switched to the terminal a side to select the first peaking amplifier 361.

On the other hand, when the playback track position is at the 26th to 50th tracks, the signal "0" is output, the analog switch 37 is switched to the terminal side, and the second peaking circuit 36b is selected. .

In the above configuration, during playback, the playback track position is the 26th track position.
If it is located outside the track, the switching means 37
The first peaking amplifier 36a is selected, and according to the frequency characteristics described above, peaks the reproduced Y-FM signal whose gain has been automatically controlled by peak detection, and outputs the upper and lower side bands of the Y-FM signal reproduced from the outer track. Corrects wave level imbalance. Further, when the reproduction track position is at the 26th to 5ith rack positions (inside), the second peaking amplifier 36b is selected by the switching means 37, and the reproduction Y-FM signal is to correct the imbalance between the upper and lower sideband levels of the Y-FM signal reproduced from the inner track. Figure 5 shows the results.

For the signals played from each track position in this way,
Since a peaking amplifier having a peaking frequency and amplification degree set in advance for each track position is selected and peaking is performed using this, the level imbalance of the upper and lower sidebands of the reproduced FM signal is eliminated. Since a sufficient signal level can be obtained, inversion phenomena and the like can be reliably prevented and good signal reproduction can be performed.

In the above embodiment, two peaking amplifiers 36a, 3
6b was used, but as shown in Fig. 3,
Three or more peaking amplifiers 36a 36b36c...
. . . may be provided, and these may be selected by a multiplexer serving as the switching means 37 in accordance with reproduction track position information from the system control circuit 19.

In addition, although a magnetic disk is illustrated as the recording disk 21, the present invention is not limited to this, and it may be possible to perform FM modulation of a signal and record/reproduce it on a disk-shaped medium, such as optical or magneto-optical recording. It can be applied to anything.

〔Effect of the invention〕

As described above, according to the present invention, by peaking according to the recording/reproducing frequency characteristics of each track of a recording disk, the imbalance in the levels of the upper and lower sidebands of the reproduced FM signal is eliminated, and Since a high signal level can be obtained, it is possible to reliably prevent inversion phenomena and the like for all tracks and perform good signal reproduction.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the signal reproducing device according to the present invention, FIG. 2 is a circuit diagram showing an example of the configuration of the peaking amplifier shown in FIG. 4 is a waveform diagram showing the frequency characteristics of the peaking amplifier shown in FIG. 2, and FIG. 5 is a diagram schematically showing the reproduced signal processed by the peaking amplifier.
Fig. 6 is a block diagram for explaining a conventional example, Fig. 7 is a waveform diagram showing a color difference line sequential signal and a luminance signal, and Fig. 8 is a waveform diagram showing a color difference line sequential signal and a luminance signal applied to the head during recording. Figure 9 is a diagram showing the difference in playback level between the outermost track and the innermost track in color, and Figure 10 is a diagram showing how the peak of the Y-FM signal is detected by a conventional peak detection AGC circuit. FIG. 3 is a diagram schematically showing that the value is almost constant. 18... Head, 19... System control circuit having reproduction track position detection means as a function, 21...
Recording disk, 25... Automatic gain control circuit, 28.2
9 - FM demodulation circuit, 36a, 36b - multiple peaking amplifiers, 37... switching means. Open base Lt'lH illusion

Claims (1)

[Claims] (1) FM recorded on the track of the recording disc
A signal reproducing device that reproduces a modulated signal by a head, performs automatic gain control on the reproduced signal, and then performs FM demodulation, includes a plurality of peaking amplifiers set to mutually different peaking frequencies and amplification degrees, and the recording disk. a reproduction track position detection means for detecting the position of a track reproduced by the head; and selecting a corresponding one from the plurality of peaking amplifiers according to the track position detected by the reproduction track position detection means, and setting the peaking amplifier. A signal reproducing device comprising: switching means for peaking the automatically gain-controlled reproduced signal according to the frequency characteristic of the frequency characteristic, and outputting the peaked signal to an FM demodulation side.