JPH0810538B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus, and particularly to recording a video signal FM-modulated by a magnetic head on a rotating magnetic disk, or reading and reproducing the video signal from the magnetic disk. The present invention relates to a magnetic recording / reproducing apparatus used to write data on a magnetic disk by superimposing data other than the video signal on the video signal by a frequency multiplexing method or to read from the magnetic disk.

Recently, with imaging devices such as solid-state image sensor and camera tube,
A television set provided with a recording device that uses a magnetic disk, which is inexpensive and has a relatively large storage capacity, as a recording medium, electronically captures a subject, records a still image of the subject on the magnetic disc, and reproduces the image separately. An electronic still camera system has been developed which is performed by a John system or a printer. Also, a magnetic video recording system has been realized in which a still image recorded on a visible recording medium such as a normal film or photographic paper is photographed and recorded on a magnetic disk.

Video signals are recorded on such a magnetic disk by FM-modulating the video signals over a wide frequency range of approximately 10 MHz and at relatively high frequencies. Relatively low frequency range (for example, about 200kHz)
Can be opened for recording data other than video signals. In this type of inter-industry format standard, various types of data should be recorded on the magnetic disk by frequency multiplexing using such a low frequency. Is recognized.

As a modulation method for recording this kind of data, the differential phase shift keying (DPSK) is used.
ng) is used. Although this modulation method will be described in detail later, a circuit using an analog type PLL is known as a modulation / demodulation circuit based on this modulation method (for example, Shoukai 59-164918). Since this modulation / demodulation circuit is an analog type, there are problems that it is difficult to determine and adjust the circuit constants, and the circuit configuration is relatively complicated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems by digitizing a recording / reproducing circuit.

Another object of the present invention is to accurately demodulate modulated data.

In the magnetic recording / reproducing apparatus according to the first aspect of the present invention, a modulated video signal including a horizontal synchronizing signal and a modulated data signal generated by an exclusive logical sum of a carrier signal and a data signal synchronized with the horizontal synchronizing signal have a frequency band. A magnetic head that reproduces a video signal and a data signal from a magnetic recording medium that is differently multi-recorded, and that reads a modulated video signal and a modulation data signal that are multiple-recorded on the magnetic recording medium, and the carrier signal. A band pass filter that has a pass band in the frequency band of the above and extracts and outputs a modulated data signal from the signal read by the magnetic head, and generates a carrier signal for data reproduction having the same period as the carrier signal at the time of data modulation. It is a circuit for outputting the horizontal synchronizing signal extracted from the modulated video signal read by the magnetic head. The carrier signal generating circuit that adjusts the rising or falling timing of the output carrier signal, and the exclusive OR of the modulated data signal output from the band pass filter and the carrier signal output from the carrier signal generating circuit. A demodulation circuit for demodulating the modulated data signal output from the band pass filter is provided.

According to a second aspect of the present invention, a modulated video signal including a horizontal synchronizing signal and a modulated data signal generated by an exclusive OR of a carrier signal synchronized with the horizontal synchronizing signal and a data signal are recorded in different frequency bands. In a recording / reproducing apparatus for reproducing a video signal and a data signal from a magnetic recording medium, and performing multiple recording on the magnetic recording medium with the carrier signal and the modulated data signal having different frequency bands. Magnetic head for reading modulated video signals and modulated data signals multiplexed and recorded on a recording medium, band having a pass band in the frequency band of the carrier signal and extracting and outputting the modulated data signal from the signal read by the magnetic head Generates and outputs a carrier signal for data reproduction, which has the same period as the carrier signal at the time of data modulation and pass filter A carrier signal generating circuit that adjusts the rising or falling timing of the carrier signal to be output by using the horizontal synchronizing signal extracted from the modulated video signal read by the magnetic head, from the band pass filter. A demodulation circuit that demodulates the modulated data signal output from the band pass filter by an exclusive OR of the output modulated data signal and the carrier signal output from the carrier signal generation circuit, and a signal representing the data to be recorded are described above. A recording circuit for generating the modulated data signal to be recorded on the magnetic recording medium by an exclusive OR of the output of the latch circuit for latching in synchronization with the horizontal synchronizing signal and the carrier signal for recording is characterized. And

According to the present invention, since the recording / reproducing circuit is digitized, the circuit configuration can be relatively simplified and the adjustment thereof is almost unnecessary. Moreover, since it is not necessary to use analog parts, the problems of temperature characteristics consideration and compensation are extremely reduced. In addition to being able to easily open the way to ICs and expect cost reductions, digitalization can simplify the interface with computers, especially microprocessors.

Further, according to the present invention, the rising or falling timing of the carrier signal for data reproduction is adjusted by using the horizontal synchronizing signal extracted from the modulated video signal read by the magnetic head. Since the modulated data signal is generated by the exclusive OR of the carrier signal synchronized with the horizontal synchronizing signal and the data signal, the rising edge of the carrier signal for data reproduction exactly matches the rising edge or falling edge of the modulated data signal. To do. Accurate demodulation of the modulated data signal can be achieved.

Description of Embodiments FIG. 1 shows a frequency spectrum of an FM-modulated color video signal recorded on or reproduced from a magnetic disk. Chrominance (chrominance) signals and luminance (luminance) signals are distributed over a wide frequency range of about 10 MHz. The frequency f _c of the carrier signal of the data multiplex recording signal, which is weighted and recorded on the video signal by the frequency multiplex method, is set to 204.54 kHz (= 13f _h , f _h : horizontal scanning frequency) in the format standard. There is.

The data format of the data in the data multiplex recording is also defined, which is the initial bit (1 bit), field / frame data (2 bits), track address data (7 bits), date data (19 bits). Bit) and user data (27 bits). In a device capable of recording a frame image, it is essential to record field / frame data for distinguishing whether a recorded video signal is a frame image or a field image. User usage data is data needed by the user of the device for controlling the device or for other purposes.

The DPSK method as the above-mentioned modulation method is as follows.

Initial bit, field / frame
In a series of data to be recorded such as data, track address data, etc., as shown in FIG. 2, when the bit of this recording data changes (for example, from 1 to 0 or from 0 to 1) , The corresponding bit of the difference data is set to 1, and if there is no change in the bit of the recording data, the corresponding bit of the difference data is set to 0 to create the difference data.

With such difference data, the carrier (frequency f _c
= 13f _h ) is phase-shift keyed between two phases (0 and π) as shown in FIG. That is, when the difference data bit is 0, the carrier phase is 0, and when the difference data bit is 1, the carrier phase is π.

The bit rate of the difference data is basically 4H section (H:
1 bit in the period between horizontal sync pulses). That is, the phase of the carrier is changed according to the difference data for each 4H section (including the case where the phase is the same if the difference data is the same). However, according to the format standard, the bit rate of user data may be 1 bit in the 2H section.

FIG. 3 shows the case where the difference data is 011 ..., and ▲ ▼ is a signal synchronized with the horizontal synchronization signal. Further, regarding the waveform of the carrier, the frequency is enlarged and illustrated only at the portion where the phase shifts, and the illustration is omitted at other portions.

FIG. 4 shows the basic configuration of the modulation circuit according to the present invention. Further, FIG. 5 shows waveforms of various input signals and output signals in the circuit of FIG.

Since the differential data signal represents the change of the data to be recorded as described above, it can be easily obtained from the signal of the data to be recorded by using a known simple logic circuit. This difference data signal is the exclusive OR (Ex-O
R) is given to one input terminal of the circuit 11. Ex-OR circuit 11
The carrier signal of the above-mentioned frequency f _c is given to the other input terminal of. The carrier signal could be obtained from its generation circuit.

As a result of taking the Ex-OR logic between the differential data signal and the carrier signal, the phase of the carrier signal is shifted by π when the bit of the differential data is inverted. This Ex-OR output is sent to a band pass filter (BPF) 12 that passes only signals of frequencies near the frequency f _c of the carrier signal, and is converted by the filter 2 into a recording signal that changes smoothly.

The data recording signal is combined with the video signal, that is, the chrominance signal and the luminance signal, and magnetically recorded on a predetermined track on the magnetic disk by the magnetic head.

The reproduction of the data signal is similarly achieved by demodulating the data read signal using the Ex-OR circuit. That is, a video signal is separated from a read signal by passing a signal read from a magnetic disk by a magnetic head through a bandpass filter having a carrier signal frequency f _c as a center pass frequency, and a data modulated carrier signal is obtained. To be This modulated carrier signal is waveform-shaped and then sent to the Ex-OR circuit together with the carrier signal. It can be easily understood from FIG. 5 that the signal representing the difference data can be obtained from the Ex-OR circuit. Conversion from difference data to data can also be performed by a simple logic circuit.

FIG. 6 shows a modulation / demodulation device assembled in consideration of various timings based on the basic idea of the above-mentioned modulation and demodulation.

Ex-OR circuit 11 and band pass filter 1 shown in FIG.
2 is included in the modulation circuit 10. The output signal of the circuit 10, that is, the data recording signal after modulation is given to the output terminal 8, is sent from the terminal 8 to the synthesizing circuit, is mixed with the video signal, and is then recorded on the magnetic disk by the magnetic head.

In the reproduction mode, the read signal read from the magnetic disk by the magnetic head is sent from the input terminal 9 to the bandpass filter 22 having the carrier frequency f _c as the center frequency, and the signal modulated by the data is converted from the video signal. To be separated. The data-modulated read signal is waveform-shaped by the waveform shaping circuit 23, and then the differential data signal is demodulated by the Ex-OR circuit 21 as described above. The low pass filter 24 removes noise such as "whiskers" from this signal, and the comparison circuit
The waveform is shaped in 25 and sent to the differential data signal output terminal 4.

A switching signal between the reproduction (PB) mode and the recording (Rec) mode is given to the input terminal 1. As shown above the terminal 1, this signal becomes H level during reproduction and L level during recording. This switching signal is sent to the reset signal switching circuit 50 and the carrier switching circuit 70.

The carrier signal having the frequency f _c is generated from the frequency dividing circuit 30.
The frequency divider circuit 30 has counters 31 and 32, a NAND circuit 33 which receives the predetermined count outputs thereof, and an output of the NAND circuit 33 is fed back to a clock input terminal and an inverted output thereof is fed back to a data input terminal. It is composed of a D flip-flop 34 and counts down a clock pulse of about 14 MHz supplied from the input terminal 7 to generate an inverted signal of the carrier signal of the frequency of 13f _h described above. The counters 31 and 32 of the frequency dividing circuit 30 synchronize with the carrier signal and other signals, for example, the differential data signal, in order to synchronize the carrier signal with other signals, for example, a synchronous differentiating circuit 40 described later every horizontal scanning period.
It is reset by a reset pulse applied from the NOT circuit 43 through. The reset timing differs between the recording mode and the reproduction mode as described later. After resetting, the counters 31 and 32 start counting from 1 again.

The inverted signal of the carrier signal generated in the frequency dividing circuit 30 is sent to the carrier switching circuit 70. This carrier switching circuit 70
Is the carrier signal of the modulation circuit 10 in the recording mode.
In the reproduction mode, the Ex-OR circuit 11 operates so as to supply the carrier signal to the Ex-OR circuit 21 of the demodulation circuit 20.
That is, this circuit 70 is the NOT circuit 7 for the reproduction / recording switching signal.
It includes a NAND gate 71 controlled by an inversion signal by 3 and a NAND gate 72 controlled by a reproduction / recording switching signal. In the recording mode, the switching signal is at the L level, and therefore the NAND gate 71 is provided with the control signal at the H level. Therefore, the inverted signal of the carrier signal input to the NAND gate 71 is inverted again by the NAND gate 71. It is given to one input terminal of the Ex-OR circuit 11.
On the contrary, in the reproducing mode, an H level switching signal is given to the NAND circuit 72, and the inverted signal of the carrier signal is the NAND signal.
The signal is inverted by the circuit 72 and applied to one input terminal of the Ex-OR circuit 21 of the demodulation circuit 20.

Similarly, in the reset signal switching circuit 50, the NAND gate 52 controlled by the reproduction / recording switching signal inverted by the NOT circuit 54 and the NA directly controlled by the reproduction / recording switching signal.
This circuit 50 includes an ND gate 53.
NAND circuit 51 that takes the NAND logic of the output signals of the ND gates 52 and 53
It has. Therefore, in the recording mode, the inverted signal ▲ ▼ synchronized with the horizontal synchronizing signal in the recording mode applied to the input terminal 3 is input to the synchronous differentiating circuit 40 through the NAND gates 52 and 51, and in the reproducing mode, the demodulation described later is performed. The reset signal generated from the reset signal generating circuit 60 is applied to the synchronous differentiating circuit 40 through the NAND gates 53 and 51.

The synchronous differentiating circuit 40 includes two D flip-flops 41 and 42, the output signal of the reset signal switching circuit 50 is given to the clock input terminal of one flip-flop 41, and the non-inverted output of this flip-flop 41 is the other. The data input terminal of the flip-flop 42 is supplied with a clock signal of about 14 MHz to the clock input terminal of the flip-flop 42. When the reset signal is input from the switching circuit 50, a reset pulse having a very short pulse width (for example, 70 ns) synchronized with the 14 MHz clock signal is output from the non-inverting output terminal of the flip-flop 42, and the NOT circuit 43 is output. It is then given to the clear terminals of the counters 31 and 32 of the frequency dividing circuit 30.

The modulation timing in the recording mode will be described with reference to FIG.

The difference data to be recorded is given from the input terminal 2 to the data input terminal of the D flip-flop 13. An inverted signal ▲ ▼ synchronized with the horizontal synchronizing signal in the recording mode is input to the clock input terminal of the flip-flop 13. Therefore, the difference data is latched in the flip-flop 13 at the timing of this signal (). Further, since the reset pulse is given from the synchronous differentiating circuit 40 to the frequency dividing circuit 30 at the timing of this signal ▲ ▼, the frequency dividing circuit 30 always outputs a carrier signal accurately synchronized with the signal ▲ ▼. Become.

As described above, the carrier signal is
-The non-inverted output of the flip-flop 13 applied to one input terminal of the OR circuit 11 and representing the latch output of the difference data is
Since the signal is given to the other input terminal of the Ex-OR circuit 11, the phase of the carrier signal is inverted (shifted) at the timing synchronized with the signal ▲ ▼ (when the difference data changes).

In the reproduction mode, the counters 31 and 32 of the frequency dividing circuit 30 for synchronizing the carrier signal and the data read signal are reset near the center between the inverted signals ▲ ▼ synchronized with the horizontal synchronization signal during reproduction. Be done. this is,
This is because the phase shift included in the data read signal occurs near the signal {circle around ()} so that the demodulation error can be prevented.

Referring to FIG. 8, in the demodulation reset signal generation circuit 60, the signal ▲ ▼ is inverted by the NOT circuit 64 and the delay circuit 6
At 3, the delay is about half the horizontal scanning period H.
This delayed signal is sent to NAND gate 62.

On the other hand, the output of the comparison circuit 25 after demodulation and the output of the waveform shaping circuit 23 before demodulation are input to the Ex-OR circuit 61, and as a result, the output of the waveform shaping circuit 23 is phase-shifted (shifted) by phase modulation (shift). Although there is a part where is deviated by π, a carrier signal for demodulation with the same phase is always obtained, and this signal is
Input to NAND gate 62. Therefore, a timing signal for resetting is output from the NAND gate 62 in the vicinity of the center of the signal ▲ ▼, and this signal is sent to the synchronous differentiating circuit 40 via the reset signal switching circuit 50. A pulse is output and the frequency divider circuit 30
The counters 31, 32 of are reset. As a result, the rising edge of the carrier signal exactly matches the rising edge or falling edge of the data read signal, and accurate demodulation is achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing frequency spectra of a video signal and a data recording signal recorded on a magnetic disk. FIG. 2 is a diagram showing how the data to be recorded is converted into difference data. FIG. 3 is a waveform diagram showing how the phase shift keying of the carrier is performed by the DPSK method. FIG. 4 is a circuit diagram showing the principle of the modulation circuit according to the present invention, and FIG. 5 is a waveform diagram showing its operation. FIG. 6 is a circuit diagram showing a detailed embodiment of the present invention,
7 and 8 are waveform charts showing the operation. 10 …… Modulation circuit, 11, 21 …… Ex-OR circuit, 20 …… Demodulation circuit, 3
0: Frequency divider circuit (carrier signal generation circuit).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Izumi Miyake 2-26-30, Nishiazabu, Minato-ku, Tokyo Within Fujisha Shin Film Co., Ltd. (72) Inventor Kiyotaka Kaneko 2-26-30 Nishiazabu, Minato-ku, Tokyo Fuji Shashin Film Co., Ltd. (72) Inventor Kazuya Oda 2-26-30 Nishiazabu, Minato-ku, Tokyo Fuji Shashin Film Co., Ltd. (56) References: Actual Development Sho 56-127922 (JP, U)

Claims (5)

[Claims] 1. A modulated video signal including a horizontal synchronizing signal, and a modulated data signal generated by an exclusive OR of a carrier signal synchronized with the horizontal synchronizing signal and a data signal are multiplexed and recorded in different frequency bands. A magnetic head for reproducing the video signal and the data signal from the magnetic recording medium, the magnetic head reading the modulated video signal and the modulated data signal multiplexed and recorded on the magnetic recording medium, and the pass band in the frequency band of the carrier signal. A bandpass filter for extracting and outputting a modulated data signal from the signal read by the magnetic head, and a circuit for generating and outputting a carrier signal for data reproduction having the same period as the carrier signal at the time of data modulation. Yes, a carrier for outputting using the horizontal synchronizing signal extracted from the modulated video signal read by the magnetic head. A carrier signal generation circuit for adjusting the rising or falling timing of a signal, and the band pass filter by exclusive OR of the modulated data signal output from the band pass filter and the carrier signal output from the carrier signal generation circuit. A magnetic recording / reproducing apparatus including a demodulation circuit for demodulating a modulated data signal output from the. 2. The carrier signal generating circuit is an exclusive circuit which receives a frequency dividing circuit including a counter for counting a high frequency clock signal, a modulated data signal output from the band pass filter and an output signal of the demodulating circuit. An OR circuit and a reset pulse generation circuit that generates an output signal of the exclusive OR circuit in synchronization with the horizontal synchronization signal and generates a reset pulse for resetting the counter. The magnetic recording / reproducing apparatus according to claim (1). 3. The magnetic recording / reproducing apparatus according to claim 1, wherein the reset pulse generating circuit generates a reset pulse at a substantially midpoint of a horizontal scanning period. 4. A modulated video signal including a horizontal synchronizing signal, and a modulated data signal generated by exclusive OR of a carrier signal synchronized with the horizontal synchronizing signal and a data signal are multiplexed and recorded in different frequency bands. A magnetic recording medium for reproducing a video signal and a data signal, and the carrier signal and the modulated data signal are recorded on the magnetic recording medium in different frequency bands. Magnetic head for reading modulated video signal and modulated data signal multiplexed and recorded on medium, band pass for extracting modulated data signal from signal read by the magnetic head and having a pass band in the frequency band of the carrier signal and outputting Generates and outputs a carrier signal for data reproduction, which has the same cycle as the carrier signal at the time of filter and data modulation A carrier signal generation circuit for adjusting the rising or falling timing of the carrier signal to be output by using the horizontal synchronizing signal extracted from the modulated video signal read by the magnetic head, and the band pass filter. A demodulation circuit for demodulating the modulated data signal output from the band pass filter by an exclusive OR of the output modulated data signal and the carrier signal output from the carrier signal generation circuit, and a signal representing data to be recorded are described above. A magnetic recording device is provided with a recording circuit for generating the above-mentioned modulated data signal to be recorded on a magnetic recording medium by an exclusive OR of an output of a latch circuit which latches in synchronization with a horizontal synchronizing signal and a carrier signal for recording. Playback device. 5. The carrier signal generating circuit also generates a carrier signal for the recording, the carrier signal generating circuit includes a frequency dividing circuit including a counter for counting a high frequency clock signal, and the modulation data. An exclusive OR circuit that receives the signal and the output signal of the demodulation circuit as an input, and the above-mentioned signal at a substantially midpoint of the horizontal scanning period in synchronization with the horizontal synchronizing signal separated from the modulated video signal read from the magnetic recording medium. Synchronized with the horizontal sync signal of the video signal to be recorded on the magnetic recording medium, and the reproduction reset pulse generation circuit that takes out the output signal of the exclusive OR circuit and generates the reproduction reset pulse for resetting the counter And a recording reset pulse generating circuit for generating a recording reset pulse for resetting the above-mentioned counter, and a reproduction recording switching signal. And a reset pulse switching circuit for switching and giving the reproducing reset pulse or the recording reset pulse to the counter, and the demodulating circuit or the demodulating circuit using the output signal of the frequency dividing circuit as a carrier signal according to the reproducing / recording switching signal. The magnetic recording / reproducing apparatus according to claim (4), further comprising a carrier switching circuit for switching and supplying to a recording circuit.