JPH02139765A - Fm modulating circuit for magnetic recording - Google Patents

Abstract

PURPOSE:To utilize the title FM modulating circuit as a simple type magnetic recording and reproducing device by setting up crossover points on mutually symmetrical positions correspondingly to digital data. CONSTITUTION:The data of (n-1) bits obtained by deleting the least significant bit (LSB) from the data of n bits (n is an integer) outputted from an AD converter is formed and a value corresponding to a half of a value corresponding to the data of bits is outputted from the (n-1) bits by digital comparators 31, 32, latches 35, 36 and logical circuits 40 to 46. In the case of FM-modulating a digitally converted video signal, symmetrical waveform can be obtained so that the position of a symmetrical wave characteristic such as a sine wave, i.e. a crossover point passes just a half point at the time of passing the crossover point and an FM waveform having excellent characteristics can be formed. Consequently, a tape cassette called as a simple type, cassette, i.e. an audio cassette can be used for a magnetic recording/reproducing device capable of recording/reproducing data.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of the Invention The present invention relates to an FM modulation circuit most suitable for a magnetic recording/reproducing device, particularly a simple type device.

(b) Conventional technology In general, for home color VTRs, the following systems have been put into practical use: the β system using the β format as a cassette type, the VH3 system using the VHS format, and the 8mm system with standardized specifications. A dedicated cassette is used, and VTRs of the same format are compatible with each other for recording and playback.

As an example, the signal processing during recording and playback is an analog signal processing method, as shown in 'NHK Home Video Technology JP, 67 and P, 93-96, edited by Japan Broadcasting Publishing Association, published by Japan Broadcasting Publishing Association. .

(c) Problems to be Solved by the Invention In the conventional example described above, most of the signal processing, especially the luminance signal and color signal, is analog processing, so there are many various adjustment points, and it is difficult to assemble the equipment. The drawback is that there are a large number of steps, which leads to increased equipment costs.

In view of the above drawbacks, the present invention provides an FM modulation circuit for magnetic recording that can be used in a magnetic recording and reproducing device capable of recording and reproducing information using a simple tape cassette called a C cassette for audio. It is.

(d) Means for solving the problem An analog video signal obtained by a photoelectric conversion element is
In a magnetic recording/reproducing device comprising an AD converter for conversion, an FM modulation circuit connected to the output side of the AD converter, and a magnetic head for recording FM on a magnetic tape with the addition of the FM modulation output of the FM modulation circuit. , said AD
The least significant bit (LSB) is deleted from the n-bit (n is an integer) data output from the converter (n-1)
The configuration is such that bit data is generated, and from the (n-1) bits, a value corresponding to 172, which is a value corresponding to the n-bit data, is outputted by a digital comparator, a latch, and a logic circuit.

(*) Effect In the present invention, when FM modulating a digitally converted video signal, when it passes through a symmetrical wave characteristic like a sine wave, that is, a crossover point, its position passes through a point at 1/2 g. As a result, a symmetrical waveform is obtained, and an FM waveform with good characteristics is generated.

(f) Embodiments To explain the present invention according to the drawings, FIG. 1 is a FM modulation circuit for magnetic recording of the present invention, FIG. 2 is a block diagram of a magnetic recording and reproducing apparatus using the same modulation circuit, and FIG. A timing chart for explaining the modulation circuit is shown. In the drawing, (1) is an image sensor as a photoelectric conversion element, (2)
is the first preamplifier, (3) is the DC regeneration circuit, and (4) is the A
D converter, (5) is pre-emphasis circuit, (6)
is a counter type FM modulation circuit, (7) is a head driver,
(8) is a magnetic head, (9) is a first switching circuit,
(10) is the second preamplifier, (11) is the limiter amplifier, (12) is the counter type FM demodulator, (13) is the controller that outputs various control signals, (14) is the sensor driver, and (15) is the iris. Adjustment circuit, (16) is a video integration circuit, (17) is an iris adjustment terminal, (18) is a control input terminal, (19) is a de-emphasis circuit, (20)
) is a dropout detection circuit, (21) is a second switching circuit, (22) is an image memory, (23) is a DA converter, (24) is a mixer, (25) is an RF modulator, and (26) is a magnetic tape. The image signal is obtained as an analog video signal from the image sensor (1), and the image sensor output is amplified by the first preamplifier (2) and only the effective signal components contained therein are extracted.

The next stage DC regeneration circuit (3) outputs OP B (0ptical Black) of the image sensor (1).
DC reproduction is performed using the signal as a reference, and the DC reproduced video signal is passed through a video integration circuit (16) and an AD humbatterer (4).
). In the former case, a value corresponding to an average value, peak value or intermediate value is obtained by setting a desired time constant.

As a result, the video integrated output signal is sent to the iris adjustment circuit (15).
The sensor driver (14) is connected to the sensor driver (14) through the iris, and iris adjustment is performed by reverse charge transfer or the like. In this case, when using a mechanical iris adjustment method, the output of the iris adjustment circuit drives the driver of the mechanism.

On the other hand, the latter is incorrectly applied to the AD humbater (4).

This is a circuit that performs AD conversion by making step changes in accordance with the input. Its function is oven loop automatic gain control (AGC), which maintains a nearly constant average value even if the average value of the input signal fluctuates. Conversion data can be obtained. One of the outputs of the AD converter (4) is applied as a direct display signal to the image memory 22) through the second switching circuit (21), and after being stored in the memory (22), it is sent to the DA converter (23)-mixer. A composite video signal is output through (24).

On the other hand, data corresponding to high frequency parts of the image is emphasized through a pre-emphasis circuit (5), and applied to a counter-type FM modulation circuit (6), where the digital signal is FM-modulated and sent to the head driver (7) and the first switching It is applied to the magnetic head (8) via the circuit (9) and recorded on the magnetic tape (26).

Next, during reproduction, the video signal recorded on the magnetic tape (26) is detected as an FM signal by the magnetic head (8), and the video signal is detected as an FM signal by the first switching circuit (9) - second preamplifier (10) -
Limiter amplifier (11) - Power counter 2 FM demodulator (12)
) - second switching circuit (21) - image memory (22
)-DA converter (23)-mixer (24), a composite video signal is obtained.

The specific configuration is shown in FIG. 1 as the counter type FM modulation circuit (6) shown in FIG. 2, and (27 bar 28) (29)
(30) is a digital input terminal, (31) and (32) are first and second digital comparators, (33) is a counter, (34) is a clock terminal, (35) and (36) are latches, and (37) is a D -F F (3g) (39), inverter (40) (41) (42), AND circuit (43)
(44), a logic circuit consisting of an OR circuit (45) and a NAND circuit (46), and (47) an FM output terminal.

FIG. 1 shows a, b, and c as digital data.

An example of 4 bits of d is shown, where a is the MSB (most significant bit) and d is the LSB (least significant bit).

Generally, if you delete the LSB data of n-bit data, you will get a value equivalent to 172 of the original value, but if the original value is an even number, you will get a value equivalent to 1/2. However, in the case of an odd number, the value becomes 1 less than 1/2, and this cannot be used as an FM wave, so the logic circuit sets the crossover point to 172 for both even and odd inputs. The present invention is configured to enable this. Next, to explain the following using the above 4-bit example, '1ooo' is input as data to the input terminals (27), (28), (29), and (30) in response to the clock signal (CLK) shown in FIG. 3 (A). In this case, the data with the LSB removed becomes '100 J (Fig. 3 (2υ).

The input data A (1000) is an even number and the counter (33
) is compared with the output B of the first digital comparator (31), and when B≧A, the latches (36) and (35) are set by the output of the first digital comparator (31), so the terminal (47 ) is shown in Figure 3 (*
), the pulse has one cycle every four clock cycles, that is, it has a characteristic of falling at the timing of rising at 172 of the input data. The waveforms are shown in FIG. 3 (d) and (*).

On the other hand, when '100IJ is applied as a digital input to the input terminals (27), (28), (29), and (30), the input A and the counter output B are connected to the second digital comparator (
32). At this time, the input of the second digital comparator (32) becomes '100', but since the value of the input data '100IJ is an odd number, B
When ≧A (when it exceeds 1/2), D-FF (3
8), the output shown in FIG. 3 (8) is obtained from the NAND circuit (46) constituting a one-cycle single-shot circuit from the waveform delayed by one clock, and along with this, the output of the latch (35>, that is, the terminal ( 47), the FM output shown in Figure 3 (G) is obtained for the data (shown in Figure 3 (F)).The FM output in Figure 3 (G) is based on the clock signal (CLK). The pulse waveform has 5 cycles as one cycle, and the crossover point appears at a timing corresponding to 5/2 cycles of the CLK.

Therefore, the digital data applied to the input terminals (27), (28), (29), and (30) is modulated into an FM wave from the terminal (47) and a modulated output is obtained.

(g) Effects of the invention According to the FM modulation circuit of the invention, the analog video signal is
When magnetically recording D-converted digital data,
In response to the digital data, the circuit configuration for setting crossover points at mutually symmetrical positions is extremely simple, and the configuration of the present invention can be used in a camera-integrated device as a simple magnetic recording/reproducing device. Then, the effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an FM modulation circuit for magnetic recording of the present invention, FIG. 2 is a block diagram of a magnetic recording/reproducing apparatus using the same circuit, and FIG. 3 is a timing chart for explaining FIG. 1. shows. (1)...Image sensor, (4)...AD converter, (6)...Counter type FM modulation circuit, (8
)...magnetic spatula)", (31)(32)...digital comparator, (33)...counter,
(35) (36)...Latch, (37)...Single-shot generation circuit, (47)...FM output terminal.

Claims (1)

[Claims] (1) An AD converter that AD converts the analog video signal obtained by the photoelectric conversion element, an FM modulation circuit connected to the output side of the AD converter, and the FM modulation output of the FM modulation circuit are added to the magnetic tape. In a magnetic recording/reproducing device configured with a magnetic head for FM recording, n bits (n is an integer) output from the AD converter.
The least significant bit (LSB) is removed from the data of (n
-1) bit data is generated, and a value corresponding to 1/2 of the value corresponding to the n-bit data is outputted from the (n-1) bits by a digital comparator, a latch, and a logic circuit. FM modulation circuit for magnetic recording.