JPS61224694A - Video signal transmitter - Google Patents

Abstract

PURPOSE:To solve problems in a direct FM system, a color-under system and a two-channel component recording system and to record and reproduce satisfactorily a composite video signal by transmitting the composite video signal after its high frequency component is demodulated in terms of quadrant two phases. CONSTITUTION:An NTSC video signal inputted to an input terminal 1 is supplied to a high-pass filter 2, a low-pass filter 3 and a carrier generating circuit 5. The output signal of the high-pass filter 2 is supplied to the 1st transmitting means 6 and the 2nd transmitting means 7 through a quadrant two phase demodulating means 4. The output signal of the carrier generating circuit 5 is supplied to the quadrant two phase demodulating means 4. On the other hand, the output signal of the low-pass filter 3 is supplied to the 3rd transmitting means 8. Signals transmitted through the 1st and 2nd transmitting means 6 and 7 are supplied to a quadrant two phase modulating means 9. The signal transmitted through the 3rd transmitting means 8 is supplied to the carrier generating circuit 10 and an adding means 11. The output signal of the quadrant two phase modulating means 9 is supplied to the adding means 11. Its output signal is supplied to an output terminal 12.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal transmission device such as a video tape recorder.

BACKGROUND OF THE INVENTION Conventionally, in video signal transmission devices such as video tape recorders that transmit video signals using magnetic recording media, a direct FM method is used in which an input video signal is directly FM'd and recorded.
The so-called color under method converts the carrier color signal component of the input video signal to a low frequency, and then frequency-multiplexes it onto a frequency-modulated luminance signal and records it.The other method converts the input video signal into a luminance signal and two color difference signals. (Or! signal, Q signal)
A component recording method (for example, Broadcasting Technology Magazine October 1986 No. F, 872-P, 8
90).

Problems to be Solved by the Invention In the direct FM method, the carrier color signal is FM recorded and played back at its frequency, so tape consumption is large and the S of the carrier color signal is
There are problems such as a poor N ratio and moiré interference occurring in the carrier color signal.

The so-called color under method has good recording efficiency and low tape consumption, but the S/N ratio of the reproduced conveyance color signal is poor.
The band of the carrier color signal is also narrow, and the luminance signal has problems such as cross-modulation moiré caused by the low-frequency conversion carrier color signal.

In the 2-channel component recording method, each component signal is recorded as FM, so although the S/N ratio is good,
When recording a composite signal such as an NTSC signal, it must be converted to a component signal once.
There is a problem in that signal deterioration occurs during this conversion process.

Means for Solving the Problems The present invention solves the above-mentioned problems and, in order to record and reproduce a composite video signal well, uses a video signal as an input signal and a high-pass filter that filters the high-frequency components of the input signal. a filter, a low-pass filter that converts the low-frequency component of the input signal into a p-wave, a quadrature two-phase demodulation means for demodulating the output signal of the high-pass filter into two quadrature phases, and two outputs of the quadrature two-phase demodulation means. a first and second transmission means for transmitting each of the two output signals obtained from the terminal; a third transmission means for transmitting the output signal of the low-pass filter; It is composed of quadrature two-phase modulation means for quadrature two-phase modulation of each of the signals transmitted by the second transmission means, and addition means for adding the signals transmitted by the third transmission means.

According to the above-described configuration, the present invention performs quadrature two-phase demodulation of the high-frequency components of the composite video signal before transmitting it, so that good transmission is achieved.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the main configuration of the present invention.

Input terminal 1 receives a composite video signal such as NTS
A C video signal is supplied. NT input to input terminal 1
The SC video signal is supplied to a high-pass filter 2, a low-pass filter 3, and a carrier generation circuit 6. The output signal of the high-pass filter 2 is supplied to the first transmission means 6 and the second transmission means 7 via the quadrature two-phase demodulation means 4. The output signal of the carrier generation circuit 6 is supplied to the quadrature two-phase demodulation means 4. On the other hand, the output signal of the low-pass filter 3 is supplied to the third transmission means 8. The first transmission means 6 and the second transmission means 6
The signal transmitted by the transmission means 7 is transmitted to the quadrature two-phase modulation means 9.
supplied to Further, the signal transmitted by the third transmission means 8 is supplied to the carrier generation circuit 10 and the addition means 11, and the output signal of the quadrature two-phase modulation means 9 is also supplied to the addition means 11. The output signal of the adding means 11 is supplied to an output terminal 12.

Figure 2 shows the signal waveforms of each part in Figure 1. Figure 2a shows an example of the frequency spectrum of the NTSC video signal input to input terminal 1. Signal C is frequency multiplexed. Figure 2 shows the frequency spectrum of the output signal of the low-pass filter 3, which includes the low-frequency component YI of the luminance signal Y, and the cutoff frequency is set to, for example, 2.4 MHz. O
FIG. 2C shows the frequency spectrum of the output signal of the high-pass filter 2, which includes the high-frequency component YH of the luminance signal Y and the carrier color signal C. The lower cutoff frequency of YH is set to 2.4 MHz, for example.

In other words, from the color subcarrier frequency (f BC = -x fH, where fH: horizontal scanning frequency), the lower frequency side is 1.2 MH
z is the cutoff frequency of YJ (0) Figure 2 d is the frequency spectrum of the output signal of the A-phase output terminal 13 of the quadrature two-phase demodulation means 4, and Figure 2 e is the frequency spectrum of the output signal of the B-phase output terminal. 1
4 shows the frequency spectrum of the output signal. The cutoff frequency of each will be 1.2MHz.

The A-phase input terminal 15 of the quadrature two-phase modulation means 9 is connected to the
A signal having a frequency spectrum shown in is input. Similarly, a signal having a frequency spectrum shown in FIG. 2e is input to the B-phase input terminal 16. Quadrature two-phase modulation means 9
A signal having the frequency spectrum shown in FIG. 2C is outputted to the output terminal of the third transmission means 8, and a signal having the frequency spectrum shown in FIG. 2 is outputted to the output terminal of the third transmission means 8. By adding these signals at 11, a signal having the frequency spectrum shown in FIG. 2a is obtained at the output terminal 12.
It consists of a multiplier 15.16 and a low pass filter 17.18. The multiplier 16 receives the output signal of the high-pass filter 2 and one of the output signals A of the carrier generation circuit 5.
The output signal of the high-pass filter 2 and the B-phase carrier, which is another output signal of the carrier generation circuit 6, are supplied to the zero multiplier 16, which is supplied with the phase carrier.

A low-pass filter 17 is connected to the multiplier 16 to remove unnecessary high-frequency components, and then output the signal to the A-phase output terminal 13 of the quadrature two-phase demodulation means 4. Further, a low-pass filter 18 is connected to the multiplier 16, and after unnecessary high-frequency components are removed, the B-phase output terminal 18 of the quadrature two-phase demodulation means 4 is connected.
is output to.

As illustrated in FIG. 3, the first transmission means 6 includes, for example, an FM modulation circuit 19. Recording head 20. It is composed of a magnetic tape (not shown), a reproducing head 21, and an FM demodulation circuit 22. The second transmission means 7 includes, for example, an FM modulation circuit 23 . Recording head 24. It is composed of a magnetic tape (not shown), a reproducing head 25, and an FM demodulation circuit 26. As illustrated in FIG. 5, the third transmission means 8 includes, for example, an FM modulation circuit 27. Recording head 28. It is composed of a magnetic tape (not shown); a reproducing head 29 and an FM demodulation circuit 3o.

The carrier generation circuit 6 has a predetermined phase relationship with the luminance signal included in the input video signal, and has a phase of 9oO.
It outputs different A-phase carriers and B-phase carriers. As illustrated in FIG. 6, the carrier generation circuit 6 includes, for example, a horizontal synchronizing signal separation circuit 31, a phase
The 0-phase locked loop 32, which is composed of a locked loop 32° and a 90' phase shifter 33, receives a horizontal synchronizing signal (
Frequency: fH) is input, and a signal having a frequency of -1-fH, that is, a color subcarrier frequency, and whose phase matches, for example, the front edge of the horizontal synchronizing signal is outputted. The 90° phase shifter 33 has almost the same configuration as the 0 carrier generation circuit 1o that outputs the A-phase carrier whose phase matches that of the front edge of the horizontal synchronization signal and the B-phase carrier delayed by 9oo. An A-phase carrier and a B-phase carrier that have a predetermined phase relationship with the luminance signal containing the YL acid component transmitted by the means 8, that is, the same phase relationship as the luminance signal in the carrier generation circuit 5, and have a phase difference of 900 This is what is output. As illustrated in FIG. 7, the carrier generation circuit 1o includes, for example, a horizontal synchronization signal separation circuit 34.
, phase locked loop 35,900 phaser 36
It consists of

The horizontal synchronization signal separation circuit 34 separates the horizontal synchronization signal from the YL multiplied signal which is the output signal of the third transmission means 8. The phase-locked loop 36 receives a horizontal synchronization signal (frequency: fH), has an output frequency, and outputs a signal whose phase matches, for example, the front edge of the horizontal synchronization signal. The 90° phase shifter 36 outputs an A-phase carrier whose phase matches the front edge of the horizontal synchronizing signal and a B-phase carrier whose phase is delayed by 90°.

The quadrature two-phase modulation means 9 includes, for example, square multipliers 37 and 38;
The 0 multiplier 37 includes an adder circuit 39 and a low-pass filter (or band-pass filter) 40.
The output signal of the first transmission means 6 and the carrier generation circuit 1o
0 to which the A-phase carrier, which is one of the output signals of
The multiplier 38 is supplied with the output signal of the second transmission means 7 and the B-phase carrier which is the divided output signal of the carrier generation circuit 10.

The results obtained by multiplying each signal by multipliers 37 and 38 are added by an adder circuit 39, and unnecessary components are removed by a low-pass filter (or band-pass filter) 40. At the output end of the modulation means 9,
A frequency multiplexed signal of the YH multiplied signal C signal as shown in FIG.

In the embodiment described above, three channels of transmission means are required. However, the present invention is not limited to the number of channels of the transmission means. For example, one-channel transmission means can be used as a replacement for the first transmission means 6 and the second transmission means 7.

An example of a one-channel transmission means is the format shown in the so-called M format standard (for example, described in Broadcasting Technology Magazine, January 1986 issue, P, 70-P, 7B). Frequency multiplexing means similar to FM and FM frequency multiplexing transmission methods can be used for signals and Q signals.In addition, Official EBU Technical Text R3
2-1984 (so-called BCAM standard) can be used.

In these configurations, a total of two channels consisting of one channel transmission means as a replacement for the first transmission means 6 and the second transmission means 7, and the third transmission means 8 are required as transmission means.

Furthermore, the first transmission means 6. It is also possible to replace the second transmission means 7 and the third transmission means with one-channel transmission means. An example of a 1-channel transmission means is SMPTE journal, 0ctover 1
As shown in 984P, 904-P, 910, it is possible to use means for converting each of the three types of signals into a one-channel signal by compressing the time axis and transmitting the signal by FM.

Effects of the Invention As described above, the video signal transmission device of the present invention transmits a composite video signal to three parts while retaining the properties of the composite signal.
Since this is a device that divides signals into channels and transmits them through a transmission path, it does not convert them into component signals unlike the component recording method, so it is possible to provide a transmission device that does not cause signal deterioration.

In addition, since the signal divided into three channels is transmitted via FM, the SN of the reproduced carrier color signal is
A transmission device that does not cause the problem of poor ratio can be provided.

In addition, the carrier color signal included in the composite video signal is
Since the channel signal is demodulated and transmitted, it is possible to provide a transmission device that does not have the problem of poor SN of the carrier color signal and moiré interference as in the direct FM system.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a video signal transmission device in an embodiment of the present invention, and FIGS. 2a, b, c, and d. e is a diagram showing the frequency spectrum of each part signal in the block diagram shown in FIG. 1, FIG. 3 is a block diagram showing one embodiment of the first transmission means 6, and FIG. 6 is a block diagram showing an embodiment of the third transmission means 8; FIG. 6 is a block diagram showing an embodiment of the carrier generation circuit 5; FIG. 7 is a block diagram showing an embodiment of the carrier generation circuit 5. FIG. 1 is a block diagram showing an embodiment of 1o. 2...High-pass filter, 3...Low-pass filter, 4...Right-angle two-phase demodulation means, 6.
...Carrier generation circuit, 6...First transmission circuit, 7...Second transmission circuit, 8...
・Third transmission circuit, 9... Quadrature two-phase modulation circuit,
1o...Carrier generation circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person
2 Figure

Claims (4)

[Claims] (1) A high-pass filter that takes a video signal as an input signal, filters out the high-frequency components of the input signal, a low-pass filter that filters the low-frequency components of the input signal, and an output signal of the high-pass filter. a quadrature two-phase demodulation means for demodulating the quadrature two-phase demodulation, first and second transmission means for respectively transmitting two output signals obtained from two output terminals of the quadrature two-phase demodulation means, and a low-pass filter. a third transmission means for transmitting the output signal; a quadrature two-phase modulation means for quadrature two-phase modulation of each of the signals transmitted by the first and second transmission means; 1. A video signal transmission device comprising: an addition means for adding a signal and a signal. (2) As an input video signal, a composite video signal in which a carrier color signal is frequency-multiplexed on the high frequency portion of a luminance signal is used, and as a demodulation carrier used in the quadrature two-phase demodulation means, a sub-band of the carrier color signal is used. A demodulation carrier having a carrier frequency and a predetermined phase relationship with the synchronization signal of the input video signal is used as a modulation carrier used in the quadrature two-phase modulation means, which is a subcarrier frequency of the carrier color signal. 2. The video signal transmission apparatus according to claim 1, further comprising a demodulation carrier having a predetermined phase relationship with a synchronization signal included in the signal transmitted by the third transmission means. (3) As a first transmission means, a first FM modulator and a first magnetic recording/reproducing system for recording and reproducing the output signal thereof;
a first FM demodulator for FM demodulating the output signal; a second FM modulator serving as a second transmission means; and a second magnetic recording and reproducing system for recording and reproducing the output signal.
a second FM demodulator for FM demodulating the output signal, a third FM modulator as a third transmission means, and a third magnetic recording and reproducing system for recording and reproducing the output signal;
3. The video signal transmission device according to claim 1, further comprising a third FM demodulator that performs FM demodulation of the output signal. (4) After time-base compressing each of the two output signals obtained from the two output terminals of the quadrature two-phase demodulation means and converting them into one-channel signals, as an alternative to the first and second transmission means,
Claim 1, characterized in that the transmitted signal is transmitted using a fourth transmission means, and the transmitted signal is time-axis expanded, converted into a two-channel signal, and then subjected to the quadrature two-phase modulation.
3. The video signal transmission device according to any one of Items 1, 2, and 3.