JPS6134718B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for separating interpolation multiplexed signals, and particularly for separating a video signal in the NTSC color television system into a luminance signal and a chrominance signal when used in a video device that uses different frequency bands. The present invention relates to a separation circuit for separation.

For example, in a video signal in the NTSC color television system, a color signal is interpolated and multiplexed in the form of a carrier signal onto the high frequency portion of a luminance signal.

Therefore, unless the luminance signal and color signal are completely separated using a bandpass filter or the like, they will interfere with each other and degrade the image quality.

Normally, if the color signal is simply extracted from the video signal using a bandpass filter centered around the carrier frequency of the color signal, the high frequency components of the luminance signal contained in this signal will become color noise and cause cross color interference. cause. Furthermore, if the carrier color signal remains in the high frequency component of the luminance signal, dot interference will occur.

Conventionally, in order to reduce these interferences, the transmitting side lowers the high-frequency components of luminance, and the receiver's luminance signal amplification system lowers the high-frequency amplification.
All of these methods involve a decrease in resolution and cannot be said to be optimal means.

Recently, research has been carried out to remove these interferences using a comb-type filter that uses an ultrasonic solid-state delay line.As shown in Figure 1, the video signal input from input terminal 1 is The horizontal scanning time is delayed and the color signal is synthesized with the direct signals from the bypass circuits 3 and 4 to obtain a difference signal between the two.The color signal is extracted from the output of the C-type filter 5, and the luminance signal is obtained from the output of the Y-type filter 6, which obtains the sum signal of both. A circuit to extract the signal has been developed.

According to this circuit, a video signal, a color signal, and a luminance signal are converted into a video signal, a color signal, and a luminance signal by a combination of a C-type filter with the characteristics shown in FIG. 2 and a Y-type filter with the characteristics shown in FIG. can be separated into

On the other hand, in general, in order to operate a solid-state delay line, such as a glass delay line, it is necessary to insert an anti-resonant coil in parallel with the input/output transducer, which allows the glass delay line to This shows bandpass characteristics with a cut region. Therefore, if the passband of the glass delay line is set to a range centered on the frequency band of the color signal, the low-frequency component of the luminance signal is blocked in the circuit shown in FIG.
It is necessary to separately provide a low-pass filter and mix it with the luminance signal output shown in FIG.

However, in such a mixing circuit, it is difficult to accurately phase match the signals, and because the frequency characteristics are not flat, ghost-like ringing appears on the screen, especially due to the transient response of the glass delay line. It requires a complicated circuit, which increases costs, and it has not yet been put into practical use.

Improvements to comb filters have also been proposed (Japanese Utility Model Application Publication No. 157839/1983), but since the frequency characteristics do not become flat, multiple processes are required.
Moreover, there is a drawback that other characteristics are also deteriorated.

Generally, when video devices that use different frequency bandwidths are used in combination, it is necessary to adjust the bands to suit each device.

For example, each channel of NTSC television is assigned a frequency band of 6 MHz width, while a video tape recorder may have a frequency bandwidth of only 4 MHz for each channel.

Therefore, in order to use the video input signal of television broadcasting as the video signal of a video tape recorder, it is necessary to limit the high frequency band of the video signal, for example, in the luminance signal and color signal separation circuit in the video tape recorder. I'm getting older.

As such a frequency band limiting circuit, the circuit shown in FIG. 4 is conventionally known.

This circuit separates a video input signal 7 into a luminance signal and a chrominance signal using a comb filter 8 (Fig. 1), extracts the luminance signal using a well-known emitter follower circuit 9, and extracts the low frequency band using a low-pass filter LPF. It is configured to pass through and cut out the high frequency band. Here, the color signal is separately output from a terminal (not shown).

However, in such a band-limiting circuit,
Transistors T ₁ and T ₂ are used to remove the phase distortion of the signal caused by passing it through the low-pass filter.
It becomes necessary to provide a phase correction circuit 10 consisting of the following. This has resulted in the disadvantage that the circuit configuration is complicated and expensive.

In addition, in color video tape recorders, the bandwidth of the color signal reproduction circuit is narrower than that of the luminance signal, so the signal delay time is large, and to compensate for this, a delay line must be inserted in the luminance signal amplification circuit. , which required an extra number of amplification stages.

The present invention has been made to solve the above-mentioned difficulties, and consists of a series circuit consisting of an input transducer of an ultrasonic solid-state delay line and a partial voltage load connected in series with the input transducer, and a luminance signal and a color signal are transmitted. A composite video input signal included is applied across the series circuit, and the delayed output signal from the output transducer of the ultrasonic solid state delay line and the signal across the voltage divider load are combined to determine the luminance. It is an object of the present invention to provide an interpolation multiplex signal separation circuit comprising a comb filter for obtaining a signal and a color signal, and an LC type delay line directly connected to the output end of the luminance signal of the comb filter.

Examples of the present invention will be described in detail below.

As shown in the block diagram of FIG. 5, the comb-type filter using a glass delay line used in the present invention transmits an input signal from a signal power source 11 to an input transducer 13 of an ultrasonic solid state delay line 12. The delayed output signal obtained from the output transducer 13' of the delay line 12 is applied across the divided voltage load 14 connected in series, and the delayed output signal obtained from the output transducer 13' of the delay line 12 and the divided voltage load 14 are
The configuration is such that the signals at both ends of the signal are combined to obtain a sum signal and a difference signal between the two. That is, in FIG.
4, and at low frequencies below the passband of the delay line, the signal applied to both ends of the divided voltage load is sent to the output side, and within the passband of the delay line, the above-mentioned comb filter characteristics are used. This effectively separates the interpolated multiple input signal into two.

Further, the LC type delay line used in the present invention is a delay line using a lumped constant circuit or a distributed constant circuit including a coil L, a capacitor C, etc.

Next, a specific embodiment of the present invention will be described in the case where a color television video signal is input to a video tape recorder.

As shown in FIG. 6, the comb filter 16 has the glass delay line 17 and the midpoint 20 of the anti-resonator coil 19 inserted in parallel with the input transducer 18 of the glass delay line 17 grounded by a capacitor 21. The midpoint 2 of the inductive M-type circuit, the partial voltage load 22 connected in series to the input transducer 18 and the anti-resonant coil 24 inserted in parallel to the output transducer 23 of the glass delay line 17
5 is grounded by a capacitor 26, and an inductive M type circuit,
The voltage of the divided voltage load 22 is transferred to the anti-resonator coil 2.
and a level adjustment circuit 27 that leads to the midpoint 25 of 4.

Here, as the level adjustment circuit 27, a well-known fixed resistor or a volume resistor can be used, but if an emitter follower circuit is used, the input circuit and the output circuit are less likely to interfere with each other, and moreover, the output functions as a current source. This makes it easy to adjust the volume.

Note that 28 is a composite video input signal power supply containing a luminance signal and a color signal, and 29 and 30 are resistors.

The LC type delay line 31 is directly connected to the luminance signal output terminals 33, 33' of the comb filter.
A luminance signal output terminal YY is provided at the output end of 1. In addition, the coil side of the input end of the LC type delay line 31 is connected to the anti-resonate coil 24, and the capacitor side is grounded.
A new delay line may be configured with the capacitor 26 and the LC type delay line 31. In this case, the anti-resonate coil 24 will be configured as a part of the LC type delay line.

In addition, YY is the output terminal of the luminance signal, CC is the output terminal of the color signal, 32 is the characteristic impedance, L, C
are a coil and a capacitor, respectively.

Next, the operation of this circuit will be explained.

In a video signal, a luminance signal and a chrominance signal are multiplexed within the same frequency band, but the energy of the luminance signal is mainly concentrated in low frequencies, and the chrominance signal is
It is concentrated around 3.58MHz. Therefore, as an ultrasonic solid-state delay line, the pass frequency band is approximately 2.5 to 4.5M.
Hz, a glass delay line with a center frequency of 3.58MHz was used.

The input signal from the signal power source 28 is applied across the input transducer 18 and the voltage dividing load 22 connected in series thereto, and from the output transducer 23, a comb-shaped characteristic centered at 3.58 MHz is applied. A delayed output signal having . This delayed output signal is combined with the video signal sent out through the level adjustment circuit, and by taking the difference, a color signal is obtained at the terminal CC, and by taking the sum, the color signal is obtained at the terminal CC.
A delayed luminance signal is obtained which is delayed by the LC type delay line 31 in YY and has the high frequency band removed. Here, the reason why the high frequency range of the luminance signal is deleted is because the LC type delay line constitutes a low-pass filter depending on the density of the interstage coupling.

Therefore, the obtained delayed luminance signal has a compressed band and becomes a signal suitable for color videotape.

The delay time of the luminance signal of the LC type delay line is set to the delay time necessary for phase adjustment of the luminance signal and color signal. Then, the delay time is proportional to the circuit constant and the number of stages, so the number of stages of the LC type delay line is selected in advance so that it is the same as the delay time of the delay line installed in the conventional processing circuit such as a luminance signal amplifier. By delaying the luminance signal by the necessary time, the conventional delay line provided in the processing circuit can be omitted.

As explained above, according to the present invention, since a partial voltage load is configured in series with the transducer of the delay line, the frequency characteristics are flat, and the anti-resonant coil is formed as a part of the LC type delay line. As a result, the frequency band can be narrowed, the frequency band can be narrowed, and it can be manufactured compactly and at low cost.In addition, the interstage coupling of the LC type delay line provides low-pass filter characteristics, so the phase It has very good characteristics, does not require a phase correction circuit like the conventional one, and has the effect of omitting the delay line provided in the conventional luminance signal processing circuit by setting an appropriate number of stages.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional comb filter, Figures 2 and 3 are passband characteristic diagrams of the filter shown in Figure 1, and Figure 4 is a conventional interpolation multiplex signal separation circuit with a limited frequency band. Figure 5 is
A basic embodiment diagram of a comb filter used in the present invention, and FIG. 6 is a wiring diagram of a specific embodiment of the present invention. 12, 17... Glass delay line, 16... Comb filter, 18, 23... Transducer, 1
9, 24...Anti-resonate coil, 31...
LC type delay line, 33, 33'...output end, YY...
Output terminal for luminance signal, CC...Output terminal for color signal.

Claims (1)

[Claims] 1 Consists of a series circuit consisting of an input transducer of an ultrasonic solid state delay line and a partial voltage load connected in series with the input transducer, and a composite video input signal containing a luminance signal and a color signal is applied to both ends of the series circuit. a comb-shaped filter that combines the delayed output signal obtained from the output transducer of the ultrasonic solid-state delay line and the signals at both ends of the partial voltage load to obtain a luminance signal and a color signal; An interpolation multiplex signal comprising: an LC type delay line directly connected to the output end of the luminance signal of the filter and having low-pass filter characteristics, a part of which constitutes an anti-resonant coil of the output transducer. separation circuit.