JPH012491A - comb filter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a comb filter used for processing video signals in VTRs and the like.

[Conventional technology] FIG. 2 is a diagram showing a conventional comb filter.

In the figure, (1) is the input terminal into which the lVpp video signal is input, (2) is the luminance signal output terminal, and (3) is the color signal output terminal.In the figure, DL+ has a band of 3.58MHz.
±800KHz delay line, Q++Lt, C++R3,
Ra and R5 constitute a phase distortion correction circuit (4) that corrects phase distortion caused by the delay line DLI.

Q2 is a buffer amplifier for video input signals.

Q3•RIIe C31Rlo + and R11 constitute a delay line insertion loss compensation amplifier (5) that compensates for loss in the delay line DL+. The output signals of the delay line DLI are R12, R13, RI4 . R15, and L3
The signal is input to the A and B ends of the bridge circuit (6) consisting of the following. The output signals of the delay line DLI are signals with opposite phases to the ground, and are connected to the bridge circuit (6).
A non-delayed video signal is applied to another end C of the buffer amplifier Q2, and the other end is grounded.

Addition and subtraction are performed in the bridge circuit (8), and an addition signal (one-time signal) is obtained at point A of the bridge circuit (8), a subtraction signal (color signal) is obtained at point B, and the buffer Amplifier Q4. output terminals (2) and (3) through Q5, respectively.
) is output.

[Problems to be Solved by the Invention] Conventional comb filters are expensive due to their complicated configurations, and it has been desired to realize an inexpensive comb filter.

The object of the present invention is to obtain a comb-shaped filter that has equivalent performance, is simple in construction, and is inexpensive.

[Means for Solving the Problems] The comb filter according to the present invention uses a glass delay line with a wide band, flat frequency characteristics, and low characteristic impedance, and has a high input level of a video signal. It is characterized by

[Operation] Since the delay line has a wide band and a flat frequency characteristic, a phase distortion correction circuit can be omitted. Furthermore, since the characteristic impedance of the delay line is low, buffer amplifiers for the luminance signal and color signal can be omitted.

Furthermore, since the input level of the video signal is increased, a delay line insertion loss compensation amplifier can be omitted.

[Embodiments of the invention] FIG. 1 is a circuit diagram of one embodiment of this generator 11.

In the figure, Q2 is a buffer amplifier, VR is a variable resistor connected between the output end of the buffer amplifier and the C terminal r of the bridge circuit (6), and L2 is connected between the sending end of the 8-wire DL+ and ground. The variable impedance DL+ is a glass delay line with a band of 3.58 MH2±1.1 M)12, a flat frequency characteristic, and a characteristic impedance that is about the same as a conventional delay line.

The filter circuit of this embodiment has a configuration in which the level of the input video signal is 4 to 5 Vpp, and the balance and characteristics of the input/output side are corrected by VRI and L2.

In this way, since the input level of the video signal is raised, a delay line insertion loss compensation amplifier can be omitted, and the glass delay line DLI has a wide band.

Moreover, since the frequency characteristics are flat, a phase distortion correction circuit can be omitted, and furthermore, since the characteristic impedance of the glass delay line DL+ is low, a buffer amplifier for the output signal can be omitted.

[Effects of the Invention] This invention uses a glass delay line that has a wide band, flat frequency characteristics, and low characteristic impedance as a delay line, and has a configuration in which a video signal is input at a high level, so that the characteristics can be improved. Since the phase distortion correction circuit, delay line insertion loss compensation amplifier, and output signal buffer amplifier can be omitted without any loss, a comb-shaped filter circuit with a simple configuration and low cost can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional comb filter. (8) Bridge circuit, DL, glass delay line, Q2 buffer amplifier, VRI T transformer, L2 variable inductance. Codes indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A buffer amplifier to which a video signal is input, a glass delay line having a wide band, flat frequency characteristics, and low characteristic impedance to which the output signal of this buffer amplifier is input, and a glass delay line connected to the sending end of this delay line. a variable resistor, a bridge circuit that outputs a sum signal and a difference signal of the input signal to the delay line through the variable resistor and the output signal of the delay line, and a bridge circuit at the sending end of the delay line. A comb filter comprising a connected variable inductance.