JPH02312471A - Noise elimination device - Google Patents

Abstract

PURPOSE:To avoid rounded large amplitude part and attenuated level of a small signal part by providing a trap circuit comprising a capacitive element and an inductive element into a main transmission line and providing a high pass filter, a detector and a control circuit into a sub transmission line. CONSTITUTION:A trap circuit 10 comprising a capacitive element 5 and an inductive element 6 is provided in a main transmission line, and a high pass filter 2, a detector 3 detecting a level of an output signal of the high pass filter 2 and a control circuit 8 controlling the trap circuit 10 with an output signal of the detector 3 are provided to the sub transmission line. Since the trap circuit 10 provided to the main transmission line is controlled with a control signal outputted from the detector 3 detecting a reproduced video signal including noise, signal high frequency component and noise component, rounded edge of the signal after noise elimination or attenuation of a level of a small signal part is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic reproducing apparatus (hereinafter referred to as a VTR) that frequency-modulates a video signal and records and reproduces it using a magnetic tape as a recording medium.
This relates to noise removal (abbreviated as ).

2. Description of the Related Art An example of the above-mentioned conventional noise removal device will be described below with reference to the drawings.

FIG. 2 shows a block diagram of a conventional noise removal device. FIG. 4 is a waveform diagram of each part of FIG. 2.

A reproduced signal from a VTR containing noise as shown in FIG. 4(A) is inputted from an input terminal 1. The high-pass filter No. 2 extracts high frequency components from the signal shown in FIG. 4(A) and outputs a signal as shown in FIG. 4(B). The limiter 12 is shown in FIG. 4(B).

It is limited at the limiter level shown in C, and a signal as shown in FIG. 4(C) is output. The subtracter 11 subtracts the output signal of the limiter 12 shown in FIG. 4(C) from the reproduced video signal shown in FIG. 4(A), and outputs the signal shown in FIG.
D) Outputs a signal in which the noise in the flat part of the input reproduced video signal containing noise has been removed.

Problems to be Solved by the Invention However, in the above configuration, 1 in FIG. 4(D)
As shown in FIG. 1, the large amplitude part (edge part) of the video signal is blunted, and in the video signal part shown in FIG.
, the output amplitude at the output terminal 9 is g, then g=a−f, and the signal amplitude of the high-frequency small signal portion is attenuated, but the level of the noise component remains unchanged, and the S/F of the small signal portion is attenuated.
N deteriorates. In addition, in the frequency characteristics of the noise level below the limiter level, peaks as shown in Figure 6 occur in the main transmission line, sub-transmission line, and frequency F, and the S/
N has problems such as deterioration.

Means for Solving the Problems In order to solve the above-mentioned problems, the noise removal device of the present invention is provided with a trap circuit constituted by a capacitive element and an inductive element in the main transmission line, and a trap circuit in the sub-transmission line. The present invention includes a high-pass filter, a detector that detects the level of an output signal of the high-pass filter, and a control circuit that controls the trap circuit using the output signal of the detector.

Operation The present invention controls the trap circuit provided in the main signal path by the control signal output from the detector that detects the reproduced video signal containing noise, the high-frequency component of the signal, and the noise component. Therefore, the edge portions of the signal after noise removal will not become dull, and the level of the small signal portion will not be attenuated.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a noise removal device according to the present invention. In FIG. 1, parts with the same reference numerals as those in FIG. 2 are the same or equivalent parts, and therefore their explanation will be omitted. 3 is a detector, 4 and 7 are resistors, 5 is a capacitive element,
6 is an inductive element, 8 is a switching circuit, and 10 is a trap circuit.

In the noise removal device of the present invention configured as described above, a reproduced video signal containing noise as shown in FIG. 3(A) is input to input terminal 1, and ten trap circuits and two 1 pass filter. The trap circuit 10 is composed of 4 and 7 resistors, 5 capacitive elements, and 6 inductive elements. 2! - In the i-pass filter, as shown in FIG. 3(B), high-frequency components of the input signal are extracted and output to the detector 3. In the detector No. 3, when the signal level of the input signal shown in FIG. 3(B) is greater than b and less than C,
), otherwise a control signal as shown in FIG. 3(C) is supplied to the switching circuit 8, which is Hi. The switching circuit 8 operates to turn on the trap circuit 10 when the control signal shown in FIG. 3(C) is Hi, and turns off the trap circuit 10 when the control signal is Lo. Therefore, as shown in FIG. 3(D), the output terminal 9 has the following
When the noise component in the flat part is removed, the large amplitude part (edge part) shown in e is not dulled, and the amplitude of the small signal part of the input signal is a, the small signal part of the output signal is The amplitude d of is set to a=d, and a signal without deterioration of the S/N of the small signal portion is output.

Effects of the Invention As described in ``2'', the present invention includes a trap circuit constituted by a capacitive element and an inductive element in the main transmission line,
The sub-transmission line includes a high-pass filter, a detector that detects the level of the output signal of the high-pass filter, and a control circuit that controls the trap circuit using the output signal of the detector. Also, in the small signal portion, the trap circuit for noise removal provided in the main transmission path is turned off, so that the large amplitude portion is not dulled and the level of the small signal portion is not attenuated. In addition, since noise removal is performed by a trap circuit installed in the main transmission path, the minute signal frequency characteristics of the noise level are as shown in Figure 5, which is an excellent feature in that there are no peaks or rises in the frequency characteristics. You can get the desired effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a noise removal device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of each part of a conventional example, FIG. 5 is a frequency characteristic diagram of the noise removal device of this embodiment, and FIG. FIG. 3 is a block diagram of a conventional noise removing device, FIG. 3 is a waveform diagram of various parts in the present embodiment of FIG. 1, and FIG. 4 is a frequency characteristic diagram of the conventional noise removing device shown in FIG. 1... Signal input terminal, 2... High pass filter, 3... Detector, 4, 7...
Resistor, 5... Capacitive element, 6... Inductive element, 8... Switching circuit, 9... Signal output terminal. Name of agent: Patent attorney Shigetaka Awano (1 person) 1st figure 2nd figure 3rd figure 4th figure

Claims (1)

[Claims] A trap circuit composed of a capacitive element and an inductive element is provided in the main transmission line, and the sub transmission line includes a high-pass filter, a detector for detecting the level of the output signal of the high-pass filter, and a trap circuit for detecting the level of the output signal of the high-pass filter. A noise removal device comprising a control circuit that controls the trap circuit using an output signal.