JPH03235583A - Noise reduction circuit - Google Patents

Abstract

PURPOSE:To attain noise reduction processing at a minute level by outputting an output of a band pass filter when an input of a limiter is less than an optional level and outputting a signal smaller than a reference level other than zero when the input of the limiter is larger than the optional level. CONSTITUTION:When a signal outputted from an absolute section 11 is less than a reference value inputted from a reference value input terminal 13, a comparator 14 regards the signal as a noise component and control a selector 15 and a signal inputted to an input terminal 10 is outputted as it is from an output terminal 16. When the signal outputted from the absolute value section 11 is larger than the reference value inputted from the reference input terminal 13, the selector 15 is controlled so that a level other than 0 outputted by an offset generating section 12 and smaller than the reference value inputted from the reference value input terminal 18 is outputted from the output terminal 16. Thus, the noise reduction processing of a minute level is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a noise reduction circuit for removing noise contained in a signal.

2. Description of the Related Art The structure of a conventional noise resolver circuit and a limiter of a noise reducer circuit are shown in FIGS. 3 and 2.

In FIG. 2, 10 is a limiter input terminal, 11 is an absolute value section that outputs the absolute value of the input signal, 14 is a comparator, and 13
1 is a reference value input terminal of the comparator, 17 is a switch, and 16 is a limiter output terminal.

In Fig. 143, 1 is a signal input terminal, 2 is a bandpass filter that extracts a frequency band containing noise components in the input signal, and 3 is a limiter whose configuration is shown in Fig. 2.
4 is a subtracter that subtracts the output of limiter 3 from the input signal;
Reference numeral 5 denotes a delay element that corrects the delay time generated by the processing of the bandpass filter 2 and limiter 3, and adjusts the time of the reproduced video signal in the subtracter and the output of the limiter.

The operation of the conventional noise reduction circuit will be described below with reference to FIGS. 2 and 3.

In FIG. 3, a signal input from an input terminal 1 is supplied to a bandpass filter 2 and a delay element 5. The bandpass filter 2 extracts a signal in the frequency band including noise components from the signal supplied from the input terminal 1, and outputs it to the limiter 3 shown in FIG.

In the limiter 3 shown in FIG. 2, the limiter input terminal 1
After the signal inputted from 0 is converted into an absolute value by the absolute value section 11, it is compared with the reference value inputted from the reference value input terminal 13 by the comparator 14. When the output of the absolute value section 11 is less than or equal to the reference value input from the reference value input terminal 13, the comparator 14 treats it as a noise component and controls the switch 17, and the limiter output terminal 16 is connected to the limiter input terminal. 10
so that the input signal is output as is. Further, the output of the absolute value section 11 is inputted from the reference value input terminal 13! If it is larger than the value, the switch 17 is controlled so that the output from the output terminal 16 becomes O. The output of this limiter 3 is input to a subtracter 4, where it is subtracted by a delay element 5 from the input signal delayed by the time delay caused by the processing of the bandpass filter 2 and limiter 3, thereby performing noise reduction processing. It will be done.

Problems to be Solved by the Invention However, the noise reduction circuit described in the conventional example determines whether the input signal is a noise component or not based on the magnitude of the amplitude level of the signal extracted by the band-pass filter. Therefore, for example, if a signal with a large amplitude level contains a very small level of noise, there is a problem in that the very small level signal is not considered as noise.

Means for Solving the Problems In order to solve the above problems, the present invention has a limiter of a noise reduction circuit that outputs the output of the bandpass filter as it is when the input is below an arbitrary amplitude level, If it is larger than the reference value, a signal other than O is output with an amplitude level smaller than the reference value.

Effect of the Invention The present invention has the above-described configuration, and even when the input signal to the limiter in the noise reduction circuit has a large amplitude level, and furthermore, the input signal contains minute level noise, it is possible to perform noise reduction processing at that minute level. It is something to do.

EXAMPLES Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 3.

FIG. 1 is a diagram showing the configuration of a limiter of a noise reduction circuit according to the present invention.

In FIG. 1, 10 is a limiter input terminal, 11 is an absolute value section that outputs the absolute value of the input signal, and 12 is an offset generation section that outputs a value other than O that is smaller than the reference value input from the reference value input terminal 13. , 14 is a comparator, 13 is a reference value input terminal of the comparator, 15 is a selector that outputs the limiter input signal supplied from the output of the offset generator 12 and the limiter input terminal 10, and 16 is a limiter output terminal. be.

The operation of the conventional noise resolution circuit will be described below with reference to FIGS. 2 and 3.

In FIG. 3, a signal inputted from input terminal 1 is supplied to bandpass filter 2 on one side and delay element 5 on the other. The bandpass filter 2 extracts a signal in a waste wave number band containing noise components from the supplied signal. The output signal of this Hunt'pass filter 2 is input to a limiter 3 shown in FIG.

In the limiter 3 shown in FIG. 1, the input signal is converted into an absolute value in an absolute value section 11, and then compared with a reference value inputted from a reference value input terminal 13 in a comparator 14. When the signal output from the absolute value section 11 is less than the reference value input from the reference value input terminal 13, the comparator 14 treats it as a noise component, controls the selector 15, and inputs the signal from the output terminal 16 to the input terminal 10. If the signal output from the absolute value unit 11 is larger than the reference value input from the reference value input terminal 13, the reference value other than 0 output by the offset generation unit 12 is output. The selector 15 is controlled so that the output terminal 16 outputs a value smaller than the reference value manually input from the input terminal 13. The output of the limiter 3 in FIG. 1 is input to a subtracter 4,
Here, noise reduction processing is performed by subtracting the input signal delayed by the time delay caused by the processing of the bandpass filter 2 and limiter 3 by the delay element 5. At this time, the limiter 3 shown in FIG.
The output always has a value other than ◯, and the subtracter 4 also performs noise reduction processing on minute amplitude level noise included in the large amplitude level video signal.

Effects of the Invention As described above, the present invention allows the limiter of the noise reduction circuit to output the output of the band pass filter as is when the input is below a given amplitude level, and to use a reference value other than O when the input is greater than the given amplitude level. By configuring the noise reduction circuit to output a signal with an amplitude level smaller than the limiter value, even if the input signal to the limiter has a large amplitude level and the input signal contains a small level of noise, the This enables level noise reduction processing.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a limiter in a noise reduce circuit according to an embodiment of the present invention, FIG. 2 is a block diagram of a limiter in a conventional noise reduce circuit, and FIG. 3 is a block diagram of a noise resolver circuit. 1...Input terminal, 2...Band pass filter, 3...Limiter, 4...Subtractor, 5...Delay element, 6...Output terminal, 1o...IJ Mitter input terminal, 11...
... Absolute value part, 12 ... Offcent occurrence part, 1
3...Reference value input terminal, 14...Comparison section, 15...Selector, 16...Limiter output terminal, 17...Switch .

Claims (1)

[Claims] A band-pass filter extracts an arbitrary frequency component of an input signal, and if the output of the band-pass filter is below an arbitrary amplitude level, the output of the band-pass filter is output as is, and when it is larger than an arbitrary amplitude level, it is output as 0. A noise characterized by comprising: a limiter that outputs a signal with an amplitude level smaller than a reference value; a delay element that adjusts a delay time; and a subtracter that subtracts the output of the limiter from the input signal. reduce circuit.