JPS5839126A - Noise eliminating device - Google Patents

Abstract

PURPOSE:To improve the eliminating capacity of an impulsive noise eliminating circuit, by arranging a filter circuit, which stops the passage of a continuously generated impulsive noise signal when this signal is received, in the output side of a single-generated noise pulse eliminating circuit. CONSTITUTION:When a single impulsive noise signal is included in the wave detection output from a wave detecting circuit 1, the output of a noise amplifier 8 is not changed much, and therefore, the level of the amplification degree control signal of an amplification degree controlling circuit 10 is low, and a switching transistor TR 14 is turned off, and a filter circuit 11 does not function. Consequently, the held level signal of a capacitor 4 for holding the storage which is provided in the output side of a switch 3 for eliminating the single noise pulse is sent to a voice part 6 as it is. When a continuously generated impulsive noise is included in the wave detection output, the switching TR 14 is turned on, and therefore, the noise signal which passes through the switch 3 erroneously is eliminated by a low pass filter consisting of a resistance 12 and a capacitor 13 and is not sent to the voice part 6.

Description

[Detailed description of the invention] The present invention relates to a noise removal device that accurately removes noise.

As a conventional noise removal device, for example, there is one shown in FIG. 1, which includes a detection circuit 1 that detects an intermediate frequency signal and outputs an audio signal, and a delay circuit 2 that delays the audio signal by a noise detection time, which will be described later. , the gate switch 3 that passes or blocks the delayed audio signal, and the sound just before the gate switch 3 blocks it.

A holding capacitor 4 that holds the voice signal and a buffer 1 line 5
an audio unit 6 that inputs an audio signal via the audio unit and emits audio;
A bypass filter 7 that passes the noise component when the audio signal contains noise, an amplifier 8 that amplifies the passed noise signal and outputs a cutoff signal, and a drive path that cuts off the audio signal in response to the cutoff signal. 9 (the above-mentioned noise detection time refers to the time from detecting the noise signal to turning off the gate switch 3), and when the output value of the $Peng amplifier 8 becomes large, the amplification degree of the amplifier 8 is It has an amplification control circuit 10 that controls the amplification of the amplifier 8 to increase when the output value becomes small.

This amplification control circuit prevents gate switch 1 from malfunctioning due to white noise generated inside the receiver when receiving in a weak electric field, preventing the audio signal from being output for a long time or worsening waveform distortion. , controls the gain of the M-sound amplifier 8.

In the above configuration, when the bypass filter 7 detects a noise signal in the audio signal, if the noise signal is a single-shot noise signal such as ignition noise, the amplifier 8 outputs a cutoff signal. to turn off the gate switch 3. By turning off the gate switch 30, the voltage held in the capacitor 4 is output to the audio section 6, thereby preventing the output of noise.

However, if the skeleton noise signal is a pulsed noise signal that occurs continuously in a short cycle, the control of the gate switch 3 of the amplifier 8 becomes unstable under the control of the amplification control circuit 10, and some of the noise leaks out. In addition, waveform distortion caused by the holding operation becomes noticeable.

In this way, there is a possibility that the noise component is inputted as is to the audio section 6 and generates harsh noise.

In view of the above, the present invention provides a noise removal device that is provided with a low-pass filter that blocks passage of continuously generated pulse noise when the noise occurs.

The noise removal device according to the present invention will be explained in detail below.

FIG. 2 shows an embodiment of the present invention, and since the same parts as in FIG. 1 are indicated by the same reference numerals, repeated explanation will be omitted. ] A filter circuit 11 that operates according to the output value of 0 is inserted before the audio section 6.

The filter circuit J] includes a resistor ]2 and a capacitor 13,
It consists of a switching transistor 4 with an input resistor 15.

In the above configuration, when a single pulsed noise signal is detected, the output of the noise amplifier 8 does not change much, so
Amplification control circuit Since the amplification control signal of 0 is small, the switching transistor 14 is not turned on, and the filter circuit 11 does not function, so the level signal held by the capacitor 4 is input to the audio section 6. On the other hand, when a continuously occurring pulsed noise signal is detected, the amplification control signal of the amplification control circuit 10 becomes large and the switching transistor 14 is turned on, so that the noise that has passed through the gate switch 3 is The high frequency components are blocked by the filter circuit 11). This allows noise-free audio to be output.

FIG. 3 shows a second embodiment of the present invention. In the first embodiment, the filter circuit j1 is composed of a capacitor ]3 and a field effect transistor 19 having a bias resistor 17.18. The effect transistor 19 acts as a resistor that continuously changes depending on the gate voltage.

In the above configuration, when the output value of the amplification control circuit 0 becomes large, the gate voltage of the field effect transistor 19 becomes large, and its resistance value becomes large. Therefore, the cutoff frequency of the filter circuit 1j becomes high ( Therefore, when a continuously generated pulse noise signal is input, the amplification control circuit 1
Since the Tagata value of 0 becomes large and the cutoff frequency of the filter circuit 1 becomes high, the noise component that has passed through the gate switch 3 is blocked by the filter circuit JIK and is not input to the audio section 6.

Although the above example has been explained using a complete holding circuit using the gate switch 3 and the holding capacitor 4, it is not limited to this.
It may be an incomplete holding circuit in which a resistor (which constitutes the holding capacitor 4 and the Hass filter) is connected in parallel with the gate switch 3, or a resistor whose resistance value can be changed electronically may be used in place of the gate switch 3. together with the capacitor 4 to form a four-bass filter whose cut-off frequency can be varied.

As explained above, according to the noise removal device according to the present invention, a filter circuit is provided that blocks the passage of a nuclear signal according to the output of the amplification control circuit that is activated when there is a continuously generated pulse noise signal. Therefore, it is possible to accurately remove pulse noise that occurs continuously in a short period.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional noise removal device, and FIGS. 2 and 3 are explanatory diagrams showing a second embodiment of the present invention. Explanation of symbols 1... 1 detection path 2... Delay circuit 3... Gate switch 4... Holding capacitor 5... Buffer circuit 6... Audio section 7... Bypass filter
8...Amplifier 9...Drive circuit 10...Amplification production control m circuit 11...Filter circuit

Claims (1)

[Claims] A bypass filter i that detects noise from an input audio signal and outputs a noise signal; and a noise amplification i that amplifies the noise signal and outputs a cutoff signal.
an amplification control circuit that outputs an amplification control signal for controlling the cutoff signal to a predetermined level to the saddle sound amplification port; In a noise removal device having a gate switch circuit that passes or blocks a signal, and a holding circuit that holds the level of the audio signal immediately before the cutoff when the gate switch circuit blocks passage of the delayed audio signal, the amplification control signal 1. A noise removal device comprising a filter circuit that attenuates high-frequency components of the output signal of the first holding path in accordance with the above.