JPH0722905A - Noise elimination filter - Google Patents

Abstract

PURPOSE:To obtain a noise elimination filter having little lag in a signal processing. CONSTITUTION:From the signal transmitting the signal line 1 of a digital circuit, noise component is separated in a noise filter circuit 2, and the phase of the separated noise component is reversed relative to the noise component transmitted through the signal line 1. Subsequently, the noise component whose phases is reversed is added to the original signal transmitted through the signal line 1, and the noise component of the original signal is eliminated by cancellation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention separates a noise component from a signal transmitted through a digital circuit, and generates a noise component having an opposite phase from the separated noise component.
The present invention relates to a noise removal filter that removes a noise component in a signal by synthesizing an antiphase noise component with a signal transmitted through a digital circuit.

[0002]

2. Description of the Related Art In recent years, various circuits such as a plant control device are often composed of digital circuits.
In these digital circuits, an unwanted noise component may be superimposed on a signal to be transmitted due to a signal jumping in from the surroundings or opening / closing of a power supply. As a method for removing such a noise component, conventionally, a synchronous circuit for synchronizing a signal in a digital circuit with a clock signal is used, or a filter circuit including passive elements such as capacitors, resistors, and inductors is used. There is a method of letting it escape to the ground.

[0003]

By the way, in the method using the synchronous circuit, the signal transmitted in the digital circuit is synchronized with the clock signal. In this method, since the clock signal has a time delay with respect to the signal transmitted in the digital circuit, the signal transmission is delayed accordingly.

Further, in the method of using a filter circuit composed of passive elements such as capacitors, resistors and inductors, and releasing the noise component to the ground, there is a time delay in the rise and fall of the signal in the filter circuit, and There is a delay in processing.

It is an object of the present invention to provide a noise elimination filter with less delay in signal processing.

[0006]

A noise removal filter of the present invention comprises a separation circuit for separating a noise component from a signal transmitted through a signal line of a digital circuit, and the phase of the noise component separated by the separation circuit is the above-mentioned. A phase adjustment circuit that adjusts the phase of the noise component separated by the separation circuit and a noise component whose phase is adjusted by the phase adjustment circuit so that the noise component transmitted in the signal line has an opposite phase. ,
And a synthesizing circuit for adding to the signal transmitted through the signal line.

[0007]

According to the above construction, the noise component is separated from the signal transmitted through the digital circuit, and the noise component having the opposite phase to this is generated from the separated noise component. And
The antiphase noise component is combined with the original signal of the digital circuit. At the time of this synthesis, the noise component of the signal transmitted through the digital circuit is canceled by the noise component of the opposite phase. Therefore, unlike the case of using a synchronous circuit or using a filter circuit composed of passive elements, there is little time delay, and high-speed signal processing can be supported.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention. Reference numeral 1 is a signal line constituting a digital circuit. The signal line 1 is branched at a point A, and the noise filter circuit 2 is connected to the branched line. The output side of the noise filter circuit 2 is connected to the point B of the signal line 1.

The noise filter circuit 2 detects the phase of the noise component separated by the noise separation circuit 21 and the noise separation circuit 21 for separating the noise component from the signal signal branched as shown in FIG. It is composed of a phase adjusting circuit 22 which adjusts the noise component of the signal transmitted through the line 1 (FIG. 1) so as to have an opposite phase. The noise separation circuit 21 that separates the noise component is composed of, for example, a capacitor, and points A and B in FIG. 2 correspond to points A and B in FIG. 1, respectively.

In the noise removal filter having the configuration shown in FIG. 1, the digital signal S as shown in FIG. 3A is transmitted to the signal line 1, and the noise component N is superposed on the digital signal S. To do. The horizontal axis of FIG. 3 represents time t,
The vertical axis represents the signal magnitude.

At this time, the noise component N of the digital signal S transmitting the point A (FIG. 1) is separated by the noise separation circuit 21 (FIG. 2) which constitutes the noise filter circuit 2. In addition, the separated noise component has a phase adjustment circuit 22.
Added to. Then, the phase adjusting circuit 22 adjusts the phase of the separated noise component N so as to be opposite to the phase of the noise component N of the digital signal S transmitted through the signal line.

For example, when the noise separating circuit 21 is composed of a capacitor, the noise component N advances by π / 2 radian phase in the noise separating circuit. Therefore, the separated noise component N is the noise component N of the signal S transmitted through the signal line.
In contrast, the phase adjusting circuit 22 further advances the phase of the noise component N by π / 2 radians so that the phase becomes opposite.

As a result, when viewed from the output side of the phase adjustment circuit 22, the phase of the noise component N is as shown by the solid line in FIG. The size is the same, but the phase is reversed.

The noise component whose phase is adjusted by the phase adjusting circuit 22 is combined with the original signal S transmitted through the signal line 1 at the point B in FIG.

At this time, the noise component N of the signal transmitted through the signal line 1 has a phase opposite to that of the noise component N added from the noise filter circuit 2 and therefore cancels each other out. The signal S from which the noise component N has been removed is shown in FIG.

In the above embodiment, the phase adjusting circuit 2
At 2, the phase of the noise component is advanced by π / 2 radians. However, the phase adjustment in the phase adjustment circuit 22 is performed so that the phase of the noise component is opposite to the noise component of the signal transmitted through the signal line, and the phase adjustment amount configures the noise filter circuit 2. It is appropriately determined according to the circuit conditions to be used.

In the above embodiment, by adding a circuit for appropriately adjusting the magnitude of the noise component separated by the noise filter circuit 2, a noise removal filter compatible with various digital circuits can be realized. .

[0019]

According to the present invention, it is possible to obtain a noise elimination filter with a small time delay.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram illustrating an example of a noise filter circuit used in the present invention.

FIG. 3 is a waveform diagram illustrating an example of the present invention.

[Explanation of symbols]

 1 ... Signal line 2 ... Noise filter circuit 21 ... Noise separation circuit 22 ... Phase adjustment circuit

Claims (1)

[Claims] 1. A separation circuit for separating a noise component from a signal transmitted through a signal line of a digital circuit, and a phase of the noise component separated by the separation circuit is opposite in phase to a noise component transmitted through the signal line. And a phase adjusting circuit for adjusting the phase of the noise component separated by the separating circuit, and a combining circuit for adding the noise component whose phase is adjusted by the phase adjusting circuit to a signal transmitted through the signal line. And a noise removing filter, which removes a noise component of a signal transmitted through the signal line.