JPH05300056A - Crosstalk prevention circuit - Google Patents

Abstract

PURPOSE:To prevent crosstalk between input signals caused in a changeover circuit used to select plural kinds of different analog signals as signal sources such as a video signal and an audio signal. CONSTITUTION:Power from a power supply B21 to each of signal processing circuits 24-26 for input signals A, B, C is supplied only to the processing circuit selected by a 1st changeover circuit 27 for the substantial signal changeover and the power for the other signal processing circuits is interrupted. A 2nd changeover circuit 1 is switched interlockingly so as to select the same circuit as by the 1st changeover circuit 27. The interlocking changeover is implemented by using a switching signal 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for preventing crosstalk between input signals generated in a switching circuit for switching a plurality of different analog signals as a signal source such as a video signal or an audio signal.

[0002]

2. Description of the Related Art Conventionally, there are a plurality of signals as input signals, and when switching between them, a switching circuit as shown in FIG. 2 is generally used. FIG. 2 shows an example of switching three inputs. In FIG. 2, 21 to 23 are
Analog input signals A, B and C, 24-26 are independent signal processing (for example, amplification, buffer) circuits for each input signal, 27 is a switching circuit for switching signals from each signal processing circuit, and 28 is an output signal. Is. In addition, the power supply B is always provided to each signal processing circuit regardless of the switching position of the switching circuit 27.
21 are being supplied. When the switching circuit 27 selects, for example, the input A through the signal processing circuit A, so-called crosstalk occurs in which the components of the inputs B and C through the circuits B and C are mixed in the output signal 28. . This crosstalk similarly occurs when the switching circuit 27 selects another signal (for example, the input C). This crosstalk is greatly influenced by the performance of the switching circuit itself, and becomes more remarkable as the frequency of the input signal becomes higher.

[0003]

The above-mentioned crosstalk must be reduced as much as possible because an unwanted signal is mixed with the original signal selected. The present invention aims to provide one method of preventing such crosstalk.

[0004]

The present invention provides a switching circuit provided with a first switching circuit for switching a plurality of signals input via independent signal processing circuits, respectively. Provided is a crosstalk prevention circuit including a second switching circuit which is interlocked with switching and switches so that power is supplied only to the signal processing circuit corresponding to the signal selected by the first switching circuit.

[0005]

The power supply for each signal processing circuit is supplied only by the processing circuit selected by the first switching circuit. for that reason,
The second switching circuit interlocks and switches so as to select the same circuit as the first switching circuit.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A crosstalk prevention circuit according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of essential parts showing an embodiment of a crosstalk prevention circuit according to the present invention.
It shows an example of switching three inputs. In the figure,
2 are designated by the same reference numerals, 1 is a second switching circuit, and 2 is a switching signal for interlockingly switching the first switching circuit 27 and the second switching circuit 1.

Next, the operation of the present invention will be described. The basic idea of the present invention is to operate only necessary processing circuits,
The other processing circuits stop the operation by stopping the power supply. To this end, the configuration shown in FIG. 1 is provided and a second switching circuit is provided. The second switching circuit 1 selects the same processing circuit as the signal processing circuits (24 to 26) selected by the first switching circuit which performs the original signal switching. Therefore, the second switching circuit 1 is switched in conjunction with the first switching circuit 27 by the switching signal 2 which is common. As a result, the power (B21) is supplied only to the processing circuit selected by the first switching circuit 27, the other processing circuits are powered off, and the operation is stopped. Due to such operation stop, other input signals do not leak and mix (crosstalk) with the input signal selected by the first switching circuit. In the present embodiment, a so-called electronic switching circuit that switches both the first switching circuit 27 and the second switching circuit 1 by a switching signal is used. Technical effect can be obtained. The same applies to the case where the number of input signals is three or more.

[0008]

As described above, according to the present invention, in a switching circuit for switching a plurality of analog input signals having different signal sources, power is supplied only to a necessary circuit among the signal processing circuits provided for each input signal. Since the other circuits are supplied and the power is turned off, crosstalk between the input signals generated in the switching circuit or the like can be prevented. Therefore, in particular, it improves the switching isolation when switching a high frequency signal such as a video signal or an audio signal, and contributes to improving the performance of the switching circuit.

[Brief description of drawings]

FIG. 1 is a block diagram of essential parts of an embodiment of a crosstalk prevention circuit according to the present invention.

FIG. 2 is a principal block diagram showing an embodiment of a conventional switching circuit.

[Explanation of symbols]

 1 Second switching circuit 2 Switching signal 21 Input signal A 22 Input signal B 23 Input signal C 24 Signal processing circuit A 25 Signal processing circuit B 26 Signal processing circuit C 27 First switching circuit 28 Output signal

Claims (1)

[Claims] 1. A switching circuit provided with a first switching circuit for switching a plurality of signals input via independent signal processing circuits, the first switching circuit interlocking with the switching, 2. A crosstalk prevention circuit comprising a second switching circuit for switching so that power is supplied only to the signal processing circuit corresponding to the signal selected by the switching circuit.