JPH0265523A - Signal switch - Google Patents

Abstract

PURPOSE:To obtain a high attenuation characteristic at a narrow band with no continuity of the switch by connecting a resonance circuit comprising a capacitor and an inductor to a path of an AC signal, and configurating the resonance circuit which is interposed with the switch turning on/off part of the resonance circuit. CONSTITUTION:A signal path 1 is connected in series with an LC parallel resonance circuit comprising an inductor 2 and a capacitor 3 offering a capacitive component. Then the inductor 2 is connected in series with a diode 4 as a switch element and the diode 4 is driven by a transistor(TR) 5. With the TR 5 turned on and the diode 4 turned on, the inductor 2 and the capacitor 3 constitute the LC parallel resonance circuit, and a large attenuation is obtained by the Q of the LC resonance circuit regardless of the narrow band. Moreover, with the diode 4 turned off, an AC signal passes through the capacitor 3 as the path of the AC signal. Then the signal switch is applied to a communication equipment requiring high attenuation with narrow band.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal switch used in a communication device.

(Prior Art) Conventionally, signal switches used in communication equipment switch AC signals into conduction or non-conduction by turning on and off switching elements such as relays and diodes. For example, Fig. 3 is a circuit diagram showing an example of a conventional signal switch, in which a diode 24 as a switching element is inserted in the signal path 21, and the diode 24 is driven. A transistor 25 and a choke coil 26 are connected to the signal diameter B21.

In this configuration, when the transistor 25 is on, the diode 24 is turned on and the signal becomes conductive.

Furthermore, when the transistor 25 is turned off, the diode 2
4 is turned off and the signal becomes non-conductive.

[Problem to be solved by the invention]

An example of the characteristics of the conventional signal switch mentioned above is shown in FIG. In the figure, the vertical axis is the attenuation amount, and the horizontal axis is the frequency. The curves shown by broken lines here and here are characteristic examples of the signal switch mentioned above. As shown by this characteristic, the attenuation characteristic of the conventional signal switch when it is not conducting is wideband, but the amount of attenuation is small overall. The problem is that it is difficult to recruit.

An object of the present invention is to provide a signal switch that can obtain a high attenuation amount for narrowband signals.

[Means for Solving the Problems] The signal switch of the present invention connects a resonant circuit consisting of a capacitor and an inductor to the path of an AC signal, and the resonant circuit includes a switch that turns on and off a part of the resonant circuit. The structure is such that the following is inserted.

[Effect]

In the above-described configuration, the Q characteristic in the resonant circuit makes the attenuation characteristic during non-conduction a narrow band and high attenuation characteristic.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram for explaining the first embodiment of the present invention, in which a signal path 1 is connected in series with an LC parallel resonant circuit composed of an inductor 2 and a capacitor 3 as a capacitor. . A diode 4 as a switching element is connected in series to the inductor 2, and the diode 4 is connected to be driven by a transistor 5. Note that 6 is a choke coil.

According to this signal switch, when the transistor 5 is on and the diode 4 is on, the inductor 2 and capacitor 3
An LC parallel resonant circuit is constructed, and as shown in the characteristic shown by the solid line in FIG. 4, the Q of the LC resonant circuit allows a large attenuation amount to be obtained, albeit in a narrow band. Further, when the diode 4 is off, the AC signal passes through the capacitor 3, making the AC signal conductive.

Therefore, this signal switch can be applied to communication devices that require high attenuation in a narrow band.

FIG. 2 is a circuit diagram of a second embodiment of the present invention.

Here, an inductor 12 is connected between the signal path 11 and the ground.
Connect the capacitor 13 to configure an LC series resonant circuit,
Furthermore, a diode 14 is connected between this circuit. This diode 14 is connected to be driven by a transistor 15.

In this configuration, when the diode 14 is on, the inductor 12 and the capacitor 13 form an LC series resonant circuit,
As in the case of the first embodiment, a large amount of attenuation can be obtained in a narrow band. Further, when the diode 14 is off, the signal passes through the signal path 11.

〔Effect of the invention〕

As explained above, the present invention connects an LC resonant circuit to the signal path and inserts a switch that turns on and off a part of this resonant circuit, so that the resonance formed when the switch is turned on Due to the Q characteristic of the circuit, the attenuation characteristic when non-conducting has the effect of being able to obtain a high amount of attenuation in a narrow band.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a first embodiment of the present invention, Fig. 2 is a circuit diagram of a second embodiment of the invention, Fig. 3 is a circuit diagram of an example of a conventional signal switch, and Fig. 4 is a conventional circuit diagram. FIG. 3 is a diagram showing signal attenuation characteristics of the signal switch of the present invention. 1.11.21...Signal path, 2.12...Inductor, 3,13...Capacitor, 4,14.24...
・Diode (switch), 5.15.25...Transistor, 6,26...Choke coil. Figure 1 Figure 2

Claims (1)

[Claims] 1. In a signal switch that switches an AC signal into conduction or non-conduction, a resonant circuit consisting of a capacitor and an inductor is connected to the signal path, and a switch is connected to this resonant circuit to turn on and off a part of the resonant circuit. A signal switch characterized by the fact that it is inserted.