JPH0348694B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is connected to the antenna input terminal of a home television receiver, for example, and is capable of inputting a signal into the television receiver into either a television broadcast signal or a video disc signal. This invention relates to a high frequency signal switching device used for switching between signals.

2. Description of the Related Art Conventionally, this type of high frequency signal switching device has had a configuration as shown in FIG. In Fig. 1, when forward bias is supplied to diode 1 and transistor 2 from power supply B, the signal from input terminal 3 that inputs television broadcasting is blocked by transistor 2, and the input terminal that inputs video disc signals The signal from terminal 4 was passed through and output from output terminal 8 to be supplied to the antenna terminal of a television receiver (not shown) so that a video playback screen could be viewed.

On the other hand, when reverse biased or the power is off, the signal from the input terminal 4 that inputs the video disc signal is blocked by the diode 1, and the signal from the input terminal 3 that inputs the TV broadcast is blocked by the inductance element. The signal is sent to an output terminal 8 through a low-pass filter consisting of 5, 6 and a capacitor 7, and the television receiver can receive the television broadcast.

Note that this low-pass filter is designed to transmit up to the highest frequency range of television broadcast waves. Its function is to eliminate the effects of turning on and off the transistor 2 and to transmit television broadcast waves without loss.

Here, 9 and 10 are DC blocking capacitors, 1
Reference numeral 1 denotes a high frequency choke coil, 12 and 13 resistors for supplying DC bias, and 14 a high frequency bias capacitor.

Problems to be Solved by the Invention However, in such a conventional high frequency signal switching device, when a forward bias is supplied to the transistor 2 and the diode 1 by the B power supply as shown in FIG. It will be grounded by transistor 2.

The equivalent circuit at this time is shown in FIG.
In FIG. 2, the inductance element 5 has low impedance in the low range. Therefore, input terminal 4
As for the transmission characteristics from the output terminal 8 to the output terminal 8, the loss increases in the low frequency range, and there is a problem in that the signal of the video disc using the relatively low frequency range (1ch/2ch) is attenuated.

Furthermore, when capacitors are used in place of the inductance elements 5 and 6, and an inductance element is used in place of the capacitor 7, the capacitor used in place of the inductance element 5 has a low impedance in the high frequency region. In this case, even if the output signal of the video disk has a relatively low frequency, there is a problem in that this loss affects the transmission loss of the output frequency of the video disk.

The present invention solves these conventional problems by improving the loss in the low frequency range due to the inductance element used in the circuit on the input terminal side or the high frequency loss due to the capacitor, and reducing the loss between the input terminal and the output terminal. The purpose is to improve the transmission characteristics of

Means for Solving the Problem In order to achieve this object, in the high frequency signal switching device of the present invention, a plurality of reactance elements are connected in series between a first input terminal and an output terminal, and the plurality of reactance elements are connected in series between a first input terminal and an output terminal. A signal switching active element is connected between the intermediate connection point of the reactance element and the ground, and a reactance element is inserted and connected between the second input terminal and the output terminal, and this reactance element and the intermediate connection point are connected. and a reactance element connected between the point and the output terminal to configure a filter circuit or a tuning circuit that allows the signal from the second input terminal to pass to the output terminal when the signal switching active element is turned on. It is.

Effect With this configuration, the reactance element inserted and connected between the second input terminal and the output terminal, and the reactance element on the first input terminal circuit side when the signal switching active element is turned on, can be used to form a filter circuit or tuning. Since the circuit is configured, good transmission characteristics with little loss can be obtained between the second input circuit and the output circuit.

Embodiment Hereinafter, a high frequency signal switching device according to the present invention will be explained using the drawings of FIGS. 3 to 7. In addition, in FIGS. 3 to 7, the same parts as in FIG. 1 are given the same numbers.

FIG. 3 shows a high frequency signal switching device according to an embodiment of the present invention. In the embodiment shown in FIG. A transistor 2 is inserted and connected between the terminal 4 and the diode 1, and serves as a signal switching active element.
When the inductance element 5 and the capacitor 15 turn on, a high-pass filter circuit is constructed.

Further, FIG. 4 shows a high frequency signal switching device according to another embodiment of the present invention. In the embodiment shown in FIG. A low-pass filter circuit is constructed by an inductance element 16 as a reactance element connected between the transistor 2 and the output terminal 8, and a capacitor 17 connected between the transistor 2 and the output terminal 8. In this embodiment, an inductance element 18 is used in place of the capacitor 7, and a capacitor 19 is used in place of the inductance element 6.

Furthermore, FIG. 5 shows a high frequency signal switching device according to another embodiment of the present invention, and in the embodiment shown in FIG. 2
0, 21, 22, 23 and an inductance element 24, and when the transistor 2 becomes conductive and the inductance element 5 is added, a tuned circuit is formed together with the inductance element 25. FIG. 6 shows the transfer characteristics of the high frequency signal switching device shown in FIG. In other words, the tuning characteristics of the capacitors 20 and 21 and the inductance element 24 and the tuning characteristics of the capacitor 23 and the inductance elements 25 and 5 are combined by the capacitor 22, resulting in an ideal trapezoidal bandpass as shown in FIG. This provides filter characteristics.

Next, FIG. 7 compares the transmission characteristics of the conventional high frequency signal switching device shown in FIG. 1 (curve A) and the high frequency signal switching device according to the present invention shown in FIG. 3 (curve B).

As is clear from FIG. 7, in the high frequency signal switching device according to the present invention shown in FIG.
Since high-frequency filter characteristics can be obtained, it is possible to significantly improve the loss in the low frequency range as shown in conventional examples.
Low-loss transmission characteristics can be obtained.

Effects of the Invention As described above, the present invention is a high frequency signal switching device that can selectively couple the first and second input terminals to the output terminal depending on the operating state of one signal switching active element. A filter circuit for the signal flowing to the second input circuit is formed by a reactance element inserted and connected between the input terminal and the output terminal of No. 2, and the reactance element on the first input circuit side when the signal switching active element is turned on. Alternatively, a tuned circuit is configured, and good transfer characteristics with little loss can be obtained between the second input terminal and the output terminal.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing a conventional high frequency signal switching device, Figure 2 is an equivalent circuit diagram when the transistor of the same device is turned on, and Figures 3 to 5 are high frequency signal switching devices according to embodiments of the present invention. A circuit diagram showing the device, FIG. 6 is a transmission characteristic diagram of the high frequency signal switching device shown in FIG. 5, and FIG. 7 shows a comparison of the transmission characteristics of the conventional high frequency signal switching device and the high frequency signal switching device of the present invention. It is a transmission characteristic diagram. 1...Diode, 2...Transistor, 3,
4...Input terminal, 5, 6, 16, 18, 24, 2
5...Inductance element, 7, 9, 10, 1
5, 17, 19, 20, 21, 22, 23... Capacitor, 8... Output terminal.

Claims (1)

[Claims] 1 A plurality of first filters connected in series between the first input terminal and the output terminal and forming a filter circuit.
A reactance element connected between the intermediate connection point of the first reactance element and the ground, and output terminals for a signal input to the first input terminal and a signal input to the second input terminal. a signal switching active element for switching the output of the second reactance element, a second reactance element is inserted and connected between the second input terminal and the output terminal, and the second reactance element and the first reactance a reactance element connected between an intermediate connection point of the element and the output terminal, and a filter circuit or tuning that passes the signal from the second input terminal to the output terminal when the signal switching active element is turned on; A high-frequency signal switching device consisting of a circuit.