JPH0430826Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) This invention provides
The present invention relates to a high frequency switch circuit that can achieve input impedance matching for a signal of a predetermined frequency.

(Prior Art) FIG. 2 shows a circuit diagram of an example of a high frequency switch circuit.

In FIG. 2, a switching diode 3 is connected in series between an input terminal 1 and an output terminal 2 to function as a high frequency switch. The anode of the switching diode 3 is connected to a switch control terminal 5 via a resistor 4, and the cathode is grounded via a resistor 6. Furthermore, DC blocking capacitors 7 and 8 are interposed between the switching diode 3 and the input/output terminals 1 and 2, respectively.

In such a configuration, the switch control terminal 5
A positive voltage is applied to make the switching diode 3 conductive, and a negative voltage is applied to make the switching diode 3 conductive.

By the way, the above-mentioned high frequency switch circuit is used with some circuits connected to the front stage and the rear stage. Further, when the switching diode 3 is cut off, it is desirable that input impedance matching can be obtained for a signal of a predetermined frequency f.

Therefore, matching circuits are usually interposed between the input/output terminals 1 and 2 of the high frequency switch circuit and the ground, respectively. FIG. 3 shows a circuit diagram of an example of a conventional matching circuit.

In Fig. 3, the terminal 10 is connected to the input/output terminals 1 and 2 in Fig. 2. The terminal 10 is connected to a DC bias grounding choke coil 11.
The terminal 11 is grounded via a resistor 12 for impedance matching, a switching diode 13 for switching resonance, and a resonance capacitor 14, which are connected in series. A series connection of a resonance coil 15 and a DC blocking capacitor 16 is connected in parallel with the switching diode 13.
Furthermore, the cathode of the switching diode 13 is connected to a resonance control terminal 18 via a resistor 17 .

In the configuration of such a matching circuit, a positive voltage is applied to the resonance control terminal 18 to cut off the switching diode 13, and the capacitance of the switching diode 13 in the cut-off state and the resonance coil 15 etc. are used to connect the switching diode 13 in parallel to a predetermined frequency f. Make it resonate. Then,
As shown in FIG. 4, the reactance between the terminal 10 and the ground becomes infinite for a predetermined frequency f. Further, a negative voltage is applied to the resonance control terminal 18 to make the switching diode 13 conductive, and series resonance is caused by the inductance of the conducting switching diode 13, the resonance coil 15, the resonance capacitor 14, etc. Then, the reactance between the terminal 10 and the ground becomes zero for a predetermined frequency f as shown in FIG. Note that the resonance coil 15 and the resonance capacitor 14 are appropriately set so that parallel resonance and series resonance occur at a predetermined frequency f.

Therefore, when the switching diode 3 interposed between the input and output terminals 1 and 2 is made conductive,
By applying a positive voltage to the resonance control terminal 18, the matching circuit is caused to resonate in parallel, the reactance is made infinite, and the signal at the predetermined frequency f is not attenuated. Furthermore, when the switching diode 3 is cut off, by applying a negative voltage to the resonance control terminal 18, the matching circuit is made to resonate in series and the reactance is made zero, and the signal of the predetermined frequency f is passed through the impedance matching resistor 12. The input impedance can be matched by grounding the input impedance.

(Problem to be solved by the invention) In the case of a high frequency switch circuit in which a matching circuit as shown in Fig. 3 is interposed between input/output terminals 1 and 2 and ground, the matching circuit resonates at a predetermined frequency f. Since adjustment for this purpose is performed using the resonance coil 15 and the resonance capacitor 14, there is a problem in that the degree of freedom in setting constants is small and the circuit design is complicated.

The purpose of this invention was to solve the above-mentioned problems of the high-frequency switch circuit, and to provide a high-frequency switch circuit in which the resonance of the matching circuit can be adjusted to a predetermined frequency by adjusting the control voltage. It is about providing.

(Means for solving the problem) In order to achieve the above object, the high frequency switch circuit of the present invention has a high frequency switch interposed in series between the input terminal and the output terminal, and A matching circuit formed by connecting in series a resistor having a predetermined impedance, a capacitor, a variable capacitance diode, and a coil in parallel is interposed between each ground, and when the high frequency switch is made conductive, the A control voltage is applied to the variable capacitance diode so that the matching circuit resonates in parallel at a predetermined frequency, and when the high frequency switch is cut off, the matching circuit resonates in series at the predetermined frequency.

(Function) A matching circuit is constructed by connecting in series a resistor having a predetermined impedance, a capacitor, a parallel circuit of a variable capacitance diode, and a coil, and this matching circuit is interposed between the input/output terminal and the ground. Therefore, by adjusting the control voltage applied to the variable capacitance diode, the matching circuit can be easily caused to resonate in parallel and in series at a predetermined frequency f.

(Description of Embodiments) Hereinafter, embodiments of the present invention will be described with reference to FIG. FIG. 1 is a circuit diagram of an embodiment of the high frequency switch circuit of the present invention. In Figure 1, the second
Circuit elements that are the same as those in the figures are given the same reference numerals and redundant explanations will be omitted.

In FIG. 1, one end of a matching resistor 20 having a predetermined impedance is connected to the input terminal 1, and the other end of this resistor 20 is connected to a capacitance correction/DC blocking capacitor 30 via a series resonance capacitor 21. It is connected to one end of a parallel circuit of a series body of variable capacitance diodes 22 and a resonant coil 23.
The other end of this parallel circuit, one end of which is connected to the series resonance capacitor 21, is grounded. Further, a connection point between the capacitor 30 and the variable capacitance diode 22 of this parallel circuit is connected to the resonance control terminal 24. In this way, the matching circuit interposed between the input terminal 1 and the ground is configured by the series connection of the resistor 20, the capacitor 21, the series body of the variable capacitance diode 22 and the capacitor 30, and the parallel circuit of the coil 23. has been done.

Similarly, between the output terminal 2 and the ground, a matching resistor 25 having a predetermined impedance, a series resonance capacitor 26, a capacitance correction/DC blocking capacitor 13, a variable capacitance diode 27, and a series body for resonance are connected between the output terminal 2 and the ground. A matching circuit formed by connecting the parallel circuit of the coil 28 in series is interposed. Then, the parallel circuit capacitor 31 and variable capacitance diode 2
The connection point 7 is connected to the resonance control terminal 29 .

In such a configuration, when the switching diode 3 as a high frequency switch is made conductive,
Appropriate small control voltages are applied to the resonance control terminals 24 and 29 to make the variable capacitance diodes 22 and 27 have a large capacitance value, and the matching circuit is caused to resonate in parallel at a predetermined frequency f, thereby making the reactance infinite.
Then, the signal of the predetermined frequency f passing through the input/output terminals 1 and 2 is not attenuated at all. Furthermore, when the switching diode 3 is cut off, a suitably large control voltage is applied to the resonance control terminals 24 and 29 to make the variable capacitance diodes 22 and 27 have a small capacitance value, and a matching circuit is set up for a predetermined frequency f. Series resonance is made to make the reactance zero, and equivalently there are resistors 20 and 2 between the input/output terminals 1 and 2 and the ground.
Connected at 5. As a result, the input/output terminals 1 and 2 can match the input impedance with the circuits connected to the previous and subsequent stages, and can prevent the switching diode 3 from affecting other circuits by cutting off the switching diode 3. There is no.

In the above embodiment, the switching diode 3 is used as the high frequency switch, but the high frequency switch is not limited to this, and a transistor element or the like may be used.

(Effects of the invention) As explained above, according to the high frequency switch circuit of the invention, by providing a variable capacitance diode in the matching circuit, the control voltage can be adjusted to absorb variations in the constants of the constituent circuit elements, and the circuit Easy to adjust. Further, by changing the control voltage, the matching circuit can be made to resonate at another predetermined frequency, and this has the excellent effect of being able to respond to changes in the frequency of the signal applied to the high frequency switch circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the high frequency switch circuit of the present invention, FIG. 2 is a circuit diagram of an embodiment of the high frequency switch circuit, and FIG. 3 is an example of a conventional matching circuit. FIG. 4 is a parallel resonance characteristic diagram of the matching circuit, and FIG. 5 is a series resonance characteristic diagram of the matching circuit. 1... Input terminal, 2... Output terminal, 3... Switching diode, 20, 25... Resistor having a predetermined impedance, 21, 26... Series resonant capacitor, 22, 27... Variable capacitance diode, 23 , 28... Resonance coil, 24, 29...
...Resonance control terminal.

Claims (1)

[Scope of utility model registration request] A high frequency switch is interposed in series between the input terminal and the output terminal, and a resistor having a predetermined impedance is connected between the input terminal and the output terminal and ground,
A matching circuit formed by connecting a capacitor and a parallel circuit of a variable capacitance diode and a coil in series is interposed in each of them, and when the high frequency switch is made conductive, the matching circuit resonates in parallel at a predetermined frequency, and the high frequency A high frequency switch circuit characterized in that a control voltage is applied to the variable capacitance diode so as to cause the matching circuit to resonate in series at the predetermined frequency when the switch is cut off.