JP2002111301A - Microwave circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave switch circuit, which has a good isolation characteristic for reception. SOLUTION: The microwave switch circuit comprises a plurality of transmission systems to input signal, including a power amplifier 12a to 12n, a Wilkinson power synthesizer 15 for synthesizing and outputting the plural input signals coming from the above plural transmission systems for input signal, an outputting transmission line 16 connected to the Wilkinson power synthesizer 15, an antenna terminal 17 connected to the outputting transmission line 16, a receiving transmission line 18 connected to the antenna terminal 17, the receiving transmission line 18 having the one-fourth the wavelength, a reception terminal 19 connected to the receiving transmission line 18, and a receiving switch 20 connected to the receiving transmission line 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a microwave circuit used for switching between transmission and reception.

[0002]

2. Description of the Related Art A microwave circuit used for switching between a transmission signal and a reception signal, for example, transmits a high-power transmission signal output from a power amplifier to an antenna terminal and receives the signal at an antenna. It has a function of transmitting a reception signal to a reception terminal.

Here, regarding a conventional microwave circuit,
An example of switching between transmission and reception will be described with reference to FIG.

[0004] A power amplifier 32 is connected to a signal input terminal 31. The power amplifier 32 is connected to an antenna terminal 34 and a transmission line 35 via a one-input one-output switch 33. The transmission line 35 is connected to a receiving terminal 36 and a one-input one-output switch 37.

The one-input and one-output switches 33 and 37 are, for example, field effect transistors (hereinafter referred to as FETs), and have respective electrodes of a drain D, a gate G and a source S.

In the above configuration, at the time of transmission, one input and one input
A bias voltage of 0 V is applied to each of the gate terminals Tg of the FETs constituting the output switches 33 and 37 to make the FETs conductive and the one-input / one-output switches 33 and 37 are closed. At this time, one input and one output switch 3
The impedance of the FETs 3 and 37 is determined mainly by the resistance between the drain and the source, and is low.

Therefore, the transmission signal input from the signal input terminal 31 is amplified by the power amplifier 32, passes through the one-input one-output switch 33, and is output to the antenna terminal 34.

At this time, looking at the side of the receiving terminal 36 from the antenna terminal 34, the impedance of the FET constituting the one-input / one-output switch 37 is converted by the transmission line 35 having a length of a quarter of the effective wavelength. , Becomes sufficiently large and is considered substantially open. Therefore, the transmission signal is not transmitted to the transmission line 35 side.

At the time of reception, one-input / one-output switches 33, 3
7, a voltage less than the pinch-off is applied to each of the gate terminals Tg of the FETs to make the FETs non-conductive.
The input 1 output switches 33 and 37 are set in an open state. At this time, the FE of the one-input / one-output switches 33 and 37
The impedance of T is mainly determined by the depletion layer capacitance,
High impedance.

At this time, looking at the side of the receiving terminal 36 from the antenna terminal 34, the impedance of the FET of the one-input / one-output switch 37 is converted by the transmission line 35 having a length of a quarter of the effective wavelength. Becomes smaller. Therefore, the reception signal input from the antenna terminal 34 is output to the reception terminal 36 via the transmission line 35, and is supplied from the reception terminal 36 to a reception circuit (not shown).

In this case, the F of the one-input one-output switch 33
Since the impedance of ET is large, it is not transmitted to the one-input / one-output switch 33 side.

[0012]

In a conventional microwave circuit, a high power transmission signal is output from the power amplifier 32 during transmission. For this reason, if the one-input / one-output switch 33 is configured by an FET having sufficient power handling characteristics, it becomes difficult to maintain the transmission characteristics of the FET, for example, linearity and broadband characteristics.

Therefore, in order to obtain good linearity, F
When the gate width of the ET is increased, the capacitance when the FET is not conducting increases in proportion to the gate width. As a result, the isolation characteristic when the FET of the one-input / one-output switch 33 is set to the non-conductive state at the time of reception deteriorates.

An object of the present invention is to solve the above-mentioned disadvantages and to provide a microwave circuit having good isolation characteristics when switching signals.

[0015]

A microwave circuit according to the present invention comprises a power amplifier for amplifying a signal, a first switch connected to the power amplifier, and a fourth switch connected to the first switch.
A plurality of transmission systems each having a first transmission line having a line length of one-half wavelength; a power combiner for combining and outputting a plurality of signals input from the plurality of transmission systems; A second transmission line having one end connected to the output side, a first terminal connected to the other end of the second transmission line, and a quarter-wavelength line having one end connected to the first terminal. A third transmission line, a second terminal connected to the other end of the third transmission line, and a second switch having one end connected to the other end of the third transmission line and the other end grounded. ing.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. 1 taking an example of switching between a transmission signal and a reception signal.

Power amplifiers 12a to 12n are respectively connected to a plurality of signal input terminals 11a to 11n to which transmission signals are input.
And one-input / one-output switches 13a to 13 for input signals
n, input signal transmission lines 14a to 14n having a quarter wavelength line length for impedance conversion are connected in order. The power amplifiers 12a to 12n, the one-input / one-output switches 13a to 13n, and the transmission lines 14a to 14n are connected in order, and a plurality of transmission systems connected in parallel to each other are each connected to an input of a power combiner, for example, a Wilkinson power combiner 15. Connected to the side. The output side of the Wilkinson power combiner 15 is connected via an output side transmission line 16 to an antenna terminal 17 and a reception side transmission line 18 having a quarter wavelength line length. Reception-side transmission line 18
Is a receiving terminal 19 and a receiving-side one-input one-output switch 20
It is connected to the. One terminal of the receiving-side one-input / one-output switch 20 is grounded.

An antenna (not shown) for transmitting a signal, for example, is connected to the antenna terminal 17.
Is connected to a receiving circuit for processing a signal received by an antenna, for example.

In the above configuration, at the time of transmission, one-input one-output switches 13a to 13n for input signals and one
The input 1 output switch 20 is set to a closed state.

At this time, the plurality of signal input terminals 11a to 11a
1n are transmitted from the power amplifier 12a.
, And passes through the one-input / one-output switches 13a to 13n in the conductive state, and passes through the Wilkinson power combiner 15
Synthesized by The combined transmission signal is output-side transmission line 1
6 to an antenna terminal 17.

On the other hand, at the time of reception, the one-input / one-output switches 13a to 13n for input signals and the one-input / one-output switch 20 on the receiving side are set in an open state.

At this time, the reception signal input from the antenna terminal 17 is output to the reception terminal 19 via the transmission line 18 on the reception side.

Here, in the above microwave circuit,
A more specific description will be given with reference to FIG. 2 taking a case where there are two signal input terminals as an example. In FIG. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and a duplicate description will be partially omitted.

First and second signal input terminals 11a, 1
1b includes a first and a second power amplifier 12a, respectively.
12b is connected. The first and second power amplifiers 12a, 12b are connected to first and second input signal one-input, one-output switches 13a, 13b, respectively, and are connected to the first and second one-input, one-output switches 13a, 13b, respectively.
Are respectively the first and second input signal transmission lines 14.
a and 14b are connected to the input terminal 15a of the Wilkinson power combiner 15.

The Wilkinson power combiner 15 is composed of stubs S1 and S2 each having a quarter wavelength line length connected to each input terminal 15a and a resistor R connected between the input terminals 15a. .

An output terminal 15 b of the Wilkinson power combiner 15 is connected to an antenna terminal 17 and a reception transmission line 18 via an output transmission line 16. The receiving-side transmission line 18 is connected to a receiving terminal 19 and a receiving-side one-input one-output switch 20.

Note that the line length of the output-side transmission line 16 connected to the output side of the Wilkinson power combiner 15 is in a state where the input signal one-input one-output switches 13a and 13b are open, that is, the input signal one-input one-input. Output switch 13a,
The length is set such that the impedance when viewed from the antenna terminal 17 side to the force-side transmission line 16 side is sufficiently large when the FET constituting 13b is non-conductive.

A one-input one-output switch 1 for input signals
3a, 13b and receiving side 1 input 1 output switch 20
Are formed of, for example, FETs, and each has a drain D,
It has a gate G and a source S electrode. The source S of the receiving one-input one-output switch 20 is grounded.

In the above configuration, at the time of transmission, one-input / one-output switches 13a and 13b for input signals and one
A bias voltage of 0 V is applied to each of the gate terminals Tg of the FETs constituting the input 1 output switch 20,
Is set to the conducting state.

At this time, the transmission signals input from the first and second signal input terminals 11a and 11b
And one-input / one-output switches 13a, 1a for the input signal in a closed state, which are amplified by the second power amplifiers 12a, 12b.
3b and the characteristic impedance is 50Ω, 4
The signal is input to the Wilkinson power combiner 15 through the first and second input signal transmission lines 14a and 14b having a line length of one-half wavelength. Wilkinson power combiner 1
The transmission signal input to 5 is power-combined and output to the antenna terminal 17 via the output-side transmission line 16.

In this case, the receiving side 1 input 1 output switch 2
Since 0 is in the conductive state, the impedance when the reception side transmission line 18 side is viewed from the antenna terminal 17 is converted into the low impedance of the FET constituting the reception side 1 input 1 output switch 20 by the reception side transmission line 18. The impedance becomes large and is considered substantially open. Therefore, the transmission signal is not transmitted to the receiving terminal 43 side.

On the other hand, at the time of reception, a voltage equal to or less than pinch-off is applied to the gate terminals Tg of the FETs constituting the input signal one-input one-output switches 13a and 13b and the reception-side one-input one-output switch 20, respectively. Set to non-conducting state.

In this case, the impedance viewed from the antenna terminal 17 to the transmission line 18 on the reception side is equal to one input and one input on the reception side.
The high impedance of the FET constituting the output switch 20 is impedance-converted by the receiving-side transmission line 18, and the impedance is reduced. Therefore, the reception signal input from the antenna terminal 17 is
And is output to the receiving terminal 19.

At this time, the line length of the transmission line 16 is selected so that the impedance seen from the antenna side to the transmission line 16 side is sufficiently large.
Is not transmitted to the output side transmission line 16.

In the above configuration, for example, the power supplied to the antenna terminal 17 during transmission is set to 33 dBm,
The gate width of an FET having a linear transmission characteristic at 33 dBm is 4 mm. The capacitance of the FET having a gate width of 4 mm in the non-conductive state is 1 pF.

In this case, the gate width of the FET constituting the conventional one-input one-output switch shown in FIG. 3 needs to be 4 mm, and the impedance formed by the FET at the time of reception is 2G.
It becomes j80Ω for the frequency of Hz.

On the other hand, in the case of the present invention shown in FIG. 2, the gate width of the FET constituting the one-input one-output switch may be 2 mm, and the capacitance in the non-conductive state is 0.5 pF. Therefore, at the time of reception, the impedance formed by the FET is −j159Ω. Therefore, the impedance seen from the antenna terminal to the Wilkinson power combiner side is larger in the present invention, and good isolation characteristics can be obtained.

In the above embodiment, the Wilkinson power combiner is used as the power combiner, but other power combiners can be used. Also, the case of switching between a transmission signal and a reception signal has been described, but the present invention
The present invention can be applied not only to switching between the transmission signal and the reception signal but also to other uses.

According to the above configuration, for example, at the time of transmission, the power of transmission signals input from a plurality of input terminals is combined by the power combiner and output to the antenna terminal or the like. In addition, for example, at the time of reception, the plurality of switches are turned off, and at this time, the impedance on the input side is set to be large by adjusting the line length of the transmission line connected to the output side of the power combiner. . In the case of this configuration, the linearity of the power supplied to the antenna terminal or the like is maintained at the time of transmission or the like, and a microwave circuit having good isolation characteristics at the time of reception or the like is obtained.

[0040]

According to the present invention, a microwave circuit having good isolation characteristics when switching signals can be realized.

[Brief description of the drawings]

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

FIG. 2 is a circuit configuration diagram for explaining the operation of the present invention.

FIG. 3 is a circuit diagram illustrating a conventional example.

[Explanation of symbols]

 11a to 11n: signal input terminals 12a to 12n: power amplifiers 13a to 13n: one input and one output switch for input signals 14a to 14n: transmission lines for input signals 15: Wilkinson power combiner 16: output transmission lines 17: antenna Terminal 18: Reception-side transmission line 19: Reception terminal 20: Reception-side one-input, one-output switch

Claims (4)

[Claims] A plurality of transmission circuits each having a power amplifier for amplifying a signal, a first switch connected to the power amplifier, and a first transmission line connected to the first switch and having a quarter wavelength line length. System, a power combiner that combines and outputs a plurality of signals input from the plurality of transmission systems, a second transmission line having one end connected to the output side of the power combiner, and a second transmission line. A first terminal connected to the other end, a third transmission line having a quarter wavelength line length having one end connected to the first terminal, and a third transmission line connected to the other end of the third transmission line. A microwave circuit comprising: two terminals; and a second switch having one end connected to the other end of the third transmission line and the other end grounded. 2. The microwave circuit according to claim 1, wherein the first switch comprises a field effect transistor. 3. The microwave circuit according to claim 1, wherein an antenna is connected to the first terminal. 4. The microwave circuit according to claim 1, wherein an antenna is connected to the first terminal, and a receiving circuit for processing a signal received by the antenna is connected to the second terminal.