JP3259941B2 - Transmission / reception switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission / reception switch for switching an antenna for transmission and reception and sharing the antenna in a time-division manner, and more particularly to a transmission / reception switch used for communication in a microwave band or a millimeter wave band. Related.

[0002]

2. Description of the Related Art In a radio communication apparatus, an antenna is commonly used for transmission and reception. When the antenna is shared by time division, switching must be performed depending on whether the antenna is connected to a receiving circuit or a transmitting circuit. FIG. 6 shows an example of a conventional transmission / reception changeover switch and its peripheral circuit used at this time.

In FIG. 1, a portion surrounded by a broken line indicated by numeral 1e indicates a transmission / reception changeover switch, 2 is an antenna, 3 is a high output amplifier for transmission, 4 is a low noise amplifier for reception, and 25 Is the first diode, 26 is the second diode, 27 is the first λ / 4 line, and 28 is the second λ /
Four lines, 29 is a capacitor for short-circuiting high frequency, and 30 is a switching control terminal.

At the time of transmission, a first voltage is applied to the switching control terminal 30 to turn on both the first diode 25 and the second diode 26. At this time, when the high-frequency short-circuit capacitor 29 is viewed through the first λ / 4 line 27, it is open at high frequencies, and when the second diode 26 is viewed through the λ / 4 line 28, it is open at high frequencies. Open.

For this reason, the output of the high-power amplifier 3 of the transmission circuit is output to the antenna 2 but not to the reception circuit. At the time of reception, the voltage applied to the switching control terminal 30 is changed to turn off both the first diode 25 and the second diode 26.

At this time, the transmitting circuit is disconnected from the antenna, and the signal input from the antenna 2 is input to the low noise amplifier 4 of the receiving circuit. A switch having one common input / output terminal and two input / output terminals switched and connected to the common input / output terminal like the transmission / reception switch is SPDT (single-pole, double-switch).
throw) called a switch.

FIG. 7 shows another example of a conventional transmission / reception changeover switch and its peripheral circuits. In this figure, a portion surrounded by a broken line indicated by numeral 1f is a transmission / reception changeover switch, 35, 36, 37 and 38 are FETs, and 39 and 40 are changeover control terminals.

In this circuit, when the voltage between the gate and the source of the FET is changed, the resistance between the drain and the source is several Ω.
It is used as a switching element by utilizing the characteristic that greatly changes from several kΩ to several kΩ. That is, when transmitting, the FET
35 and 38 are turned on, and the FETs 36 and 37 are turned off. During reception, the antennas are used at the transmitter by turning off the FETs 35 and 38 and turning on the FETs 36 and 37. Or use it at the receiver.

[0009]

In the conventional transmission / reception changeover switch as described above, there is a problem that as the frequency to be handled becomes higher, the isolation characteristic is deteriorated by the capacitance associated with the diode or FET. Such deterioration of the isolation characteristics is a problem particularly in that a high-output transmission signal leaks to a receiving circuit.

In order to solve this problem, various configurations have been proposed to improve the isolation characteristics by adding a resonance circuit composed of a capacitive element and an inductive element. Such a system utilizes resonance. Therefore, there is a problem that the frequency characteristic becomes extremely narrow.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and has as its object to realize a transmission / reception changeover switch which can greatly increase isolation between a transmission circuit and a reception circuit. I have.

[0012]

According to the invention, the above-mentioned object is solved by the means described in the claims.

That is, the first aspect of the present invention is an SPDT having one common input / output terminal and two input / output terminals alternately connected to the common input / output terminal by a switching operation.
Two switches and one input signal at 9
A 90-degree distribution circuit that distributes and outputs two signals having a phase difference of 0 degree;

A 90-degree synthesizing circuit for synthesizing two input signals into one signal by giving a phase difference of 90 degrees, and a 90-degree distribution synthesizing circuit having bidirectionality. One of the output terminals of the 90-degree distribution circuit, which is connected to the input terminal of the degree distribution circuit and outputs the signal whose phase is advanced by 90 degrees, is connected to one of the input / output terminals of the first SPDT switch. Connect to

The other of the output terminals of the 90-degree distribution circuit is connected to one input / output terminal of a second SPDT switch, and the other input / output terminal of the second SPDT switch is connected to the 90-degree synthesis circuit. One of the input terminals of the circuit is connected to one input terminal that is synthesized with a phase delay of 90 degrees, and the other input / output terminal of the first SPDT switch is connected to the other input terminal of the 90 degree synthesis circuit. ,

An output terminal of the 90-degree synthesizing circuit is connected to an input terminal of a receiving circuit, and a common input / output terminal of the first and second SPDT switches is connected via a bidirectional 90-degree distribution synthesizing circuit. This is a transmission / reception switch configured to be connected to the antenna element.

According to a second aspect of the present invention, in the first aspect of the present invention, the 90-degree distribution circuit is configured such that an input circuit is divided into two branches, one of which is used as one output of the 90-degree distribution circuit, and the other is used as the other output. A 90-degree phase shifter is inserted in series in the circuit of
The output side of the phase shifter is configured to be the other output of the 90-degree distribution circuit,

A 90-degree synthesizing circuit is provided by inserting a 90-degree phase shifter in series with one of the two-input circuits, and the output side of the 90-degree phase shifter and the other of the two-input circuit are connected to each other. And a 90-degree distribution / synthesis circuit that branches the circuit connected to the antenna element into two,

One of them is connected to the common input / output terminal of the second SPDT switch, and the other is connected to a bidirectional 90 terminal.
It is configured to be connected to a common input / output terminal of a first SPDT switch via a phase shifter.

According to a third aspect of the present invention, in the first aspect, a 90-degree hybrid circuit is used as a 90-degree distribution circuit, a 90-degree synthesis circuit, and a bidirectional 90-degree distribution / combination circuit. When the numbers of ~ are assigned to the four input / output terminals of

Each of the signals input from か ら and か ら has a power that is １ ／ the power of the input signal, and the signal output from ９０ is output with a phase delay of 90 ° from that of の. Each of the signals is a signal whose power is の of that of the input signal, and a signal output from the signal is output with a phase delayed by 90 degrees from that of the input signal.

A terminal of the 90-degree hybrid circuit used as the 90-degree distribution circuit is used as an input terminal of the 90-degree distribution circuit, a terminal and a terminal are used as output terminals of the 90-degree distribution circuit, and a non-reflection terminator is connected between the terminal and the ground. Connect, 90
The terminal of the 90-degree hybrid circuit used as the degree-combining circuit and the terminal are used as input terminals of the 90-degree combining circuit,

A terminal is used as an output terminal of the 90-degree combining circuit, a non-reflection terminator is connected between the terminal and ground, an antenna is connected to a terminal of the 90-degree hybrid circuit used as the 90-degree distribution combining circuit, and the terminal is Connect to the common input / output terminal of the two SPDT switches and connect the terminal to the first SPD switch.
This is connected to a common input terminal of a T switch, and a reflectionless terminator is connected between the terminal and ground.

According to a fourth aspect of the present invention, in the third aspect of the present invention, a high-output amplifier is inserted into each of the terminals of the 90-degree hybrid circuit used as the 90-degree distribution circuit and the circuits connected to the terminals. It is.

According to a fifth aspect of the present invention, there are provided two SPDT switches each having one common input / output terminal and two input / output terminals alternately connected to the common input / output terminal by a switching operation, and one input / output terminal. A 90-degree distribution circuit that distributes the signal into two signals having equal amplitudes and a phase difference of 90 degrees from each other and outputs the two signals;

A 90-degree synthesizing circuit for synthesizing two input signals into one signal by giving a phase difference of 90 degrees, and connecting an output terminal of the transmission circuit to an input terminal of the 90-degree distribution circuit; One of the output terminals of the degree distribution circuit, to which the signal whose phase is advanced by 90 degrees is output, is connected to the first SP
Connect to one input / output terminal of DT switch,

The other of the output terminals of the 90-degree distribution circuit is connected to one input / output terminal of a second SPDT switch, and the other input / output terminal of the second SPDT switch is connected to the 90-degree synthesizing switch. Of the input terminals of the circuit, connect to one input terminal that is synthesized with a phase delay of 90 degrees,

The other input / output terminal of the first SPDT switch is connected to the other input terminal of the 90-degree synthesizing circuit, and the output terminal of the 90-degree synthesizing circuit is connected to an input terminal of a receiving circuit. The common input / output terminal of the first and second SPDT switches is configured to be directly connected to each feed point of an antenna element having two orthogonal feed points.

[0029]

According to the present invention, the output of the transmitting circuit is divided into two signals having a phase difference of 90 degrees, and each signal is divided into two SPDs.
The signal is input to one of the input / output terminals on the switchable side of the T switch. The other of the two input / output terminals on the switchable side of the two SPDT switches is configured to be connected to a receiving circuit via a 90-degree synthesizing circuit.

According to the above configuration, even if the isolation of the single SPDT switch cannot be sufficiently obtained, the leakage power of the transmission signal is canceled in the input unit of the receiving circuit because it has an opposite phase. The isolation between the circuit and the receiving circuit can be increased. Hereinafter, the operation and the like of the present invention will be described in detail based on examples.

[0031]

FIG. 1 shows a first embodiment of a transmission / reception changeover switch according to the present invention. In this figure, a portion surrounded by a broken line indicated by numeral 1a indicates a transmission / reception changeover switch.
2 is an antenna, 3 is a high power amplifier for transmission, 4 is a low noise amplifier for reception, 5 is a first SPDT switch, 6 is a second SPDT switch, 7 is a first 90 degree phase shifter, 8 Denotes a second 90-degree phase shifter, and 9 denotes a third 90-degree phase shifter.

In particular, it is assumed that the first 90-degree phase shifter 7 has bidirectionality that, even if input is made from either of the two input / output terminals, the phase is delayed by 90 degrees to the other terminal. This can be realized by using only passive elements. The SPDT switch is a switch having one common input / output terminal and two input / output terminals that are connected to the common input / output terminal.

During transmission, the first SPDT switch 5 has input / output terminals 10 and 11 connected thereto, and the second SPDT switch 6 has input / output terminals 13 and 14 connected thereto. The transmission signal passes through the high-power amplifier 3 and is then divided into two equal amplitude signals, and one signal is transmitted through the first SPDT switch 5 to the first 90
Is input to the phase shifter 7.

The other signal, which has been divided into two, passes through the second 90-degree phase shifter 8 and is combined with the output signal of the first 90-degree phase shifter 7 via the second SPDT switch 6. You.
Since each of the two divided signals passes through the 90-degree phase shifter once, the signals are in-phase synthesized at the input terminal of the antenna 2.

Here, consider the case where the SPDT switch has a leak. That is, from the input / output terminal 11 of the first SPDT switch 5 to the input / output terminal 12 and the second SPDT switch 5
It is assumed that there is a leak from the input / output terminal 14 of the switch 6 to the input / output terminal 15.

At this time, the leakage signal of the second SPDT switch 6 passes through the second 90-degree phase shifter 8 and the third 90-degree phase shifter 9 and then passes through the leakage signal of the first SPDT switch 5. , And is reversed-phase synthesis and canceled. That is, the transmission signal does not leak into the receiving circuit.

In this embodiment, the first and second SPDTs
The circuit configuration of the switch may be the conventional configuration shown in FIG. 3 and FIG. 4, and even if there is leakage due to insufficient isolation of a single SPDT switch, the isolation characteristics between the transmission circuit and the reception circuit will jump. Increase.

SPD at the time of reception in the first embodiment shown in FIG.
FIG. 2 shows the state of the T switch. The first SPDT switch 5 has input / output terminals 10 and 12 connected, and the second SPD switch 5
The input / output terminals 13 and 15 are connected to the T switch 6.

The received signal received by the antenna 2 is divided into two equal amplitude signals, and after passing through a first 90-degree phase shifter 7 and a third 90-degree phase shifter 9, respectively, are combined. You. Since each of the two divided signals passes through the 90-degree phase shifter once, the signals are in-phase synthesized at the input terminal of the low noise amplifier 4.

FIG. 3 shows a second embodiment of the transmission / reception changeover switch of the present invention. In this figure, a portion surrounded by a broken line indicated by numeral 1b is a transmission / reception changeover switch.
7, 58 and 59 are all 90-degree hybrid circuits 6.
Numerals 0, 61 and 62 are non-reflection terminators.

In the 90-degree hybrid circuit, a half-power is output to a signal input from the figure, and the other half-power is output with a delay of 90 degrees with respect to a signal supplied thereto. Also, the input signal is output by half each, and the signal is delayed by 90 degrees.

Conversely, a signal input from the beginning has a symmetry that the signal is output by half, and the signal is delayed by 90 degrees. Therefore, similarly to the first embodiment shown in FIG. 1, the transmission signal output from the high-power amplifier 3 is in-phase synthesized at the input terminal of the antenna 2.

The received signal received by the antenna 2 is in-phase synthesized at the input terminal of the low-noise amplifier 4, while the leakage power of the transmission signal at the SPDT switch is anti-phase synthesized at the input terminal of the low-noise amplifier 4 and canceled. Is done.

Therefore, even if a single SPDT switch does not have sufficient isolation and leaks, the isolation characteristics between the transmission circuit and the reception circuit are enhanced. This embodiment is different from the first embodiment shown in FIG. 1 in that a 90-degree hybrid in which a distribution / synthesis circuit and a 90-degree phase shifter are integrated is used, so that the configuration is simpler. .

FIG. 4 shows a third embodiment of the transmission / reception changeover switch of the present invention. In this figure, a portion surrounded by a broken line indicated by numeral 1c indicates a transmission / reception changeover switch, and reference numerals 70 and 71 denote high-output amplifiers, which are disposed after the 90-degree hybrid 58.

Therefore, at the time of transmission, the transmission signal is split into two, amplified by the high-power amplifier, and then in-phase synthesized at the antenna input terminal, so that the isolation characteristics between the transmission circuit and the reception circuit are maintained well. As it is, the transmission power can be doubled.

FIG. 5 shows a fourth embodiment of the transmission / reception changeover switch of the present invention. In this figure, a portion surrounded by a broken line indicated by numeral 1d indicates a transmission / reception changeover switch, and reference numeral 80 denotes an antenna element having two orthogonal feeding points.

The two feeding points are equal in amplitude and in phase 9
The antenna element 80 operates as a circularly polarized antenna because it is excited by signals that differ by 0 degrees. Since the phase relationship at the feed point is the same at the time of transmission and the time of reception, the same polarization plane is used. On the other hand, the leakage power of the transmission signal at the SPDT switch is reversed-phase synthesized at the input terminal of the low-noise amplifier 4 and is canceled.

Therefore, while maintaining good isolation characteristics between the transmission circuit and the reception circuit, the bidirectional connection to the antenna element required in the other embodiments is achieved.
A 0-degree phase shifter and a 90-degree hybrid can be omitted. In the present embodiment, two feeding points are used as antenna elements.
Although two antenna elements are used, two antenna elements that excite mutually orthogonal polarized waves may be used as a pair.

[0050]

As described above, according to the present invention,
Even if the isolation of a single SPDT switch is not sufficient in the high frequency band, the leakage power of the transmission signal is canceled at the input of the receiving circuit, so the isolation between the transmitting circuit and the receiving circuit can be reduced. There is an advantage that can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a state at the time of reception according to the first embodiment.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a third embodiment of the present invention.

FIG. 5 is a diagram showing a fourth embodiment of the present invention.

FIG. 6 is a diagram showing an example of a conventional transmission / reception changeover switch.

FIG. 7 is a diagram showing another example of a conventional transmission / reception changeover switch.

[Explanation of symbols]

 1a to 1d Transmission / reception switch 2 Antenna element 3 High power amplifier for transmission 4 Low noise amplifier for reception 5,6 SPDT switch 7 90 degree phase shifter with bidirectionality 8,9 90 degree phase shifter 10,13 Common input / output terminals 11, 12, 14, 15 Input / output terminals 57 to 59 90-degree hybrid circuit 60 to 62 Non-reflection terminator 70, 71 High-power amplifier 80 Antenna element having two orthogonal feeding points

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-8-181631 (JP, A) JP-A-59-70323 (JP, A) JP-A-59-70324 (JP, A) JP-A-62 208721 (JP, A) JP-A-62-208722 (JP, A) JP-A-55-26711 (JP, A) JP-A-6-510127 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 1/44 H01P 1/15

Claims (5)

(57) [Claims] 1. Two SPDT switches each having one common input / output terminal and two input / output terminals alternately connected to the common input / output terminal by a switching operation. A 90-degree distribution circuit that distributes and outputs two signals having a 90-degree phase difference, a 90-degree synthesis circuit that provides two input signals with a 90-degree phase difference and combines them into one signal, A 90-degree distribution / synthesis circuit having the following configuration. An output terminal of the transmission circuit is connected to an input terminal of the 90-degree distribution circuit, and a signal whose phase is advanced by 90 degrees among the output terminals of the 90-degree distribution circuit is provided. One terminal to be output is connected to the first SPDT
A second input terminal of the second SPDT switch; a second input terminal of the second SPDT switch; a second input terminal of the second SPDT switch; An output terminal is connected to one of the input terminals of the 90-degree synthesizing circuit that is synthesized with a phase delay of 90 degrees, and the other input / output terminal of the first SPDT switch is connected to the 90-degree synthesizing circuit. And the output terminal of the 90-degree synthesizing circuit is connected to the input terminal of a receiving circuit. The common input / output terminal of the first and second SPDT switches is a 90-degree bi-directional switch. A transmission / reception changeover switch connected to an antenna element via a distribution / synthesis circuit. 2. The 90-degree distribution circuit has an input circuit divided into two, one of which is used as one output of the 90-degree distribution circuit, and a 90-degree phase shifter inserted in series with the other circuit. ,
The output side of the 90-degree phase shifter is configured to be the other output of the 90-degree distribution circuit. The 90-degree synthesizing circuit includes a 90-degree phase shifter provided to one of the two input circuits. Are connected in series, and the output side of the 90-degree phase shifter is connected to the other circuit of the two-input circuit. The 90-degree distribution / combination circuit branches the circuit connected to the antenna element into two. One of them is connected to the common input / output terminal of the second SPDT switch, and the other is connected to the bidirectional 9
2. The transmission / reception changeover switch according to claim 1, wherein the transmission / reception changeover switch is connected to a common input / output terminal of the first SPDT switch via a 0-degree phase shifter. 3. A 90-degree hybrid circuit is used as a 90-degree distribution circuit, a 90-degree synthesis circuit, and a bidirectional 90-degree distribution / combination circuit.
When the numbers are assigned, the signals input from are each one of the input signals.
A signal having a power of / 2 is output, and a signal output from is output with a phase delay of 90 degrees from that of the signal, and the signals input from are each one of the input signals.
A signal having a power of / 2 is output, and a signal output from is output with a phase delayed by 90 degrees from that of the signal of. The terminal of the 90-degree hybrid circuit used as the 90-degree distribution circuit is distributed by 90 degrees. The terminal and the terminal of a 90-degree hybrid circuit used as a 90-degree hybrid circuit are used as an input terminal of a circuit, a terminal and a terminal are used as output terminals of a 90-degree distribution circuit, a non-reflective terminator is connected between the terminal and ground, Used as an input terminal of the 90-degree synthesis circuit, and used as an output terminal of the 90-degree synthesis circuit,
A non-reflective terminator is connected between the terminal and ground, an antenna is connected to a terminal of a 90-degree hybrid circuit used as a 90-degree distribution / combination circuit, a terminal is connected to a common input / output terminal of a second SPDT switch, and a terminal is connected. 2. The transmission / reception switch according to claim 1, wherein the switch is connected to a common input terminal of the first SPDT switch, and a reflectionless terminator is connected between the terminal and ground. 4. The transmission / reception switch according to claim 3, wherein a high-output amplifier is inserted in each of the terminals of the 90-degree hybrid circuit used as the 90-degree distribution circuit and the circuit connected to the terminal. 5. Two SPDT switches each having one common input / output terminal and two input / output terminals alternately connected to the common input / output terminal by a switching operation, and one input signal being mutually equal in amplitude. A 90-degree distribution circuit that distributes and outputs two signals having a 90-degree phase difference, and a 90-degree synthesis circuit that combines two input signals with a 90-degree phase difference to synthesize one signal; An output terminal of the circuit is connected to an input terminal of the 90-degree distribution circuit, and one of the output terminals of the 90-degree distribution circuit, from which a signal whose phase is advanced by 90 degrees is output, is connected to a first SPDT.
A second input terminal of the second SPDT switch; a second input terminal of the second SPDT switch; a second input terminal of the second SPDT switch; An output terminal is connected to one of the input terminals of the 90-degree synthesizing circuit which is synthesized with a phase delay of 90 degrees, and the other input / output terminal of the first SPDT switch is connected to the 90-degree synthesizing circuit. And the output terminal of the 90-degree synthesizing circuit is connected to the input terminal of a receiving circuit. The common input / output terminals of the first and second SPDT switches are connected to two orthogonal feeding points. A transmission / reception switch, which is directly connected to each feeding point of an antenna element having the following.