JPH09191268A - Antenna switch circuit for transmitter-receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend the operating time of the transmitter-receiver by avoiding a power supply of the transmitter-receiver from being consumed in the reception mode. SOLUTION: Diodes D21, D22 in resonance circuits A, B for receiver and transmitter sides are nonconductive in the reception mode and both the diodes D21, D22 are conductive in the transmission mode to avoid power consumption in the reception mode. In the reception mode a signal from an antenna ANT is given to a reception circuit Rx via a resonance element C21 in the resonance circuit A and cut off toward the transmission circuit Tx by the resonance of the resonance circuit B, and in the transmission mode, the input of the transmission signal to the reception circuit Rx is cut off by the resonance operation of the resonance circuit A and outputted to the antenna ANT via the conductive diode D22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna switch circuit suitable for use in a transceiver such as a mobile phone driven by a battery.

[0002]

2. Description of the Related Art A transceiver such as a mobile phone is provided with a receiving circuit Rx and a transmitting circuit Tx as shown in FIG. 2, and is connected to an antenna ANT in order to share the antenna ANT for receiving and transmitting. The transmission / reception common signal line Lc, the reception side signal line Lr between the common signal line Lc and the reception circuit Rx, and the transmission side signal line Lt between the common signal line Lc and the transmission circuit Tx In the mode, the signal line is switched so that the reception signal received by the antenna ANT is guided from the shared signal line Lc to the reception circuit Rx only via the reception side signal line Lr. In the transmission mode, the transmission signal from the transmission circuit Tx is transmitted. It is necessary to switch the signal lines from the side signal line Lt to the antenna ANT only via the shared signal line Lc.

For this reason, this transceiver is provided with an antenna switch circuit as shown in FIG. This antenna switch circuit includes a receiving diode D11 whose on / off operation is controlled by a bias voltage applied through a resistor R11 from a power supply terminal T11 in a receiving side signal line Lr, and two capacitors connected in series. C1
1 and C15 and a high-pass T-type matching circuit MT including an inductor L13 connected between the connection between these capacitors C11 and C15 and the ground, and a power supply terminal inside the transmission-side signal line Lt. A transmission diode D12 whose on / off operation is controlled by a bias voltage applied via a resistor R12 from T12 and a coupling capacitor C14 are provided, and a shared signal line Lc is provided.
Inductor L1 for DC bias between ground
4 are provided.

The operation will be described below.

In the reception mode, the reception side power supply terminal T1
1 is applied with a bias voltage, and the current resulting from this application flows through the resistor R11, the diode D11, and the inductor L14 to the ground to turn on the diode D11. However, since the bias voltage is not applied to the transmission side power supply terminal T12, The diode D12 is off. Therefore, the signal received by the antenna ANT can pass through the shared signal line Lc through the receiving side signal line Lr, but cannot pass through the transmitting side signal line Lt. Then, the signal received by the antenna ANT passes through the matching circuit MT in the reception side signal line Lr and is input to the reception side circuit Rx to be processed for reception, and the transceiver can perform the reception operation. .

In the transmission mode, the transmission side power supply terminal T1
A bias voltage is applied to the diode 2, and the current resulting from this application flows through the resistor R12, the diode D12, and the inductor L14 to the ground to turn on the diode D12, but the bias voltage is not applied to the reception side power supply terminal T11. The diode D11 is off. Therefore, the signal from the transmitting circuit is transmitted from the antenna ANT through the transmitting side signal line Lt, but cannot pass through the receiving side signal line Lr. The transceiver can then transmit the signal.

[0007]

In the above-described conventional antenna switch circuit, it is necessary to apply a bias voltage to the power supply terminal on the reception side to keep the diode on the reception side always on during the reception mode. When the power supply of the transceiver is a battery as in a mobile phone, there is a problem that the battery is consumed and the operating time of the mobile phone cannot be extended.

Further, the inductor between the shared signal line and the ground is provided for the purpose of direct current bias so as to prevent the high frequency signal from the antenna from flowing into the ground. There is a problem in that the inductor becomes a large value and the manufacturing cost of the mobile phone is increased.

[0009]

In a transceiver antenna switch circuit according to the present invention, an antenna is connected to a common connection portion, and a reception circuit and a transmission circuit are respectively connected to the reception side signal line and the transmission side signal. It is provided for a transceiver connected via a line, and a resonance circuit is provided in each of the reception side signal line and the transmission side signal line, and both are turned off in the reception mode in each resonance circuit. In the transmission mode, each has a diode that is turned on by applying a bias voltage.By turning the diode on and off, the reception signal at the antenna is sent to the reception circuit via the resonance element in the resonance circuit on the reception side in the reception mode. While inputting, inputting is blocked by the resonance operation of the transmitting side resonance circuit, and transmission from the transmitting circuit is performed in transmission mode. Signal is output to the antenna side through the diode in the transmission side resonance circuit, and the input of the transmission signal to the reception circuit is blocked by the resonance operation of the reception side resonance circuit. Has been resolved.

In the present invention, preferably, in the reception mode, an element forming a high-pass T-type matching circuit together with a resonance element in the reception side resonance circuit may be provided in the reception side signal line.

In the present invention, preferably, the matching circuit has an inductor connected to the ground, the both diodes are connected in series in the same polarity direction, and the both diodes are connected from a power supply terminal in a transmission mode. When a bias voltage that turns on is applied, a bias current due to the application may flow to the ground via the diodes and the inductor.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A transceiver antenna switch circuit according to an embodiment of the present invention will be described with reference to FIG. 1, parts corresponding to those in FIG. 2 are designated by the same reference numerals. The transceiver according to the present embodiment includes an antenna ANT, a reception circuit Rx connected to the antenna ANT via a shared signal line Lc and a reception-side signal line Lr, and a shared signal line Lc to the antenna ANT. And a transmission circuit Tx connected via the transmission-side signal line Lt. Shared signal line Lc
The signal line Lr on the receiving side and the signal line Lt on the transmitting side are commonly connected by a common connecting portion CC.

A capacitor C26 for DC cutting / signal coupling is inserted in the shared signal line Lc between the antenna ANT and the common connection CC. A resonance circuit A for blocking the transmission frequency and a high-pass T-type matching circuit MT are inserted and connected in the reception-side signal line Lr between the common connection CC and the reception circuit Rx. The resonance circuit A includes a diode D2 on the receiving side whose anode is connected to the common connection CC.
1 and an inductor L21 which is a resonance element connected to the cathode of the diode D21, and a capacitor C21 which is a resonance element connected in parallel with the diode D21 and the inductor L21. Further, the matching circuit MT is, as will be described later in the reception mode, a capacitor C21 in the resonance circuit A, an inductor L32 connected between the output part of the resonance circuit A and the ground and also serving as a DC bias, and the resonance circuit A. A capacitor C25 for DC cutting / signal coupling is connected in series between the output section and the receiving circuit Rx.

On the other hand, in the signal line Lt on the transmission side between the common connection CC and the transmission circuit Tx, the resonance circuit B for blocking the reception frequency and the capacitor C24 for DC cutting / signal coupling are provided.
And are inserted and connected. The resonance circuit B has a common connection C
A diode D22 on the transmission side with the cathode connected to C
, And the diode D
A capacitor C23 for DC cutting / signal coupling and an inductor L22 which is a resonance element connected in parallel to
And a capacitor C22, which is a resonant element connected in parallel to the diode D22, and is connected to the power supply terminal T22 via the resistor R22.

The operation will be described.

Reception Mode In the antenna switch circuit of this embodiment, the bias voltage is not applied to the power supply terminal T22 in the reception mode. A circuit for controlling the application of the bias voltage to the power supply terminal T22 is omitted. For this reason,
Both diodes D21 and D22 on the receiving side and the transmitting side are off. As a result, the transmitter / receiver, for example, the mobile phone, can avoid the consumption of the battery in the reception mode and can extend its operation time.

(A) Considering the transmitting side in this receiving mode, since the diode D22 is off,
The resonance circuit B operates at a resonance frequency determined by the capacitor C23, the inductor L23, and the capacitor C22, and the signal at the resonance frequency is blocked, so that it cannot pass through the transmission-side signal line Lt. Since the capacitor C23 is short-circuited in terms of high frequency, the resonance frequency of the resonance circuit B when the diode D22 is off is the inductor L.
22 and the capacitor C22, the antenna AN is set by setting this resonance frequency to the frequency of the reception signal (reception frequency) received by the antenna ANT.
The reception signal received at T cannot pass through the transmission side signal line Lt after passing through the capacitor C26 within the shared signal line Lc, and is all introduced into the reception side signal line Lr.

(B) Next, considering the receiving side, the received signal from the antenna ANT is given to the receiving circuit Rx via the capacitors C21 and C25 in the resonance circuit A because the diode D21 is off. . In this case, the receiving side signal line Lr between the capacitors C21 and C25 is provided with the inductor L23 which also functions as a direct current bias between the capacitor C21 and the capacitor C25. A high-pass T-type matching circuit MT is formed. The constant of each element in the matching circuit MT is determined by such a value that the antenna input impedance, which is generally 50 ohms, and the input impedance of the receiving circuit Rx are matched, so that the received signal from the antenna ANT has no impedance. The signal is input to the receiving circuit Rx without being subject to signal attenuation due to matching.

Transmission Mode In the transmission mode, a bias voltage is applied to the power supply terminal T22. As a result, the bias current is
22, the diodes D22, D21, and the inductor L23 flow to the ground, so that the diodes D22, D
21 turn on together.

(A) In this way, both diodes D2
On the transmission side in the transmission mode in which both D2 and D21 are turned on, the transmission signal output from the transmission circuit Tx is the capacitor C24, the diode D22, and the capacitor C2.
It is transmitted from the antenna ANT via 6. Further, in this case, since the transmission circuit Tx is connected to the antenna ANT at a high frequency, the output impedance of the transmission circuit Tx needs to match the impedance of the antenna ANT, and is therefore 50 ohms. . The resistance value of the resistor R22 is 1 of the antenna impedance.
When the size is set to about 0 times, the amount of the transmission signal from the transmission circuit Tx flowing into the power supply terminal T22 side through the resistor R22 is sufficiently smaller than that of the transmission signal from the transmission circuit Tx and can be ignored. .

(B) On the other hand, on the receiving side in the transmission mode, the receiving side diode D21 is turned on, so that the resonance circuit A formed by the inductor L21 and the capacitor C21 is formed in the receiving side signal line Lr. The input of the signal of the resonance frequency of the resonance circuit A to the reception circuit Rx is cut off. Therefore, by setting the resonance frequency of the resonance circuit to the frequency of the transmission signal (transmission frequency), the transmission signal from the transmission circuit Tx can be blocked from being input to the reception circuit Rx via the reception-side signal line Lr. In this case, since the capacitor C21 is a part of the matching circuit MT and its constant is fixed, the resonance frequency of the resonance circuit A is set by adjusting the constant of the inductor L23.

[0022]

As described above, according to the present invention, the following effects can be obtained.

According to the first aspect of the invention, in the receiving mode, the diodes in the resonance circuits on the receiving side and the transmitting side are both turned off, and both diodes are turned on in the transmitting mode, so that power consumption in the receiving mode can be eliminated. . At this time, in the reception mode, the signal from the antenna is input to the reception circuit through the resonance element in the resonance circuit on the reception side, but on the transmission circuit side, it is cut off by the resonance operation by the resonance circuit on the transmission side. Since the input of the transmission signal to the reception circuit is blocked by the resonance operation of the resonance circuit on the reception side, and the signal is output to the antenna side through the diode on the transmission side that is turned on, transmission and reception can be smoothly performed.

According to a second aspect of the present invention, in the receiving mode, when an element forming a high-pass T-type matching circuit together with a resonance element in the resonance circuit on the reception side is provided in the signal line on the reception side, Since the resonance element of the resonance circuit can be shared with the matching circuit, the element of the circuit can be simplified.

According to a third aspect of the present invention, the matching circuit includes an inductor connected to the ground, the diodes are connected in series in the same polarity direction, and the diodes are connected from the power supply terminal in the transmission mode. When a bias voltage to turn on is applied and a bias current due to the application is made to flow to the ground via the both diodes and the inductor, a high frequency signal from the antenna will flow to the ground as in the conventional case. Since it is not necessary to eliminate the above, it is not necessary for this inductor to have a large inductance value for DC bias, and the cost can be reduced accordingly.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a transceiver antenna switch circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a transceiver antenna switch circuit according to a conventional example.

[Explanation of symbols]

ANT Antenna C26 DC cutting / signal coupling capacitor Lc Shared signal line Lr Reception side signal line Lt Transmission side signal line CC Common connection A Transmission frequency cutoff resonance circuit D21 Transmission frequency cutoff resonance circuit reception side diode L21 Transmission Inductor in resonance circuit for frequency cutoff C21 Capacitor in resonance circuit for transmission frequency cutoff L23 DC bias / high-pass T-type matching circuit inductor C25 DC cut / high-pass T-type matching circuit capacitor Rx reception circuit B Reception frequency cutoff resonance Circuit D22 Transmitting diode in resonance circuit for cutoff of reception frequency C23 Capacitor for DC cut / signal coupling L22 Inductor in resonance circuit for cutoff of reception frequency C22 Capacitor in resonance circuit for cutoff of reception frequency C24 DC cut / transmission circuit Roadside coupling capacitor R2 Bias current resistor T22 Bias voltage application input terminal Tx transmitter circuit

Claims (3)

[Claims] 1. A transmitter / receiver provided in a transceiver in which an antenna is connected to a common connection part, and a reception circuit and a transmission circuit are connected to the common connection part via a reception-side signal line and a transmission-side signal line, respectively. In the antenna switch circuit for a machine, a resonance circuit is provided in each of the reception-side signal line and the transmission-side signal line, and in each resonance circuit, both are turned off in the reception mode and both bias voltages are set in the transmission mode. In the reception mode, the reception signal at the antenna is input to the reception circuit through the resonance element in the resonance circuit on the reception side by the on / off operation of the diode, and on the transmission side, the transmission side. Input signal is blocked by the resonance operation of the resonance circuit of the transmission circuit, and the transmission signal from the transmission circuit is transmitted in the transmission mode. And outputs to the antenna side through a de, transceiver antenna switching circuit, characterized in that it blocked by resonant operation of the reception side resonance circuit the input to the receiving circuit of the transmission signal. 2. In the reception mode, an element forming a high-pass T-type matching circuit together with a resonance element in the resonance circuit on the reception side is provided in the signal line on the reception side. Antenna switch circuit for transceiver. 3. The matching circuit has an inductor connected to the ground, the diodes are connected in series in the same polarity direction, and a bias for turning on the diodes from a power supply terminal in a transmission mode. The transceiver antenna switch circuit according to claim 1 or 2, wherein when a voltage is applied, a bias current due to the application flows to the ground via the both diodes and the inductor.