JP2013236145A - Transmission diversity high-frequency circuit and method of transmitting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-frequency circuit excellent in electric characteristics, configured with a balanced amplifier, and capable of suppressing insertion loss increase and avoiding enlargement of a circuit while antenna diversity is usable.SOLUTION: The transmission diversity high-frequency circuit includes a first circulator connected to a first output port of a balanced amplifier through a switch circuit, a second circulator connected to a second output port through the switch circuit, and a terminal circuit between each output port and a ground.

Description

  The present invention relates to a high-frequency circuit using a balanced amplifier that operates a pair of unit amplifiers in parallel, and more particularly to a high-frequency circuit capable of transmission diversity with high output power and a diversity transmission method.

  In providing wireless communication services, it is always an issue to reduce the cost for installing and maintaining communication facilities. As one of the solutions, it has been proposed to increase the communication distance between a fixed station and a mobile station and to configure a wide area for one fixed station to reduce the number of base stations. The fixed station is a base station, for example, and the mobile station is a wireless communication device such as a mobile phone.

  To increase the communication distance, it is necessary to increase the transmission output power of each station. However, simply increasing the output requires narrowing the frequency band that can be handled and increasing the number of transistors. . In a mobile phone or the like that operates with low power and is composed of small components, it is not easy to simply increase the transmission output power. For this reason, it has been proposed to increase the output power of a high-frequency signal using a balanced amplifier.

  FIG. 2 is an equivalent circuit of a balanced amplifier. This balanced amplifier is configured by connecting a pair of unit amplifiers 15 and 16 between hybrid circuits 21 and 20, and a high-frequency signal input to the input port IN1 is 90 ° through the first hybrid circuit 20. The high frequency signal having a phase difference is divided into two and input to the first amplifier 15 and the second amplifier 16, respectively. The high-frequency signal amplified by the first and second amplifiers is input to the second hybrid circuit 21 and is combined with the in-phase high-frequency signal and output from the output port OUT2. The output power is approximately twice that of the signals output from the first amplifier 15 and the second amplifier 16. In this case, the input port IN2 and the output port OUT1 are grounded by a terminating resistor.

  The termination resistor connected to the first hybrid circuit 20 absorbs the reflected wave from the input side of the first and second amplifiers 15 and 16. Ideally, no voltage appears at the port to which the termination resistor is connected. In addition, the termination resistor connected to the second hybrid circuit 21 absorbs the reflected wave input to the output port OUT2, and absorbs the combined loss caused by the variation in phase and output power.

  As the hybrid circuit, a Wilkinson type hybrid synthesis / distribution circuit is known. However, since the resistance to be used is required to have a withstand voltage, there is a problem that a small resistor cannot be used. Therefore, as a hybrid circuit, a branch line type hybrid combiner / distributor and a 90 ° hybrid coupler are often used.

  By the way, as a high frequency circuit capable of transmission diversity, a circuit composed of a plurality of switches shown in FIG. 5 is known (Patent Document 1). This high-frequency circuit uses three SPDT switch circuits S1-1, S1-2, and S2. The common port of the switch circuit S1-1 is connected to the antenna ANT1, and one of the single ports is connected to the reception circuit RX1. The common port of the switch circuit S1-2 is connected to the antenna ANT2, and one of the single ports is connected to the reception circuit RX2. The common port of the switch circuit S2 is connected to the transmission circuit TX1, and each of the single ports is connected to the remaining single ports of the switch circuits S1-1 and S1-2. Each switch circuit is switched to selectively connect the transmission circuit TX and the two antennas ANT1 and ANT2, and to switch the connection between the antennas ANT1 and ANT2 and the reception circuits RX1 and RX2.

International Publication No. 97/13320 Pamphlet

  In order to obtain a high-frequency circuit capable of increasing transmission output power and enabling antenna diversity, a balanced amplifier may be simply used in the high-frequency circuit disclosed in Patent Document 1. However, as the transmission output power increases, power of +26 dBm (0.4 W) or more is input from the transmitter to each switch circuit.

  In order to operate at a low voltage and transmit even when the transmission output power is high, a plurality of switching elements are connected in series to increase the number of stages and to be multi-gated. The area increases and the switch circuit also increases. An increase in the number of switching elements arranged in the signal path also causes a problem of an increase in insertion loss.

  Therefore, an object of the present invention is to provide a transmission diversity high-frequency circuit and a transmission method that are configured by using a balanced amplifier, can suppress increase in insertion loss, and can use antenna diversity while preventing an increase in circuit size.

  The first invention is a first output port connected to the first antenna via the first circulator, a second output port connected to the second antenna via the second circulator, and a first connected to the transmission circuit. A balanced amplifier having an input port and a second input port, and a switch circuit connected to each input port and each output port of the balanced amplifier, and a switch element and a resistor are connected in series to all the switch circuits The transmission diversity high-frequency circuit is characterized in that the switch circuit is controlled so as to selectively connect the transmission circuit and the antenna.

  In the transmission diversity high-frequency circuit of the present invention, it is preferable that the first circulator is connected to a first receiving circuit and the second circulator is connected to a second receiving circuit.

  Preferably, the switch circuit is a single pole double throw switch, and a common port of a single pole double throw switch is connected to each input port and each output port of the balanced amplifier.

  The balanced amplifier is preferably configured by connecting a pair of unit amplifiers between an input-side hybrid circuit and an output-side hybrid circuit, and the input hybrid circuit and the output hybrid circuit are connected by a 90-degree hybrid coupler. It is also preferable to configure. Each 90-degree hybrid coupler includes two coupling lines arranged opposite to each other, a signal input to the first input port is output from the second output port, and a signal input to the second input port is the first output. The balanced amplifier is configured to output from the port.

  In addition, the high frequency circuit of the present invention is provided in parallel and an antenna is connected to the output port side of each balanced amplifier to realize MIMO (Multi-Input Multi-Output), which is a wireless communication technology that widens the data transmission / reception bandwidth. A possible configuration is also possible.

  A second invention is a transmission method using a transmission diversity high-frequency circuit according to the first invention, wherein the connection between the first antenna and the transmission circuit is disconnected between the transmission circuit and the first input port of the balanced amplifier. And connecting the first input port of the balanced amplifier and the ground, connecting the transmission circuit and the second input port of the balanced amplifier, and connecting the second input port of the balanced amplifier and the ground. Between the second port of the first circulator and the first output port of the balanced amplifier, and between the first output port of the balanced amplifier and the ground, 2 Disconnecting the second port of the circulator and the second output port of the balanced amplifier, connecting the second output port of the balanced amplifier and the ground, and connecting the second antenna and the transmission circuit There is balanced with the transmission circuit The first input port of the balanced amplifier, the first input port of the balanced amplifier and the ground are disconnected, and the second input port of the balanced amplifier is disconnected. , Connecting the second input port of the balanced amplifier and the ground, disconnecting the second port of the first circulator and the first output port of the balanced amplifier, Connecting between the output port and ground, connecting between the second port of the second circulator and the second output port of the balanced amplifier, and connecting between the second output port of the balanced amplifier and ground. Disconnect and selectively connect the transmission circuit and the antenna during transmission.

  According to the transmission diversity high-frequency circuit of the present invention, a circulator and a switch circuit are provided between the antenna and the balanced amplifier, and between the plurality of input ports, the plurality of output ports, and the ground of the balanced amplifier, A termination circuit including a switch element and a resistor included in the switch circuit is connected. Since a different antenna is connected to each output port, the high-frequency signal input port and the antenna are selected and connected by controlling the ON / OFF state of the switching elements constituting the switch circuit.

  Antenna diversity can be used in spite of such a simple configuration, and the required switching elements can be reduced. Therefore, it is possible to reduce the increase in insertion loss and prevent the circuit from becoming large. And the transmission method can be obtained.

It is a figure which shows the equivalent circuit of the high frequency circuit by one Example of this invention. It is a block diagram which shows the structural example of the balanced amplifier used for one Example of this invention. 1 is a block diagram illustrating a configuration example using a 90-degree hybrid coupler, which is a balanced amplifier used in an embodiment of the present invention. FIG. It is an equivalent circuit of the circulator as a branching circuit used for the high frequency circuit by one Example of this invention. It is a circuit block diagram which shows the high frequency circuit part of the radio | wireless communication apparatus in which antenna diversity is possible.

  The high-frequency circuit of the present invention will be described with reference to FIGS. FIG. 1 is a circuit block diagram of a high-frequency circuit using a balanced amplifier. The configuration of the balanced amplifier is the same as that shown in FIG. 2, and a pair of unit amplifiers 15 and 16 are connected between the hybrid circuits 20 and 21. Each of the hybrid circuits 20 and 21 is a two-terminal pair circuit. One side of the hybrid circuit 20 is connected to the first input port IN1 and the second input port IN2, and the other side is connected to the input side of the first amplifier 15. 2 Connect to the input side of the amplifier 16. One side of the hybrid circuit 21 is connected to the first output port OUT1 and the second output port OUT2, and the other side is connected to the output side of the first amplifier 15 and the output side of the second amplifier 16. In addition, a directional coupler for power monitoring and a filter circuit for suppressing harmonics may be connected to the output side of each amplifier, and the invention is not limited to the disclosed circuit configuration and can provide an effect. Within the range, it can be appropriately changed.

  The transmission diversity high-frequency circuit of the present embodiment includes a first port Pda1 connected to the first antenna ANT side, a second port Pda2 connected to the transmission circuit TX side, and a first port connected to the first reception circuit RX1 side. Connected to the first circulator 5a having the three-port Pda3, the first port Pd1b connected to the second antenna ANT2 side, the second port Pd2b connected to the transmitter circuit TX side, and the second receiver circuit RX2 A second circulator having a third port Pd3b, a first input port IN1 connected to the transmission circuit TX via the first switch circuit S1, and via the transmission circuit TX and the second switch circuit S2. A second input port IN2 to be connected, a second port Pd2a of the first circulator, and a first output port to be connected via a third switch circuit S3. Provided with OUT1, and a balanced amplifier 10 having a second output port OUT2 to be connected via a second port Pd2b fourth switch circuit S4 in the second circulator. Note that a control circuit and a power supply circuit of the switch circuit are not shown and are omitted.

  Switching elements SWi1, SWi2, SWo1, and SWo2 are connected in series to the first input port IN1, the second input port IN2, the first input port IN1, the first input port OUT1, and the second input port OUT2 of the balanced amplifier. And controls the passage of high-frequency signals. Termination circuits Si1, Si2, So1, and So2 are provided between each port and the ground. Each termination circuit is configured as a series circuit in which a switch element and a resistor are connected in series as a basic configuration. If the impedance between the input and output ports of the series circuit can be electrically switched between an open state and a terminal resistance value defined by a resistor, circuit elements may be added as appropriate. Absent.

  An FET (field effect transistor) or a diode can be used as the switch element. The switch element is supplied with a control voltage from a control port (for example, the gate of the FET) to control the ON / OFF state.

  In this embodiment, as the hybrid circuits 20 and 21, high-frequency circuits are configured using balanced amplifiers using 90-degree hybrid couplers. FIG. 3 shows a configuration example of a balanced amplifier. The 90-degree hybrid couplers 20 and 21 include a pair of coupled lines LC1 and LC2 and coupled lines LC3 and LC4, respectively. Each coupling line is configured to have a length of ¼ of the operating wavelength λ, and the input high-frequency signal is divided into two high-frequency signals having a phase difference of 90 °. Further, the high-frequency signal distributed in two and having a phase difference of 90 ° is synthesized into a high-frequency signal having the same phase.

  From the operation based on the configuration of the balanced amplifier 10, the switch elements SWi3, SWi4, SWo3, SWo4 of the termination circuits Si1, Si2, So1, So2 and the switch circuits SWi1, SWi2, SWo1, SWo2 are as shown in Table 1. Be controlled. In the table, the port (drain-source for FET, anode-cathode for diode) is connected when ON, and disconnected when OFF. The condition 1 is a condition for connecting the transmission circuit TX and the second antenna ANT2, and the condition 2 is a condition for connecting the transmission circuit TX and the first antenna ANT1.

  Under condition 1, the switching element SWi3 of the termination circuit Si1 on the input port side of the balanced amplifier is controlled to be in an OFF state, and the impedance between the first input port IN1 and the ground becomes high, and the switching element SWi4 of the termination circuit Si2 is turned on. The impedance is controlled to be low impedance, and the second input port IN2 and the ground are connected by the terminating resistor Ri2. Further, the switch element SWo4 of the termination circuit So2 on the output port side is controlled to be in the OFF state, and the impedance between the second output port OUT2 and the ground becomes high impedance, and the switch element SWo3 of the termination circuit So1 is controlled to be in the ON state to reduce the impedance. The first output port OUT1 and the ground are connected by the terminating resistor Ro1.

By such control of the switch element, the high frequency signal input from the first input port IN1 of the balanced amplifier is output from the second output port OUT2. The reflected wave and the combined loss are absorbed by the terminating resistors Ro1 and Ri2. The switch circuit SWo2 between the second output port OUT2 and the second demultiplexing circuit 5b and the switch circuit SWi1 between the first input port IN1 and the transmission circuit Tx are controlled to be in the ON state and become low impedance. The other switch circuits are controlled to be in the OFF state and become high impedance, and the first input port IN1 and the second output port OUT2 are connected.
The amplified high frequency signal is radiated from the second antenna ANT2 through the second circulator 5b, so that the transmission circuit TX and the second antenna ANT2 are connected.

  Under condition 2, the switching element SWi3 of the termination circuit Si1 on the input port side of the balanced amplifier is controlled to be in an ON state and has a low impedance, and the first input port IN1 and the ground are connected by a termination resistor Ri1. The switch element SWi4 of the circuit Si2 is controlled to be in an OFF state, and a high impedance is provided between the second input port IN2 and the ground. Further, the switching element SWo4 of the termination circuit So2 on the output port side is controlled to be in the ON state and becomes low impedance, the second output port OUT2 and the ground are connected by the termination resistor Ro2, and the switching element SWo3 of the termination circuit So1 is turned off. The impedance is controlled between the first output port OUT1 and the ground by being controlled by the state.

  By such control of the switch element, the high-frequency signal input from the second input port IN2 is output from the first output port OUT1, and the reflected wave and the combined loss are absorbed by the termination resistors Ro2 and Ri1. The switch circuit SWo1 between the first output port OUT1 and the first branching circuit 5a and the switch circuit SWi2 between the second input port IN2 and the transmission circuit Tx are controlled to be in the On state, and become low impedance. The other switch circuits are controlled to be in the OFF state and become high impedance, and similarly, the transmission circuit TX and the first antenna ANT1 are connected.

  According to the high frequency circuit of the present invention, an antenna is provided corresponding to each output port, each switch element is controlled under the conditions shown in Table 1, and the output port from which the high frequency signal is output is switched. Even if the number of switch elements provided on the side is smaller than in the prior art, antenna diversity for selecting an antenna with good communication state can be realized. In addition, since the number of switch elements arranged in the signal path can be reduced, an increase in loss can be prevented and the configuration can be reduced.

  If the fixed station and the mobile station are close to each other and a large transmission output power is required, one of the amplifiers may be set in a non-operating state. In this case, although a distribution loss is generated by the first and second hybrid circuits, power consumption by the amplifier can be suppressed.

10 balanced amplifier 15 first amplifier 16 second amplifier 20 first hybrid circuit 21 second hybrid circuit IN1 first input port IN2 second input port OUT1 first output port OUT2 second input port

Claims (6)

A first output port connected to the first antenna via the first circulator, a second output port connected to the second antenna via the second circulator, a first input port and a second input connected to the transmission circuit A balanced amplifier having a port, and a switch circuit connected to each input port and each output port of the balanced amplifier,
All of the switch circuits include a termination circuit in which a switch element and a resistor are connected in series, and the switch circuit is controlled to selectively connect the transmission circuit and the antenna. The transmit diversity high-frequency circuit according to claim 1,
The transmit diversity high-frequency circuit, wherein the first circulator is connected to a first receiving circuit, and the second circulator is connected to a second receiving circuit. The transmit diversity high-frequency circuit according to claim 1 or 2,
The switch circuit is a single pole double throw switch, and each input port and each output port of the balanced amplifier is connected to a common port of a single pole single throw double throw switch. Diversity high frequency circuit. The transmit diversity high-frequency circuit according to any one of claims 1 to 3,
The balanced amplifier includes a pair of unit amplifiers connected between an input-side hybrid circuit and an output-side hybrid circuit. The transmit diversity high-frequency circuit according to claim 4,
The input hybrid circuit and the output hybrid circuit are configured by 90-degree hybrid couplers, and each 90-degree hybrid coupler includes two coupling lines arranged opposite to each other, and a signal input to the first input port is the second output. A transmit diversity high-frequency circuit, wherein a signal output from a port and input to the second input port is output from the first output port. A transmission method using the transmission diversity high-frequency circuit according to claim 5,
For connection between the first antenna and the transmission circuit,
Disconnect between the transmitter circuit and the first input port of the balanced amplifier;
Connecting between the first input port of the balanced amplifier and the ground;
Connecting between the transmitter circuit and the second input port of the balanced amplifier;
Disconnect between the second input port of the balanced amplifier and ground;
Connecting between the second port of the first circulator and the first output port of the balanced amplifier;
Disconnect between the first output port of the balanced amplifier and ground;
Disconnect between the second port of the second circulator and the second output port of the balanced amplifier;
Connecting between the second output port of the balanced amplifier and the ground;
For connection between the second antenna and the transmission circuit,
Connecting between the transmitter circuit and the first input port of the balanced amplifier;
Disconnect between the first input port of the balanced amplifier and ground;
Disconnect between the transmitter circuit and the second input port of the balanced amplifier;
Connecting between the second input port of the balanced amplifier and the ground;
Disconnect between the second port of the first circulator and the first output port of the balanced amplifier;
Connecting between the first output port of the balanced amplifier and the ground;
Connecting between the second port of the second circulator and the second output port of the balanced amplifier;
Disconnect between the second output port of the balanced amplifier and ground;
A transmission method characterized by the above.

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