JP2012222490A - High-frequency circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-frequency circuit that is configured by using a balanced amplifier, suppress an increase in insertion loss, is capable of using antenna diversity while preventing enlargement of a circuit, and has excellent electrical characteristics.SOLUTION: A high-frequency circuit comprises: a first switch SC1 disposed between a first port and a sixth port; a second switch SC2 disposed between a second port and the sixth port; a third switch SC3 disposed between the first port and a third port; a fourth switch SC4 disposed between the second port and a fourth port; and a balanced amplifier disposed between a fifth port and the sixth port. The connection between the fifth port and the first port or the second port is switched by the first switch SC1 and the second switch SC2, the connection between the third port and the first port or the ground is switched by the third switch SC3, and the connection between the fourth port and the second port or the ground is switched by the fourth switch SC4.

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.

  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 transistor stages. In a mobile phone or the like that operates with small power and is composed of small parts, it is not easy to simply increase the transmission output power. For this reason, the output power of high-frequency signals has been increased using balanced amplifiers.

  FIG. 3 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 20 and 21, and a high-frequency signal input to the transmission port P 1 (IN) passes through the first hybrid circuit 20. The high frequency signal having a phase difference of 90 degrees 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 a high-frequency signal having the same phase and output from the output port P2 (OUT). The output power is approximately twice that of the signals output from the first amplifier 15 and the second amplifier 16.

Terminal resistors R1 and R2 are connected to the first and second hybrid circuits 20 and 21, respectively.
Reflected waves from the input sides of the first and second amplifiers 15 and 16 are absorbed by the terminating resistor R1 connected to the first hybrid circuit 20. Ideally, no voltage appears at the port to which the termination resistor R1 is connected. Further, the termination resistor R2 connected to the second hybrid circuit 21 absorbs the reflected wave input to the output port P2 (OUT), and is generated by the variation of the phase and output power of the first and second amplifiers 15 and 16. Absorb the loss. Ideally, no voltage appears at the port to which the termination resistor R2 is connected.

  A Wilkinson hybrid synthesis / distribution circuit is known as the hybrid circuit. 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 synthesizer and a 90-degree hybrid coupler are often used as the hybrid circuit.

  An antenna switch circuit shown in FIG. 6 is disclosed in Patent Document 1 as a high-frequency wave circuit using such a balanced amplifier. This antenna switch circuit includes a balanced amplifier 10 whose input port is connected to the transmitter 125, an SPDT switch circuit 127 connected to the output port of the balanced amplifier 10, and an antenna ANT connected to the SPDT switch circuit 127. , A low noise amplifier 128 connected to the receiver 126. The SPDT switch circuit 127 switches between one antenna ANT and the transmitter 125 and between the antenna ANT and the receiver 126.

  Patent Document 1 also discloses a high-frequency wave circuit shown in FIG. Compared with the circuit shown in FIG. 6, this circuit further includes an SPDT switch circuit 129 connected to the input port of the balanced amplifier 10 and an SPDT switch connected to one of the output ports to which the terminating resistor of the balanced amplifier 10 is connected. Circuit 130 and termination resistors 132 and 133 are connected to one port of each of the switch circuits 129 and 130.

In this circuit, the other output terminal is connected to the antenna without a switch circuit. At the time of transmission, the antenna ANT and the transmitter 125 are connected by the SPDT switch circuit 129 disposed between the transmitter 125 and the balanced amplifier 10. The SPDT switch circuit 130 connected to the output port of the balanced amplifier 10 is grounded via the termination resistor 133, and the high frequency signal is radiated from the transmitter 125 via the antenna ANT.
On the other hand, a high frequency signal incident from the antenna ANT reaches the receiver 126 through the balanced amplifier 10, the SPDT switch circuit 130, and the low noise amplifier 128. The SPDT switch circuit 129 is controlled so that the transmitter 125 is grounded via the termination resistor 132, and the SPDT switch circuit 130 is controlled so that the balanced amplifier 10 and the low noise amplifier 128 are connected. The high-frequency signal is input to the second hybrid circuit of the balanced amplifier 10 and appears on the output side of the unit amplifier, but is reflected when the unit amplifier is controlled to the non-operating state, and the SPDT switch circuit 130 side of the second hybrid circuit. Appears at the output port.

The high-frequency circuit illustrated here has a basic configuration in which a transmitter and a receiver are connected to one antenna. However, in recent high-frequency circuits, antenna diversity is used in consideration of the influence of disturbance such as fading. It is requested to do.
Next, a configuration example of antenna diversity in the high frequency circuit will be described. Patent Document 2 discloses a high-frequency circuit shown in FIG. In this high-frequency circuit 170, three SPDT switch circuits 180, 181, and 182 are connected to the output side of the amplifier 184, two antennas ANT1, ANT2, a first reception side Rx1, a second reception side Rx2, and a transmission side Tx. Switch the connection between.

Special table 2010-511353 International Publication No. 97/13320 Pamphlet

  In order to obtain a high-frequency circuit capable of increasing the transmission output power and enabling antenna diversity, the balanced amplifier described in Patent Document 1 may be simply used in the high-frequency circuit disclosed in Patent Document 2.

  FIG. 9 shows a basic configuration of the SPDT switch circuit. A switching element 190 made of FET is provided between the first port P1 and the second port P2, and a switching element 191 made of FET is provided between the first port P1 and the third port P3. A control voltage is applied to the gate electrode of each switching element from the control port V, and the electrical connection state between the ports is controlled by the ON / OFF state of each switching element. As another configuration, the second port P2 and the third port P3 may be grounded by another switching element.

When an antenna diversity circuit is configured using such an SPDT switch circuit, a plurality of switching elements of three SPDT switch circuits 180, 181, and 182 are provided in the path of the transmission signal.
In the case of a high-frequency circuit using a balanced amplifier, the number of stages is increased by connecting multiple switching elements in series so that transmission is possible even when the transmission output power is high. However, the area occupied by the switching element increases and the SPDT switch circuit also increases. If three SPDT switch circuits are used, the space required for constructing the SPDT switch circuit is also tripled in a single order, and the increase in switching elements arranged in the signal path leads to an increase in insertion loss. There is also.

  Therefore, the present invention has an object to provide a high-frequency circuit that is configured using a balanced amplifier and has excellent electrical characteristics that can use antenna diversity while suppressing an increase in insertion loss and preventing an increase in circuit size. .

  The present invention includes a first switch disposed between the first port and the sixth port, a second switch disposed between the second port and the sixth port, the first port, and the third port. A third switch disposed between the ports, a fourth switch disposed between the second port and the fourth port, and a balanced type disposed between the fifth port and the sixth port An amplifier, and the connection between the fifth port and the first port or the second port is switched by the first switch and the second switch, and the third port and the first port or by the third switch The high-frequency circuit is characterized in that the connection with the ground is switched and the connection between the fourth port and the second port or the ground is switched by the fourth switch.

  In the present invention, the first port is connected to the first antenna, the second port is connected to the second antenna, the third port is connected to the first receiver circuit, and the fourth port is the second receiver. The fifth port is connected to a transmission circuit.

  The balanced amplifier has two input ports and two output ports, and can input a signal to one input port and output the amplified signal to one output port. The other input port and output port are Terminated with a resistor.

  In the present invention, an SPST switch circuit is connected between the output port side of the balanced amplifier and the first antenna or the second antenna. For this reason, it is possible to configure a small number of switching elements provided from the balanced amplifier to the transmission signal with each antenna.

Preferably, the input port of the balanced amplifier is connected to a transmission circuit of a high frequency semiconductor circuit (RFIC), and the antenna is connected to a reception circuit of the RFIC.
In addition, a configuration capable of realizing MIMO (Multi-Input Multi-Output), which is a wireless communication technology that extends a data transmission / reception band by providing a plurality of high-frequency circuits and connecting an antenna to the output port side of each balanced amplifier. Also good.

  According to the high frequency circuit of the present invention, it is possible to simplify the switch circuit, suppress an increase in insertion loss, prevent an increase in the size of the high frequency circuit, and provide a balanced amplifier excellent in electrical characteristics that can use antenna diversity. It is possible to provide a high-frequency circuit configured by using.

It is a figure which shows the equivalent circuit of the high frequency circuit by one Example of this invention. It is a figure for demonstrating the SPDT switch circuit used for the high frequency circuit by one Example of this invention. It is a circuit block diagram for demonstrating the balanced amplifier used for the high frequency circuit by one Example of this invention. (A) It is an equivalent circuit diagram which shows an example of the hybrid circuit of the balanced amplifier used for the high frequency circuit by one Example of this invention. (B) It is an equivalent circuit diagram which shows the other example of the hybrid circuit of the balanced amplifier used for the high frequency circuit by one Example of this invention. It is a circuit block diagram of the high frequency circuit part of the radio | wireless communication apparatus comprised using the high frequency circuit of this invention. It is a figure which shows the circuit block which shows the structural example of the conventional high frequency circuit. It is a figure which shows the circuit block which shows the other structural example of the conventional high frequency circuit. It is a figure which shows the circuit block which shows the other structural example of the conventional high frequency circuit. It is a figure which shows the structure of a SPDT switch circuit.

  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. Although the configuration of the balanced amplifier has already been described, 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, and one side of the hybrid circuit 20 is connected to the input port P1 and the termination resistor R1, and the other side is connected to the input side of the first amplifier 15 and the second amplifier 16 Connect to the input side. One side of the hybrid circuit 21 is connected to the output port P2 and the termination resistor R2, and the other side is connected to the output side of the first amplifier 15 and the output side of the second amplifier 16.

The high-frequency circuit of the present invention includes a first switch SC1 disposed between the first port Po1 and the sixth port Po6, and a second switch SC2 disposed between the second port Po2 and the sixth port Po6. A third switch SC3 disposed between the first port Po1 and the third port Po3, a fourth switch SC4 disposed between the second port Po2 and the fourth port Po4, and a fifth switch SC4. A balanced amplifier 10 is provided between the port Po5 and the sixth port Po6.
The connection between the fifth port Po5 and the first port Po1 or the second port Po2 is switched by the first switch SC1 and the second switch SC2, and the third port Po3 and the first port are switched by the third switch SC3. The connection with the port Po1 or the ground GND is switched, and the connection between the fourth port Po4 and the second port Po2 or the ground GND is switched by the fourth switch SC4.

The first to fourth switches SC1, SC2, SC3, and SC4 can be configured by switching elements made of FETs. FIG. 2A shows the first switch SC1 and the third switch SC3 connected to the first port Po1 as a switch circuit SWA, and FIG. 2B shows the second switch SC2 and the fourth switch SC4 connected to the second port Po2. Is shown as a switch circuit SWB.
A balanced amplifier with higher transmission output power is used, but multiple switching elements are connected in series to increase the number of stages so that transmission is possible even with high transmission output power. The configuration can be adopted as appropriate. Even if such a power-resistant structure is adopted, the switch circuit disposed in the signal path is reduced compared to the conventional high-frequency circuit, so that the high-frequency circuit is relatively small and has excellent electrical characteristics. I can do it.

  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.

  FIGS. 4A and 4B show configuration examples of the hybrid circuit used in the present invention. The hybrid circuit shown in FIG. 4A is a 90-degree hybrid coupler having four ports Pb1 to Pb4, and two coupling lines Lc1 and Lc2 each having a length corresponding to a quarter wavelength are arranged opposite to each other. Configured. The coupled lines Lc1 and Lc2 are formed as distributed constant lines having a predetermined characteristic impedance (for example, 50Ω). In some cases, a capacitance element is connected to both ends of each of the coupling lines Lc1 and Lc2 to form a low-pass filter, or an inductance element may be used instead of the distributed constant line. Here, the length corresponding to 1/4 wavelength includes not only the case where the actual length between ports is 1/4 wavelength, but also the case where the wavelength is shortened and equivalently 1/4 wavelength. Say the length to function as.

  When a 90-degree hybrid coupler is used as the first hybrid circuit 20, when the port Pb2 is connected to the input port P1, the port Pb1 is connected to the input side of the second amplifier 16, the port Pb3 is connected to the termination resistor R1, and the port Pb4 is connected to the input side of the first amplifier 15. The signal input to the port Pb2 is divided into two, and the signals appearing at the ports Pb1 and Pb4 have a phase difference of 90 degrees due to the phase delay.

  When a 90-degree hybrid coupler is used as the second hybrid circuit 2, when its port Pb2 is connected to the output side of the first amplifier 15, the port Pb1 is connected to the output port P2, and the port Pb3 is connected to the output side of the second amplifier 16. The port Pb4 is connected to the termination resistor R2. The output signals amplified by the first amplifier 15 and the second amplifier 16 are input to the ports Pb2 and Pb3 with a phase difference of 90 degrees. Due to the phase delay between the ports Pb3 and Pb4, a high-frequency signal which is in-phase with the output port P2 and synthesized and amplified by about twice is output.

  FIG. 4B shows another configuration example of the hybrid circuit used in the present invention. The hybrid circuit shown here is a branch line type hybrid synthesizer / distributor having four ports Pb1 to Pb4. It is composed of four distributed constant lines Lh1 to Lh4 each having a length corresponding to a quarter wavelength. If the characteristic impedance of the distributed constant lines Lh3 and Lh4 is aΩ, the characteristic impedance of the distributed constant lines Lh1 and Lh2 is bΩ (b is a value obtained by dividing a by the square root of 2). Moreover, you may comprise with the lumped constant element of an inductance element and a capacitance element.

  When the branch line type hybrid combiner / distributor is the first hybrid circuit 20, when the port Pb1 is connected to the input port P1, the port Pb2 is connected to the input side of the first amplifier 15, and the port Pb3 is connected to the termination resistor R1. Then, the port Pb4 is connected to the input side of the second amplifier 16. In the case of the second hybrid circuit 21, when the port Pb1 is connected to the output side of the first amplifier 15, the port Pb2 is connected to the termination resistor R2, the port Pb3 is connected to the output side of the second amplifier 16, and the port Pb4 Is connected to the output port P2.

FIG. 5 shows a front end circuit portion of a wireless communication apparatus including the high frequency circuit of the present invention.
In the high-frequency circuit, the transmission signal from the RFIC is input to the input port side of the balanced amplifier 10 from the fifth port Po5, and the reception signal is output from the third port Po3 and the fourth port Po4 toward the RFIC. In the path of the received signal from the third port Po3 and the fourth port Po4 to the RFIC, bandpass filters 140, 141, 147 and 148, a low noise amplifier 145 sandwiched between the bandpass filters 140 and 147, and a bandpass filter 141 and 148 are connected to a low-noise amplifier 146, a band-pass filter 147 and a balun 149 for converting a reception signal which is an unbalanced signal into a balanced signal, and a band-pass filter 148 and connected to an unbalanced signal. And a balun 150 for converting a received signal into a balanced signal.

  In the high-frequency circuit of the present invention, the switching element of each switch is controlled as shown in Table 1 by the control voltage applied to each control port V. Here, a case where one signal path is connected to one of the antennas and the other path is disconnected is shown. In the switch circuit SWA, the control ports V of the switching elements SW1-1 and SW3-2 can be shared. Similarly, in the switch circuit SWB, the control ports V of the switching elements SW2-1 and SW4-2 can be shared.

  Here, the first amplifier 15 in the case where the first port Po1 and the fifth port Po5 are connected (Tx1 mode) and the second port Po2 and the fifth port Po5 are connected (Tx2 mode). The second amplifier 16 is in an operating state, and in condition 3 (Rx1 mode) in which the first port Po1 and the third port Po3 are connected, and in condition 4 (Rx2 mode) in which the second port Po2 and the fourth port Po4 are connected. Non-operating state. When transmitting and receiving simultaneously using different antennas, the operational state of the amplifier and the operational state of each switch element are controlled so that Condition 1 and Condition 3 and Condition 2 and Condition 4 are satisfied simultaneously. It may be different from the operation shown. Further, the ON / OFF state of the switching element that does not directly affect the transmission / reception operation can be set as appropriate.

  When the first and second amplifiers 15 and 16 are operated in a region, nonlinear operation is performed. In addition to the fundamental frequency component, an even-order harmonic component (2n harmonic wave; n is a natural number of 1 or more), an odd-order harmonic component ( Harmonic components such as 3n harmonics) are generated. The second hybrid circuit 21 reflects the even harmonic components instead of a predetermined impedance load and inputs them to the first and second amplifiers 15 and 16 to be mixed with the fundamental wave and have the same frequency as the fundamental wave. Thus, the frequency component is shifted in phase. This may cause ripples in the high-frequency signal output from the output port. Further, the high frequency signal input to the high frequency circuit 10 may also contain harmonic components and be amplified by the first and second amplifiers 15 and 16.

  In the harmonic circuit of the present invention, it is preferable to reduce the ripple and loss by attenuating harmonics by providing harmonic attenuation means on the output sides of the first and second amplifiers 15 and 16, respectively. The harmonic attenuation means is preferably composed of a filter, and a low-pass filter or a notch filter can be used. According to the low-pass filter, both the even-order harmonic component and the odd-order harmonic component can be attenuated. When only the even-order harmonic component is selectively attenuated, a stub may be used. When the harmonic attenuation means is provided, one having the same characteristics (phase shift and loss) is used in each path from the viewpoint of reducing the combined loss.

DESCRIPTION OF SYMBOLS 10 Balance type amplifier 15 1st amplifier 16 2nd amplifier 20 1st hybrid circuit 21 2nd hybrid circuit R1, R2 Termination resistance IN Input port OUT Output port

Claims (3)

Between the 1st switch arranged between the 1st port and the 6th port, the 2nd switch arranged between the 2nd port and the 6th port, and between the 1st port and the 3rd port A third switch disposed between the second port and the fourth port, and a balanced amplifier disposed between the fifth port and the sixth port. ,
The connection between the fifth port and the first port or the second port is switched by the first switch and the second switch,
The third switch switches the connection between the third port and the first port or the ground,
A high frequency circuit characterized in that the connection between the fourth port and the second port or the ground is switched by the fourth switch. The third switch has a switching element connected between the first port and the third port, and a switching element connected between the third port and the ground,
The fourth switch includes a switching element connected between the second port and the fourth port, and a switching element connected between the fourth port and the ground. The high frequency circuit described in 1. The first port is connected to a first antenna, the second port is connected to a second antenna, the third port is connected to a first receiver circuit, and the fourth port is connected to a second receiver circuit; The high-frequency circuit according to claim 1, wherein the fifth port is connected to a transmission circuit.

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