WO2006035531A1

WO2006035531A1 - High frequency signal switching circuit

Info

Publication number: WO2006035531A1
Application number: PCT/JP2005/010663
Authority: WO
Inventors: Akira Kato
Original assignee: Murata Manufacturing Co., Ltd.
Priority date: 2004-09-27
Filing date: 2005-06-10
Publication date: 2006-04-06
Also published as: DE112005002018B4; DE112005002018T5; JPWO2006035531A1; JP4404093B2

Abstract

When a diode (D1) is in the conduction state and a diode (D2) is in the interruption state, a transmission signal inputted from a transmission signal input terminal (101) is inputted to the tertiary winding (31) of a balun transformer (1) and a transmission signal having phase shift of 180° is excited in the secondary winding (21) and outputted to the diode (D2). Even if the diode (D2) is in the interruption state, the transmission signal having phase shift of 180° leaks to the reception signal output terminal (102) side. On the other hand, a signal cancel network (2) outputs the inputted transmission signal to the reception signal output terminal (102) side without varying the phase. Since these two transmission signals have phase shift of 180°, they are offset and attenuated. Consequently, the transmission signal is not transmitted to the reception signal output terminal (102).

Description

Specification

High frequency signal switching circuit

Technical field

[0001] The present invention relates to a high-frequency signal switching circuit for switching two high-frequency input / output terminals to another high-frequency input / output terminal, and in particular, switching and connecting either a transmission circuit or a reception circuit to an antenna. It relates to an antenna switch.

Background art

[0002] The antenna switch includes an antenna input / output terminal (ANT terminal), a transmission signal input terminal (TX terminal), and a reception signal output terminal (RX terminal). The antenna switch is switched so that the TX and ANT terminals are connected during transmission, and the ANT and RX terminals are connected during reception.

[0003] Conventionally, in such an antenna switch, a SPDT switch using a diode for each of a transmission signal path and a reception signal path is often used. In this case, one diode is installed in each signal path. It was.

[0004] However, with an antenna switch with one diode installed in each signal path, the isolation cannot be made large enough, and the TX terminal force causes a large power transmission signal to be input to the RX terminal. There was a problem if the SAW filter etc. that was transmitted and connected to the RX terminal was damaged. As an antenna switch that solves this problem, Patent Document 1 discloses a high-frequency signal switching circuit in which a plurality of diodes are installed in each signal path.

Patent Document 1: Japanese Patent Laid-Open No. 7-288458

Disclosure of the invention

Problems to be solved by the invention

However, the high-frequency signal switching circuit described in Patent Document 1 can increase isolation by increasing the number of installed diodes. The high-frequency signal switching circuit is complex and large depending on the number of installed diodes. Become. In addition, an increase in the number of diodes connected to the signal path increases insertion loss as a high-frequency signal switching circuit. In other words, even necessary signals are attenuated. [0006] Accordingly, an object of the present invention is to provide a high-frequency signal switching circuit having a simple structure with a large isolation without increasing insertion loss.

Means for solving the problem

[0007] A high-frequency signal switching circuit according to the present invention comprises an unbalanced-balanced conversion comprising one unbalanced terminal, a first balanced terminal having the same phase as the unbalanced terminal, and a second balanced terminal having an opposite phase to the unbalanced terminal. A first signal input / output terminal connected to the first balanced terminal via the first switch element; a second signal input / output terminal connected to the second balanced terminal via the second switch element; A switch element, a switch control means for performing on / off control of the second switch element, and a first signal input / output terminal and a second signal input / output terminal are connected to transmit a signal without changing the phase. And a signal cancel circuit network for transmission.

[0008] With this configuration, when a high-frequency signal is input from the first signal input / output terminal in a state where the first switch element is in a conductive state and the second switch element is in a disconnected state, the high-frequency signal is converted into an unbalanced balanced converter. Input to the first balanced terminal. With this high-frequency signal, a high-frequency signal with the same phase is output as the unbalanced terminal force of the unbalance-equilibrium change, and a high-frequency signal with the opposite phase (180 ° phase shift) is output from the second balanced terminal. The 180 ° phase-shifted high-frequency signal output from the second balanced terminal leaks through the disconnected second switch element and is transmitted in the direction of the second signal input / output terminal. On the other hand, the signal cancellation network transmits the signal in the direction of the second signal input / output terminal without changing the phase of the high frequency signal input from the first signal input / output terminal. The high-frequency signal transmitted through this signal cancellation circuit network (the high-frequency signal without phase shift) and the high-frequency signal with 180 ° phase shift leaking through the second switch circuit are combined to cancel each other and be attenuated. It is not output to the signal input / output terminal.

[0009] When this is applied to an antenna switch, when a high-frequency signal input to the transmission signal input terminal, that is, a transmission signal is transmitted to the reception signal output terminal side, a 180 ° phase passing through an unbalance-balance converter is transmitted. Since there is no phase shift via the signal cancellation circuit network and / or the transmission signal cancels each other and attenuates, the signal is not transmitted to the reception signal output terminal.

[0010] Further, the present invention is characterized in that the first switch element and the second switch element are PIN diodes. In this configuration, the structure and control are simplified by the PIN diode. The invention's effect

[0012] According to the present invention, it is possible to suppress transmission of a high-frequency signal that has also received a predetermined first terminal force without increasing the number of switch elements to a second terminal that is not desired to receive this signal. it can. Further, since the number of switch elements is small, a necessary signal can be transmitted to the second terminal without being attenuated. Specifically, in an antenna switch, transmission of a transmission signal to a reception signal output terminal can be suppressed without increasing the number of switch elements. At this time, the received signal is hardly attenuated before being transmitted to the received signal output terminal due to the small number of diodes!

[0013] Thereby, it is possible to configure a high-frequency signal switching circuit with a simple structure and a large isolation with a small insertion loss.

[0014] Further, according to the present invention, the structure and control are simplified because the switch element is a diode. As a result, it is possible to construct a high-frequency signal switching circuit having a simpler structure and a large isolation with less insertion loss.

Brief Description of Drawings

FIG. 1 is a block diagram showing a configuration of an antenna switch according to the present embodiment.

FIG. 2 is a diagram showing a simulation result of isolation according to the configuration of the present embodiment, the configuration of the conventional example, and further the configuration of the present embodiment excluding the signal cancel circuit network.

Explanation of symbols

[0016] 1-banolene transformer

11-Balun Trans 1 primary shoreline

21—Secondary shoreline of Balun Trans 1

31-3rd shoreline of Balun Trans 1

2—Signal cancellation network 2

101—Transmission signal input terminal

102—Received signal output terminal

103—Antenna input / output terminal 104—First switch control signal input terminal

105—Second switch control signal input terminal

BEST MODE FOR CARRYING OUT THE INVENTION

The high-frequency signal switching circuit of the present invention will be described with reference to FIGS. In the following description, an antenna switch is shown as an example of the high-frequency signal switching circuit.

FIG. 1 is a block diagram showing the configuration of the antenna switch of this embodiment.

[0018] The balun transformer 1 is a trifilar wound balun transformer comprising a primary winding 11 on the unbalanced terminal side, a secondary winding 21 on the balanced terminal side, and a tertiary winding 31. When a signal is input to 11, the in-phase signal is excited on the tertiary winding 31, and a reverse-phase (180 ° phase shift) signal is excited on the secondary winding 21. In this case, when a signal is input to the tertiary winding 31, an in-phase signal is excited on the primary winding 11, and a 180 ° phase shift signal is excited on the secondary winding 21.

[0019] One end (unbalanced signal input / output end) of primary winding 11 of balun transformer 1 is connected to antenna input / output terminal 103, and the other end is grounded.

[0020] In addition, the connection between the secondary winding 21 on the balanced terminal side of the balun transformer 1 and the tertiary winding 31 (center tap on the balanced terminal side) is grounded, and the center tap of the secondary winding 21 The end facing the diode T2 is connected to the power sword of the diode D2 made of a PIN diode, and the end facing the center tap of the tertiary winding 31 is connected to the power sword of the diode D1 also having the PIN diode force.

Here, the balun transformer 1 corresponds to the “unbalanced / equilibrium variation” of the present invention. One end of the primary winding 11 of the current transformer 1 corresponds to the “unbalanced terminal” of the present invention, and the end facing the center tap of the secondary winding 21 of the noren transformer 1 is the “second balanced terminal”. The end facing the center tap of the tertiary winding 31 of Baluntrans 1 corresponds to the “first balanced terminal”. The diodes Dl and D2 correspond to “switch elements” of the present invention.

[0022] The anode of the diode D1 is connected to the transmission signal input terminal 101 via the DC cut capacitor C1, and the anode of the diode D2 is connected to the reception signal output terminal 102 via the DC cut capacitor C2.

[0023] The anode of the diode D1 is the first switch control signal input terminal via the resistor R40. This first switch control signal input terminal 104 is grounded at a high frequency by a capacitor C40. The anode of the diode D2 is connected to the second switch control signal input terminal 105 via the resistor R50, and the second switch control signal input terminal 105 is grounded at high frequency by the capacitor C50. Here, resistors R40 and R50 should have high impedance for high-frequency signals, so replace them with RF choke coils.

[0024] The signal cancellation circuit network 2 also includes a resistor R20 and a capacitor C20 connected in series, and is connected between the anode of the diode D1 and the anode of the diode D2.

Next, the operation of the antenna switch having such a configuration will be described.

[0026] (1) When sending

At the time of transmission, the first switch control signal VD1 in the Hi state is input from the first switch control signal input terminal 104 and supplied to the diode D1. The diode D1 is turned on by the first switch control signal VD1 in the Hi state. Also, the second switch control signal VD2 that is in a DC low state is input from the second switch control signal input terminal 105 and supplied to the diode D2, and the second switch control signal VD2 is not input to the diode D2. The second switch control signal is not supplied. As a result, the diode D2 is cut off.

In this state, when a high-frequency transmission signal is input from the transmission signal input terminal 101, it passes through the diode 1 and is supplied to the tertiary winding 31 of the balun transformer 1. When a transmission signal is input to the tertiary winding 31 of the balun transformer 1, an in-phase (no phase shift) transmission signal is excited to the primary winding 11 and output to the antenna input / output terminal 103.

[0028] In addition, when a transmission signal is input to tertiary winding 31, a transmission signal with a phase shift of 180 ° is excited to secondary winding 21 and output to diode D2. Here, since the diode D2 is in the cut-off state, the transmission signal input from the force sword is attenuated by a predetermined amount, but a part of the transmission signal leaks and is output from the anode.

On the other hand, the transmission signal input from the transmission signal input terminal 101 is also input to the signal cancellation circuit network 2. Signal cancellation network 2 is a series circuit of resistor R20 and capacitor C20, but the transmission signal is set to depend mainly on resistor R20. The signal is attenuated by a certain amount without changing the phase. And output to the reception signal output terminal 102 side. At this time, the amount of attenuation of the transmission signal by the signal cancellation network 2 is set so as to correspond to the amount of attenuation of the transmission signal having a phase shift of 180 ° by the diode D2.

[0030] As described above, the transmission signal without phase shift transmitted through the signal cancellation circuit 2 and the transmission signal with 180 ° phase shift output from the anode of the diode D2 are the diode D2 and the signal cancellation circuit network. Join at the connection point with 2. Here, as described above, these two signals have almost the same amplitude and are 180 ° out of phase, that is, opposite in phase, so that they cancel each other and attenuate. As a result, the transmission signal is not transmitted to the reception signal output terminal 102. In other words, it is possible to increase the isolation of the reception signal output terminal 102 with respect to the transmission signal.

[0031] When the circuit configuration of the signal cancellation network 2 is set to a circuit mainly composed of the capacitor C20, a transmission signal passing through the signal cancellation network 2 and a transmission signal output from the diode D2 The frequency characteristics can be matched. As a result, it is possible to suppress degradation of isolation even if the frequency of the transmission signal changes (rises).

[0032] FIG. 2 is a diagram showing a simulation result of isolation according to the configuration of the present embodiment, the configuration of the conventional example, and further the configuration of the present embodiment excluding the signal cancellation circuit network. Isolation in this case means insertion loss from the transmission signal input terminal 101 to the output terminal 102. Here, the conventional example corresponds to the high-frequency signal switching circuit described in Patent Document 1 described above. In this simulation, the signal level was 0.1 lVrms at a frequency of 10 MHz to 100 MHz, a 1N4148 type diode was used, and the voltage of the switch control signal was 6V.

As shown in FIG. 2, by using the configuration of the present embodiment, it is possible to secure an isolation higher than that of the conventional high-frequency signal switching circuit in almost all frequency bands. In particular, in the frequency band of 40 MHz or higher, it is possible to secure an isolation of 10 dB or more higher than the conventional example.

On the other hand, when there is no signal cancellation circuit network, the isolation is lower than in the conventional example. As a result, as shown in the present embodiment, by using a signal cancellation circuit network together with the balun transformer, it is possible to ensure isolation higher than that of the conventional example. [0035] (2) When receiving

At the time of reception, the second switch control signal VD2 in the Hi state is input from the second switch control signal input terminal 105 and supplied to the diode D2. The diode D2 is turned on by the second switch control signal VD2 in the Hi state. Also, the first switch control signal VD1 that is in a DC low state is input from the first switch control signal input terminal 104 and supplied to the diode D1, and the first switch control signal VD1 is not input to the diode D1. 1 Switch control signal is not supplied. As a result, the diode D1 is cut off.

In this state, when a high frequency received signal is input from the antenna input / output terminal 103, this received signal is supplied to the primary winding 11 of the balun transformer 1. When a received signal is input to the primary winding 11 of the balun transformer 1, a reverse-phase (180 ° phase shift) received signal is excited to the secondary winding 21 and output to the force sword of the diode D2. Since the diode D2 is in a conducting state, the received signal input to the force sword is output from the anode to the received signal output terminal 102 with almost no attenuation. Since the received signal output from the anode is weak V, even if it is input to the signal cancellation circuit 2, it is attenuated by the resistor R20 and is not transmitted to the transmission signal input terminal 101.

[0037] Further, when a reception signal is input to primary winding 11, it is excited by in-phase (no phase shift) reception signal force S3rd winding 31 and is output to diode D1. Since the diode D1 is cut off, the received signal input to the force sword is attenuated by a predetermined amount. At this time, the signal level of the received signal is lower than that of the transmitted signal! Therefore, the received signal is blocked by the diode D1 and not transmitted to the transmission signal input terminal 101.

In this way, at the time of reception, the reception signal can be transmitted to the reception signal output terminal 102 with almost no attenuation. That is, the insertion loss of the received signal can be kept small.

[0039] As described above, by using the configuration of the present embodiment, an antenna switch that suppresses insertion loss of a received signal and ensures large isolation from the received signal output terminal with respect to the transmitted signal is realized with a simple structure. can do.

[0040] In the above description, the force diode showing the structure in which the force swords of the diodes Dl and D2 are connected to the balun transformer 1 functions as a switch element. A structure in which the polarity of the nodes Dl and D2 is reversed, that is, the anode is connected to the balun transformer 1 may be used. In this case, the switch control signal may be changed to one using a negative voltage.

[0041] In the above description, an example has been described in which one diode is inserted in each of the transmission signal path and the reception signal path as the switch element, but the number of diodes is not limited to one. A plurality of diodes may be connected in series.

[0042] In the above description, a semiconductor element such as an FET may be used instead of a force using a diode as a switch element.

[0043] In the above description, the shape of the trifilar winding is shown as the balun transformer. Furthermore, a transformer having a transformer formed on a multilayer ceramic substrate having a thick film Z thin film may be used instead of a winding type. Alternatively, a merchandise balun using a 1Z4 wavelength line may be used.

[0044] In the above description, the high-frequency signal switching circuit that transmits and receives a high-frequency signal by switching and connecting two input / output terminals to one input / output terminal described as an example of an antenna switch. If so, the above-described configuration can be applied, and the above-described effects can be achieved.

Claims

The scope of the claims

[1] An unbalanced-balanced converter comprising one unbalanced terminal, a first balanced terminal having the same phase as the unbalanced terminal, and a second balanced terminal having an opposite phase to the unbalanced terminal;

A first signal input / output terminal connected to the first balanced terminal via a first switch element; a second signal input / output terminal connected to the second balanced terminal via a second switch element; and the first switch Element, switch control means for performing on / off control of the second switch element, and

A signal cancellation circuit connected between the first signal input / output terminal and the second signal input / output terminal and transmitting a signal without changing a phase;

A high-frequency signal switching circuit comprising:

2. The high-frequency signal switching circuit according to claim 1, wherein the first switch element and the second switch element are PIN diodes.