JP2008193238A - High frequency switch circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an electric power resistance in a high frequency switch circuit. <P>SOLUTION: One of a circuit part by a plurality of serially connected switching elements 4a-4n is connected to a connection point A on a transmission line 3 connecting an input terminal 1 and an output terminal 2, and one end of a circuit part by a plurality of serially connected switching elements 5a-5n is connected to a connection point B separated from the connection point A on the transmission line 3 by the length of the odd number multiple of 1/4 wavelength. The respective control ends of the switching elements 4a-4n and 5a-5n are connected to a control terminal 6 in order to control the conduction. In the high frequency switch circuit configured in such a manner, high frequency signals from the input terminal 1 to the output terminal 2 are interrupted when the switching elements 4a-4n and 5a-5n are controlled to be off and are transmitted when the switching elements 4a-4n and 5a-5n are controlled to be on. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high frequency switch circuit, and more particularly to a high frequency switch circuit suitable for use in a frequency band from a microwave band to a millimeter wave band.

  As a conventional high-frequency switch circuit, for example, there is one shown in Patent Document 1 below. In Patent Document 1, in a high-frequency switch circuit that selectively connects an antenna terminal (1) to two input / output terminals (2, 3), a transmission line that connects the two input / output terminals (2, 3) A semiconductor switching element (6, 7) is provided between the ground and a 1/4 wavelength line (4, 5) is inserted in the transmission line, and the semiconductor switching is performed between the point on the transmission line and the ground. A high-frequency switch circuit is disclosed in which inductive reactance circuits (101, 102) that constitute a resonance circuit in combination with an element are provided.

  In this high-frequency switch circuit, the semiconductor switching element connected to one end of the 1/4 wavelength line is turned on, while the semiconductor switching element connected to the other end of the 1/4 wavelength line is turned off, so that the input The impedance when the one end side of the 1/4 wavelength line is viewed from the side is opened, and conversely, the impedance is not opened when the other end side of the 1/4 wavelength line is viewed from the input side. ing.

  That is, in the conventional high-frequency switch circuit, control is performed using one path from the input side toward one end side of the quarter wavelength line as a cutoff path, and the other side from the input side toward the other end side of the quarter wavelength line. The path switching of the high-frequency signal is realized by performing the control using the path No. 1 as the passing path.

JP-A-8-213802

  However, in the technology common to the conventional high-frequency switch circuit represented by the above-mentioned Patent Document 1 and the like, consideration is given to the viewpoint of passage loss and signal leakage, but consideration is not given to the viewpoint of power durability. For this reason, the conventional high-frequency switch circuit has a problem that it is difficult to apply to a high-frequency circuit having a large input power.

  In the configuration of the conventional high-frequency switch circuit, the power durability of the high-frequency switch circuit itself depends only on the power durability of the semiconductor switching element. Therefore, when applied to a high-frequency circuit with relatively large input power, the semiconductor switching There is a problem in that the size of the element itself needs to be increased, and the high-frequency switch circuit becomes larger.

  The present invention has been made in view of the above, and an object of the present invention is to provide a high-frequency switch circuit with improved power durability.

  In order to solve the above-described problems and achieve the object, a high-frequency switch circuit according to the present invention is provided with a transmission line, a first terminal provided at one end of the transmission line, and the other end of the transmission line. A first switching element circuit unit configured by a second terminal and a plurality of switching elements connected in series, one end of which is connected to the first connection point of the transmission line, and a plurality of switching elements connected in series A second switching element circuit unit connected at one end to a second connection point separated by an odd multiple of a quarter wavelength from the first connection point of the transmission line, and connected in series. And a control terminal configured to control conduction of each switching element of the first and second switching element circuit units.

  According to the high frequency switch circuit of the present invention, the circuit unit for controlling the passage and blocking of the high frequency signal from the input terminal to the output terminal is configured by a plurality of switching elements connected in series, and one end of the transmission line is A first switching element circuit unit connected to the first connection point and a plurality of switching elements connected in series, one end of which is an odd number of 1/4 wavelength from the first connection point of the transmission line Since the second switching element circuit portion connected to the second connection point separated by the double length is provided, there is an effect that it is possible to provide a high-frequency switch circuit with improved power durability. .

  Hereinafter, a high frequency switch circuit according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment.

(Configuration of high-frequency switch circuit)
FIG. 1 is a diagram showing a circuit configuration of a high-frequency switch circuit according to a preferred embodiment of the present invention. The high-frequency switch circuit shown in the figure includes a transmission line 3, an input terminal 1 provided at one end of the transmission line 3, an output terminal 2 provided at the other end of the transmission line 3, for example, switching elements 4a to 4n that are FETs, 5a to 5n and a control terminal 6 for ON / OFF control of these switching elements are provided.

  In FIG. 1, a plurality of switching elements 4 a to 4 n are connected in series, and one end of the circuit section connected in series (in the example of FIG. 1, the drain of the switching element 4 a) is connected to point A on the transmission line 3. ing. Similarly, one end (a drain of the switching element 5a in the example of the figure) of the circuit unit formed by the plurality of switching elements 5a to 5n connected in series is connected to a point B different from the point A on the transmission line 3. Yes. Each of the other ends of the circuit unit including the switching elements 4a to 4n and the circuit unit including the switching elements 5a to 5n (the sources of the switching elements 4n and 5n in the example shown in the figure) is grounded. Further, the control terminals (gates) of the switching elements 4a to 4n and 5a to 5n are connected to the control terminal 6, respectively. That is, the switching elements 4a to 4n and the switching elements 5a to 5n are simultaneously controlled by the control signal input from the control terminal 6.

  In addition, the length (electric length) d between the connection points A and B is ¼ of the input signal wavelength (hereinafter referred to as “¼ wavelength”) in order to effectively bring out the action described later. It is preferable to set so as to satisfy an odd multiple, that is, d = (2m + 1) × λ / 4 (m is a natural number). Furthermore, when considering the viewpoint of circuit miniaturization, the length (electric length) between the connection points A and B is set to ¼ (d = λ / 4) of the input signal wavelength. More preferably.

(High-frequency switch circuit operation)
Next, the operation of the high-frequency switch circuit shown in FIG. 1 will be described with reference to FIGS. 2 is a circuit diagram showing an equivalent circuit when the switching elements 4a to 4n and 5a to 5n are off-controlled, and FIG. 3 is an equivalent circuit when the switching elements 4a to 4n and 5a to 5n are on-controlled. It is a circuit diagram which shows a circuit.

(Operation when switching element is turned off)
First, the operation when the switching elements 4a to 4n and 5a to 5n are off-controlled will be described. In FIG. 1, when a control signal for controlling the switching elements 4a to 4n and the switching elements 5a to 5n to be turned off is input to the control terminal 6, the equivalent circuit of the connection circuit portion by the switching elements 4a to 4n is as shown in FIG. In addition, the equivalent circuit 16 in which the capacitors 8a to 8n, which are the off-capacitances of the switching elements 4a to 4n, and the parasitic inductances 7a to 7n are connected in series. Similarly, the equivalent circuit of the connection circuit unit using the switching elements 5a to 5n is an equivalent circuit 18 in which capacitors 10a to 10n, which are the off-capacitances of the switching elements 5a to 5n, and parasitic inductances 9a to 9n are connected in series. It becomes.

  Here, by setting the number of connected switching elements such that the capacitors 8a to 8n and the parasitic inductances 7a to 7n in the equivalent circuit 16 are in series resonance in a desired frequency band, the equivalent circuit 16 in the frequency band is set. The impedance can be substantially zero, and the point A can be a short-circuit point in the frequency band.

  Further, by setting the number of switching elements connected so that the capacitors 10a to 10n and the parasitic inductances 9a to 9n in the equivalent circuit 18 are in series resonance in a desired frequency band, the impedance of the equivalent circuit 18 in the frequency band is set. Can be substantially zero, and the point B can also be a short-circuit point in the frequency band.

  On the other hand, since the length between the connection points A and B is set to an odd multiple of 1/4 wavelength as described above, the impedance viewed from the A point to the B point side is a 1/4 wavelength distributed constant line. The impedance in the case where the terminal portion of the circuit is short-circuited, that is, substantially infinite.

  In this way, by switching off the switching elements 4a to 4n and 5a to 5n, the point A is set as a short circuit point, while the point A viewed from the point B side (the output terminal 2 side) is caused to function as an open point. Therefore, it is possible to effectively block a signal from the input terminal 1 to the output terminal 2.

Now, assuming that the parasitic inductances of the switching elements 4a to 4n are Lp (p = a to n) and the off-capacitance is Cp (p = a to n), the series resonance frequency fc in the equivalent circuit 16 is expressed by the following equation. The
fc = 1 / (2 × π × √ (Lt × Coff)) (1)
However, in the above equation (1), Lt = La +... + Ln, 1 / Coff = (1 / Ca +... + 1 / Cn).

  The same applies to the equivalent circuit 17. The series resonance frequency fc in the equivalent circuit 17 is such that the parasitic inductances of the switching elements 5a to 5n are Lp (p = a to n) and the off capacitance is Cp (p = a to n). ) Can be expressed by the above formula (1).

(Operation when switching element is on-controlled)
Next, an operation when the switching elements 4a to 4n and 5a to 5n are on-controlled will be described. In FIG. 1, when a control signal for turning on the switching elements 4 a to 4 n and the switching elements 5 a to 5 n is input to the control terminal 6, an equivalent circuit of the connection circuit unit by the switching elements 4 a to 4 n is as shown in FIG. 3. In addition, an equivalent circuit 17 is formed in which the resistors 11a to 11n, which are the on-resistances of the switching elements 4a to 4n, and the parasitic inductances 7a to 7n are connected in series. Similarly, an equivalent circuit of a connection circuit unit using the switching elements 5a to 5n is an equivalent circuit 19 in which resistors 12a to 12n, which are on-resistances of the switching elements 5a to 5n, and parasitic inductances 9a to 9n are connected in series. It becomes.

  Here, in the equivalent circuit 17, as described above, the number of connected switching elements is set such that the off-capacitance of each switching element and each parasitic inductance resonate in series in a desired frequency band. For this reason, in the equivalent circuit 17, a plurality of switching elements 4 a to 4 n are connected in series and connected in series, and the resistors 11 a to 11 n and the parasitic inductances 9 a to 9 n are added to each other. A point to which 4n is connected can be an open point in the frequency band.

  Also in the equivalent circuit 19, a plurality of switching elements 5 a to 5 n are connected in series and connected in series, and the resistors 12 a to 12 n and the parasitic inductances 9 a to 9 n are added. The point B to which 5n is connected can also be an open point in the frequency band.

  On the other hand, since the length between the connection points A and B is set to an odd multiple of 1/4 wavelength as described above, the impedance viewed from the A point to the B point side is a 1/4 wavelength distributed constant line. The impedance in the case where the terminal portion of the terminal is open, that is, substantially zero can be set.

  In this way, by switching on the switching elements 4a to 4n and 5a to 5n, the point A is set as an open point, while the point A viewed from the point B side (output terminal 2 side) is caused to function as a short-circuit point. Therefore, it is possible to effectively transmit a signal from the input terminal 1 to the output terminal 2.

  Further, since the switching elements 4a to 4n and 5a to 5n are connected in series in multiple stages, the input high frequency voltage is divided and applied to each switching element, so that it is compared with a conventional high frequency switch circuit. Thus, it is possible to achieve higher power durability.

(Study on bonding wire inductance)
In the high-frequency switch circuit shown in FIG. 1, the input terminal 1 and the output terminal 2 are provided at one end and the other end on the transmission line, respectively, but only between points A and B to which the switching elements are connected. It is also conceivable that the transmission line is used as a transmission line, and the connection between the point A and the input terminal 1 and the point B and the output terminal are bonded by a gold wire or the like. In such a bonding connection, the inductance of the bonding wire to be bonded often becomes a problem.

  Here, for example, a conventional high-frequency switch circuit in which a PIN diode is mounted with a bonding wire will be considered. For example, FIG. 4 is a diagram showing an example of a conventional configuration in which a PIN diode is mounted with a bonding wire, and FIG. 5 is a diagram showing an equivalent circuit of the high-frequency switch circuit shown in FIG.

  In the high-frequency switch circuit shown in FIG. 4, the PIN diode 30 and the input / output lines 22 and 23 formed on the substrates 20 and 21 are connected by bonding wires 24 and 25, respectively. In the case of such a configuration, the equivalent circuit has an LPF configuration with an inductance L of the bonding wire and a capacitance Cj of the PIN diode, as shown in FIG.

  Here, the inductance of the bonding wire is, for example, about 0.4 nH due to mounting restrictions, and the capacitance of the PIN diode is, for example, about 0.1 pF. In this case, the cut-off frequency of the high-frequency switch circuit is about 39 GHz, and for example, the loss in the quasi-millimeter wave band and the millimeter wave band becomes very large.

  On the other hand, when the inductance L of the bonding wire is reduced in order to reduce the loss in the quasi-millimeter wave band or the millimeter wave band, matching with the transmission line becomes difficult. Therefore, the high-frequency switch circuit according to the configuration of the prior art as shown in FIG. 4 cannot be employed as a high-frequency switch circuit used in, for example, a quasi-millimeter wave band or a millimeter wave band.

  On the other hand, in the high-frequency switch circuit according to the present embodiment, the high-frequency switch circuit itself switches between a ground state (switching element on state) and a matching state (switching element off state) by a quarter wavelength line (50Ω). Therefore, the influence of the inductance of the bonding wire connected to the input / output terminal can be ignored. Therefore, the high-frequency switch circuit according to the present embodiment can be suitably used, for example, in a quasi-millimeter wave band or a millimeter wave band.

  As described above, according to the high-frequency switch circuit of this embodiment, a plurality of switching elements 4a connected in series as a circuit unit for controlling the passage and blocking of a high-frequency signal from the input terminal 1 to the output terminal 2 are used. 4n, one end of which is connected to a connection point A of the transmission line 3, and a plurality of switching elements 5a to 5n connected in series, one end of which is a connection point of the transmission line 3. Since the switching element circuit portion connected to the connection point B separated from A by an odd multiple of a quarter wavelength is provided, a high-frequency switch circuit with improved power durability can be provided.

  In the above embodiment, an example in which a field effect transistor (FET) is used as a switching element has been described. However, for example, a bipolar transistor having a junction capacitance such as an IGBT can also be used.

  As described above, the high-frequency switch circuit according to the present invention is useful as a high-frequency switch circuit with improved power durability.

It is a figure which shows the circuit structure of the high frequency switch circuit concerning suitable embodiment of this invention. It is a circuit diagram which shows the equivalent circuit at the time of carrying out OFF control of each switching element. It is a circuit diagram which shows the equivalent circuit at the time of carrying out ON control of each switching element. It is a figure which shows an example of the conventional structure which mounted the PIN diode with the bonding wire. It is a figure which shows the equivalent circuit of the high frequency switch circuit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input terminal 2 Output terminal 3 Transmission line 4a-4n, 5a-5n Switching element 6 Control terminal 7a-7n, 9a-9n Parasitic inductance 8a-8n, 10a-10n Off-capacitance 11a-11n, 12a-12n On-resistance 16- 19 Equivalent circuit 20, 21 Substrate 22, 23 Input / output line 24, 25 Bonding wire 30 PIN diode

Claims (2)

A transmission line;
A first terminal provided at one end of the transmission line;
A second terminal provided at the other end of the transmission line;
It is composed of a plurality of switching elements connected in series, one end of which is composed of a first switching element circuit unit connected to the first connection point of the transmission line, and a plurality of switching elements connected in series, A second switching element circuit portion having one end connected to a second connection point separated from the first connection point of the transmission line by an odd multiple of a quarter wavelength; and a plurality of switching elements connected in series A control terminal configured to control conduction of each switching element of the first and second switching element circuit units;
A high-frequency switch circuit comprising: A transmission line having a length that is an odd multiple of a quarter wavelength;
A first terminal provided from one end of the transmission line;
A second terminal provided by being pulled out from the other end of the transmission line;
A first switching element circuit unit configured by a plurality of switching elements connected in series, one end of which is connected to one end of the transmission line;
A second switching element circuit unit configured by a plurality of switching elements connected in series, one end of which is connected to the other end of the transmission line;
A control terminal for controlling the first and second switching element circuit units;
A high-frequency switch circuit comprising:

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