JPH06132701A - Semiconductor switch - Google Patents

Abstract

PURPOSE:To improve reflection/loss characteristics by combining three lines whose length become specified wavelengths by means mutually of a prescribed frequency and mutually compensating reflection occurring on account of susceptance. CONSTITUTION:In an equivalent circuit, a load resistance which an external resistance connected to a second line 9, a third line 11 and a third input/output terminal 7 shows is loaded on a third input/output terminal 7-side in a capacitor Ca connected to a first connection point 2. When first and second field effect transistors 4 and 6 are selected in such a way that an impedance that the capacitor Ca shows as against an impedance which the load shows, the influence of the load can be ignored. In such a case, two capacitors are loaded at the intervals of a 1/4-wavelength. Thus, reflection generated by the capacitors are mutually compensated by a wide frequency, and a satisfactory transmission characteristic can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor switch for switching the propagation path of incident radio waves, and more particularly to a semiconductor switch having high power resistance and wide band.

[0002]

2. Description of the Related Art FIG. 12 shows, for example, Japanese Patent Publication No. 3-6684.
2 is an example of the configuration of the conventional semiconductor switch shown in FIG.

At the first connection point 2, the first input / output terminal 1 is electrically connected to one end of the first line 3 having a length of ¼ wavelength at the center frequency and the drain of the first field effect transistor 4. It is connected to the. The second input / output terminal 5 is connected to the other end of the first line 3 and the drain of the second field effect transistor 6. The source of the first field effect transistor 4 is connected to the third input / output terminal 7,
On the other hand, the source of the second field effect transistor 6 is grounded. The inductor 8 is connected between the drain and the source of the first field effect transistor 4, and the inductor 8 is similarly connected between the drain and the source of the second field effect transistor 6. Further, a bias is externally applied to the gate of the first field effect transistor 4 and the gate of the second field effect transistor 6, but the bias circuit for that purpose is omitted here.

Next, the operation will be described. First, a case where a low power level radio wave is incident from the first input / output terminal 1 will be described, and then a case where a high power level radio wave is incident will be described.

First, consider a switch state in which a radio wave of a low power level enters from the first input / output terminal 1 and propagates to the second input / output terminal 5 with low loss. This state is called a reception state for convenience, and FIG. 13 shows an equivalent circuit in this case. In this state, a negative bias voltage lower than the pinch-off voltage is applied to the gates of the first and second field effect transistors 4 and 6, and the drains of the first and second field effect transistors 4 and 6 are applied. -It exhibits a capacitive impedance between sources. By setting the value of the inductor 8 connected between the drain and the source of the first and second field effect transistors 4 and 6 so as to resonate in parallel with the capacitance C ₁ between the drain and the source, the drain and the source are connected. Has a high impedance. Therefore, the impedance viewed from the connection point 2 to the third input / output terminal 7 side and the impedance exhibited by the second field effect transistor 6 become high. As a result, the equivalent circuit is approximately the same as in FIG.
As shown in FIG. 3, the low power level radio wave incident from the first input / output terminal 1 passes through the first line 3 and is hardly affected by the field effect transistor, and the second input / output terminal 5
Propagate to.

Next, consider a switch state in which a radio wave of a high power level is incident from the first input / output terminal 1 and propagates to the third input / output terminal 7 with low loss. This is called a transmission state for convenience, and FIG. 15 shows an equivalent circuit in this case. In this state, the first and second field effect transistors 4, 6
A gate bias voltage of 0V equal to the ground potential is applied to the gate of the. As a result, low impedance is exhibited between the drain and source of the first and second field effect transistors 4 and 6. If the impedance is sufficiently low, the drain and the source are short-circuited, and the equivalent circuit becomes the circuit shown in FIG. Here, since the tip of the first line 3 having a length of ¼ wavelength connected to the first connection point 2 is grounded, the first connection point 2 is connected to the second input / output terminal 5 side. The impedance seen is a high impedance close to the open state. Therefore, the high-power radio wave incident on the first input / output terminal 1 propagates to the third input / output terminal 7 through the first connection point 2.

[0007]

The conventional semiconductor switch is configured as described above, and since the field effect transistor is used as a low impedance state in a transmission state where a large amount of power is incident, a high voltage is applied to the field effect transistor. Therefore, the breakdown of the field effect transistor is prevented and a high power switch is realized. However, the impedance when the second input / output terminal 5 is viewed from the first connection point 2 becomes a high impedance close to an open state only in the vicinity of the center frequency, and at other frequencies, the above impedance is As a result of the decrease, the susceptance is loaded on the transmission path, the reflection increases, and the radio waves propagating to the third input / output terminal 7 decrease, so that there is a problem that the band is narrow.

The present invention has been made to solve such problems, and an object thereof is to widen the band of a high power withstanding semiconductor switch.

[0009]

In a semiconductor switch according to the present invention, a first terminal of a first switching element is provided at one end of a first line having a length of ¼ wavelength at a predetermined frequency. Connected at one branch point, the first terminal of the second switching element with the second terminal grounded, is connected to the other end of the first line, further the second of the first switching element. One end of a second line having a length of ¼ wavelength at a predetermined frequency is connected to the terminal, and the other end of the second line has a first line of ¼ wavelength at a predetermined frequency. One end of the third line is connected to form a second branch point, and the other end of the third line is grounded.

[0010]

In the present invention, the reflection caused by the susceptance loaded at the first branching point and the reflection caused by the susceptance loading at the second branching point cancel each other when a radio wave of a high power level is incident. In addition, the reflection and loss characteristics can be improved in a wide frequency band.

[0011]

EXAMPLES Example 1. FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. Various switching elements having at least two terminals and having a switching function by varying the impedance between the terminals by external control are conceivable. Here, as an example, a field effect transistor which is a semiconductor element. The case of using will be described. At the first connection point 2, the first input / output terminal 1 is electrically connected to one end of the first line 3 having a length of ¼ wavelength at a predetermined frequency f1 and the drain of the first field effect transistor 4. It is connected to the. The other end of the first line 3 is connected to the drain of the second field effect transistor 6 and the second input / output terminal 5. The source of the first field effect transistor 4 has a predetermined frequency f
2 is connected to one end of the second line 9 having a length of 1/4 wavelength, and the other end is connected to the second input / output terminal 7 at the third input / output terminal 7 and the predetermined frequency f3 and has a wavelength of 1/4 wavelength. It is connected to a third line 11 which has a length and is grounded at one end.
Further, a bias is applied to the gates of the two field effect transistors through a bias circuit (not shown). Here, the predetermined frequencies f1, f2, f3 may all be the same or different,
Here, as an example, the same case will be described.

Next, the operation of this embodiment will be described. In the following description, first, consider a state in which a radio wave of a low power level enters from the first input / output terminal 1 and propagates to the second input / output terminal 5. This is called a reception state for convenience.
Next, consider a state in which a radio wave of a high power level is incident from the first input / output terminal 1 and propagates to the third input / output terminal 7. This is called a transmission state for convenience.

First, the operation in the receiving state will be described. FIG. 2 shows an equivalent circuit in this case. A negative bias voltage lower than the pinch-off voltage of the field effect transistors is applied to the gates of the first and second field effect transistors 4 and 6, and the sources of the first and second field effect transistors 4 and 6 are The capacitance between the drains is represented by Ca. Here, for simplicity, the case where the two field effect transistors are the same is shown.

Next, the operation will be described. The capacitance Ca connected to the first connection point 2 is connected to the third input / output terminal 7 side by the second line 9, the third line 11 and the external resistance connected to the third input / output terminal 7. The load resistance to be exhibited is loaded. However, if the first and second field effect transistors 4 and 6 are selected so that the impedance of the capacitance Ca is sufficiently larger than the impedance of the load, the effect of the load can be ignored. The equivalent circuit in this case is shown in FIG.
Since the above two capacitors are loaded at a quarter wavelength interval, reflections caused by these capacitors cancel each other out in a wide frequency as is well known, and good propagation characteristics are obtained.

Next, the operation in the transmission state will be described.
FIG. 4 shows an equivalent circuit in this case. The gates of the first and second field effect transistors 4 and 6 are 0V which is equal to the ground potential.
And the first and second field effect transistors 4,
The drain-source of 6 is represented by a resistance Ra. Resistance R
If the value of a is small, the equivalent circuit is represented in FIG.
The first line 3 is considered to be grounded at the tip and the second line 9 is considered to be directly connected to the first connection point 2.

Next, the operation will be described. The first line 3 and the third line 11 whose tips are grounded exhibit a capacitive or inductive susceptance jB at frequencies other than a predetermined frequency. Figure 6
Shows this state. Since the two susceptances are loaded at a quarter wavelength interval, reflections caused by these discontinuities cancel each other out over a wide band as is known, and good propagation characteristics are obtained.

Example 2. In the first embodiment, for simplicity, the predetermined frequencies f1, f2, f3 are the same, but the present invention is not limited to this, and the predetermined frequencies f1, f2, f3 may be different values. By doing
A wider band is possible. For example, the frequency f3
Is set equal to the frequency f1 and the frequency f2 is selected to be lower than the frequency f1. The circuit in this case is shown in FIG. At this time,
The drains of the first and second field effect transistors 4 and 6
If the value of the resistance Ra between the sources is small, the equivalent circuit in the transmission state is shown in FIG. The first line 3 is considered to be grounded at the tip and the second line 9 is considered to be directly connected to the first connection point 2. At the frequency f1, since the lengths of the first and third lines 3 and 11 are ¼ wavelength and the tips are grounded, the impedance when viewed from the first connection point 2 to the first line 3 side is The impedances of the third line 11 and the third connection point 10 are both high impedance close to an open state. An equivalent circuit in this case is shown in FIG. Therefore, the high-power radio wave incident on the first input / output terminal 1 propagates to the third input / output terminal 7 through the first connection point 2 and the second line 9. Frequency f2 lower than frequency f1
Then, the first and third lines 3 and 11 whose ends are short-circuited exhibit a capacitive susceptance jB. An equivalent circuit in this case is shown in FIG. The two susceptances have a frequency f2 of 1
Since they are loaded at / 4 wavelength intervals, the reflections caused by these discontinuities cancel each other out over a wide band centered on the frequency f2, and the first input / output terminal 1 to the third input / output are known. Good propagation characteristics to the terminal 7 can be obtained.

Example 3. In the above embodiments, the case where the field effect transistor is used has been described, but the present invention is not limited to this, and a diode such as a PIN diode or another three-terminal element such as a bipolar transistor may be used. Although the case where the two field effect transistors are the same has been described, the present invention is not limited to this, and the two field effect transistors may be different.

Example 4. In the above embodiment, the case where two field effect transistors and one first line, second line and third line are used, respectively, is described, but the present invention is not limited to this, and a larger number of electric field lines are used. Effect transistor, first,
The second and third lines may be used. For example, as shown in FIG. 11, a third field effect transistor 12 is added, and two first, second, and third lines are used, and as a result, the transmission line is multistaged, resulting in a wider band. Can be achieved.

[0020]

As described above, according to the present invention, as a result of the configuration in which three lines having a length of ¼ wavelength at a predetermined frequency are combined, as a result, when a radio wave of a high power level is incident, The reflection caused by the susceptance loaded at one branch point and the reflection caused by the susceptance loaded at the second branch point cancel each other out, and as a result, a semiconductor switch having good reflection and loss characteristics in a wide frequency band can be realized.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a semiconductor switch according to a first embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram for explaining the operation of the semiconductor switch according to the first embodiment of the present invention when low power is incident.

FIG. 3 is an equivalent circuit diagram for explaining the operation of the semiconductor switch according to the first embodiment of the present invention when low power is incident.

FIG. 4 is an equivalent circuit diagram for explaining the operation of the semiconductor switch according to the first embodiment of the present invention when high power is incident.

FIG. 5 is an equivalent circuit diagram for explaining the operation of the semiconductor switch according to the first embodiment of the present invention when high power is incident.

FIG. 6 is an equivalent circuit diagram for explaining the operation of the semiconductor switch according to the first embodiment of the present invention when high power is incident.

FIG. 7 is a circuit configuration diagram of a semiconductor switch according to a second embodiment of the present invention.

FIG. 8 is an equivalent circuit diagram for explaining the operation of the semiconductor switch according to the second embodiment of the present invention when high power is incident.

FIG. 9 is an equivalent circuit diagram for explaining the operation of the semiconductor switch according to the second embodiment of the present invention when high power is incident.

FIG. 10 is an equivalent circuit diagram for explaining the operation of the semiconductor switch according to the second embodiment of the present invention when high power is incident.

FIG. 11 is a circuit configuration diagram of a semiconductor switch according to a fourth embodiment of the present invention.

FIG. 12 is a circuit configuration diagram of a conventional semiconductor switch.

FIG. 13 is an equivalent circuit diagram for explaining the operation of a conventional semiconductor switch when low power is incident.

FIG. 14 is an equivalent circuit diagram for explaining the operation of a conventional semiconductor switch when low power is incident.

FIG. 15 is an equivalent circuit diagram for explaining the operation of a conventional semiconductor switch when high power is incident.

FIG. 16 is an equivalent circuit diagram for explaining the operation of a conventional semiconductor switch when high power is incident.

[Explanation of symbols]

 1 1st input / output terminal 2 1st connection point 3 1st line 4 1st field effect transistor 5 2nd input / output terminal 6 2nd field effect transistor 7 3rd input / output terminal 8 Inductor 9 Second line 10 Second connection point 11 Third line 12 Third field effect transistor

Claims (1)

[Claims] 1. A first and a second switching element having at least two terminals and having a switch function by varying an impedance between the terminals under external control, wherein the first switching element is a first switching element. And the first terminal of the second switching element are respectively connected through a first line having a length of ¼ wavelength at a predetermined frequency, and the first switching element of the second switching element is connected. The second terminal is grounded, and one end of a second line having a length of ¼ wavelength at a predetermined frequency is connected to the second terminal of the first switching element. On the edge
To connect one end of a third line having a length of ¼ wavelength at a predetermined frequency, ground the other end of the third line, and control the first and second switching elements A semiconductor switch comprising the control means of 1.