JPH09107203A - Switching element and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a high isolation characteristic with a small-scale circuit constitution by providing an inductor forming a resonance circuit on the outside of a transmission line. SOLUTION: A first transmission line between an input/output terminal RC and a reception terminal RX through which a weak signal inputted from an antenna 1 is transmitted to an amplifier and a second transmission line between a transmission terminal TX and the input/output terminal RC through which a transmission signal from the amplifier is transmitted to the antenna 1 exist. The first transmission line is provided with FETs 2 and 3, and the second transmission line is provided with FETs 4 and 5. An inductor 6 to constitute the resonance circuit is provided between the reception terminal RX and the transmission terminal TX on the outside of first and second transmission lines like a bridge between first and second transmission lines. Thus, a high isolation characteristic is obtained without degrading the insertion loss by the small-scale circuit constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching element for switching transmission to a plurality of transmission paths for transmitting a signal, and a semiconductor device mounted with the switching element.

[0002]

2. Description of the Related Art An antenna switch is used to switch between transmission and reception in mobile communication such as mobile phones and car phones. As a switching element for switching the transmission path of one system for transmitting a weak signal received by the antenna, and a transmission path of the other lines for transmitting a level signal moderate for transmission to the antenna, a plurality of A FET switching element composed of a FET has been generally used conventionally.

FIG. 14 is a circuit diagram showing the structure of a conventional FET switching element. The high frequency signal input from the input / output terminal RC is output to the reception terminal RX via the FET 51. The FET 53 is interposed between the reception terminal RX and the ground. The high frequency signal input from the transmission terminal TX is output to the input / output terminal RC via the FET 52. The FET 54 is interposed between the transmission terminal TX and the ground. The gate of the FET 51 is connected to the control voltage terminal V2 via the resistor R1, and the gate of the FET 54 is connected to the control voltage terminal V2 via the resistor R4. The gate of the FET 52 is through the resistor R2,
The gate of the FET 53 is connected to a control voltage terminal V1 via a resistor R3.

An S having such a configuration using a plurality of FETs
In a PDT (Single Pole Dual Through) switching element, for example, when a high frequency signal is input from the antenna to the input / output terminal RC, the control voltage terminals V1 and V2
0V and -3V are applied to each. FET51,54 is on, F
The ETs 52 and 53 are turned off, and the high frequency signal input to the input / output terminal RC is transmitted to the reception terminal RX. On the other hand, when a high frequency signal is input to the transmission terminal TX, -3V and 0V are applied to the control voltage terminals V1 and V2, respectively. FET5
2, 53 is on, FETs 51, 54 are off, and the transmission terminal T
The high frequency signal input to X is transmitted to the input / output terminal RC.

[0005]

In the switching element as described above, the isolation characteristic generally becomes worse as the frequency becomes higher, and particularly in the millimeter wave band, a sufficient isolation characteristic is obtained. Is difficult. Therefore, various improved techniques for obtaining high isolation characteristics in a desired band of a high-frequency signal to be used, in particular, techniques for achieving high isolation by utilizing resonance action have been conventionally proposed. For example, 1993
C-86 "Low Voltage Drive Low Distortion T / R Switch MMIC by Switching LC Resonance" at IEICE Spring Meeting,
C-70 “Millimeter wave M at the 1994 IEICE Autumn Meeting
Examination of high isolation of MICFET switch ”
The technology is shown in.

The former technique uses an LC resonance switching circuit as shown in FIG. 15 which realizes an OFF state by using an FET in an ON state for the FET 51 and the FET 54 shown in FIG. In the circuit shown in FIG. 15, when the FET is on, the terminal is open (parallel resonance), and when the FET is off, the terminal is conductive (series resonance).

The latter technique has a circuit configuration in which a transmission line is added to a switch circuit in which three FETs are connected in series-parallel-series to cause resonance, as shown in FIG. It utilizes that a kind of resonance circuit is formed when is off. The frequency at resonance can be set to a desired value by appropriately selecting the characteristic impedance of the transmission line and the line length.

In the above-mentioned two prior arts, since the resonance circuit is formed in the transmission path, it is necessary to provide an inductor or a transmission line for each transmission path, and the circuit scale becomes large as a whole. There are challenges.

The present invention has been made in view of the above circumstances, and by providing an inductor for forming a resonance circuit outside the transmission path, it is possible to obtain a high isolation characteristic with a small circuit configuration. It is an object of the present invention to provide a switching element capable of obtaining the above and a semiconductor device mounted with the switching element.

Another object of the present invention is to provide a switching element capable of increasing isolation without degrading insertion loss, and a semiconductor device mounted with the switching element.

Still another object of the present invention is to provide a switching element capable of changing the magnitude relation of isolation between terminals according to a difference in frequency band, and a semiconductor device mounted with the switching element. is there.

[0012]

A switching element according to claim 1 of the present application has a first transmission path between a first terminal and a second terminal and a second transmission path between a third terminal and the first terminal. The switching element for switching between the path and the path includes an inductor provided between the second terminal and the third terminal.

A switching element according to a second aspect of the present application has a first transmission path for transmitting a reception signal received by an antenna to a reception terminal through an input / output terminal and a transmission signal from the transmission terminal. A switching element for switching between a second transmission path for transmission to the antenna via an output terminal is characterized by including an inductor provided between the reception terminal and the transmission terminal.

A switching element according to claim 3 of the present application is the switching element according to claim 1 or 2, wherein the first terminal (input / output terminal) and the third terminal (transmission terminal) are arranged between the first terminal (input / output terminal) and It is characterized in that the size of the inductor is set so that the isolation between the three terminals (transmission terminals) becomes high.

The switching element according to claim 4 of the present application is the switching element according to claim 1, 2 or 3, wherein the inductor is a chip inductor.

The switching element according to claim 5 of the present application is the switching element according to claim 1, 2, 3 or 4,
It is characterized by having.

A switching element according to claim 6 of the present application is a first switching element having a FET between a first terminal and a second terminal.
Of the FE between the third transmission path and the first terminal.
A switching element for switching between a second transmission path having T and an inductor provided between the second terminal and the third terminal, wherein the first transmission path that is off and the second transmission path that is on And the inductor, or the first transmission path that is on and the second transmission path that is off and the inductor are configured to exhibit a resonance effect.

The semiconductor device according to claim 7 of the present application is the first
A chip switching element for switching between a first transmission path between the terminal and the second terminal and a second transmission path between the third terminal and the first terminal; and between the second terminal and the third terminal It is characterized in that it has a configuration in which the connected chip inductor is mounted on a printed circuit board.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments.

FIG. 1 is a circuit diagram showing the configuration of an antenna switch for a mobile phone using the switching element of the present invention. The switching element includes a first transmission path between the input / output terminal RC and the reception terminal RX for transmitting a weak signal input from the antenna 1 to an amplifier (not shown), and an amplifier (not shown). There is a second transmission path between the transmission terminal TX and the input / output terminal RC for transmitting the transmission signal from the antenna 1 to the antenna 1. FET2 and FET3 are provided in the first transmission path, and FET4 and F are provided in the second transmission path.
And ET5 are provided.

The FET 2 of the first transmission path has an input / output terminal R
It is interposed between C and the receiving terminal RX, and FET3 is the receiving terminal R
It is interposed between X and the ground. The gate of the FET2 is connected to the control voltage terminal V2 via the resistor R1, and the gate of the FET3 is connected to the control voltage terminal V1 via the resistor R3. On the other hand, F of the second transmission path
ET4 is interposed between the transmission terminal TX and the input / output terminal RC,
The FET 5 is interposed between the transmission terminal TX and the ground. The gate of the FET4 is connected to the control voltage terminal V1 via the resistor R2, and the gate of the FET5 is connected to the resistor R4.
Is connected to the control voltage terminal V2 via. Further, between the reception terminal RX and the transmission terminal TX, which is outside any of the first and second transmission paths and extends over the first and second transmission paths, the characteristic part of the present invention is provided. Is provided.

Next, the operation will be described. Each of these FETs constituting the switching element is on / off controlled by the gate voltage applied to the control voltage terminals V1 and V2. When a voltage of 0V is applied to the voltage terminal V1, a voltage of -3V is applied to the voltage terminal V2,
On the contrary, when a voltage of -3V is applied to the voltage terminal V1, a voltage of 0V is applied to the voltage terminal V2. Then, when a voltage of -3V is applied to the gate, each FET is turned on, and when a voltage of 0V is applied to the gate, each FET is turned off.

When the antenna 1 receives a signal, a voltage of 0 V is applied to the voltage terminal V1 and -3 is applied to the voltage terminal V2.
A voltage of V is applied. Then, the FETs 2 and 5 are turned on and the FETs 3 and 4 are turned off. Therefore, the signal received by the antenna 1 enters the first transmission path via the input / output terminal RC and does not enter the second transmission path. And F
Since ET3 is in the off state, its reception signal reaches the reception terminal RX. Here, the reason that the FET 5 is turned on is to prevent a signal leaking into the second transmission path from flowing to the ground and preventing it from reaching the transmission terminal TX.

When transmitting a signal for transmission to the antenna 1, a voltage of -3V is applied to the voltage terminal V1 and a voltage of 0V is applied to the voltage terminal V2 to turn on the FETs 3 and 4,
Turn off ET2,5. Since the FETs 2 and 5 are in the OFF state, the transmission signal input to the transmission terminal TX is reliably supplied to the antenna 1 via the second transmission path and the input / output terminal RC. Here, the reason that the FET 3 is turned on is to prevent the signal leaking into the first transmission path from flowing to the ground and preventing it from reaching the receiving terminal RX.

Next, the circuit characteristics of the switching element of the present invention provided with the inductor 6 will be described in detail.

FIG. 2 shows the simplified equivalent circuit of FIG. 1 described above (the first transmission path is on and the second transmission path is off). Since the signal is conducted through the first transmission path, it is represented by a resistor Ron, and the signal is cut off through the second transmission path, so that the capacitor C
Expressed as off. Here, the resistance Ron in FIG. 2 is generally a small value of about several Ω, so that the input / output terminal RC and the receiving terminal RX have almost the same potential. Therefore, FIG.
3 can be further modified into a circuit as shown in FIG. FIG.
In the above, due to the resonance action of the inductor L and the capacitor Coff, the insulation degree between the input / output terminal RC and the transmission terminal TX and between the reception terminal RX and the transmission terminal TX is improved at a frequency that satisfies the resonance condition.

Next, a case where the switching element of the present invention is mounted on a printed board will be described. 4 is a plan view of the board 11 to be mounted, and FIG. 5 is a chip-shaped switching element 20 and a chip inductor (inductor element) 21 on the board 11.
It is a figure which shows the state which mounted. As shown in FIG. 4, conductive patterns made of a gold film are formed on the upper surface of the substrate 11 in a scattered manner. This conductor pattern has a T-shaped ground pattern 12 existing in the center of the substrate 11 and two RF patterns 13a and 13b symmetrically extending to the edges of the substrate 11 with the T-shaped handle portion sandwiched therebetween. And T in the opposite direction of this T-shaped handle
An RF pattern 14 extending from a position slightly apart from the U-shaped umbrella to the edge of the substrate 11, and two DC patterns 15a and 15b for DC power supply symmetrically provided with the RF pattern 14 sandwiched therebetween.
It is composed of Then, several via holes 16 are formed in the T-shaped region in which the ground pattern 12 is formed. A gold film for ground is also formed on the inner wall of each via hole 16 and the lower surface of the substrate 11, and the gold film forming the ground pattern 12 and the gold film on the lower surface of the substrate 11 are the gold film on the inner wall of each via hole 16. Are electrically connected via.

On the printed circuit board 11 having the above structure,
A chip-shaped switching element 20 having the above-described circuit configuration and sealed with a resin and packaged, and a chip inductor 21 which is also a packaged inductor 6 are mounted by soldering or the like. (Fig. 5
reference). The switching element 20 has six pins for electrical connection, and these six pins are one ground pin 22 and three RF pins 23a, 23b, 23c and two. It consists of DC pins 24a and 24b. The ground pin 22 is connected to the ground pattern 12. One RF pin 23a of the three RF pins is connected to the RF pattern 14,
The remaining two RF pins 23b and 23c are RF patterns 13a and 13b.
Connected to each other. The RF pattern 14 corresponds to the input / output terminal RC, and the RF patterns 13a and 13b correspond to the transmission terminal TX and the reception terminal RX, respectively. Two D
The C pins 24a and 24b are connected to the DC patterns 15a and 15b of the substrate 11, respectively.

Further, the chip inductor 21 is mounted on the printed circuit board 11 in a manner that both terminals thereof are connected to the RF patterns 13a and 13b, respectively. As shown in FIG. 6, even if the chip inductor 21 is added, it suffices to add one chip inductor 21 to one switching element 20, so that the mounting area remains almost unchanged and the overall size is reduced. Does not change so much, and there is no fear of increasing the circuit scale.

The inductance required for the inductor used in the present invention is about 22 nH. This is a large value as an inductor component, and it is difficult to incorporate it into a switching element and create it on the same chip. Therefore, the inductor is also formed in a chip shape and externally attached to the chip-shaped switching element.

Next, a comparison of characteristics with and without the inductor 6 will be described. FIG. 6 shows the characteristics in the conventional example (see FIG. 14) in which the inductor 6 is not provided, and FIG. 7 shows the characteristics in the example of the present invention in which the inductor 6 is provided (see FIG. 1). 6 and 7, the solid line a is the isolation between the input / output terminal RC and the transmission terminal TX, and the broken line b is the reception terminal R.
The isolation between X and the transmission terminal TX and the alternate long and short dash line c represent the insertion loss. In the example of the present invention shown in FIG. 7, it can be seen that the isolation characteristic is improved in the vicinity of 1.6 GHz. Further, the insertion loss at this time is not deteriorated.

Differences in isolation characteristics between terminals between the conventional example of the SPDT switching element and the example of the present invention will be described in detail below with reference to FIGS.

FIG. 8A shows a circuit configuration of the present invention in which an inductor is attached between the second terminal and the third terminal of the simplest switch circuit, and FIG. 8B shows the first FET thereof.
Shows an equivalent circuit when is ON and the second FET is OFF. A 50Ω system is normally used for the measurement system such as switches. In other words, this means that the measuring device and cable have an impedance of 50Ω. For example, in FIG. 8B, when the switch is designed by setting the first terminal, the second terminal, and the third terminal as the above-mentioned input / output terminal RC, reception terminal RX, and transmission terminal TX, respectively, an antenna and a reception unit , The transmitter can be considered by replacing it with an impedance of 50Ω.

The isolation between the second and third terminals is
It is the degree of insulation between the second and third terminals when 50Ω is connected to the first terminal as shown in FIG. 8 (c). The circuit in this case can be modified as shown in FIG. Also, the isolation between the first and third terminals is as shown in FIG.
It is the insulation between the first and third terminals when 50Ω is connected. The circuit in this case can be modified as shown in FIG.
8 (e) and 8 (f), the coil L and the capacitor C are shown.
A resonance circuit can be configured by off and the second and third terminals can be separated in the case of FIG. 8 (e), and the first and third terminals can be separated in the case of FIG. 8 (f).

Comparing FIGS. 8 (e) and 8 (f), the positions of the coil L and the capacitor Coff are different, and this difference in position is reflected in the isolation characteristic. In FIG. 9, Ron = 7.5Ω, Coff = 0.174pF, L = 22nH
The calculation example of the isolation between the 2nd and 3rd terminals (e of ○-○ in the figure) and the isolation between the 1st and 3rd terminals (f of □-□ in the figure) There is. As shown in FIG. 9, the resonance points can be separated.

In this case, the resonance point f1 in the circuit of FIG. 8 (f) becomes higher than the resonance point e1 in the circuit of FIG. 8 (e). Therefore, on the high frequency side, the isolation between the first and third terminals can be made higher than that between the second and third terminals.
As described above, it is possible to change the magnitude relationship between the isolation between the first and third terminals and the isolation between the second and third terminals depending on the difference in the frequency band. This is seen in the graph of the isolation characteristic of the example of the present invention shown in FIG.

On the other hand, considering the case where the inductor is not connected between the second and third terminals (conventional example), the signal is attenuated only by Coff between the first and third terminals, but between the second and third terminals. Then, since the signal is attenuated by Coff and Ron,
Due to the presence of Ron, the isolation characteristic between the second and third terminals is always better. This is seen in the graph of the isolation characteristic of the conventional example of FIG.

Next, the calculation for obtaining the isolation characteristic will be described. Circuits in the case where a signal source (internal resistance 50Ω) and a load (resistance 50Ω) are connected to the circuits of FIGS. 8 (e) and 8 (f) are shown in FIGS. 10 (a) and 10 (b). Figure 10 (a),
FIG. 12 shows a case where the Δ type circuit constituted by ABC of (b) is changed to a Y type circuit as shown in FIG. Here, Za, Zb, and Zc in FIG. 12 are expressed as follows. Za = (Zab.Zca) / (Zab + Zbc + Zca) Zb = (Zab.Zbc) / (Zab + Zbc + Zca) Zc = (Zca.Zbc) / (Zab + Zbc + Zca) Further, in the circuit of FIG. 8 (e), Zab = j.omega.L, Zca = R
on, Zbc = 1 / (jωCoff), and in the circuit of FIG. 8 (f), Zab = 1 / (jωCoff), Zca = Ron, Zbc = j
ωL.

The overall impedance Z in the circuit of FIG. 12 is as follows. Z = 100 + Za + Zc- (50 + Zc) ² / (100 + Zb +
Zc) The fact that the resonance point differs between the circuit of FIG. 8 (e) and the circuit of FIG. 8 (f) can be seen from the difference in the point where Z becomes the largest in the above calculation.

As described above, in the conventional example, the magnitude relation of the isolation between the terminals is always constant irrespective of the used frequency, but in the present invention example, the magnitude relation can be changed in association with the used frequency. it can. Therefore, it is possible to effectively use the isolation characteristics as described in the example of the present invention, such as setting the frequency so that high isolation can be obtained between the terminals that require particularly high isolation. Hereinafter, this application example will be described.

When the switching element of the present invention is used in the antenna switch as described above (see FIG. 1), it is necessary that the signal on the transmission terminal TX side (power amplifier side) does not leak to the reception terminal RX side. In this case, since high isolation between the transmission terminal TX and the reception terminal RX is required,
The inductor 6 is attached so that the highest isolation can be obtained between the transmission terminal TX and the reception terminal RX.

FIG. 13 shows the structure of a dual synthesizer using the switching element of the present invention. This configuration is
This is a configuration adopted in the base unit or base station of the HS system. The oscillation frequencies of the two first and second synthesizers (oscillators) 31 and 32 are slightly different, and it is a system that switches both of them with a switch. In this case, the two first and second
It is necessary to obtain high isolation between the synthesizers (oscillators) 31 and 32. Second to fifth switches of this system
34 to 37 are required to have high isolation corresponding to the first and third terminals shown in FIG. 8, and the first switch 33 has high isolation between the second and third terminals. Required. In this case, by providing an inductor having an inductance suitable for each of the switches 33 to 37, higher isolation can be obtained as compared with the case where the switches are not attached as a whole.

Note that MESFET is desirable as an element used for the SPDT switch in a mobile phone or the like.
The reason will be described below. A switch using a diode requires a bias current in order to pass a forward current in an ON state, and cannot adapt to the trend of low power consumption. In a switch using a bipolar transistor, the collector current is controlled by the base current, and therefore the current for controlling switching (base current) affects the signal current, which is not preferable. A switch using a MOSFET cannot operate in the GHz band used in mobile phones. On the other hand, the switch using the MESFET has advantages that it does not consume a large amount of power, that switching is controlled by voltage, there is no problem like a bipolar transistor, and that operation in the GHz band is possible. MESFET is often used for the switch.

[0044]

As described above, in the switching element of the present invention, the inductor is provided outside the signal transmission path to configure the resonance circuit, so that the insertion loss is deteriorated in the circuit configuration of a small scale. It is possible to obtain high isolation characteristics.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an antenna switch using a switching element of the present invention.

FIG. 2 is a simplified equivalent circuit diagram of FIG.

FIG. 3 is a circuit diagram obtained by modifying the circuit of FIG.

FIG. 4 is a plan view showing a substrate on which a switching element of the present invention is mounted.

FIG. 5 is a diagram showing a state in which the switching element of the present invention is mounted on a substrate.

FIG. 6 is a graph showing characteristics (isolation, insertion loss) in a switching element of a conventional example.

FIG. 7 is a graph showing characteristics (isolation, insertion loss) in the switching element of the present invention.

FIG. 8 is a circuit diagram for explaining a magnitude relation of isolation between terminals.

FIG. 9 is a graph showing a calculation result of isolation between terminals.

10 is a circuit diagram in which a signal source and a load are connected to the circuit of FIG.

FIG. 11 is a circuit diagram showing a relationship between a Δ-type circuit and a Y-type circuit.

FIG. 12 is a circuit diagram obtained by modifying the circuit of FIG.

FIG. 13 is a configuration diagram of a local switch using the switching element of the present invention.

FIG. 14 is a circuit diagram showing a configuration of a conventional FET switching element.

FIG. 15 is a diagram showing an example of a conventional technique for achieving high isolation by utilizing a resonance effect.

FIG. 16 is a diagram showing another example of a conventional technique for achieving high isolation by utilizing a resonance effect.

[Explanation of symbols]

 1 antenna 2, 3, 4, 5 FET 6 inductor 11 substrate 20 switching element 21 chip inductor RC input / output terminal (first terminal) RX receiving terminal (second terminal) TX transmitting terminal (third terminal)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuro Sawai 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. 5-5, Sanyo Electric Co., Ltd.

Claims (7)

[Claims] 1. A switching element that switches between a first transmission path between a first terminal and a second terminal and a second transmission path between a third terminal and the first terminal, wherein the second terminal and the A switching element comprising an inductor provided between the three terminals. 2. A first transmission path for transmitting a reception signal received by an antenna to a reception terminal via an input / output terminal,
A switching element for switching between a second transmission path for transmitting a transmission signal from a transmission terminal to the antenna via the input / output terminal, comprising an inductor provided between the reception terminal and the transmission terminal. And a switching element. 3. The size of the inductor is set such that the isolation between the first and third terminals is higher than the isolation between the second and third terminals. Switching element. 4. The switching element according to claim 1, wherein the inductor is a chip inductor. 5. The switching element according to claim 1, comprising a plurality of FETs. 6. A switching element for switching between a first transmission path having a FET between a first terminal and a second terminal and a second transmission path having a FET between a third terminal and the first terminal, wherein: The first terminal which is off and includes an inductor provided between the second terminal and the third terminal.
And a second transmission path that is turned on and the inductor, or a first transmission path that is turned on and the second transmission path that is turned off and the inductor are configured to exhibit resonance action. A switching element characterized by the above. 7. A chip switching element for switching between a first transmission path between the first terminal and the second terminal and a second transmission path between the third terminal and the first terminal, the second terminal and the A semiconductor device having a structure in which a chip inductor connected between a third terminal and the third terminal is mounted on a printed circuit board.