JPH07202505A - High frequency switch - Google Patents

Abstract

PURPOSE:To provide the small-sized high frequency switch by forming a ground electrode and a capacitor electrode in the same layer in a multilayered substrate. CONSTITUTION:A high frequency switch 10 includes a laminated body 12. A ground electrode 14 and a capacitor electrode 20 are formed in the same layer in the laminated body 12. Strip line electrodes 16 and 18 are formed so as to face the ground electrode 14. Another capacitor electrode 24 is formed so as to face the ground electrode 20. The ground electrode 14 and strip line electrodes 16 and 18 constitute a strip line or a micro strip line. Capacitor electrodes 20 and 24 constitute a capacitor. Required chip parts 26 are attached on the laminated body 12. These internal electrodes and chip parts are connected by vie holes or external electrodes to form the high frequency switch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency switch, and more particularly to a high frequency switch for switching a signal path in a high frequency circuit such as a digital mobile phone.

[0002]

2. Description of the Related Art A high frequency switch, as shown in FIG.
In a digital mobile phone, etc., the connection between the transmission circuit TX and the antenna ANT and the reception circuit RX and the antenna ANT
Used to switch the connection with.

FIG. 10 is a circuit diagram showing an example of a high frequency switch which is the background of the present invention and to which the present invention is applied. The high frequency switch is connected to the antenna ANT, the transmission circuit TX and the reception circuit RX. Transmission circuit TX
Is connected to the anode of the first diode D1 via the first capacitor C1. The cathode of the first diode D1 is connected to the antenna ANT via the second capacitor C2. The anode of the first diode D1 is connected to the first transmission line SL1 and the third capacitor C3.
It is grounded through the series circuit. Further, at the midpoint between the first transmission line SL1 and the third capacitor C3, the first
The first control terminal T1 is connected via the resistor R1. A control circuit for switching the high frequency switch is connected to the first control terminal T1. The second capacitor C2 connected to the antenna ANT includes a second transmission line SL2 and a fourth capacitor C2.
The receiving circuit RX is connected via a series circuit with the receiving circuit RX.
The anode of the second diode D2 is connected to the midpoint between the second transmission line SL2 and the fourth capacitor C4. The cathode of the second diode D2 is grounded.

When transmitting using the high frequency switch shown in FIG. 10, a positive voltage is applied to the first control terminal T1. This voltage turns on the first diode D1 and the second diode D2. At this time, the direct current component is cut by the first to fourth capacitors C1 to C4, and the voltage applied to the first control terminal T1 is applied only to the circuit including the first diode D1 and the second diode D2. I am trying to do it. By turning on the first diode D1 and the second diode D2, the signal from the transmission circuit TX is transmitted to the antenna ANT.
And the signal is transmitted from the antenna ANT. In addition, the transmission signal of the transmission circuit TX is the second transmission line SL2.
Is grounded by the second diode D2 and resonates to greatly increase the impedance seen from the connection point A toward the receiving circuit RX side, so that it is not transmitted to the receiving circuit RX.

On the other hand, at the time of reception, by not applying a voltage to the first control terminal T1, the first diode D1 and the second diode D2 are turned off.
Therefore, the reception signal is transmitted to the reception circuit RX and is not transmitted to the transmission circuit TX side. In this way, transmission / reception can be switched by controlling the voltage applied to the first control terminal T1.

FIG. 11 is a plan view showing an example of a conventional high frequency switch having the circuit shown in FIG. This high-frequency switch 1 includes a substrate 2, and stripline electrodes 3a and 3b as first and second transmission lines and a large number of lands are formed on one main surface of the substrate 2, and these stripline electrodes and lands are formed. To the first and second diodes 4a and 4b, and the first, second, third and fourth diodes.
The chip capacitors 5a, 5b, 5c and 5d are connected to the first chip resistor 6.

[0007]

However, in the conventional high frequency switch 1 shown in FIG. 11, the lengths of the first and second stripline electrodes 3a and 3b are generally set to the wavelengths of the transmission signal and the reception signal. The length is required to be 1/4, and depending on the dielectric constant of the substrate 2, it is required to be about several tens of millimeters, and the portions related to the first and second stripline electrodes 3a and 3b are on the substrate 2. Occupies a large area. Therefore, the high-frequency switch 1 has a problem in downsizing.

Therefore, by forming a stripline electrode for a transmission line, a ground electrode, a capacitor electrode for a capacitor, etc. in a multilayer substrate, the chip parts to be mounted on the substrate surface can be minimized to realize a high frequency switch. It was thought to be small. In such a high-frequency switch, a ground electrode and a capacitor electrode are formed on each layer of the multilayer substrate, and a capacitor is formed by the capacitor electrodes facing each other with the dielectric layer in between.
In order to reduce the stray capacitance, the capacitor electrode and the ground electrode are formed so as not to face each other.

However, when the number of electrodes formed inside the multi-layer substrate increases, the number of sheets to be laminated increases, and in particular, the thickness of the multi-layer substrate increases and the size becomes large.

Therefore, a main object of the present invention is to provide a compact high frequency switch.

[0011]

The present invention is directed to a transmitter circuit,
A high frequency switch connected to a receiving circuit and an antenna for switching between a transmitting circuit and an antenna and a receiving circuit and an antenna, the anode being connected to the transmitting circuit side and the cathode being connected to the antenna side. 1
, A first transmission line connected between the anode of the first diode and the ground side, a second transmission line connected between the antenna side and the receiving circuit side, and a receiving circuit side A second diode having an anode connected to and a cathode connected to the ground side; and a multi-layer substrate having a built-in capacitor used for connection to the transmission circuit, the reception circuit, and the antenna and for grounding. An electrode and a capacitor electrode for the capacitor are formed,
A high frequency switch in which the ground electrode and the capacitor electrode are formed on the same layer.

[0012]

By forming the ground electrode and the capacitor electrode in the multilayer substrate on the same layer, the number of laminated sheets can be reduced as compared with the case where they are formed on a plurality of layers. Further, since the ground electrode and the capacitor electrode do not face each other, the stray capacitance is small.

[0013]

According to the present invention, it is possible to obtain a small-sized high-frequency switch having a particularly small thickness as compared with a conventional high-frequency switch using a multilayer substrate. Moreover, since the stray capacitance is small, a high frequency switch having good characteristics can be obtained.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The high frequency switch of this embodiment is structurally characteristic, but the circuit itself is also characteristic.
The circuit of the high frequency switch of this embodiment will be described with reference to FIG. Compared with the high-frequency switch shown in FIG. 10, the high-frequency switch of this embodiment particularly has a series circuit of a first diode D1, an inductance element L1 and a fifth capacitor C5, a second resistor R2 and a sixth resistor C2. The capacitor C6 is connected in parallel. Furthermore, the second
The cathode of the diode D2 of the
Grounded through. Further, the third resistor R3 is connected in parallel to the second diode D2, and the cathode of the second diode D2 is connected to the second resistor R4 via the fourth resistor R4.
Control terminal T2 is connected. Another control circuit for switching the high frequency switch is connected to the second control terminal T2.

When transmitting using the high frequency switch shown in FIG. 1, a positive voltage is applied to the first control terminal T1, and the first and second diodes D1 and D2 are applied.
Are turned on. Therefore, the transmission circuit T
The transmission signal from X is transmitted from the antenna ANT, and the second transmission line SL2 transmits to the second diode D2.
Is grounded and resonates, and the impedance seen from the connection point A to the receiving circuit RX side becomes infinite, so that the receiving circuit R
It is not transmitted to the X side.

In the high frequency switch shown in FIG. 1, the first diode D1 and the second diode D2 are turned on during transmission, but these diodes have an inductance component. When such an inductance component exists, the antenna ANT and the second transmission line SL
The impedance does not become infinity when the receiving circuit RX side is viewed from the connection point A with 2. In order to eliminate the influence of such an inductance component, the second diode D
A series resonance circuit is formed by the second inductance component and the seventh capacitor C7. Therefore, the capacitance C of the seventh capacitor C7 is expressed by the following equation, where L _{D is} the inductance of the second diode D2 and f is the operating frequency. C = 1 / {(2πf) ² · L _D }

By setting the capacitance C of the seventh capacitor C7 to the condition of the above equation, the second diode D2 becomes O
At N hours, a series resonance circuit is formed, and the impedance when the receiving circuit RX side is viewed from the connection point A between the antenna ANT and the second transmission line SL2 can be made infinite. Therefore, the signal from the transmission circuit TX is not transmitted to the reception circuit RX, and the insertion loss between the transmission circuit TX and the antenna ANT can be reduced. Furthermore, good isolation can be obtained between the antenna ANT and the receiving circuit RX. The first control terminal T1
When a voltage is applied to the current, the current flows through the first, second, third, fourth and seventh capacitors C1, C2, C3, C4 and C7.
It is cut by and flows only in the circuit including the first diode D1 and the second diode D2, and does not affect other parts.

Further, when reception is performed using the high frequency switch shown in FIG. 1, a positive voltage is applied to the second control terminal T2. In this case, the voltage dropped by the second resistor R2 is applied as the reverse bias voltage to the first diode D1, and the voltage dropped by the third resistor R3 is applied by the reverse bias voltage to the second diode D2. Applied as a voltage. Therefore, the first diode D1 and the second diode D2 surely maintain the OFF state. Therefore, the received signal is transmitted to the receiving circuit RX. However, at this time, since the diode has a capacitance component, the reception signal may leak to the transmission circuit TX side. However, in this high frequency switch, the inductance element L1 is connected in parallel with the first diode D1. A parallel resonant circuit is formed by the inductance element L1 and the capacitance of the first diode D1. Therefore, the inductance L of the inductance element L1 is expressed by the following equation, where C _{D is} the capacitance of the first diode D1 and f is the operating frequency. L = 1 / {(2πf) ² · C _D }

By setting the inductance L of the inductance element L1 to the condition of the above equation, the transmission circuit TX
The isolation between the antenna and the antenna ANT can be improved. Therefore, the received signal is the transmission circuit TX.
Without leaking to the side, the insertion loss between the antenna ANT and the receiving circuit RX can be reduced. The same effect can be obtained by using a high-impedance transmission line instead of the inductance element L1.

Further, in the high frequency switch shown in FIG. 1, in order to prevent a current from flowing through the inductance element L1 when a voltage is applied to the first and second control terminals T1 and T2, the inductance element L1 is connected to the inductance element L1. The fifth capacitor C5 is connected in series. Further, in the high frequency switch shown in FIG. 1, a sixth capacitor C6 is connected in parallel with the first diode D1. This increases the combined capacitance of the first diode D1 and the sixth capacitor C6,
The influence of the variation in the capacitance of the diode D1 is reduced. Therefore, a high frequency switch having stable characteristics can be obtained. Needless to say, when the fifth capacitor C5 or the sixth capacitor C6 is connected, the above equation is corrected according to the capacitance thereof, if necessary.

As described above, the high frequency switch shown in FIG. 1 has excellent characteristics both during transmission and during reception.

Next, the structure of the high-frequency switch of this embodiment will be described with reference to FIGS. 2, 3 and 4. The high frequency switch 10 includes a multilayer substrate or a laminated body 12. The laminated body 12 is formed by laminating a large number of dielectric layers and the like.

A plurality of ground electrodes 1 are provided in the laminated body 12.
4 is formed. These ground electrodes 14 are formed on a plurality of dielectric layers and are arranged so as to face each other. A stripline electrode 16 is formed between these ground electrodes 14. A stripline is formed by the stripline electrode 16 and the ground electrode 14 facing each other with the dielectric layer in between. The strip line thus formed is used as the first transmission line SL1 and the second transmission line SL2. Further, a stripline electrode 18 for forming another transmission line SLt is formed so as to face one ground electrode 14. A microstrip line is formed by this strip line electrode 18 and one ground electrode 14 facing it.

Further, the capacitor electrode 20 is formed on the same dielectric layer as the ground electrode 14. As shown in FIG. 4, the capacitor electrode 20 is formed on the dielectric layer 22 with a space from the ground electrode 14. Further, as shown in FIG. 3, another capacitor electrode 24 is provided on another dielectric layer 22 so as to face the capacitor electrode 20.
Is formed. By these opposing capacitor electrodes 20 and 24, capacitors C1, C
2, C3, C4, C5, C6, C7, etc. are formed.

Electrodes (not shown) such as lands are formed on the laminated body 12, and the chip parts 26 are attached to the lands. As the chip component 26, for example, the first
Diode D1, second diode D2 and resistor R
1, R2, R3, R4, etc. The resistors R1 and R
2, R3, R4, etc. may be formed by printing a resistor on the laminate 12. The transmission lines, capacitors, resistors, diodes, etc. formed in this way are
Connection is made by via holes 28 formed in the dielectric layer and external electrodes formed on the side surfaces of the laminated body 12. Thereby, the high frequency switch 10 having the circuit shown in FIG. 1 is manufactured.

As a comparative example, a high frequency switch using a conventional laminated body is shown in FIG. In the high frequency switch 50, as in the high frequency switch 10 shown in FIG.
A plurality of ground electrodes 54 that face each other are formed in the inner space 2. Then, between these ground electrodes 54, strip line electrodes 56 for the transmission lines SL1 and SL2 are provided.
Is formed. Further, the strip line electrode 5 for the transmission line SLt is opposed to the one ground electrode 54.
8 is formed.

Further, capacitor electrodes 62 and 64 are provided on the dielectric layer 60 on which the ground electrode 54 and the strip line electrodes 56 and 58 are not formed so as to face each other.
Is formed. These capacitor electrodes 62 and 64 are
As shown in FIGS. 6, 7 and 8, the ground electrode 54
It is formed at a position not facing. This is because stray capacitance is likely to occur when facing the ground electrode 54, and a high frequency switch having stable characteristics cannot be obtained. Then, the chip component 66 is attached on the laminated body 52, and the internal electrode and the chip component are connected by the via hole 68, the external electrode and the like.

As can be seen by comparing the high frequency switch 10 of the present invention with the high frequency switch 50 of the comparative example, the ground electrode 14 and the capacitor electrode 20 are formed on the same dielectric layer 22.
By forming and, the number of dielectric layers can be reduced. Therefore, the thickness of the laminated body 12 can be reduced, and a small high frequency switch can be obtained. Further, as shown in FIG. 2, stripline electrodes 16, 1
If the capacitor electrode 24 is formed on the same dielectric layer 22 as the layer 8, the laminated body 12 can be further downsized.

Further, by reducing the number of dielectric layers 22, the number of via holes for connecting the electrodes can be reduced, and the manufacture of the high frequency switch can be simplified. For example, a high frequency switch in which a ground electrode and a capacitor electrode are formed on different dielectric layers requires 28 dielectric layers, whereas the high frequency switch of the present invention has 15 dielectric layers. We were able to. Also,
The number of via holes was also reduced from 218 to 101. As described above, according to the present invention, the number of dielectric layers can be reduced and the manufacturing can be simplified, so that the cost of the high frequency switch can be reduced.

In the high frequency switch 10, the ground electrode 14 and the capacitor electrode 2 are formed on the same dielectric layer 22.
Since 0 is formed, a large stray capacitance is not generated unlike the case where these are opposed to each other. Therefore, it is possible to obtain a high frequency switch having stable characteristics almost as designed. As the circuit of the high frequency switch, a circuit as shown in FIG. 10 may be used in addition to the circuit shown in FIG. Thus, even if the circuit changes, a small high-frequency switch can be obtained by forming the ground electrode and the capacitor electrode on the same layer.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a high frequency switch.

FIG. 2 is an illustrative view showing one embodiment of the present invention.

3 is a plan view showing one of the dielectric layers used in the high frequency switch shown in FIG. 2. FIG.

FIG. 4 is a plan view showing another dielectric layer used in the high frequency switch shown in FIG.

FIG. 5 is an illustrative view showing one example of a high frequency switch for comparison.

6 is a plan view showing one of the dielectric layers used in the high frequency switch of the comparative example shown in FIG.

FIG. 7 is a plan view showing another dielectric layer used in the high-frequency switch of the comparative example shown in FIG.

FIG. 8 is a plan view showing still another dielectric layer used in the high frequency switch of the comparative example shown in FIG.

FIG. 9 is a conceptual diagram showing the operation of a high frequency switch.

FIG. 10 is a circuit diagram showing another example of a high frequency switch.

FIG. 11 is a plan view showing an example of a conventional high frequency switch.

[Explanation of symbols]

 10 High Frequency Switch 12 Laminated Body 14 Ground Electrode 16 Stripline Electrode 18 Stripline Electrode 20 Capacitor Electrode 22 Dielectric Layer 24 Capacitor Electrode 26 Chip Component

Claims (1)

[Claims] 1. A high-frequency switch connected to a transmission circuit, a reception circuit, and an antenna, for switching connection between the transmission circuit and the antenna and connection between the reception circuit and the antenna. A first diode having an anode connected to the antenna and a cathode connected to the antenna; a first transmission line connected between the anode of the first diode and the ground side; the antenna side and the receiving circuit side; A second transmission line connected between the two, a second diode whose anode is connected to the receiving circuit side and whose cathode is connected to the ground side, and the transmitting circuit, the receiving circuit, the connection with the antenna and grounding A multi-layer substrate having a built-in capacitor used as a capacitor, and a capacitor electrode for the ground electrode and the capacitor in the multi-layer substrate. : It is formed, and between the ground electrode and the capacitor electrode is formed on the same layer, the high-frequency switch.