JPH10276003A - Diode switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the line length of a first transmission line extremely short and to provide a compact diode switch by forming the first transmission line and a second transmission line inside a laminated element body, respectively, and parallely connecting a capacitor to the first transmission line. SOLUTION: This diode switch 600 comprises the laminated element body 601, a semiconductor device 602 with two built-in diodes and a chip capacitor 607. In the dielectric layer of the lower layer of the laminated element body 601, a first ground electrode is formed and a prescribed pull-out electrode facing a side face is formed. On the dielectric layer, some dummy layers are arranged and the two dielectric layers for constituting the transmission line are laminated. Then, the capacitor is connected parallelly to the first transmission line. By parallelly connecting the capacitor to the first transmission line, the line length of the first transmission line is made extremely short.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As shown in FIG. 4, for example, a switch circuit of a digital cellular phone is used to switch a transmission path between an antenna and a reception circuit and a transmission path between a transmission circuit and an antenna.

Further, this switch circuit is used for switching a transmission path between a reception circuit and a first antenna and a transmission path between a reception circuit and a second antenna in a telephone or the like employing a reception diversity system. Is also used. Similarly, in the case of a base station for a mobile phone adopting the transmission diversity system, the base station is used to switch the transmission path between the transmission circuit and the first antenna and the transmission path between the transmission circuit and the second antenna. Is done.

Further, this switch circuit switches between an internal circuit such as a mobile phone having a terminal for external connection to a vehicle-mounted booster or the like and a path to the terminal, and a plurality of channels such as a base station for a mobile phone. Also used for switching.

Hereinafter, using the switch circuit shown in FIG.
This will be described in detail. This switch circuit includes an antenna AN
T, the transmission circuit TX, and the reception circuit RX. An anode of a first diode D1 is connected to the transmission circuit TX via a first capacitor C1, and the first diode D1
One cathode is connected to the antenna ANT via a third capacitor C3. The antenna ANT is connected to a receiving circuit RX via a series circuit of a third capacitor C3, a second transmission line TL2, and a fourth capacitor C4. Further, the anode of the first diode D1 is grounded via a series circuit of the first transmission line TL1 and the second capacitor C2. Further, a control circuit VC1 is connected between the first transmission line TL1 and the second capacitor C2 via a resistor R1. Also, the second transmission line TL
The anode of the second diode D2 is connected between the second and fourth capacitors C4, and the cathode of the second diode D2 is grounded via the fifth capacitor C5. Further, a control circuit VC2 is connected between the cathode of the second diode D2 and the fifth capacitor C5 via a resistor R2. Here, the control circuit VC1 connected via the resistor R1 and the control circuit VC2 connected via the resistor R2 are circuits for switching the switch circuit.

In the switch circuit shown in FIG. 5, when connecting the transmitting circuit TX and the antenna ANT, a positive voltage is supplied from the control circuit VC1 to the control circuit VC2.
From 0 is applied. The positive voltage supplied from the control circuit VC1 is cut off the DC component by the first to fifth capacitors, and the first diode D1
And a first diode D1 and a second diode D2.
Is turned on. When the first diode D1 is turned on, the impedance of the transmission path between the transmission circuit TX and the antenna ANT is reduced and the connection is established. On the other hand, the second transmission line TL2 is grounded at a high frequency and resonated by the second diode D2 and the fifth capacitor which are turned on, and the first diode D2 is turned on.
1, the impedance when the receiving circuit RX side is viewed from the connection point of the third capacitor C3 and the second transmission line TL2 becomes very large, and the antenna ANT and the receiving circuit R
The transmission path to X is not connected. At this time, the transmission circuit T
Without the transmission signal from X leaking to the receiving circuit RX,
It will be transmitted to the antenna ANT.

On the other hand, when the antenna ANT is connected to the receiving circuit RX, a positive or zero voltage is applied from the control circuit VC2, and a zero voltage is applied from the control circuit VC1.
Is turned off. When the first diode D1 is turned off, the transmission circuit TX
The impedance of the transmission path between the antenna and the antenna ANT increases, and the antenna is not connected. In addition, the transmission path between the antenna ANT and the reception circuit RX is connected via the second transmission line TL2 by the second diode D2 that has been turned off. At this time, the reception signal from the antenna ANT is transmitted to the reception circuit RX without leaking to the transmission circuit TX. As described above, the control circuit VC
By controlling the voltage supplied from the control circuit 1 and the control circuit VC2, the switch circuit can be switched to perform transmission and reception.

[0008]

FIG. 6 is an exploded perspective view showing an example of a conventional switch circuit having a circuit as shown in FIG. This switch circuit includes a laminated body,
A first line electrode 31 serving as a first transmission line TL1 and a second line electrode 32 serving as a second transmission line TL2;
A first ground electrode 41, a second ground electrode 11, and a large number of lands are formed so as to sandwich the first line electrode 31 and the second line electrode 32 with a dielectric therebetween. On the layer 50, surface mount components including the first diode D1 are arranged.

This switch circuit includes a first line electrode 3
As the first and second line electrodes 32, two transmission lines each having a length of 1/4 of the wavelength of the transmission signal or the reception signal are required.
04, etc., are formed on the same layer in the laminated body. Although depending on the dielectric constant of the laminated body, the size of the transmission line is about several tens of millimeters, and there is a limit to miniaturization.

As disclosed in Japanese Patent Application Laid-Open No. 7-202503 and the like, when a first line electrode and a second line electrode are formed on different layers in a laminated body, the first line electrode and the second line electrode are formed as shown in FIG. The dielectric layer 30 on which the first line electrode 31 is formed and the second line electrode 1 are arranged so that the first line electrode 31 and the second line electrode 12 do not interfere with each other.
It is necessary to provide the dielectric layer 20 on which the shield electrode 21 is formed between the dielectric layers 10 on which the second element 2 is formed, which increases the number of layers of the laminated body as a whole and increases the production cost.

An object of the present invention is to solve the above problems and to provide a small diode switch.

[0012]

The present invention comprises a first circuit,
A switch circuit connected to the second circuit and the third circuit for switching the connection between the first circuit and the third circuit and the connection between the second circuit and the third circuit; A cathode is connected to the first circuit side;
A first diode having an anode connected to the third circuit side, a first transmission line connected to a cathode of the first diode, a capacitor connected to the other end of the first transmission line, The other end of the capacitor is connected to ground, and a second terminal connected between the third circuit and the second circuit.
And a second diode whose cathode is connected to the second circuit side and whose anode is connected to the ground via a capacitor, wherein the first transmission line and the second transmission line are: Embedded in the laminated body, the first
Is a diode switch in which a capacitor is connected in parallel to the transmission line.

Further, according to the present invention, the capacitor connected in parallel to the first transmission line is a capacitor of 0.1 to 10 pF. Further, according to the present invention, the line length of the first transmission line is reduced to 70% or less of 1 / 4λ.

[0014]

FIG. 2 is an equivalent circuit diagram of a diode switch according to an embodiment of the present invention. This died switch includes an antenna ANT, a transmitting circuit TX, a receiving circuit R
Connected to X. The transmission circuit TX includes a capacitor C
1, the cathode of the first diode D1 is connected, and the anode of the first diode D1 is connected to the capacitor C1.
3 and connected to the antenna ANT. Antenna AN
A receiving circuit RX is connected to T via a series circuit of a capacitor C3, a second transmission line L2, and a capacitor C4.

A first transmission line L1 and a capacitor C6 are connected to the cathode of the first diode D1,
They are grounded via a capacitor C2. further,
A control circuit VC1 is connected between the first transmission line L1 and the capacitor C2 via a resistor R1. The cathode of the second diode D2 is connected between the second transmission line L2 and the capacitor C4, and the anode of the second diode D2 is grounded via the capacitor C5. Further, a control circuit VC2 is connected between the anode of the second diode D2 and the capacitor C5 via a resistor R2. Here, the control circuit VC1 connected via the resistor R1 and the control circuit VC2 connected via the resistor R2 are circuits for switching the switch circuit.

In the switch circuit of this embodiment, when the transmission circuit TX and the antenna ANT are connected, a positive voltage is supplied from the control circuit VC2 to the control circuit VC2.
A voltage of 1 to 0 is provided. Control circuit VC2
Of the positive voltage supplied from the first diode D is cut off by the first to fifth capacitors.
Applied only to the circuit including the first and second diodes D2, D1 and D2
Is turned on. When the first diode D1 is turned on, the impedance of the transmission path between the transmission circuit TX and the antenna ANT is reduced and the connection is established. On the other hand, the second transmission line TL2 is grounded at a high frequency and resonated by the second diode D2 and the fifth capacitor which are turned on, and the first diode D2 is turned on.
The impedance when the receiving circuit RX side is viewed from the connection point between the anode of the first, third capacitor C3 and the second transmission line TL2 becomes very large, and the antenna ANT and the receiving circuit R
The transmission path to X is not connected. At this time, the transmission circuit T
Without the transmission signal from X leaking to the receiving circuit RX,
It will be transmitted to the antenna ANT.

On the other hand, when the antenna ANT and the receiving circuit RX are connected, a positive or zero voltage is applied from the control circuit VC1 and a zero voltage is applied from the control circuit VC2, so that the first diode D1 and the second diode D2 are connected.
Is turned off. When the first diode D1 is turned off, the transmission circuit TX
The impedance of the transmission path between the antenna and the antenna ANT increases, and the antenna is not connected. In addition, the transmission path between the antenna ANT and the reception circuit RX is connected via the second transmission line TL2 by the second diode D2 that has been turned off. At this time, the reception signal from the antenna ANT is transmitted to the reception circuit RX without leaking to the transmission circuit TX. As described above, the control circuit VC
By controlling the voltage supplied from the control circuit 1 and the control circuit VC2, the switch circuit can be switched to perform transmission and reception.

In the present invention, the connection direction of the diode is reversed as compared with the conventional example. This results in insertion loss,
The isolation characteristics have been improved.

In the present invention, 1 /
When it is shorter than 4λ, it has inductive impedance,
In the range from イ ン ピ ー ダ ン ス λ to λλ, a characteristic having a capacitive impedance is used, and in the range from λλ to λ, an inductive impedance is used. For this reason, the resonance phenomenon is caused by shortening the line length of the transmission line to less than 、 λ, providing an inductive impedance, and connecting a capacitor to the inductive impedance. The resonance frequency f0 (for example, the transmission frequency) is obtained by the following equation.

[0020]

(Equation 1)

In Equation 1, L is the equivalent inductor of the line of the transmission line, and C is the capacitance of the capacitor. L is obtained by the following equation, where the line length of the transmission line is 1.

[0022]

(Equation 2)

In Equation 2, Z0 is the characteristic impedance of the line. From these relational expressions, the line length of the transmission line and the capacitance of the capacitor are determined. In the present invention, as a result of various studies, the capacitor capacity is 0.1 to 10
It has been found that pF is desirable. More preferably, it is 0.5 to 5.0 pF. Further, as described above, the line length of the transmission line is determined by the relationship with the capacitance of the capacitor. According to the present invention, the length of the transmission line should be 70% or less of the conventional length of 1 / 4λ. Was completed. Also, 5
It was possible even at 0% or less. Therefore, the length of the transmission line requiring a space can be reduced, so that the size of the diode switch can be reduced.

In the present invention, the transmission line has a spiral shape. There is the following difference between the meander shape and the spiral shape of the transmission line. First, in the case of a meandering shape, the current directions of adjacent transmission lines are opposite. For this reason, the magnetic field between the adjacent transmission lines is weakened, and the transmission lines appear as if they were shortened. Further, if the length of the transmission line is to be increased in a narrow space, the distance between the adjacent transmission lines is shortened and the weakening of the magnetic field is increased, so that a certain space is required.

On the other hand, in the case of the spiral shape, the current directions of the adjacent transmission lines are the same. For this reason,
The magnetic fields between adjacent transmission lines reinforce, and the transmission lines appear to be longer. In the case of this spiral transmission line, there is no problem even if the distance between adjacent transmission lines is shortened. Thus, when the transmission line is formed in a spiral shape, the transmission line appears to be long, so that the actual line length can be shortened.

As described above, the use of the spiral shape as the transmission line also contributes to miniaturization. The spiral shape preferably has 1 to 5 turns. Further, according to the spiral shape of the present invention, １ ／ λ
To form a transmission line having a length of about 90%.

In the present invention, the parallel circuit of the transmission line and the capacitor is grounded via the capacitor. As a result, the high frequency passes through the capacitor, and R1 becomes invisible. Therefore, a signal having a frequency other than the resonance frequency band flows into this circuit and does not pass to the ANT side, but can selectively transmit the resonance frequency band to the ANT side.

Hereinafter, the present invention will be described in detail with reference to examples. (Embodiment 1) FIG. 1 is a perspective view of an embodiment according to the present invention. This diode switch 600 includes a laminated element body 60.
A semiconductor element 602 containing one or two diodes,
And a chip capacitor 607. Note that this semiconductor element may be provided with two diodes.
The equivalent circuit diagram of this diode switch is as shown in FIG. In FIG. 2, the part surrounded by a broken line is the part shown in FIG.
And the other circuit constants may be configured on a circuit board on which the diode switch is mounted. Further, the chip capacitor 607 and the like can also be formed in this laminated body. Needless to say, as in the prior art shown in FIG. 6, a circuit element other than the above can be mounted on the laminated element body, or a structure in which a capacitor is built in can be adopted.

FIG. 3 shows the internal structure of the laminated body 601. The lower dielectric layer 100 has a first ground electrode 10
1 is formed, and a predetermined lead electrode facing the side surface is formed.

On the dielectric layer 100, several dummy layers are arranged, and two dielectric layers 1 constituting a transmission line are formed.
02 and 103 are stacked. The transmission line L1 in the circuit diagram of FIG. 2 is configured by connecting a line electrode 104 of the dielectric layer 103 and a line electrode 105 of the dielectric layer 102. The connection between the two line electrodes is performed via a through-hole electrode 106. Then, a lead electrode facing the side surface of each dielectric layer is formed.

The transmission line L2 in the circuit diagram of FIG.
Are the line electrode 107 of the dielectric layer 103 and the dielectric layer 10
It is configured by connecting two line electrodes 108. This 2
The connection of the two line electrodes is performed via the through-hole electrode 109. Then, a lead electrode facing the side surface of each dielectric layer is formed.

Then, the dielectric layer 110 on which the second ground electrode 111 is formed is stacked via several dummy layers.

On the upper surface of the uppermost dielectric layer 112, a pattern electrode is formed. This pattern electrode includes a first ground electrode 101 and a second ground electrode 11.
1 and pattern electrodes 113, 114, 115 connected to
A pattern electrode 116 connected to the line electrode 104 forming the first transmission line L1, a pattern electrode 117 connected to the line electrode 105 also forming the first transmission line L1, and a second transmission line It has a pattern electrode 118 connected to the line electrode 108 forming L2, a pattern electrode 119 connected to the line electrode 107 also forming the second transmission line L2, and a pattern electrode 120 connected to a diode.

This laminated body is formed into a sheet by a doctor blade using a dielectric material, an Ag electrode is screen-printed on the sheet to form a pattern electrode, which is laminated, pressed, and integrally fired. It was done. And
Terminal electrodes 603, 604, 605, 606 on the side surfaces after firing
Was formed. The terminals of the semiconductor element 602 having two built-in diodes are the pattern electrodes 117, respectively.
118, 119 and 120, and a chip capacitor 607 is connected to the pattern electrodes 116 and 117.

In this embodiment, a capacitor C6 is connected in parallel with the first transmission line L1. By connecting a capacitor in parallel to the first transmission line, the line length of the first transmission line could be extremely reduced. In this embodiment, a diode switch for the 1.9 GHz band is configured,
The line length of the first transmission line was about 9 mm, and the capacitance of the capacitor was 0.5 pF. This line length would be 14 mm if 従 来 λ of the conventional one, and could be reduced to about 64% by the present invention. The dielectric constant of the dielectric is about 8.

Next, the first transmission line was made the same, and the line length of the second transmission line was changed to construct a diode switch for the 800 MHz band. At this time, the line length of the first transmission line is about 9 mm, and the capacitance of the capacitor is 4 p.
F could be configured. This line length is the conventional 1 / 4λ
Is 33 mm, and according to the present invention,
This was reduced to about 27%. The dielectric constant of the dielectric is about 8. As described above, according to the present invention, the line length of the transmission line can be set to 70% or less, and even 50% or less of the conventional transmission line, and it is easy to reduce the size of the diode switch. I can understand.

[0037]

According to the present invention, the first transmission line and the second transmission line are respectively formed in the laminated body, and a capacitor is connected in parallel with the first transmission line, whereby the first transmission line and the second transmission line are connected in parallel. The line length of the transmission line can be extremely reduced, and a small diode switch can be configured. As a result, miniaturization of a mobile phone or a high-frequency circuit to which the switch circuit is mounted is achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment according to the present invention.

FIG. 2 is an equivalent circuit diagram of a switch circuit using the embodiment shown in FIG.

FIG. 3 is an exploded perspective view of the laminated body of the embodiment according to the present invention shown in FIG.

FIG. 4 is a diagram illustrating functions of a switch circuit.

FIG. 5 is a circuit diagram of a conventional switch circuit.

FIG. 6 is an exploded perspective view showing a conventional technique.

FIG. 7 is an exploded perspective view showing another conventional technique.

[Explanation of symbols]

100, 102, 103, 110, 112 Dielectric layer 101 First ground electrode 104, 105, 107, 108 Line electrode 106, 109 Through hole electrode 111 Second ground electrode 113, 114, 115, 116, 117, 118 , 1
19, 120 Pattern electrode 600 Diode switch 601 Stacked element 602 Semiconductor element 603, 604, 605, 606 Terminal electrode 607 Chip capacitor

Claims (3)

[Claims] A first circuit connected to a first circuit, a second circuit, and a third circuit; a connection between the first circuit and the third circuit; and a connection between the second circuit and the third circuit. A first circuit having a cathode connected to the first circuit side and an anode connected to the third circuit side, and a switching circuit connected to a cathode of the first diode. A first transmission line connected, a capacitor connected to the other end of the first transmission line, the other end of the capacitor connected to ground, and a connection between the third circuit and the second circuit. A second transmission line to be connected, and a second diode having a cathode connected to the second circuit side and an anode connected to ground via a capacitor, wherein the first transmission line and the second diode are connected to each other. The transmission line of
A diode switch, wherein the diode switch is built in a multilayer body and a capacitor is connected in parallel to the first transmission line. 2. The diode switch according to claim 1, wherein a capacitor connected in parallel to said first transmission line has a capacitance of 0.1 to 10 pF. 3. The line length of the first transmission line is λλ.
2. The diode switch according to claim 1, wherein the length of the diode switch is reduced to 70% or less.