JP2002300080A - High frequency module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency module with reduced number of components that matches the impedance with respect to a circuit connected before and after a high frequency switch circuit while maintaining downsizing. SOLUTION: Low pass filters LPF3, LPF4 connected before and after a transmission system Tx of the high frequency switch circuit SW1 switching a transmission/reception system into the transmission system Tx and a reception system Rx are connected via the high frequency switch circuit the inductor LG2 of which is inserted between a line of the transmission system Tx and ground so as to match the impedance of the low pass filters LPF3, LPF4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency module.

[0002]

2. Description of the Related Art JP-A-2000-223901 discloses that
In a cellular phone, a configuration is disclosed that improves switch performance in a diode switch circuit that switches a transmission / reception system between a transmission system and a reception system. That is, in the diode switch circuit, a diode is provided in a transmission circuit for transmitting a transmission signal to the antenna ANT, and a transmission line as a distributed constant line functioning as a choke element is provided between the cathode of the diode and the ground. I have. With this transmission line, the isolation of the circuit between transmission and reception is improved.

In recent years, a portable telephone employing a dual-band system has been proposed in contrast to a normal portable telephone employing one transmission / reception system. The dual-band mobile phone is equipped with two transmitting / receiving systems in one mobile phone, and the convenience of selecting and transmitting a transmitting / receiving system that matches the regional characteristics and the purpose of use is provided. It is expected to be a high device. In recent years in Europe, GS has been
A dual band mobile phone equipped with both the M system and the DCS system is under study.

Japanese Patent Application Laid-Open No. 11-225088 discloses a dual-band high-frequency switch module. This conventional dual-band high-frequency switch module is a multi-band high-frequency switch module that handles a GSM / DCS transmission / reception system.
The transmission / reception system of the M system / DCS system includes a demultiplexing circuit for dividing the transmission / reception system into transmission / reception systems, and a diode switch circuit for switching the transmission / reception system between a transmission system and a reception system. As the demultiplexing circuit, two notch circuits connected in parallel with each other are used. One end of each notch circuit is connected to be a common terminal for each transmission / reception system, and the other end of each notch circuit is connected to a diode switch circuit. Connected to

By the way, each circuit is connected before and after the transmission system of the high-frequency switch circuit, and it is preferable from the viewpoint of transmission efficiency to match the impedance of both circuits.
Conventionally, a composite component having a built-in matching circuit composed of chip components such as capacitors and inductors is interposed between both circuits,
Alternatively, matching is achieved by employing a distributed constant line having a desired length.

[0006]

Problems to be Solved by the Invention JP-A-2000-223
The transmission line described in Japanese Patent Application Laid-Open No. 901 is intended only to ensure isolation for switching between a transmission system and a reception system, and does not take impedance matching between circuits connected to both sides of a switch circuit. .

Further, in the case of a dual-band type portable telephone, if a circuit is formed by using a dedicated component for each transmission / reception system, it will not be possible to meet the demand for miniaturization and cost reduction of the equipment. Where it is desired to use common parts as much as possible for common parts,
The dual-band high-frequency switch module described in Japanese Patent Application Laid-Open No. 1-225088 has a problem that the number of chip components mounted on the substrate surface is large in order to further reduce the size of the high-frequency module. Moreover, as described above, 1
In order to connect one circuit to another circuit, a matching circuit for matching the impedance of both circuits is required. However, in the above-described matching circuit, a new component or a distributed constant line is added, and a high frequency There is a problem that the module becomes large.

The present invention has been made in view of the above, and it is possible to reduce the number of components by matching the impedance of two circuits connected before and after the transmission system of the high-frequency switch circuit, or to reduce the number of components and distributed constant lines. It is an object of the present invention to provide a high-frequency module that can be realized without any additional components.

[0009]

According to the first aspect of the present invention,
In a high-frequency module, a circuit is connected before and after a transmission system of a first high-frequency switch circuit that switches a first transmission / reception system having a first pass band connected to an antenna between a transmission system and a reception system, An inductor is inserted between the signal line of the transmission system of the first high-frequency switch circuit and the ground.

According to this configuration, in the high-frequency module, signal transmission becomes possible because the impedances of the transmission system and the reception system are different between transmission and reception.
When the first and second high-frequency switch circuits look at the front and rear sides (first and second circuits) of the transmission system, the impedances are different from each other, resulting in a mismatch and a decrease in transmission efficiency in transmission. The alignment state can be easily maintained simply by providing. The inductor may be formed in a pattern such as a distributed constant line in the module, or may be a mountable chip component. As a result, the number of components of the high-frequency module can be reduced or new addition is not required, and further downsizing can be realized.

According to a second aspect of the present invention, the preceding and following circuits are each a filter circuit or a coupler that transmits a transmission signal to and from a filter circuit and feedbacks a part of the transmission signal for feedback control. The high-frequency module according to claim 1, wherein: According to this configuration, the matching between the filter circuits or the matching between the filter circuit and the coupler is achieved, so that the transmission efficiency of the transmission signal is maintained.

According to a third aspect of the present invention, there is provided a second transmitting / receiving system having a second pass band connected in parallel to the first transmitting / receiving system with respect to the antenna, wherein the antenna and the first and second antennas are provided. 2. The high-frequency module according to claim 1, further comprising a branching circuit for dividing the first and second passbands between the transmitting and receiving systems. According to this configuration, the transmission efficiency of the transmission signal is maintained for each of the first and second transmission / reception systems.

According to a fourth aspect of the present invention, there is provided a coupler wherein each of the front and rear circuits is a filter circuit, or a coupler which transmits the demultiplexing circuit, the filter circuit, and a transmission signal and partly feeds back the signal for feedback control. The high-frequency module according to claim 3, wherein: According to this configuration, the matching between the filter circuits or the matching between the two circuits of the demultiplexing circuit, the filter circuit, and the coupler is achieved, so that the transmission efficiency of the transmission signal is maintained.

The invention according to claim 5 is the high-frequency module according to any one of claims 1 to 4, wherein the inductor has a self-resonant frequency sufficiently higher than a pass band. The invention according to claim 6 is the high-frequency module according to any one of claims 1 to 4, wherein the inductor has a self-resonant frequency sufficiently lower than a pass band. According to these configurations, the inductor can be set so as to function as an inductive element or a capacitive element corresponding to the preceding and following circuits, so that suitable impedance matching can be performed regardless of the preceding and following circuits. .

[0015]

FIG. 1 is a circuit diagram showing one embodiment of a high-frequency module according to the present invention. The high-frequency module 1 is a demultiplexing circuit DI that divides each transmission / reception system of a GSM / DCS system having a different pass band into a transmission / reception system.
P1, low-pass filters LPF1, LPF2, LPF having a function of removing harmonic signals from the transmission signal amplifier
3. It is composed of high-frequency switch circuits SW1 and SW2 for switching between a transmission system and a reception system. Here, the low-pass filters LPF2 and LPF3 may also have the function of a directional coupler.

The transmission system on the DCS side, that is, the system from the DCS-TX terminal to the ANT terminal is a low-pass filter LPF.
2. High frequency switch circuit SW1, low pass filter LP
F1 and each circuit element of the demultiplexing circuit DIP1. Each of the elements has a filter function of passing a fundamental wave and attenuating a part of a harmonic component, and a DCS side transmission system is configured by electrically cascading these elements. .

In the circuit elements constituting the DCS side transmission system, the low-pass filters LPF1 and LPF2 have the same circuit configuration in this embodiment. That is, the LPF 1 includes the strip line STLD1, a capacitor CD6 electrically connected in parallel to the strip line STLD1, and capacitors CD7 and CD8 forming an electric capacitance between both ends of the strip line STLD1 and the ground electrode. Similarly, LPF2 is also a strip line STLD3.
And a capacitor CD9 electrically connected in parallel thereto
And capacitors CD10 and CD11 forming an electric capacitance between both ends of the strip line STLD3 and the ground. Further, each of the low-pass filters LPF1 and LPF2 passes the fundamental wave of the DCS transmission signal in the 1750 MHz band and attenuates harmonics related to the fundamental wave, for example, the second harmonic so as to attenuate the second harmonic. Are designed such that an attenuation pole is formed.

The demultiplexing circuit DIP1 is connected to the antenna terminal ANT, and is configured by connecting a low-pass filter LPF4 and a high-pass filter HPF1 in parallel. The high-pass filter HPF1 comprises capacitors CD1, CD2 connected in series and both capacitors CD1, CD
Inductor LD1 connected between connection point 2 and ground
It is composed of

The low pass filter LPF4 on the GSM system side constituting the demultiplexing circuit DIP1 has inductors LG1,
A filter circuit including a capacitor CG1, and a plurality of capacitors CG6 to CG9 connected in series and parallel to the strip line STLG1 and the strip line STLG1.
And a filter circuit consisting of

The low pass filter LPF3 on the GSM system side forms a strip line STLG3, a capacitor CG10 electrically connected in parallel thereto, and a capacitance between both ends of the strip line STLG3 and the ground electrode. It is composed of capacitors CG11 and CG12.

Next, the high-frequency switch circuits SW1, SW2
Will be described. High frequency switch circuits SW1, SW2
Is a control terminal DCS which connects a transmission system Tx and a reception system Rx to be described later.
-Vc and GSM-Vc can be switched in a time-sharing manner by a control voltage applied thereto.

The high-frequency switch circuit SW1 on the DCS side will be described. The switch circuit SW1 is interposed between the low-pass filters LPF1 and LPF2. The anode of the diode DD1 is connected to the low-pass filter LPF1, and the cathode is connected to the low-pass filter LPF2 via the capacitor CD3. An inductor LD2 that functions as a choke element is connected between the cathode of the diode DD1 and the ground.

One end of a distributed constant line STLD2 is connected to the anode of the diode DD1, and the other end is connected to a capacitor C.
It is connected to the receiving terminal DCS-Rx via D5. At a connection point between the distributed constant line STLD2 and the capacitor CD5, a diode DD2 having a cathode connected and a capacitor CD4 are connected in series.
A connection point between D2 and the capacitor CD4 is connected to a control terminal DCS-Vc via a control resistor RD1.

The high-frequency switch circuit SW2 on the GSM side will be described. The switch circuit SW2 is interposed between the low-pass filters LPF4 and LPF3. The anode of the diode DG1 is connected to the low-pass filter LPF4 via the capacitor CG2, and the cathode is connected to the low-pass filter LPF via the capacitor CG3.
3 is connected. An inductor LG2 that functions as a choke element is connected between the cathode of the diode DG1 and the ground.

One end of a distributed constant line STLG2 is connected to the anode of the diode DG1, and the other end is connected to a capacitor C.
It is connected to the receiving terminal GSM-Rx via G5. At a connection point between the distributed constant line STLG2 and the capacitor CG5, a diode DG2 having a cathode connected and a capacitor CG4 are connected in series.
A connection point between G2 and the capacitor CG4 is connected to a control terminal GSM-Vc via a control resistor RG1.

Next, the operation of the inductor LG2 (LD2) will be described. Since the operation of both inductors is the same, the description will be made here taking the inductor LG2 as an example.

In the GSM system, when a transmission period occurs and a predetermined positive voltage is applied to the control terminal GSM-Vc, the diodes DG2 and DG1 are biased in the forward direction. When the diode DG1 is forward biased, a transmission signal from an amplifier (not shown) transmitted from the transmission system GSM-Tx passes through the diode DG1. At this time, a series resonance circuit is formed for the GSM frequency band by the inductance of the diode DG2 itself and the capacitance of the capacitor CG4, the impedance becomes zero, and the receiving system GSM-Rx is grounded. Therefore, the transmission signal that has passed through the diode DG1 is transmitted to the low-pass filter LPF4 of the demultiplexer DIP1, and transmitted from the antenna ANT. At this time, the distributed constant line ST
The impedance when the receiving system is viewed from the transmitting system of the LG2 becomes maximum. Also, due to the presence of the inductor LG2, the current due to the positive voltage applied to the control terminal GSM-Vc is reduced by the diodes DG2, DG1 and the inductor LG
It flows to ground via 2.

On the other hand, in the reception period, the control terminal GSM-
When Vc is set to zero voltage, the diodes DG2, DG1
Is turned off, the connection between the antenna ANT and the transmission system GSM-Tx is cut off, and the reception signal from the antenna ANT is transmitted to the reception system GSM-Rx.

Further, through the interposition of the inductor LG2,
The impedance matching of the circuits before and after the high-frequency switch circuit SW2 during the transmission period is maintained by the inductor LG2.

The present invention can also take the following aspects as circuits connected before and after the transmission system of the high-frequency switch circuit. That is, in addition to a demultiplexing circuit and a low-pass filter, a high-pass filter, a band-pass filter, a band elimination filter, or a combination thereof may be used as a circuit for dividing a plurality of transmission / reception systems having different pass bands into transmission / reception systems.

In addition to the low-pass filter, a circuit for monitoring the output of an amplifier corresponding to the pass frequency of each transmission system, or a circuit for preventing harmonics of each transmission system, as the other circuit. Band pass filter, band elimination filter, or a combination thereof.

In any case, the inductors LG2, LD2
Due to the nature of the circuit connected to the front and rear of the inductor, if a self-resonant frequency of the inductor that is sufficiently higher than the frequency of the pass band of the system is adopted, it functions as an inductive element, When adopting a frequency that is sufficiently low with respect to the frequency of the pass band of the system, it functions as a capacitive element and is connected before and after.
Impedance matching can be achieved for the various circuits described above.

FIG. 2 is a partially cutaway perspective view showing a schematic configuration of an embodiment of the high-frequency module according to the present invention. As shown in FIG. 2, this high-frequency module 1 has eight dielectric layers 11, 12,.
The upper surface and the side surfaces are covered with a shield cover 10 made of metal, and a required number of end surface electrodes formed as needed are formed at appropriate positions on the side surfaces so as to extend from the upper surface to the bottom surface. . The conductive pattern on the upper surface of the uppermost dielectric layer 11 is partially omitted in the drawing. The end face electrodes are for electrically connecting the high-frequency module 1 and a circuit on a printed circuit board on which the high-frequency module 1 is mounted.

The dielectric layers 11 to 18 are ceramics for firing at a low temperature, and a conductive paste or the like is applied to the surface of the ceramic green sheet to form the electrode patterns constituting each of the circuits described above. The green sheets are laminated and thermocompression-bonded under the required pressure and temperature and fired. In each dielectric layer, via holes necessary for configuring or connecting a circuit are appropriately formed over a plurality of layers. Uppermost dielectric layer 11
In addition to various patterns, termination resistors RD21, RG2
1 and other chip components (the diode D shown in FIG. 1).
A plurality of other chip elements including D1, DD2, DG1, DG2 and the like are mounted. In addition, inductor LD
1, LD2, LG1, and LG2 are built in the laminate, or instead of being formed with a conductive pattern on the uppermost layer,
It may be a chip element. The number of dielectric layers is not limited to eight.

Further, although the present invention has been described with reference to the GSM / DCS dual system, the present invention is not limited to this, and can be similarly applied to a communication device equipped with a high-frequency module provided with one of the system circuits.

[0036]

In the high-frequency module of the present invention, the impedance of an arbitrary circuit connected before and after the high-frequency switch circuit for switching the transmission / reception system between the transmission system and the reception system is changed by inserting an inductor grounded to the transmission system. The connection can be made through the high-frequency switch circuit. This eliminates the need for a matching circuit attached to each circuit as in the related art, and makes it possible to reduce the size of the high-frequency module.

Further, by forming the inductor grounded to the ground inserted into the transmission system of the high-frequency switch circuit of the present invention using a distributed constant line built in the surface of the substrate or in the substrate, the component of the high-frequency module is provided. The number can be reduced, and further miniaturization can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a high-frequency module according to the present invention.

FIG. 2 is a partially cutaway perspective view showing a schematic configuration of an embodiment of a high-frequency module according to the present invention.

[Explanation of symbols]

1 High frequency module LPF1, LPF2, LPF3, LPF4 Low pass filter DIP1 Demultiplexer SW1, SW2 High frequency switch circuit LD1, LD2, LG1, LG2 Inductor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K011 BA03 BA10 DA21 DA25 DA27 EA06 JA01 KA18

Claims (6)

[Claims] 1. A first high-frequency switch circuit for switching a first transmission / reception system having a first passband connected to an antenna between a transmission system and a reception system before and after a transmission system of the first high-frequency switch circuit. In the high-frequency module, an inductor is inserted between a signal line of a transmission system of the first high-frequency switch circuit and a ground. 2. The circuit according to claim 1, wherein the front and rear circuits are each a filter circuit, or a coupler that transmits a transmission signal with the filter circuit and feeds back a part of the transmission signal for feedback control. The high-frequency module as described. 3. A second transmission / reception system having a second pass band connected in parallel to the first transmission / reception system with respect to the antenna, and provided between the antenna and the first and second transmission / reception systems. 2. The high-frequency module according to claim 1, further comprising a branching circuit for separating the first and second passbands between the first and second passbands. 4. The apparatus according to claim 1, wherein the first and second circuits are filter circuits, or two of the demultiplexer circuit, the filter circuit, and a coupler that transmits a transmission signal and feedbacks a part of the transmission signal for feedback control. The high-frequency module according to claim 3, wherein 5. The high-frequency module according to claim 1, wherein the inductor has a self-resonant frequency sufficiently higher than a pass band. 6. The high-frequency module according to claim 1, wherein said inductor has a self-resonant frequency sufficiently lower than a pass band.