JPH0595204A - Branching filter - Google Patents

Abstract

PURPOSE:To form a small-sized branching filter whose volume is small with stable performance by using a dielectric filter for one of filter and a surface acoustic wave filter for the other in a dielectric filter composed of a transmission filter and a reception filter. CONSTITUTION:A transmission signal inputted from a transmission system terminal 2 into the branching filter passes through a surface acoustic wave filter 4 whose input/output impedance is corrected by matching circuit microstrip lines 7 and the result is outputted from an antenna terminal 1. Moreover, a reception signal inputted from the antenna terminal 1 is given to a dielectric filter 5, the surface acoustic wave filter 4 whose boards 10, 11 are shielded by a metallic case 12 and which are formed to be a module. Microstrip lines 8 are arranged to the boards 10, 11 and the matching circuit use microstrip lines 7 are arranged on the upper side of the board 10. Since the matching circuit of the surface acoustic wave filter 4 is simplified to employ the microstrip lines 7 only, the filter is miniaturized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duplexer used in a wireless communication device or the like.

[0002]

2. Description of the Related Art A conventional duplexer is a dielectric for both a transmission filter and a reception filter, as described in "The 800MHz Band Dielectric-Filled Small Demultiplexer", Material 743, National Conference of the Institute of Electronics and Communication Engineers, 1986. I used a filter.

Alternatively, as described in Japanese Patent Laid-Open No. 63-54009, surface acoustic wave filters are used for both the transmission filter and the reception filter.

[0004]

In recent years, miniaturization of wireless communication devices has rapidly progressed, and correspondingly, the duplexer is required to be small based on high stability in a high frequency region. .. However, in the conventional duplexer that uses the dielectric filters for both the transmission filter and the reception filter, the volume of each dielectric filter is large, and the volume when the duplexer is configured is also large.

Further, in the conventional duplexer which uses the surface acoustic wave filters for both the transmission filter and the reception filter, peripheral circuits are required although the volume of each surface acoustic wave filter is small. Therefore, the volume when the duplexer is configured in the same package becomes large. This is because in a surface acoustic wave filter, the input / output impedance in the pass band is not very equal to the characteristic impedance, and the input / output impedance in the attenuation band outside the pass band does not become a reactance, so peripheral circuits are added. This is because it is necessary to perform impedance correction. At the same time, in the transmission filter and the reception filter, since the pass band of one filter is the attenuation band outside the pass band of the other filter, if the input / output impedance of one filter deviates due to variations in characteristics, the other filter However, if a peripheral circuit is added to perform impedance correction, the input / output impedance of one filter is likely to shift, and the characteristics of the other filter are also easily affected to obtain the desired performance. Sometimes you can't.

An object of the present invention is to construct a demultiplexer having a small size and stable performance, which can sufficiently cope with downsizing of a wireless communication device.

[0007]

In order to achieve the above object, the present invention uses a dielectric filter as one of a transmission filter or a reception filter and a surface acoustic wave filter as the other, and separates them into the same package. Make up a container.

[0008]

According to the above method, since one filter is a dielectric filter, a peripheral circuit is unnecessary, and deviation of input / output impedance is unlikely to occur. As a result, the other surface acoustic wave filter requires only a simple peripheral circuit to be added, so that not only the volume becomes smaller, but also the dielectric filter is less affected and stable performance can be obtained. That is, it has a small volume and stable performance,
A compact duplexer can be constructed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

A circuit diagram of a duplexer showing an embodiment of the present invention is shown in FIG. In this duplexer, a dielectric filter 5 is used as a reception filter, and a surface acoustic wave filter 4 is used as a transmission filter to form a duplexer. The input / output impedance of the surface acoustic wave filter 4 is corrected by the matching circuit microstrip line 7. The transmission surface acoustic wave filter 4 is a filter having a power-proof structure, and regarding the large transmission power, it is not necessary to cause a problem of the fine electrode pattern of the surface acoustic wave filter due to heat generation or migration.

The transmission signal input into the duplexer from the transmission system terminal 2 passes through the surface acoustic wave filter 4 whose input / output impedance is corrected by the matching circuit microstrip line 7, and the antenna terminal 1 Will be output. The reception signal input from the antenna terminal 1 passes through the dielectric filter 5 and is output to the reception system terminal 3.

FIG. 2 is a perspective view of a duplexer showing an embodiment of the present invention. In this duplexer, the dielectric filter 5, the surface acoustic wave filter 4, and the substrates 10 and 11 are shielded by a metal case 12 and packaged. The microstrip line 8 is arranged on the substrates 10 and 11, and the matching circuit microstrip line 7 is arranged on the upper surface of the substrate 10. Since the matching circuit of the surface acoustic wave filter 4 is simplified, only the microstrip line 7 is provided and the size is reduced.

Further, the surface acoustic wave filter 4 in this embodiment is a surface mounting type, which contributes to further miniaturization.

[0014]

According to the present invention, a compact duplexer having a volume smaller than that of a conventional duplexer and having stable performance can be configured to downsize a radio communication device.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a duplexer showing an embodiment of the present invention,

FIG. 2 is a perspective view of a duplexer showing an embodiment of the present invention.

[Explanation of Codes] 1 ... Antenna terminal, 2 ... Transmission system terminal, 3 ... Reception system terminal,
4 ... Surface acoustic wave filter, 5 ... Dielectric filter, 6 ... Dielectric resonator, 7 ... Matching circuit microstrip line, 8 ... Microstrip line, 9 ... Ground terminal.

Claims (2)

[Claims] 1. A duplexer comprising a transmission filter and a reception filter, wherein a dielectric filter is used for either the transmission filter or the reception filter, and a surface acoustic wave filter is used for the other. A branching filter. 2. The duplexer according to claim 1, wherein the transmission filter and the reception filter are formed in a single small package.