| US 7,498,902 B2 | ||
| Balanced/unbalanced filter module and communication apparatus | ||
| Tetsuro Harada, Otsu (Japan); Naoto Yamaguchi, Moriyama (Japan); Naoki Nakayama, Sakai (Japan); Takanori Uejima, Moriyama (Japan); Hidehiro Takano, Kyoto (Japan); and Koki Saito, Ibaraki (Japan) | ||
| Assigned to Murata Manufacturing Co., Ltd, Kyoto (Japan) | ||
| Filed on Jun. 22, 2007, as Appl. No. 11/766,868. | ||
| Application 11/766868 is a continuation of application No. PCT/JP2005/023106, filed on Dec. 16, 2005. | ||
| Claims priority of application No. 2004-381954 (JP), filed on Dec. 28, 2004. | ||
| Prior Publication US 2008/0122554 A1, May 29, 2008 | ||
| Int. Cl. H03H 9/70 (2006.01); H03H 9/72 (2006.01) | ||
| U.S. Cl. 333—133 [455/83] | 24 Claims |
| 1. A balanced/unbalanced filter module, comprising:
a switch that includes a first port, a second port, and a third port and is arranged to switch between a signal path between
the third port and the first port and a signal path between the third port and the second port, the first port inputting and
outputting unbalanced signals in a first frequency band, the second port inputting and outputting unbalanced signals in a
second frequency band, the third port inputting and outputting unbalanced signals in the first frequency band and unbalanced
signals in the second frequency band;
a first balanced/unbalanced filter that includes a fourth port, a fifth port, and a sixth port, the fourth port being connected
to the first port and inputting and outputting unbalanced signals in the first frequency band, the fifth and sixth ports inputting
and outputting balanced signals in the first frequency band, a pass band of the first balanced/unbalanced filter being the
first frequency band;
a second balanced/unbalanced filter that includes a seventh port, an eighth port, and a ninth port, the seventh port being
connected to the second port and inputting and outputting unbalanced signals in the second frequency band, the eighth and
ninth ports inputting and outputting balanced signals in the second frequency band, a pass band of the second balanced/unbalanced
filter being the second frequency band; and
a matching element that is provided between a first branch port and a second branch port and performs impedance matching for
balanced signals in the first frequency band and balanced signals in the second frequency band, the first branch port being
connected to the fifth and eighth ports, the second branch port being connected to the sixth and ninth ports; wherein
the electrical length between the fifth port and the first branch port in the first frequency band is substantially the same
as the electrical length between the sixth port and the second branch port in the first frequency band, and the electrical
length between the eighth port and the first branch port in the second frequency band is substantially the same as the electrical
length between the ninth port and the second branch port in the second frequency band.
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