US 6,982,612 B2
Duplexer and communication apparatus with a matching circuit including a trap circuit for harmonic suppression
Kiwamu Sakano, Ishikawa-ken (Japan)
Assigned to Murata Manufacturing Co., Ltd., Kyoto (Japan)
Filed on Dec. 02, 2003, as Appl. No. 10/725,877.
Claims priority of application No. 2002-365968 (JP), filed on Dec. 18, 2002.
Prior Publication US 2004/0119562 A1, Jun. 24, 2004
Int. Cl. H03H 9/70 (2006.01); H03H 9/72 (2006.01)
U.S. Cl. 333—133 18 Claims
OG exemplary drawing
 
1. A duplexer comprising:
a transmitting filter and a receiving filter which are connected in parallel to an antenna terminal; and
a matching circuit provided between the antenna terminal and at least one of the transmitting filter and the receiving filter; wherein
a portion of the matching circuit defines a trap circuit for harmonic suppression;
the trap circuit includes at least one open stub corresponding to a harmonic to be suppressed;
the matching circuit includes a parallel inductor connected between the antenna terminal and a ground; and
the parallel inductor is a wound-type chip coil.