| 摘要 |
PROBLEM TO BE SOLVED: To provide a resonator type SAW filter of which a pass bandwidth is wider than that of a conventional filter by canceling and reducing a reflection coefficient that an electrode finger has, while using a 1/4 wavelength electrode in a longitudinal duplex mode resonator type SAW filter. SOLUTION: In input side and output side interdigital electrodes of a resonator type SAW filter, when a wavelength of a surface acoustic wave is defined asλ, an electrode width L is approximately comprised ofλ/4, and each of the input side and output side interdigital electrodes is formed by alternately disposing two kinds of different blocks A and B. When P=L+S is established for an electrode term length P that is a sum of an electrode width dimension L and an electrode gap dimension S, in the block A, the electrode term length P is PA and there is one interdigital electrode couple MA. In the block B, the electrode term length P is PB and there is one interdigital electrode couple MB. All electrode fingers in the blocks A and B are connected to a feeding conductor and furthermore, an interdigital electrode for control is formed by making its electrode term length PC different from PA. At the same time, interdigital electrode couples MC are settled within a range where a full reflection coefficient is about 1. COPYRIGHT: (C)2006,JPO&NCIPI
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