| 摘要 |
<p>A ladder filter comprises series and shunt resonators (2, 4). The or each shunt resonator (4) has a static capacitance which is more than four times the static capacitance of the input or output series resonators (2i, 2o). This provides increased shunt resonator capacitance which reduces the effective coupling across the a series-shunt section, thereby enabling a smaller number of series-shunt filter sections to used to achieve good stop-band rejection, while still providing good performance in the pass-band. The invention is based on the recognition that filter bandwidth can be traded for improved out-of-band rejection.</p> |
