Passband filter having an asymmetrical filter response

摘要

A filter, such as a transmit filter (34) of a duplexer, includes an array of acoustic resonators (36, 38, 40, 42, 44, 46 and 48) that cooperate to establish an asymmetrically shaped filter response (56) over a target frequency passband. The acoustic resonators are preferably film bulk acoustic resonators (FBARs). The filter response defines an insertion loss profile in which a minimum insertion loss within the target passband is located at or near a first end of the frequency passband, while the maximum insertion loss is located at or near the opposite end of the frequency passband. In the transmit filter embodiment, the minimum insertion loss is at or near the high frequency end of the filter response, which is tailored by selectively locating poles and zeros of the array of FBARs.