Patent ID: 7969259

Claim:
An apparatus comprising: a piezoelectric substrate comprising: a signal line comprising a first electrical port and a second electrical port; a first partial filter; a second partial filter electrically connected in series with the first partial filter, the first partial filter and the second partial filter being between the first and the second electrical ports; and a serial resonator electrically connected between the first electrical port and an end-positioned transducer, the serial resonator having a constituent transducer and reflectors that bound the constituent transducer on both sides, the reflectors being directly adjacent the constituent transducer; wherein: the first partial filter comprises: a first serial transducer and a second serial transducer in series branches of the signal line, the first serial transducer and the second serial transducer being in an acoustic path and acoustically coupled with one another, and the first serial transducer and the second serial transducer being electrically connected in series with respect to the signal line, and a reflector between the first serial transducer and the second serial transducer, the reflector having a reflectivity that is less than 100%; and the second partial filter comprises a first coupler transducer and the end-positioned transducer that are in a double mode surface acoustic wave (DMS) path, the end-positioned transducer being positioned at a signal end of the second partial filter.