Patent ID: 7728698

Claim:
A surface acoustic wave filter comprising: an acoustic track bounded at both ends by reflector structures; one or more first input transducers and one or more second input transducers acoustically coupled to the acoustic track, connected in parallel, and connected to an asymmetric input port; at least two first output transducers acoustically coupled to the acoustic track, connected in parallel, and connected to a first terminal of a symmetric output port; and at least two second output transducers acoustically coupled to the acoustic track, connected in parallel, and connected to a second terminal of the symmetric output port; wherein each first input transducer is between two corresponding first output transducers, and each second input transducer is between two corresponding second output transducers; wherein one first output transducer in the acoustic track and one corresponding second output transducer are side-by-side and are electrically connected in series via a first bus bar; wherein, for each first input transducer and each first output transducer, a spacing between centers of outermost hot fingers facing one another is about an even number of half-wavelengths, and for each second input transducer and each second output transducer, a spacing between centers of outermost hot fingers facing one another is about an odd number of half-wavelengths; wherein at least one of the following conditions is satisfied: A) the first bus bar is electrically connected, via a first connecting structure between the one first output transducer and one first input transducer of the one or more first input transducers, to an opposing second bus bar of the one first input transducer, wherein the second bus bar is connected to ground; and B) the first bus bar is electrically connected, via a second connecting structure between the one second output transducer and one second input transducer of the one or more second input transducers, to an opposing third bus bar of the one second input transducer, wherein the third bus bar is connected to ground; and wherein the first and second connecting structures comprise at least one metal strip; and wherein (i) for the one or more second input transducers and centrally-arranged second output transducers, a spacing between centers of outermost hot fingers facing one another is about three half-wavelengths, and for the one or more second input transducers and terminally-arranged second output transducers, a spacing between outermost hot fingers facing one another is about a half wavelength; or (ii) for the one or more second input transducers and centrally-arranged second output transducers, the spacing between centers of outermost hot fingers facing one another is about a half-wavelength, and for the one or more second input transducers and terminally-arranged second output transducers, the spacing between outermost hot fingers facing one another is about three half-wavelengths.