Patent ID: 7728698
Filing Date: 2010-06-01
Classification: H03H

Abstract:
1. 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: 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.