Spatially varying multiple electrode acoustic wave filter and method therefor

An electronic device comprising:

• a substrate for propagating acoustic waves;
• and
• a sequence of a plurality of input transducers and a plurality of output transducers arranged in a direction of acoustic wave propagation, each input and output transducer having a number of interdigitated electrode fingers, wherein the number of interdigitated electrode fingers in a first input or output transducer at or near a first end of the sequence is larger than the number of interdigitated electrode fingers in a corresponding input or output transducer in a location more remote from the first end than the location of the first input or output transducer, wherein centerlines of the input and output transducers are normal to the direction of acoustic wave propagation, and wherein centerlines of a first adjacent pair of input and output transducers are a distance D.sub.1 apart and centerlines of other adjacent pairs of input and output transducers are distances D.sub.2 to D.sub.T-1 apart where T is the number of input and output transducers, and wherein at least one of distances D.sub.2 to D.sub.T-1 differs from distance D.sub.1 by a non-integral number of acoustic wavelengths.

An electronic apparatus for receiving and filtering high frequency waves, the apparatus comprising a sequence of T electro-acoustic transducers wherein T is the number of electro-acoustic transducers, the sequence comprising multiple transducers, wherein each electro-acoustic transducer comprises multiple interdigital electrode fingers, and wherein each electro-acoustic transducer has a predetermined centerline equidistant between outermost interdigital electrode fingers of that electro-acoustic transducer, wherein a centerline-to-centerline distance of a first adjacent pair of electro-acoustic transducers is D.sub.1, and for centerline-to-centerline distances of other adjacent pairs of electro-acoustic transducers of D.sub.2 to D.sub.T-1, then at least one of distances D.sub.2 to D.sub.T-1 differs from distance D.sub.1 by an odd number of quarter acoustic wavelengths.

An acoustic wave filter comprising a sequence of T electro-acoustic transducers wherein T is the number of electro-acoustic transducers, each electro-acoustic transducer having multiple interdigital electrode fingers and a predetermined centerline equidistant between outermost interdigital electrode fingers, the sequence of electro-acoustic transducers comprising a plurality of input and a plurality of output transducers, wherein for a centerline-to-centerline distance D.sub.1 of a first adjacent pair of an input transducer and an output transducer, and for centerline-to-centerline distances of other adjacent pairs of an input transducer and an output transducer of D.sub.2 to D.sub.T-1, then at least one of distances D.sub.2 to D.sub.T-1 differs from distance D.sub.1 by a non-integral number of acoustic wavelengths.

A surface acoustic wave filter comprising a sequence of T electro-acoustic transducers including a plurality of input transducers and a plurality of output transducers, each having multiple interdigital electrode fingers wherein T is the number of electro-acoustic transducers, and each electro-acoustic transducer has a predetermined number of interdigital electrode fingers, each electro-acoustic transducer comprises either an input or an output transducer, and an input transducer closer to an end of the sequence has more interdigital electrode fingers than another input transducer closer to a center of the sequence, or an output transducer closer to an end of the sequence has more interdigital electrode fingers than another output transducer closer to the center of the sequence, wherein each electro-acoustic transducer has a predetermined centerline equidistant between its outermost interdigital electrode fingers, wherein for a centerline-to-centerline distance D.sub.1 of a first adjacent pair of electro-acoustic transducers, and for centerline-to-centerline distances of other adjacent pairs of electro-acoustic transducers of D.sub.2 to D.sub.T-1, then at least one of distances D.sub.2 to D.sub.T-1 differs from distance D.sub.1 by a non-integral number of acoustic wavelengths.

A method for forming an electronic apparatus comprising a filtering function, the method comprising steps of:

• providing a substrate for propagating acoustic waves:
• and
• disposing on the substrate a sequence of a plurality of input transducers and a plurality of output transducers, each input and output transducer having a number of interdigitated electrode fingers, wherein the number of interdigitated electrode fingers in a first input or output transducer at or near a first end of the sequence is larger than the number of interdigitated electrode fingers in a corresponding input or output transducer more remote from the first end, wherein the plurality of input and a plurality of output transducers have predetermined centerlines normal to a direction of acoustic wave propagation, wherein each centerline is located half way between outer edges of first and last interdigitated electrode fingers of each input and output transducer, wherein centerlines of a first adjacent pair of input and output transducers are a distance D.sub.1 apart and centerlines of other adjacent pairs of input and output transducers are distances D.sub.2 to D.sub.T-1 apart where T is the number of input and output transducers and wherein at least one of distances D.sub.2 to D.sub.T-1 differs from distance D.sub.1 by a non-integral number of acoustic wavelengths.

An electronic device comprising:

• a substrate for propagating acoustic waves;
• and
• a sequence of a plurality of input transducers and a plurality of output transducers arranged in a direction of acoustic wave propagation, each input and output transducer having a number of interdigitated electrode fingers, wherein the number of interdigitated electrode fingers in a first input or output transducer at or near a first end of the sequence is larger than the number of interdigitated electrode fingers in a corresponding input or output transducer in a location more remote from the first end than the location of the first input or output transducer, wherein the input and output transducers have predetermined centerlines normal to the direction of acoustic wave propagation, and wherein centerlines of a first adjacent pair of input and output transducers are a distance D.sub.1 apart and centerlines of other adjacent pairs of input and output transducers are distances D.sub.2 to D.sub.T-1 apart where T is the number of input and output transducers, and wherein two or more of distances D.sub.2 to D.sub.T-1 differ from distance D.sub.1 by a non-integral number of acoustic wavelengths.