Method and apparatus for an acoustic wave filter

An acoustic wave device comprising:

• an acoustic wave propagating substrate for sustaining an acoustic wave;
• a first acoustic wave reflector disposed on said acoustic wave propagating substrate;
• and
• a first weakly unidirectional acoustic wave transducer disposed on said acoustic wave propagating substrate adjacent to said first acoustic wave reflector in a first direction of acoustic wave propagation, said first weakly unidirectional acoustic wave transducer for converting electrical signals to acoustic waves and vice versa, said first acoustic wave reflector and said first weakly unidirectional acoustic wave transducer thereby forming a first low-loss acoustic wave transducer structure.

An acoustic wave device including in combination:

• a piezoelectric substrate;
• a first strongly unidirectional acoustic wave transducer disposed on said piezoelectric substrate;
• and
• a second strongly unidirectional acoustic wave transducer disposed on said piezoelectric substrate, each of said first and second strongly unidirectional acoustic wave transducers acoustically coupled to one another, each of said first and second strongly unidirectional acoustic wave transducers having a directivity of at least ten decibels and further comprising:
• an acoustic wave reflector disposed on said piezoelectric substrate;
• and
• a weakly unidirectional acoustic wave transducer having a directivity of less than six decibels disposed on said piezoelectric substrate adjacent to said acoustic wave reflector, said weakly unidirectional acoustic wave transducer for converting between electrical and acoustic energy.

An electronic apparatus employing acoustic waves, including:

• at least one low-loss acoustic wave filter for providing a frequency selection function and operating to attenuate the electrical power level of signals in the passband thereof by a factor P ranging between 0.ltoreq.P.ltoreq.0.75, said at least one low-loss acoustic wave filter comprising:
• an acoustic wave propagating substrate;
• a first strongly unidirectional acoustic wave transducer disposed on the acoustic wave propagating substrate;
• and
• a second strongly unidirectional acoustic wave transducer disposed on the acoustic wave propagating substrate, said first and second strongly unidirectional acoustic wave transducers acoustically coupled to one another, each of said first and second strongly unidirectional acoustic wave transducers having a directivity of more than ten decibels and further comprising:
• an acoustic wave reflector disposed on said acoustic wave propagating substrate, said acoustic wave reflector for reflecting acoustic waves;
• and
• a weakly unidirectional acoustic wave transducer having a directivity of less than six decibels disposed on said acoustic wave propagating substrate adjacent to said acoustic wave reflector, said weakly unidirectional acoustic wave transducer for converting between electrical and acoustic energy, wherein said acoustic wave reflector reflects acoustic waves towards said weakly unidirectional acoustic wave transducer to provide in combination a strongly unidirectional acoustic wave transducer.

A method for manufacturing an acoustic wave device, said method comprising steps of:

• providing an acoustic wave propagating substrate;
• forming an acoustic wave reflector on said acoustic wave propagating substrate;
• and
• forming a weakly unidirectional acoustic wave transducer, having a directivity of less than six decibels and having distributed internal acoustic reflection elements therein, on said acoustic wave propagating substrate adjacent to said acoustic wave reflector in a direction of acoustic wave propagation, the acoustic wave reflector and the weakly unidirectional acoustic wave transducer having a directivity of more than ten decibels.

An acoustic wave device comprising:

• an acoustic wave propagating substrate for sustaining an acoustic wave;
• a first acoustic wave reflector disposed on said acoustic wave propagating substrate;
• and
• a first weakly unidirectional acoustic wave transducer having distributed internal acoustic reflection elements disposed on said acoustic wave propagating substrate adjacent to said first acoustic wave reflector in a direction of acoustic wave propagation, said first weakly unidirectional acoustic wave transducer for converting electrical signals to acoustic waves and vice versa, said first acoustic wave reflector and said first weakly unidirectional acoustic wave transducer thereby forming a first low-loss acoustic wave transducer structure.