Back to results
US 4,178,571 AGranted
Acoustic surgave wave resonator devices
AssigneeU.S. Philips Corporation
InventorRichard F. Mitchell
Life of this patent
Estimating the term…
Abstract
The input and output transducers associated with an acoustic surface wave resonator, or with respective acoustically coupled cavities, are split into staggered pairs. Furthermore they are located with respect to the standing wave pattern(s) and connected to input and output terminals in such manner as to suppress the response of the output transducer to travelling waves received directly from the input transducer and reduce the stopband level of the device associated with that response.
Claims12
An acoustic surface wave resonator comprising
- a substrate having a piezoelectric surface,
- a pair of input terminals,
- input transducing means disposed on the surface and connected to said input terminals for converting an electrical input signal into travelling acoustic surface waves with a predetermined direction of propagation,
- a pair of reflectors on said surface which are disposed on both sides of the input transducing means in the direction of propagation so as to define a resonant cavity which is capable of supporting an acoustic surface standing wave resonance pattern,
- a pair of output terminals, and
- output transducing means connected to said output terminals and disposed on said surface inside the resonant cavity for converting acoustic surface wave energy into an electrical output signal, and wherein:
- each of said transducing means comprise a first and a second interdigital transducer which are displaced relative to each other both normal to and parallel to said direction of propagation and with each transducer comprising two sets of electrodes, the electrodes of each set being electrically connected in common,
- each of said input terminals and each of said output terminals is connected to a different pair of electrode sets, one set forming part of the first and the other set forming part of the second interdigital transducer of the relevant transducing means,
- the two sets of electrodes which are jointly connected to a terminal are selected so that they are coupled to the same phase of the acoustic surface wave resonance pattern which co-operates with the relevant transducing means, whereas both the two input terminals and the two output terminals are coupled to mutually opposite phases of said resonance pattern via the sets of electrodes, and
- the first interdigital transducers of the two transducing means are spaced apart by a first distance in the direction of propagation and the second interdigital transducers of said two transducing means are spaced apart by a second distance and the two sets of electrodes, which are connected to each of said terminals, are selected in cooperation with said first and second distances in such a way that for each output terminal the two sets of electrodes connected thereto respond to travelling acoustic surface waves launched by the input transducing means with opposite potentials.
7 more elements
An acoustic surface wave resonator comprising:
- a substrate having a piezoelectric surface,
- a pair of input terminals,
- input transducing means disposed on said surface and connected to said input terminals for converting an electrical input signal into travelling acoustic surface waves with a predetermined direction of propagation,
- at least three reflectors on said surface which are disposed in alignment opposite each other in the direction of propagation, a first adjacent pair of said reflectors being disposed on both sides of the input transducing means so as to define a first resonant cavity which is capable of supporting a standing acoustic surface wave resonance pattern, and a second adjacent pair of reflectors being spaced apart and disposed so as to define a second resonant cavity, each reflector defining more than one resonant cavity having a reflectivity such that acoustic surface wave energy is coupled between said resonant cavities,
- a pair of output terminals,
- output transducing means connected to said output terminals and disposed on said surface inside the second resonant cavity for converting acoustic surface wave energy into an electrical output signal,
- and wherein:
- each of said transducing means comprises a first and a second interdigital transducer which are displaced relative to each other both normal to and parallel to said direction of propagation and with each transducer comprising two sets of electrodes, the electrodes of each set being electrically connected in common,
- each of said input terminals and each of said output terminals is connected to a different pair of electrode sets, one set forming part of the first and the other set forming part of the second interdigital transducer of the relevant transducing means,
- the two sets of electrodes which are jointly connected to a terminal are selected so that they are coupled to the same phase of the acoustic surface wave resonance pattern which co-operates with the relevent transducing means, whereas both the two input terminals and the two output terminals are coupled to mutually opposite phases of said resonance pattern via the sets of electrodes, and
- the first interdigital transducers of the two transducing means are spaced apart by a first distance in the direction of propagation and the second interdigital transducers of said two transducing means are spaced apart by a second distance and the two sets of electrodes, which are connected to each of said terminals, are selected in cooperation with said first and second distances in such a way that for each output terminal the two sets of electrodes connected thereto respond to travelling acoustic surface waves launched by the input transducing means with opposite potentials.
8 more elements
Dependencies are inferred from the claim text.