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US 5,499,003 AGranted
Differential saw filter including series coupled resonant/antiresonant tracks
AssigneeMotorola, Inc.
InventorRoger A. Davenport
Life of this patent
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Abstract
Resonant and anti-resonant inter digital transducers are coupled on acoustic tracks (302, 304, 306) of a piezoelectric substrate (301) to provide a balanced differential surface acoustic wave (SAW) filter (300).
Claims12
A balanced differential surface acoustic wave (SAW) filter for operation over a frequency passband, comprising:
- a piezoelectric substrate having a first, second, and third acoustic tracks;
- a first set of transducers electrically connected in series on the first acoustic track and having geometries tuned to operate at resonant frequency in the passband;
- a second set of transducers electrically connected in series on the third acoustic track and having identical geometries to the first set of resonators;
- a third set of transducers located on the second acoustic track, each electrically coupled in series between each of the series connections of the first and second sets of transducers and tuned for anti-resonant frequency in the passband;
- a differential input connected to the first and third acoustic tracks;
- and
- a differential output connected to the first and third acoustic tracks.
4 more elements
A communication device, comprising:
- a receiver for receiving a communication signal, the receiver including a balanced differential surface acoustic wave (SAW) filter, comprising:
- a piezoelectric film having a plurality of acoustic tracks;
- a first group of interdigital resonant transducers electrically connected in series on the plurality of acoustic tracks;
- a second group of resonant transducers substantially similar to the first group of resonant transducers, mirror imaged onto opposing acoustic tracks;
- a third group of interdigital anti-resonant transducers located on at least one acoustic track in between the first and second groups,
- each anti-resonant transducer electrically connected across opposing series connected resonant transducers and providing a predetermined impedance to the opposing series connected transducers;
- the first group of interdigital resonant transducers includes first and last transducers having substantially similar geometries, second and second to last transducers having substantially similar geometries, continuing throughout the first group;
- and
- the third group of interdigital anti-resonant transducers includes first and last anti-resonant transducers having substantially similar geometries, and a middle anti-resonant transducer having a dissimilar geometry.
6 more elements
A balanced differential surface acoustic wave (SAW) filter, comprising:
- a piezoelectric film having a plurality of acoustic tracks;
- a first group of interdigital resonant transducers electrically connected in series on the plurality of acoustic tracks;
- a second group of resonant transducers substantially similar to the first group of resonant transducers, mirror imaged onto opposing acoustic tracks;
- a third group of interdigital anti-resonant transducers located on at least one acoustic track in between the first and second groups, each anti-resonant transducer electrically connected across opposing series connected resonant transducers and providing a predetermined impedance to the opposing series connected transducers;
- the first group of interdigital resonant transducers includes first and last transducers having substantially similar geometries, second and second to last transducers having substantially similar geometries, continuing throughout the first group;
- and
- the third group of interdigital anti-resonant transducers includes first and last anti-resonant transducers having substantially similar geometries, and a middle anti-resonant transducer having a dissimilar geometry.
4 more elements
Dependencies are inferred from the claim text.