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US 10,461,720 B2Granted
Acoustic filter
AssigneeSnapTrack, Inc.
InventorsRavi Kiran Challa, Akshaya Ishwarayya Hiremath, Attieh Shahvarpour
Life of this patent
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Abstract
Techniques are disclosed for increasing capacitance, decreasing losses, and/or improving a quality factor of a SAW filter. The techniques include using a partial-IDT instead of a reflector between two groups of IDTs. The partial-IDT is implemented having a cavity transition on a first end and a reflector transition on a second end. The cavity transition facilitates propagation of main-resonance acoustic waves into, or between elements of, the partial-IDT. The reflector transition facilitates reflection of main-resonance acoustic waves.
Claims30
A surface acoustic wave (SAW) filter comprising:
- a piezoelectric material;
- a first group of inter-digital transducers (IDTs) on the piezoelectric material, the first group of IDTs configured to:
- transform a first set of electrical signals into a first set of acoustic signals for propagation via a first portion of the piezoelectric material;
- select a first set of selected acoustic signals of the first set of acoustic signals within a specified passband;
- and
- convert the first set of selected acoustic signals into a first set of filtered electrical signals;
- a second group of IDTs on the piezoelectric material, the second group of IDTs configured to:
- transform a second set of electrical signals into a second set of acoustic signals for propagation via a second portion of the piezoelectric material;
- select a second set of selected acoustic signals of the second set of acoustic signals within the specified passband;
- and
- convert the second set of selected acoustic signals into a second set of filtered electrical signals;
- and
- a partial-IDT on the piezoelectric material and positioned between the first group of IDTs and the second group of IDTs, the partial-IDT including:
- a first bus bar and a second bus bar, the first bus bar and the second bus bar uncoupled from ground such that the partial-IDT is electrically floating;
- a first side configured to facilitate a cavity transition between the partial-IDT and the first group of IDTs, the cavity transition configured to facilitate propagation of the first set of acoustic signals within, or between elements of, the partial-IDT;
- and
- a second side configured to facilitate a reflector transition between the partial-IDT and the second group of IDTs, the reflector transition configured to reduce propagation of the second set of acoustic signals within, or between elements of, the partial-IDT.
14 more elements
A surface acoustic wave (SAW) filter having a first longitudinal end and a second longitudinal end, the SAW filter comprising:
- a piezoelectric material;
- a first reflector on the piezoelectric material and at the first longitudinal end, the first reflector configured to reflect acoustic waves within the SAW filter;
- a first group of inter-digital transducers (IDTs) on the piezoelectric material and adjacent to the first reflector, the first group of IDTs including:
- a first input IDT coupled to an input terminal, the first input IDT configured to receive a first input electric signal and propagate a first set of acoustic signals via a first portion of the piezoelectric material;
- and
- a first output IDT coupled to an output terminal, the first output IDT configured to receive at least a portion of the first set of acoustic signals and propagate a first output electric signal to the output terminal;
- a partial-IDT on the piezoelectric material and adjacent to the first group of IDTs, the partial-IDT:
- configured to electrically float on the piezoelectric material;
- including a first bus bar and a second bus bar, at least one of the first bus bar or the second bus bar being uncoupled from ground;
- spaced from the first group of IDTs at a cavity distance configured to facilitate propagation of the first set of acoustic signals from the first group of IDTs within, or between elements of, the partial-IDT;
- a second group of IDTs on the piezoelectric material and adjacent to the partial-IDT, the second group of IDTs:
- including a second input IDT coupled to the input terminal, the second input IDT configured to receive a second input electric signal and propagate a second set of acoustic signals via a second portion of the piezoelectric material;
- including a second output IDT coupled to the output terminal, the second output IDT configured to receive at least a portion of the second set of acoustic signals and propagate a second output electric signal to the output terminal;
- and
- spaced from the partial-IDT at a reflector distance configured to reduce propagation of the second set of acoustic signals from the second group of IDTs within, or between elements of, the partial-IDT;
- and
- a second reflector on the piezoelectric material and at the second longitudinal end, the second reflector adjacent to the second group of IDTs and configured to reflect the second set of acoustic signals toward the second input IDT.
14 more elements
A surface acoustic wave (SAW) filter comprising:
- a piezoelectric material;
- a first reflector on the piezoelectric material and a second reflector on the piezoelectric material, the first reflector and the second reflector defining a first longitudinal end of the SAW filter and a second longitudinal end of the SAW filter, respectively;
- a series of inter-digital transducers (IDTs) on the piezoelectric material arranged between the first reflector and the second reflector;
- and
- a partial-IDT on the piezoelectric material, the partial-IDT:
- configured to electrically float on the piezoelectric material;
- positioned between, and defining, a first group of the series of IDTs and a second group of the series of IDTs;
- configured to facilitate a cavity transition between the partial-IDT and the first group of the series of IDTs;
- and
- configured to facilitate a reflector transition between the partial-IDT and the second group of the series of IDTs.
7 more elements
A surface acoustic wave (SAW) filter comprising:
- a piezoelectric material;
- a first reflector and a second reflector on the piezoelectric material and defining longitudinal ends of the SAW filter;
- a first group of inter-digital transducers (IDTs) on the piezoelectric material, the first group of IDTs configured to:
- transform a first set of electrical signals into a first set of acoustic signals for propagation via a first portion of the piezoelectric material;
- select a first set of selected acoustic signals of the first set of acoustic signals within a specified passband;
- and
- convert the first set of selected acoustic signals into a first set of filtered electrical signals;
- a second group of IDTs on the piezoelectric material, the second group of IDTs configured to:
- transform a second set of electrical signals into a second set of acoustic signals for propagation via a second portion of the piezoelectric material;
- select a second set of selected acoustic signals of the second set of acoustic signals within the specified passband;
- and
- convert the second set of selected acoustic signals into a second set of filtered electrical signals;
- and
- an element for reducing propagation of the first set of acoustic signals within the second portion of the piezoelectric material and reducing propagation of the second set of acoustic signals within the first portion of the piezoelectric material, the element including:
- means for providing a cavity transition between the element and the first group of IDTs, the cavity transition effective to facilitate propagation of at least a portion of the first set of acoustic signals through the element;
- and
- means for providing a reflector transition between the element and the second group of IDTs, the reflector transition effective to reduce propagation of the second set of acoustic signals through the element.
14 more elements
Dependencies are inferred from the claim text.