Elastic Wave Filter Design to Reduce Spuriousness and Loss
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Summary
Problems
Conventional elastic wave filters experience spuriousness in the bandpass and significant insertion loss degradation, particularly in the high-frequency part, due to their configuration.
Innovation solutions
The elastic wave filter design includes specific configurations such as asymmetric pitch spacing and electrode finger arrangements between IDT electrodes, with ground and wiring electrodes strategically connected to suppress spuriousness and improve attenuation characteristics.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If ground electrodes of IDT electrodes are arranged adjacently in conventional configuration, then the filter structure is simple, but spuriousness occurs in the bandpass
Why choose this principle:
The patent applies asymmetry by arranging ground electrodes and wiring electrodes in a non-uniform pattern. Specifically, the ground electrode of the fourth IDT electrode is positioned adjacent to the wiring electrode of the second IDT electrode rather than adjacent to both first and second IDT electrodes symmetrically. This asymmetric arrangement disrupts the symmetry of electromagnetic field distribution, thereby suppressing spuriousness in the bandpass while maintaining filter functionality.
Principle concept:
If parallel-connected elastic wave filters are used to improve bandpass characteristics, then spuriousness is reduced, but insertion loss degradation increases in high-frequency part
Why choose this principle:
The patent applies local quality by optimizing the electrode arrangement in specific local regions of the filter. The ground electrode of the fourth IDT electrode is strategically positioned adjacent to the wiring electrode of the second IDT electrode, creating a localized field distribution pattern that simultaneously suppresses spuriousness and minimizes insertion loss degradation in the high-frequency part of the bandpass.
Application Domain
Data Source
AI summary:
The elastic wave filter design includes specific configurations such as asymmetric pitch spacing and electrode finger arrangements between IDT electrodes, with ground and wiring electrodes strategically connected to suppress spuriousness and improve attenuation characteristics.
Abstract
An elastic wave filter has first, second, and third IDT electrodes whose wiring electrodes are connected to unbalanced signal terminal; fourth IDT electrode disposed between the first and second IDT electrodes; fifth IDT electrode disposed between the second and third IDT electrodes; and first and second balanced signal terminals connected to the wiring electrodes of fourth and fifth IDT electrodes, respectively. The ground electrodes of the first through fifth IDT electrodes are connected to the ground. Signals in opposite phase and in phase with a signal input to unbalanced signal terminal are output from first and second balanced signal terminals, respectively. The wiring electrodes of second and third IDT electrodes are adjacent to the ground electrode of fifth IDT electrode. The wiring electrode of one of first and second IDT electrodes is adjacent to the wiring electrode of fourth IDT electrode. The ground electrode of the other is adjacent to the ground electrode of fourth IDT electrode. This configuration can suppress spuriousness in the bandpass.