SAW Extractor Electrode Layout for Steep Passband Without Ripples
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Solution Overview
Problem
Existing band pass filters with partially eliminated electrode fingers in surface acoustic wave resonators generate unwanted ripples on the lower frequency side, leading to degraded insertion loss in band elimination filters.
Innovation Solution
The proposed extractor design includes a band pass filter with surface acoustic wave resonators arranged in a ladder configuration, where specific IDT electrodes are either fully present or partially missing to reduce ripples, and a band elimination filter with inductance and capacitance elements, optimizing the connection between the filters to minimize insertion loss degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electrode fingers of IDT electrode in surface acoustic wave resonator are partially eliminated to increase steepness in end portion of pass band, then steepness is improved, but unwanted ripples are generated on lower frequency side affecting band elimination filter performance
Solution Approach 1:
The IDT electrode is segmented into two distinct types: first IDT electrodes with all electrode fingers intact, and second IDT electrodes with partially eliminated electrode fingers. This segmentation allows different regions of the filter to have different characteristics - the first IDT electrodes prevent ripple generation while the second IDT electrodes provide steep pass band edges, resolving the contradiction between steepness and ripple suppression.
2Shape
If all IDT electrodes in band pass filter are designed with partial electrode finger elimination to maximize pass band steepness, then pass band characteristics are improved, but insertion loss of band elimination filter is degraded
Solution Approach 1:
Different IDT electrodes are assigned different qualities: first IDT electrodes (with complete electrode fingers) are placed in positions where they connect to the band elimination filter to ensure low insertion loss, while second IDT electrodes (with partially eliminated fingers) are placed in other positions to provide pass band steepness. This local differentiation of electrode quality allows simultaneous optimization of both filter performances.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration increases the steepness of the band pass filter's end portion and reduces the degradation of insertion loss in the band elimination filter, improving the overall performance by minimizing ripple generation and maintaining low insertion loss.
Implementation Method 1
a band pass filter that includes a plurality of surface acoustic wave resonators electrically connected in a ladder configuration
Implementation Method 2
an IDT (InterDigital Transducer) electrode that includes a first busbar electrode, a second busbar electrode facing the first busbar electrode
Data Source
AI summary
An extractor includes a band pass filter and a band elimination filter. In the band pass filter, an IDT electrode in at least one of a first series arm resonator and a first parallel arm resonator that are arranged at a series arm and a parallel arm, respectively, closest to a common terminal is a first IDT electrode in which neither a plurality of first electrode fingers nor a plurality of second electrode fingers is partially missing, and an IDT electrode in at least one of the first series arm resonator or the first parallel arm resonator that does not include the first IDT electrode, second series arm resonators, and second parallel arm resonators is a second IDT electrode in which at least one of a plurality of electrode fingers and a plurality of second electrode fingers is partially missing.