Acoustic Wave Multiplexer Layout for Lower Passband Insertion Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multiplexers using acoustic wave filters experience increased insertion loss due to impedance deviations in the pass band of the second filter, caused by the impedance of the acoustic wave resonator affecting the reference impedance.
Innovation Solution
The multiplexer design includes a first filter with series-arm and parallel-arm resonators, where at least one series-arm resonator has a wider resonance band width than the first pass band, and a second filter with similar resonator configurations, where the resonant frequencies and electrode finger pitches are optimized to reduce insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an acoustic wave resonator with a wider resonance band width is used in the first filter, then the resonance band width is sufficient to cover the first pass band and inter-passband gap, but the impedance in the pass band of the second filter deviates from reference impedance, causing increased insertion loss
Solution Approach 1:
The first filter is divided into multiple series-arm resonators (first, second, third series-arm resonators) with different resonance band widths and impedance characteristics. Each resonator is strategically positioned to contribute differently to the overall impedance profile, allowing the composite filter to maintain proper impedance in the second filter's pass band while still providing sufficient resonance band width coverage for the first pass band and inter-passband gap.
Solution Approach 2:
Different series-arm resonators are assigned different local impedance characteristics based on their position and function. The first series-arm resonator has impedance optimized for the first pass band region, the second series-arm resonator has impedance optimized for the inter-passband gap region, and the third series-arm resonator has impedance optimized for the second pass band region. This local optimization ensures that each resonator contributes positively to the overall impedance profile without causing deviations in other frequency regions.
2Adaptability or versatility
If the resonance band width of the acoustic wave resonator is increased to cover both pass bands and inter-passband gap, then frequency coverage is improved, but impedance control in the second pass band deteriorates
Solution Approach 1:
The frequency coverage function is segmented across multiple resonators with specialized characteristics. Rather than using a single wide-band resonator that compromises impedance control, the system uses multiple narrower-band resonators, each optimized for specific frequency regions, collectively achieving broad frequency coverage while maintaining reliable impedance control in each region.
Solution Approach 2:
Multiple series-arm resonators with different impedance characteristics are combined in the first filter to achieve both broad frequency coverage and reliable impedance control. The composite impedance profile of the combined resonators provides the necessary coverage for both pass bands and inter-passband gap while maintaining proper impedance levels in the second pass band, resolving the contradiction between adaptability and reliability.
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 reduces insertion loss in the pass bands of the filters coupled in common, by minimizing impedance deviations and optimizing the resonance characteristics of the acoustic wave resonators.
Implementation Method 1
each including an acoustic wave resonator
Implementation Method 2
acoustic wave resonator having a wider resonance band width
Data Source
AI summary
A multiplexer includes first and second filters respectively with a first pass band and a second pass band on a higher frequency side than the first pass band. The first filter includes series-arm resonators and parallel-arm resonators, a resonance band width of at least one of the series-arm resonators is wider than the first pass band, one of the series-arm resonators is coupled closest to a common terminal among the series-arm resonators and the parallel-arm resonators. An anti-resonant frequency of the one of the series-arm resonators is lower than a high frequency end of the second pass band and is lowest among anti-resonant frequencies of the series-arm resonators.