Parallel Acoustic Wave Filters With Overlapping Passbands
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Solution Overview
Problem
Developing a band pass filter with a wide passband is challenging due to the need for impedance matching across different capacitances in parallel filters, leading to increased form factor and packaging constraints.
Innovation Solution
Implementing parallel acoustic wave filters with overlapping passbands and mismatched impedances, where one filter has a higher impedance and smaller resonator area, reducing the need for additional capacitance tuning and allowing for a smaller physical area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If parallel acoustic wave filters are arranged to achieve a wide passband, then the passband width is improved, but the form factor increases and packaging becomes more constrained
Solution Approach 1:
The patent applies local quality by assigning different impedance characteristics to different filters in the parallel arrangement. Specifically, one filter is designed with higher impedance while the other has lower impedance, allowing each filter to be optimized for its specific function rather than requiring all filters to have uniform characteristics. This enables compact packaging while maintaining wide passband coverage.
Solution Approach 2:
The patent changes the impedance parameter of the parallel filters to resolve the contradiction. By designing filters with mismatched impedances (one higher, one lower), the system achieves wide passband coverage without requiring additional capacitance tuning elements that would increase the form factor. This parameter change allows compact integration while maintaining filtering performance across the extended bandwidth.
2Reliability
If impedance matching is implemented across parallel filters with different capacitances, then filtering performance is improved, but additional capacitance tuning elements are required increasing device complexity
Solution Approach 1:
Instead of attempting to match impedances across parallel filters (the conventional approach), the patent inverts the strategy by deliberately designing filters with mismatched impedances. One filter is designed with higher impedance and the other with lower impedance, eliminating the need for additional capacitance tuning elements while maintaining effective filtering performance across the wide passband.
3Area of stationary object
If one filter has higher impedance to reduce resonator area, then the physical size is reduced, but impedance mismatch issues arise
Solution Approach 1:
The patent merges two filters with opposite impedance characteristics (one higher, one lower) in a parallel configuration. This combination allows the higher impedance filter to achieve reduced resonator area while the lower impedance filter compensates for impedance mismatch issues, resulting in a system that achieves both compact size and effective filtering without requiring additional matching elements.
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
The solution enables a wider passband with reduced physical size, addressing impedance mismatch issues and minimizing packaging constraints while maintaining effective filtering performance.
Implementation Method 1
A surface acoustic wave resonator can include an interdigital transductor electrode on a piezoelectric substrate. The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer on which the interdigital transductor electrode is disposed. In BAW resonators, acoustic waves propagate in a bulk of a piezoelectric layer.
Data Source
AI summary
Aspects of this disclosure relate to an acoustic wave filter with parallel band pass filters. Each band pass filter can be an acoustic wave filter having a passband. One of the parallel band pass filters can have higher passband frequencies than another of the parallel band pass filters. The passbands of the parallel band pass filters can overlap in an overlap band. One of the parallel band pass filters can have a higher impedance in the overlap band than another of the parallel band pass filters.