Electro-Acoustic Filter Capacitance Compensation for Wider Bandwidth
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Solution Overview
Problem
Existing filters using acoustic resonators face limitations in bandwidth and selectivity due to static capacitance effects, which restrict their ability to minimize insertion loss and provide high frequency rejection while meeting various frequency bandwidth requirements.
Innovation Solution
The implementation of a compensation impedance in acoustic resonator filters, specifically a static capacitance compensation impedance, is used to balance the impedances of complementary paths, effectively absorbing static capacitance and increasing filter bandwidth without increasing the acoustic coupling coefficient, allowing for thicker electrodes and more flexible design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acoustic resonators are used in filters, then frequency selectivity is improved, but bandwidth is limited due to static capacitance effects
Solution Approach 1:
The patent extracts the harmful static capacitance effect from the resonator path by introducing a separate compensation impedance element. The static capacitance Co of the acoustic resonator is removed from the signal path's impedance calculation by adding a compensation impedance Zc that equals -j/(ωCo), effectively canceling the capacitive effect and enabling wider bandwidth operation while maintaining frequency selectivity
Solution Approach 2:
The patent changes the electrical parameter (impedance) of the resonator path by adding a compensation impedance element with specific value Zc = -j/(ωCo). This parameter change transforms the resonator's electrical characteristics, allowing the filter to achieve wider bandwidth without sacrificing the frequency selectivity provided by the acoustic resonator's mechanical properties
2Productivity
If static capacitance compensation impedance is added, then bandwidth is increased, but device complexity increases
Solution Approach 1:
The patent introduces a compensation impedance element as an intermediary component that mediates between the static capacitance of the acoustic resonator and the desired wide bandwidth performance. This intermediary element with impedance Zc = -j/(ωCo) acts as a bridge that cancels the harmful capacitive effect without requiring fundamental changes to the acoustic resonator structure itself, thus limiting the increase in device complexity
3Productivity
If acoustic coupling coefficient is increased to improve bandwidth, then manufacturing precision requirements increase
Solution Approach 1:
The patent replaces the mechanical approach of increasing acoustic coupling coefficient (which would require precise control of acoustic wave propagation and resonator geometry) with an electrical approach using compensation impedance. By substituting the mechanical coupling enhancement method with an electrical impedance cancellation method, the patent achieves bandwidth expansion without imposing stringent manufacturing precision requirements on the acoustic coupling structures
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 approach results in reduced insertion loss, enhanced frequency selectivity, increased bandwidth, and robust performance over a wide range of frequencies and temperatures, while avoiding the constraints of equalizing resonator sizes and numbers, enabling high-performance band pass filters with improved frequency isolation.
Implementation Method 1
electro-acoustic filter comprising a plurality of electrode actuated acoustic resonators
Implementation Method 2
A compensation impedance is coupled to at least one of the paths to reduce adverse effects from the static capacitances of the acoustic resonators
Data Source
AI summary
A device includes a plurality of electrode actuated acoustic resonators coupled to form complementary paths to operate as a filter. Each acoustic resonator has an electrical input and an electrical output that contributes to a static capacitance. A compensation impedance is coupled to at least one of the paths to reduce adverse effects from the static capacitances of the acoustic resonators.