Loaded Acoustic Resonators for LBAW Filter Sideband Suppression
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Solution Overview
Problem
Lateral Bulk Acoustic Wave (LBAW) filters suffer from undesired sidebands that degrade their band pass filter characteristics.
Innovation Solution
The implementation of one or more acoustic resonators in parallel with the LBAW filter to suppress sidebands by creating impedance notches at specific frequencies within the sideband range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If LBAW filters are used as band pass filters, then small size and mass-production capability are achieved, but undesired sidebands are generated that degrade filtering performance
Solution Approach 1:
The filter system is segmented into multiple functional components: the LBAW filter element for primary filtering and multiple parallel resonators (first resonator, second resonator) for sideband suppression. Each component operates at different frequencies to address specific aspects of the filtering requirement, allowing the maintain compact size while improving overall filtering performance through functional division.
Solution Approach 2:
Parallel resonators are introduced as intermediary elements that couple to the LBAW filter element. These resonators act as mediators that selectively suppress sidebands at specific frequencies (first frequency and second frequency) without interfering with the main passband operation, thereby improving filtering performance while maintaining the compact LBAW structure.
2Reliability
If parallel resonators are added to suppress sidebands, then band pass response is improved, but device complexity increases
Solution Approach 1:
Multiple resonators are merged into a parallel configuration where the first resonator and second resonator operate simultaneously to suppress different sideband frequencies. This merging approach consolidates the sideband suppression function into a unified parallel resonant circuit structure, improving band pass response while managing complexity through functional integration rather than separate independent systems.
Solution Approach 2:
The resonators are designed with specific parameters (first resonator with first frequency notch, second resonator with second frequency notch) to target different sideband frequencies. By adjusting these frequency parameters, the system can suppress multiple sidebands using relatively simple resonant circuits rather than complex multi-stage filtering, thereby improving performance without proportionally increasing complexity.
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 effectively enhances the band pass response of LBAW filters by reducing insertion loss within the sideband frequencies, thereby improving their filtering performance.
Implementation Method 1
LBAWs can be used as band pass filters. The band pass filter may include one or more undesired (or parasitic) sidebands. Implementations of the present disclosure provide techniques to suppress the undesired sidebands by adding one or more acoustic resonators in parallel with the LBAW.
Implementation Method 2
The first resonator has a first notch in resonator impedance at a first frequency. The second resonator also includes a first mass loading layer on the second resonator electrode such that the second resonator has a second notch in resonator impedance at a second frequency that is different from the first frequency.
Data Source
AI summary
The device includes an acoustic wave filter element, and a first resonator. The acoustic wave filter element includes interdigitated input electrodes and output electrodes located on a top surface of a piezoelectric layer and a counter-electrode on a bottom surface of the piezoelectric layer. The acoustic wave filter element provides a response with a sideband at a sideband frequency range. The first resonator includes a first resonator electrode on the top surface of the piezoelectric layer and a first resonator counter-electrode on the bottom surface of the piezoelectric layer. The first resonator has a first notch in resonator impedance at a first frequency. The first resonance frequency is tuned to fall within the sideband frequency range to suppress the sideband by depositing a first mass load on top of the first resonator electrode to reduce the first resonance frequency, or partly removing the first resonator electrode to increase the first resonance frequency.