Acoustic Wave Filter Resonator Segmentation for Low Insertion Loss
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Solution Overview
Problem
Existing acoustic wave filters face difficulties in making fine adjustments to the resonant and anti-resonant frequencies of series arm resonators, leading to high insertion loss on the higher frequency side of the pass band.
Innovation Solution
The acoustic wave filter design includes a first resonance circuit with a series arm resonator and a capacitive element coupled in parallel, featuring a first divided resonator and a second divided resonator in series, along with a second capacitive element in parallel with the first divided resonator, which allows for a steep attenuation slope and reduced insertion loss on the higher frequency side by adjusting the anti-resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a capacitive element is coupled in parallel with the first series arm resonator, then the anti-resonant frequency is moved toward lower frequency achieving steep attenuation slope, but fine adjustment capability of resonant and anti-resonant frequencies is lost leading to high insertion loss
Solution Approach 1:
The first series arm resonator is divided into two separate resonators (first divided resonator and second divided resonator) that are coupled in series. This segmentation allows independent frequency adjustment of each resonator, providing fine-tuning capability that was lost in the conventional single-resonator design. The division enables separate control of resonant and anti-resonant frequencies while maintaining the overall filter performance.
Solution Approach 2:
The patent introduces adjustable elements (such as variable capacitors or trimmer capacitors) in parallel with each divided resonator, enabling dynamic adjustment of the resonant and anti-resonant frequencies. This dynamic capability allows the filter to be fine-tuned during manufacturing or operation to achieve optimal insertion loss characteristics, resolving the contradiction between fixed frequency characteristics and adjustment capability.
2Reliability
If the anti-resonant frequency is moved toward lower frequency to achieve steep attenuation slope, then frequency selectivity is improved, but insertion loss on the higher frequency side increases due to lack of fine adjustment capability
Solution Approach 1:
By segmenting the first series arm resonator into two divided resonators with independent parallel capacitive elements, the patent enables separate optimization of each resonator's frequency characteristics. This allows the anti-resonant frequency to be positioned for steep attenuation while simultaneously providing fine adjustment capability to minimize insertion loss in the pass band, resolving the contradiction between frequency selectivity and energy loss.
Solution Approach 2:
The patent employs variable capacitive elements that allow continuous adjustment of capacitance values, enabling precise control of resonant and anti-resonant frequencies. By changing the capacitance parameters of the parallel elements connected to each divided resonator, the filter can achieve both steep attenuation slope (through proper anti-resonant frequency positioning) and low insertion loss (through fine frequency tuning).
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 achieves a steep attenuation slope on the higher frequency side of the pass band while reducing insertion loss, enhancing the filter's performance by fine-tuning the resonant and anti-resonant frequencies.
Implementation Method 1
a capacitive element is coupled in parallel with the first series arm resonator... By coupling a capacitive element in parallel with the first series arm resonator, it is possible to move an anti-resonant frequency of the first series arm resonator in parallel connection toward a lower frequency
Implementation Method 2
an acoustic wave filter including a first series arm resonator, a second series arm resonator coupled in series with the first series arm resonator, and a parallel arm resonator coupled to a node between a first series arm resonator and a second series arm resonator
Data Source
AI summary
An acoustic wave filter includes a first resonance circuit including a first series arm resonator and a first capacitive element. The first series arm resonator is provided on a path connecting a first terminal and a second terminal. The first capacitive element is coupled in parallel with the first series arm resonator. The first series arm resonator includes a first divided resonator and a second divided resonator coupled in series with each other. The first resonance circuit includes a second resonance circuit including the first divided resonator and a second capacitive element coupled in parallel with the first divided resonator.