Acoustic Wave Filter Harmonic Suppression via Resonator Tuning
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Solution Overview
Problem
Existing acoustic wave resonators face challenges in reducing second harmonic generation, leading to increased chip size and insufficient harmonic reduction due to parasitic capacitance in wiring lines when divided resonators are used.
Innovation Solution
A filter design incorporating series and parallel resonators with an inductor connected in parallel to the resonator closest to the output terminal, forming an attenuation pole within the frequency band twice the passband, to suppress second harmonic emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If acoustic wave resonators are divided to reduce second harmonic, then second harmonic reduction is achieved, but chip size increases
Solution Approach 1:
The patent changes the resonant frequency parameter of the series resonator closest to the output terminal to be 99.6% or less of or 102.2% or greater of the passband center frequency. This parameter adjustment enables the formation of an attenuation pole that suppresses second harmonic without requiring resonator division, thus reducing chip size while maintaining harmonic reduction effectiveness.
2Object-generated harmful factors
If resonators are divided to reduce second harmonic, then some harmonic reduction is achieved, but parasitic capacitance of wiring lines reduces the degree of reduction
Solution Approach 1:
The patent adjusts the resonant frequency of the series resonator closest to the output terminal to specific ranges (99.6% or less of or 102.2% or greater of the passband center frequency). This parameter change creates an attenuation pole that effectively suppresses second harmonic, overcoming the limitations imposed by parasitic capacitance in wiring lines that plague divided resonator approaches.
Solution Approach 2:
The patent introduces an inductor connected in parallel to the series resonator closest to the output terminal. This inductor acts as an intermediary element that, combined with the adjusted resonator, forms an attenuation pole. This intermediary mechanism provides effective second harmonic suppression without requiring physical division of resonators, thereby avoiding parasitic capacitance issues.
3Object-generated harmful factors
If an inductor is connected in parallel to the series resonator closest to the output terminal, then second harmonic is suppressed, but device complexity increases
Solution Approach 1:
The patent achieves second harmonic suppression primarily through parameter changes - specifically adjusting the resonant frequency of the series resonator closest to the output terminal to 99.6% or less of or 102.2% or greater of the passband center frequency. While an inductor is added, the simplicity of this parameter-based approach compared to dividing multiple resonators results in net reduced 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 configuration effectively reduces second harmonic emission without increasing chip size, by positioning the attenuation pole within the frequency band twice the passband, thereby improving harmonic suppression and maintaining insertion loss within acceptable limits.
Implementation Method 1
the inductor and the series resonator located closest to the output terminal forming an attenuation pole located in a frequency band twice a passband
Data Source
AI summary
A filter includes: one or more series resonators connected in series between an input terminal and an output terminal, the one or more series resonators including a series resonator located closest to the output terminal, the series resonator located closest to the output terminal having a resonant frequency that is 99.6% or less of or 102.2% or greater of a center frequency of a passband; one or more parallel resonators connected in parallel between the input terminal and the output terminal; and an inductor connected in parallel to the series resonator located closest to the output terminal.