Acoustic Wave Filter Topology With Split Grounds and Unequal Resonators
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Solution Overview
Problem
Existing acoustic wave filter devices face challenges in enhancing attenuation characteristics outside the pass band, with insufficient ground enhancement and unwanted harmonic responses at higher frequencies.
Innovation Solution
The design incorporates a longitudinally coupled resonator acoustic wave filter with a series arm and multiple parallel arms, where the input-side and output-side ground ports of the resonator are connected in common, and the parallel arm resonators have different electrostatic capacitances, allowing for distinct LC resonance characteristics and additional attenuation poles in specific frequency ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ground ports are connected in common to enhance ground, then ground enhancement is improved, but harmonic wave response appears on higher frequency side and attenuation characteristic becomes insufficient
Solution Approach 1:
The patent divides the ground connection into two separate segments: input-side ground port and output-side ground port. These are connected to different ground points rather than a single common ground, which segments the ground path to prevent harmonic wave responses while maintaining ground enhancement benefits
Solution Approach 2:
Different ground points are used for input-side and output-side ground ports, creating local quality differences in the ground connection. This allows each ground connection to be optimized for its specific location, preventing the propagation of harmonic waves while maintaining effective grounding
2Reliability
If parallel arm resonators have different electrostatic capacitances, then attenuation characteristics in specific frequency bands are improved, but device complexity increases
Solution Approach 1:
The patent changes the electrostatic capacitance parameter of parallel arm resonators by varying their physical dimensions (length, width, or number of fingers). This parameter change creates different resonance characteristics that provide attenuation poles in specific frequency bands, improving overall attenuation performance
Solution Approach 2:
The patent introduces asymmetry by making parallel arm resonators have different electrostatic capacitances. This asymmetric configuration creates diverse resonance characteristics among the resonators, enabling attenuation in multiple frequency bands while maintaining a relatively simple overall structure
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 significantly improves attenuation characteristics in specific frequency bands outside the pass band, providing excellent out-of-band attenuation for composite filter devices and multiplexers.
Implementation Method 1
the first parallel arm resonator and a second parallel arm resonator are provided on a first parallel arm and a second parallel arm, respectively, the first parallel arm and the second parallel arm being included in the plurality of parallel arms
Implementation Method 2
an electrostatic capacitance of the first parallel arm resonator is different from an electrostatic capacitance of the second parallel arm resonator
Data Source
AI summary
An acoustic wave filter device includes a longitudinally coupled resonator acoustic wave filter on a series arm that connects an input terminal and an output terminal, first and second parallel arm resonators on first and second parallel arms that connect the series arm and a ground potential, an input-side ground port of the longitudinally coupled resonator acoustic wave filter and a ground port of at least one of the first and second parallel arm resonators are connected in common, an output-side ground port of the longitudinally coupled resonator acoustic wave filter and a ground port of at least another of the first and second parallel arm resonators are connected in common, and an electrostatic capacitance of the first parallel arm resonator is different from an electrostatic capacitance of the second parallel arm resonator.