High-Frequency Filter Circuit With Acoustic Resonator-Inductor Coupling
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Solution Overview
Problem
Existing high frequency filters require large inductance values for sufficient attenuation outside the pass band, leading to increased size and difficulty in reducing the filter's overall dimensions.
Innovation Solution
Incorporating an acoustically coupled resonator with IDT electrodes connected to the inductor in the additional circuit portion, adding capacitance components to the LC resonance circuit, thereby reducing the inductance value of the inductor and allowing for a smaller filter design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inductor with a large inductance value is used to secure sufficient attenuation outside the pass band, then the attenuation amount is improved, but the size of the inductor increases
Solution Approach 1:
The patent combines the inductor with an acoustically coupled resonator structure, merging two separate components (inductor and resonator) into an integrated hybrid structure. This allows the inductor to achieve higher effective inductance through acoustic coupling mechanisms without proportionally increasing its physical size, thereby resolving the contradiction between attenuation performance and component size.
Solution Approach 2:
The patent employs a composite structure combining electromagnetic components (inductor) with acoustic wave components (resonator with IDT electrodes). This composite approach creates a hybrid resonant system that leverages both electromagnetic and acoustic resonance phenomena to achieve enhanced attenuation with reduced physical dimensions compared to a conventional inductor-only design.
2Reliability
If an inductor with a large inductance value is used to secure sufficient attenuation outside the pass band, then the attenuation amount is improved, but the overall size of the high frequency filter increases
Solution Approach 1:
The inductor is merged with the acoustically coupled resonator structure, creating a compact integrated component that performs both inductance function and acoustic resonance function simultaneously. This reduces the need for separate discrete components, thereby reducing the overall filter size while maintaining sufficient attenuation performance.
Solution Approach 2:
The hybrid inductor-resonator structure serves multiple functions: it provides inductance for the LC resonance circuit, acts as an acoustic wave resonator for frequency selectivity, and provides attenuation outside the pass band. This multi-functionality reduces the total component count and overall filter size while achieving the required attenuation specification.
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
The solution achieves effective attenuation outside the pass band with reduced inductance, resulting in a smaller filter size and improved insertion loss characteristics.
Implementation Method 1
an acoustically coupled resonator including a plurality of acoustic wave resonators
Implementation Method 2
IDT electrodes connected to the inductor in the additional circuit portion
Data Source
AI summary
A high frequency filter includes a filter circuit portion on a first path between first and second signal electrodes, and an additional circuit portion on a second path parallel or substantially parallel to at least a portion of the first path. The filter circuit portion includes series arm resonators, parallel arm resonators, and an inductor on a path connecting a portion or all of parallel arm resonators and a ground. Acoustic wave resonators of the additional circuit portion include first and second electrodes. The first electrodes are connected to the second path. The second electrodes are connected to a connection conductor on a path connecting a portion or all of the parallel arm resonators and the inductor.