SAW Filter Resonator Layout for Wide Bandwidth and Low Insertion Loss
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Solution Overview
Problem
Existing band pass filters with wider passbands experience degradation in insertion loss, particularly at the high-frequency side, due to differing anti-resonant frequencies of parallel arm resonators.
Innovation Solution
A filter device utilizing surface acoustic waves with two or more parallel arm resonators having the same or substantially the same lowest anti-resonant frequencies connected to the same connection node, and other resonators connected to different nodes, to shift the stop band ripple towards the high-frequency side, maintaining bandpass characteristics while reducing insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the anti-resonant frequencies of parallel arm resonators are made different from each other to achieve a wider pass band, then the bandwidth is improved, but the insertion loss is degraded particularly at the high-frequency side
Solution Approach 1:
The patent applies local quality by differentiating the connection configuration of parallel arm resonators based on their anti-resonant frequency characteristics. Specifically, parallel arm resonators with the lowest anti-resonant frequencies are connected to the same connection node, while others are connected to different nodes. This localized differentiation maintains high Q values for resonators with lowest anti-resonant frequencies, thereby preventing insertion loss degradation at the high-frequency side of the pass band while still achieving a wider overall pass band.
2Reliability
If two or more parallel arm resonators are connected to the same connection node, then the Q value is maintained, but the stop band ripple may be generated near the pass band
Solution Approach 1:
The patent utilizes parameter changes by strategically assigning parallel arm resonators with the lowest anti-resonant frequencies to the same connection node. This parameter-based grouping maintains high Q values for these resonators, which in turn suppresses stop band ripple generation near the pass band. The invention changes the connection configuration parameter based on the anti-resonant frequency parameter of each resonator, achieving both high Q value maintenance and stop band ripple suppression.
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 wider bandwidth while minimizing or preventing degradation of insertion loss, effectively managing the stop band ripple and maintaining high Q values for the resonators.
Implementation Method 1
A filter device according to a preferred embodiment of the present invention utilizes surface acoustic waves
Data Source
AI summary
A filter device utilizing surface acoustic waves includes one or more series arm resonators connected to each other along a path between a first input/output terminal and a second input/output terminal, and three or more parallel arm resonators each connected between a connection node provided on the path and ground and defining the pass band of the filter device. Parallel arm resonators having different anti-resonant frequencies from each other are included. Parallel arm resonators among the three or more parallel arm resonators are connected to the same connection node provided along the path. Remaining parallel arm resonators are connected to different connection nodes from the same connection node. The anti-resonant frequencies of the parallel arm resonators connected to the same connection node are identical and are the lowest anti-resonant frequencies among the anti-resonant frequencies of the three or more parallel arm resonators.