Resonator Multiplexer Filter Layout for Wide Pass Band and Low Loss
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Solution Overview
Problem
Existing filter devices with ladder configurations using acoustic wave resonators face increased pass band loss due to overlapping attenuation poles with low pass filters, which degrade filter characteristics.
Innovation Solution
A filter device configuration featuring a first and second series arm resonator in series, a parallel arm resonator between them, and a matching circuit, where the resonant frequencies of the series arm resonators and the parallel arm resonator are positioned to create a wide pass band with reduced loss, with the parallel arm resonator providing attenuation on the lower frequency side and the series arm resonators on the higher frequency side, and the matching circuit further optimizing the pass band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the attenuation pole of the low pass filter (LC resonance circuit) is overlapped with the sharp attenuation poles obtained by the resonators to improve attenuation characteristics, then attenuation characteristics are improved, but loss in the pass band increases
Solution Approach 1:
The filter is divided into multiple independent resonator sections (first series arm resonator, second series arm resonator, and parallel arm resonator) that can be independently designed and positioned. This segmentation allows each resonator's attenuation poles to be strategically placed in different frequency regions, preventing overlap with the pass band while maintaining effective attenuation characteristics.
Solution Approach 2:
Different resonators are assigned different local functions: the parallel arm resonator provides attenuation on the lower frequency side of the pass band, while the series arm resonators provide attenuation on the higher frequency side. This local quality differentiation ensures that attenuation poles are distributed away from the pass band center, reducing pass band loss while maintaining overall attenuation performance.
2Length of moving object
If resonant frequencies of series arm resonators and parallel arm resonator are positioned to create wide pass band with reduced loss, then pass band width is increased and loss is reduced, but attenuation characteristics may be compromised
Solution Approach 1:
The resonant frequencies of the resonators are positioned asymmetrically relative to the pass band: the parallel arm resonator's resonant frequency is below the pass band, while the series arm resonators' resonant frequencies are above the pass band. This asymmetric positioning creates a wide pass band with reduced loss while maintaining effective attenuation on both sides of the pass band through the strategically placed attenuation poles.
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 filter characteristics with a wide pass band and significantly reduced loss by positioning the resonant frequencies of the series and parallel arm resonators to minimize overlap and using a matching circuit to adjust the frequency response, thereby enhancing bandpass-type filter performance.
Implementation Method 1
a filter device including two series arm resonators, three parallel arm resonators, and an inductor arranged in a state bridging the two series arm resonators
Implementation Method 2
ladder filter using acoustic wave resonators
Implementation Method 3
a low pass filter (LC resonant circuit) is defined by the inductor and the two series arm resonators
Implementation Method 4
an inductor arranged in a state bridging the two series arm resonators
Data Source
AI summary
A filter includes two series arm resonators electrically connected in series between two input/output terminals, a parallel arm resonator electrically connected between a ground and a series arm between the two series arm resonators, an inductor electrically connected in parallel to the two series arm resonators, and a matching circuit electrically connected between one of the two series arm resonators and one of the input/output terminals, wherein the two series arm resonators and the parallel arm resonator define a pass band of a bandpass filter, the two series arm resonators and the inductor define an LC resonant circuit, respective anti-resonant frequencies of each of the two series arm resonators and a resonant frequency of the parallel arm resonator are located in a pass band of the LC resonant circuit, and a resonant frequency of the LC resonant circuit is lower than the resonant frequency of the parallel arm resonator.