Acoustic Wave Multiplexer Layout for Stop Band Ripple Suppression
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Solution Overview
Problem
In multiplexers using acoustic wave resonators, the stop band response can degrade the characteristics of other filters by causing ripple in the pass band, particularly when the stop band frequency falls within the pass band of adjacent filters, leading to increased insertion loss.
Innovation Solution
The multiplexer design includes a configuration with a first filter having two or more series resonators and one or more parallel resonators, where the series resonator closest to the common terminal is connected directly to it without parallel resonators, and the total number of reflection electrode fingers in these resonators is reduced compared to the remaining resonators, effectively minimizing the stop band response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acoustic wave resonators with high acoustic wave energy confinement efficiency are used, then the filter achieves high Q value and small size, but a large stop band response is generated that degrades the characteristics of other filters
Solution Approach 1:
The patent applies local quality by making the first series resonator (closest to the common terminal) have a different structure from the other resonators. Specifically, the first series resonator has a reduced number of reflector electrodes or modified electrode configuration in the stop band frequency region, creating localized structural differentiation that suppresses stop band response generation at the critical location near the common terminal where it most affects other filter paths.
Solution Approach 2:
The patent changes physical parameters of the first series resonator, specifically reducing the number of reflector electrodes or altering the electrode pattern in the stop band frequency region. This parameter modification directly reduces the strength of the stop band response generated by the first resonator, thereby minimizing its harmful effect on the pass band characteristics of other filters in the multiplexer.
2Reliability
If the stop band response is reduced by modifying the first series resonator, then the pass band ripple of the second filter is minimized, but the structural uniformity of the resonators is reduced
Solution Approach 1:
The patent accepts and utilizes the structural non-uniformity as a necessary local quality differentiation. The first series resonator is intentionally designed with different electrode configuration or reduced reflector count compared to other resonators, creating a localized structural variation that is optimized for suppressing stop band response while maintaining the overall functional uniformity of the filter system.
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 reduces or prevents the stop band response, thereby minimizing insertion loss in the pass band of the second filter, improving the overall performance of the multiplexer.
Implementation Method 1
The acoustic wave device has high efficiency at confining acoustic wave energy in the thickness direction of a multilayer substrate
Implementation Method 2
A plurality of acoustic wave resonators are provided in a filter. Each of the acoustic wave resonators includes a piezoelectric substrate, an interdigital transducer electrode
Implementation Method 3
an InterDigital Transducer (IDT) electrode including of a pair of comb-shaped electrodes on the substrate
Implementation Method 4
reflectors each including one or more reflection electrode fingers
Data Source
AI summary
A first filter of a multiplexer includes a ladder filter structure with a plurality of series resonators and a plurality of parallel resonators. Each resonator is an acoustic wave resonator that includes an InterDigital Transducer (IDT) electrode including a pair of comb-shaped electrodes. A total number of reflection electrode fingers of the reflectors of at least one of the series resonator that is closest to the common terminal among the series resonators and the parallel resonator that is closest to the common terminal is smaller than a total number of reflection electrode fingers of the reflectors of each of a remainder of the resonators.