Acoustic Wave Multiplexer Electrode Layout for Lower Passband Ripple
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Solution Overview
Problem
Multiplexers with acoustic wave resonators face issues with stop band responses affecting the pass band characteristics of interconnected filters, leading to increased ripple and insertion loss.
Innovation Solution
The arrangement of IDT electrodes with specific slant angles on acoustic wave resonators, particularly those closest to the common terminal, is optimized to reduce stop band responses and transverse-mode ripple, with angles such as the first slant angle and second slant angle being smaller than the third slant angle, and set to be less than or equal to about 2.5°, to minimize interference between filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If IDT electrodes are arranged to be slanted relative to acoustic wave propagation direction to suppress transverse-mode ripple in the pass band, then transverse-mode ripple is reduced, but stop band response occurs at the upper edge of the stop band
Solution Approach 1:
The patent applies different slant angles to different groups of IDT electrodes within the same resonator. Specifically, IDT electrodes are divided into multiple groups with different slant angles relative to the acoustic wave propagation direction, allowing local optimization of both transverse-mode ripple suppression and stop band response reduction without compromising overall filter performance
Solution Approach 2:
The patent changes the slant angle parameter of IDT electrodes from a uniform value to multiple different values. By setting at least two different slant angles for different IDT electrode groups, the patent simultaneously achieves transverse-mode ripple suppression in the pass band and reduces stop band response at the upper edge frequency
2Device complexity
If stop band response occurs in a filter, then the filter structure remains simple, but pass band ripple increases in interconnected filters
Solution Approach 1:
The patent modifies only specific IDT electrodes (dividing them into groups with different slant angles) rather than redesigning the entire filter structure. This local modification approach maintains the overall simplicity of the filter structure while effectively reducing pass band ripple in interconnected filters by suppressing stop band response
Solution Approach 2:
The patent changes the slant angle parameters of IDT electrodes to reduce stop band response, which in turn reduces pass band ripple in interconnected filters. This parameter change approach maintains filter structure simplicity while achieving the desired performance improvement
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 reduces stop band responses and insertion loss in the pass band of connected filters, enhancing the overall performance of multiplexers and communication devices by minimizing ripple and reflection losses.
Implementation Method 1
Each of the plurality of acoustic wave resonators includes an IDT electrode defined by a pair of comb-shaped electrodes provided on a substrate having piezoelectricity
Implementation Method 2
a filter device including acoustic wave resonators has been proposed
Data Source
AI summary
A first filter of a multiplexer has a ladder filter structure defined by acoustic wave resonators. An imaginary line obtained by connecting second ends of electrode fingers included in one comb-shaped electrode among a pair of comb-shaped electrodes of each resonator intersects a reference line that is a straight line extending in an acoustic wave propagation direction. When an angle defined by the reference line and the imaginary line of a first series resonator is represented by a first slant angle, an angle defined by the reference line and the imaginary line of a parallel resonator is represented by a second slant angle, and an angle defined by the reference line and the imaginary line of acoustic wave resonators is represented by a third slant angle, at least one of the first slant angle and the second slant angle is smaller than the third slant angle.