Acoustic Wave Multiplexer With Slanted IDT Resonators for Lower Ripple
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Solution Overview
Problem
Multiplexers with acoustic wave resonators suffer from higher-order mode spurious responses in the stop band, which can affect the characteristics of interconnected filters and cause pass band ripple, leading to increased insertion loss.
Innovation Solution
The design includes a multiplexer configuration with acoustic wave resonators where the IDT electrodes are slanted relative to the acoustic wave propagation direction, with specific slant angles for series and parallel resonators to reduce transverse-mode ripple and higher-order mode spurious responses, particularly by making the IDT electrode closest to the common terminal more slanted than the others.
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, then pass band characteristics are improved, but higher-order mode spurious responses occur in the stop band
Solution Approach 1:
The patent applies different slant angles to different resonators within the filter. Specifically, the first resonator has a first slant angle, while the second and third resonators have a second slant angle that is larger than the first. This local differentiation allows each resonator to contribute differently to suppressing spurious responses while maintaining pass band characteristics.
Solution Approach 2:
The patent introduces asymmetry in the IDT electrode arrangement by using different slant angles for different resonators. The first resonator has a smaller slant angle, while the second and third resonators have larger slant angles. This asymmetric configuration breaks the symmetry that would otherwise generate higher-order mode spurious responses, while still maintaining the transverse-mode ripple suppression benefit.
2Reliability
If higher-order mode spurious responses occur in the stop band of one filter, then the filter's stop band characteristics are affected, but pass band ripple increases in interconnected filters
Solution Approach 1:
The patent applies different slant angles to different resonators within the filter. Specifically, the first resonator has a first slant angle, while the second and third resonators have a second slant angle that is larger than the first. This local differentiation allows each resonator to contribute differently to suppressing spurious responses while maintaining pass band characteristics.
Solution Approach 2:
The patent introduces asymmetry in the IDT electrode arrangement by using different slant angles for different resonators. The first resonator has a smaller slant angle, while the second and third resonators have larger slant angles. This asymmetric configuration breaks the symmetry that would otherwise generate higher-order mode spurious responses, while still maintaining the transverse-mode ripple suppression benefit.
3Measurement precision
If higher-order mode spurious responses are present in the stop band, then frequency selectivity is compromised, but insertion loss increases in the pass band
Solution Approach 1:
The patent applies different slant angles to different resonators within the filter. Specifically, the first resonator has a first slant angle, while the second and third resonators have a second slant angle that is larger than the first. This local differentiation allows each resonator to contribute differently to suppressing spurious responses while maintaining pass band characteristics.
Solution Approach 2:
The patent introduces asymmetry in the IDT electrode arrangement by using different slant angles for different resonators. The first resonator has a smaller slant angle, while the second and third resonators have larger slant angles. This asymmetric configuration breaks the symmetry that would otherwise generate higher-order mode spurious responses, while still maintaining the transverse-mode ripple suppression benefit.
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 or prevents higher-order mode spurious responses in the stop band and minimizes insertion loss in the pass band of interconnected filters.
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 including acoustic wave resonators
Data Source
AI summary
A first filter of a multiplexer includes a ladder filter structure of 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 larger than the third slant angle.