Acoustic Wave Resonator Aperture Layout for Steeper Filter Skirts
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Solution Overview
Problem
Designing acoustic wave filters with a steep filter skirt is challenging, particularly for surface acoustic wave (SAW) filters, as they often struggle to meet filter skirt steepness specifications due to issues with transverse spurious modes and the difficulty of creating a sufficiently steep skirt near the passband without additional circuit components.
Innovation Solution
The implementation of acoustic wave filters with a transverse spurious mode, utilizing series and shunt acoustic wave resonators with specific interdigital transducer electrode apertures to concentrate transverse spurious modes at specific frequencies, thereby increasing the steepness of the filter skirt without the need for external circuit components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional SAW filter designs are used, then the filter structure is simple, but the filter skirt steepness is insufficient
Solution Approach 1:
The patent changes the physical parameters of the IDT electrode by reducing its aperture to less than 10 wavelengths (specifically 0.5λ to 5λ), which fundamentally alters the resonator's mode structure and enables concentration of transverse spurious modes to improve filter skirt steepness without adding external circuit components
Solution Approach 2:
The patent converts the harmful transverse spurious modes into a beneficial feature by designing the IDT aperture to concentrate these modes at specific frequencies above the passband, thereby using what was previously considered a defect to achieve the desired steep filter skirt characteristic
2Manufacturing precision
If additional circuit components are added to increase filter skirt steepness, then the filter performance is improved, but the device complexity increases
Solution Approach 1:
The resonator structure serves itself by concentrating transverse spurious modes through the specially designed IDT aperture, eliminating the need for external circuit components to achieve filter skirt steepness. The structure inherently provides the required filtering characteristic through its geometric parameters
3Manufacturing precision
If the IDT electrode aperture is reduced to concentrate transverse spurious modes, then the filter skirt steepness is improved, but the aperture becomes very small (less than 10λ)
Solution Approach 1:
The patent systematically changes the IDT aperture parameter to a specific range (0.5λ to 5λ, specifically less than 10λ) to achieve the desired mode concentration effect, demonstrating that this parameter change enables both steep filter skirts and practical device dimensions
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 approach allows for improved filter skirt steepness, achieving low insertion loss and high rejection of frequencies close to the passband, which is desirable in wireless communication systems, without the use of additional circuit components, thereby enhancing the performance of SAW filters.
Implementation Method 1
A surface acoustic wave resonator can include an interdigital transductor electrode on a piezoelectric substrate. The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer
Implementation Method 2
The transverse spurious mode of the first series acoustic wave resonator is configured to increase steepness of a skirt of the acoustic wave filter. The frequency can be above a resonant frequency of the first series acoustic wave resonator
Data Source
AI summary
Aspects of this disclosure relate to an acoustic wave filter with an acoustic wave resonator arranged to concentrate a transverse spurious mode at a frequency. Such an acoustic wave resonator can have a narrow aperture to concentrate the transverse spurious mode. The transverse spurious mode can increase steepness of a skirt of the acoustic wave filter. Related methods, acoustic wave devices, multiplexers, radio frequency front ends, radio frequency modules, and wireless communication devices are disclosed.