Multi-Mode SAW Filter With Ladder Impedance Conversion for Size Reduction
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Solution Overview
Problem
The challenge is to reduce the size of acoustic wave filters in radio frequency systems while maintaining high performance and avoiding degradation of filter rejection and ruggedness, particularly in the context of increasing frequency bands in 4G and 5G technologies.
Innovation Solution
Implementing a multi-mode surface acoustic wave filter with a ladder section connected to its output, featuring more input tracks and interdigital transducer electrodes than output, and utilizing higher impedance resonators to achieve impedance transformation, thereby reducing filter size without compromising performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional acoustic wave filter designs are used, then filter performance is maintained, but filter size is large
Solution Approach 1:
The patent changes the impedance parameter of the resonators in the ladder section from conventional values to higher impedance values. This parameter change allows for reduced component sizes while maintaining filter performance characteristics, directly resolving the contradiction between small size and reliable performance
Solution Approach 2:
The patent introduces impedance transformation as an additional design dimension by connecting a ladder section with high impedance resonators to the multi-mode SAW filter. This adds a new degree of freedom to the filter design, enabling size reduction without performance degradation
2Volume of moving object
If filter size is reduced, then compactness is improved, but impedance matching and noise floor degrade
Solution Approach 1:
The patent introduces a ladder section as an intermediary component between the multi-mode SAW filter and the load. This intermediary contains high impedance resonators that facilitate impedance transformation, enabling proper impedance matching even when the overall filter size is reduced
Solution Approach 2:
By changing the impedance parameter of the resonators to higher values, the patent achieves better impedance matching characteristics in a compact structure, counteracting the typical degradation that occurs when filters are miniaturized
3Adaptability or versatility
If more input tracks and interdigital transducer electrodes are used, then impedance conversion is improved, but device complexity increases
Solution Approach 1:
The patent segments the filter into two functional parts: a multi-mode SAW filter section and a ladder section with high impedance resonators. This segmentation allows the impedance conversion function to be distributed to the ladder section, reducing the complexity requirements of the main filter section while maintaining overall adaptability
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
The solution results in a smaller filter size with improved impedance matching and reduced noise floor, achieving better power handling and gamma performance, while maintaining or enhancing filter performance compared to traditional designs.
Implementation Method 1
A SAW resonator is arranged to generate a surface acoustic wave. SAW filters include multi-mode SAW filters, such as double mode SAW (DMS) filters.
Implementation Method 2
A SAW resonator of a SAW filter typically includes an interdigital transductor electrode on a piezoelectric substrate.
Implementation Method 3
The ladder section includes at least one shunt acoustic wave resonator and at least one series acoustic wave resonator.
Data Source
AI summary
Aspects of this disclosure relate to an acoustic wave filter that includes a multi-mode surface acoustic wave filter and a ladder section. The multi-mode surface acoustic wave filter has a higher impedance at an output than at an input. The ladder section is connected to the output of the multi-mode surface acoustic wave filter. Related radio frequency systems, radio frequency modules, wireless communication devices, and methods are disclosed.