Apodized LCRF Electrode Layout for Spurious Pass-Band Suppression
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Solution Overview
Problem
Conventional laterally coupled resonator filters (LCRFs) face challenges in designing specific pass-bands and are prone to spurious pass-bands in various spectral regions, requiring complex two- or three-dimensional finite element method simulations and having larger physical space requirements.
Innovation Solution
The implementation of an apodized LCRF geometry, which involves varying gap widths and finger widths, and skewed bus bar edges to suppress spurious resonances, allowing for a simpler design and reduced size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LCRF geometry is used, then fabrication is simple, but spurious pass-bands appear in spectral regions
Solution Approach 1:
The patent applies local quality by varying the gap widths between comb electrode fingers at different positions along the electrode length. The gaps are narrower at the ends and wider in the middle, creating non-uniform coupling that suppresses spurious pass-bands while maintaining fabrication simplicity through a single patterning process.
Solution Approach 2:
The patent introduces asymmetry by skewing the bus bar edges relative to each other. The first bus bar is shifted in one direction while the second bus bar is shifted in the opposite direction, creating an asymmetric configuration that eliminates spurious resonances without requiring complex multi-dimensional simulations.
2Device complexity
If conventional LCRF design is used, then structure is simple, but physical space requirement is larger
Solution Approach 1:
The patent changes geometric parameters of the comb electrodes, specifically varying gap widths and finger widths along the length of the electrodes. This parameter variation achieves better filtering performance and reduced footprint while maintaining the fundamental simplicity of the LCRF structure and single-layer electrode configuration.
3Ease of manufacture
If LCRF is used instead of ladder filter, then fabrication is simpler, but design of specific pass-bands is difficult
Solution Approach 1:
By implementing local quality through position-dependent gap widths and finger widths, the patent enables precise control over the frequency response and pass-band characteristics. This local variation allows designers to achieve specific pass-band requirements while maintaining the fabrication simplicity of LCRF structures.
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 apodized LCRF design achieves efficient suppression of spurious resonances, reduces footprint, power consumption, and cost, while enabling simpler fabrication and effective implementation of common circuit functions like single-ended to differential signal conversion and impedance transformation.
Implementation Method 1
An acoustic resonator may act as a transducer that converts electrical signals into acoustic signals and/or vice versa. Two acoustic resonators can be coupled acoustically to form an electrical filter. When stimulated with a time-varying input signal from an input terminal of the electrodes, the piezoelectric material vibrates at a resonance frequency
Implementation Method 2
Voltage is generated by the excited motion, which is picked up as a transmitted signal
Data Source
AI summary
A laterally coupled resonator filter device includes a bottom electrode, a piezoelectric layer disposed on the bottom electrode, and a top contour electrode disposed on the piezoelectric layer. The top contour electrode includes first and second top comb electrodes. The first top comb electrode include a first top bus bar and multiple first top fingers extending in a first direction from the first top bus bar. The second top comb electrode includes a second top bus bar and multiple second top fingers extending in a second direction from the second top bus bar, the second direction being substantially opposite to the first direction such that the first and second top fingers form a top interleaving pattern providing an acoustic filter having an apodized shape.