Bragg Layer RF Filter Structure for Higher Q Edge Filtering
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Solution Overview
Problem
Conventional radio frequency filters with film bulk acoustic resonators and LC resonant circuits in high-performance scenarios, such as 5G technology, face low quality factor (Q) values and reduced filtering performance due to the need for film bulk acoustic resonators to be positioned at the edge of the passband, leading to inefficient edge filtering.
Innovation Solution
A filter design incorporating a series resonator and a parallel resonator with distinct Bragg reflection layers and piezoelectric transduction structures, where the Bragg reflection layers have different thicknesses and acoustic impedance structures, improving transverse wave transmission coefficients and reflection efficiency within the effective frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the film bulk acoustic resonator is disposed at an edge of a passband to implement edge filtering, then the filtering coverage is improved, but the quality factor (Q) value decreases and filtering effect is reduced
Solution Approach 1:
The patent applies different thicknesses of Bragg reflection layers (first Bragg reflection layer and second Bragg reflection layer) to different locations within the resonator structure. Specifically, the first Bragg reflection layer has a first thickness and the second Bragg reflection layer has a second thickness that is different from the first thickness. This local differentiation of layer thicknesses optimizes the acoustic impedance matching and reflection characteristics at different positions, thereby improving the quality factor while maintaining edge filtering capability.
2Ease of manufacture
If the Bragg reflection layers have the same structure, then the manufacturing process is simplified, but the transverse wave transmission coefficient is high and reflection efficiency is reduced
Solution Approach 1:
The patent implements different thicknesses for the first Bragg reflection layer and the second Bragg reflection layer. The first Bragg reflection layer comprises a first high acoustic impedance structure with a first thickness, while the second Bragg reflection layer comprises a second high acoustic impedance structure with a second thickness. This local structural differentiation enhances the acoustic impedance contrast and improves transverse wave reflection efficiency without significantly complicating the overall manufacturing process, as both layers can still be formed using standard thin-film deposition techniques.
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 filter design enhances the quality factor (Q) value and filtering performance by reducing transverse wave transmission coefficients, thereby improving the overall filtering effect in high-performance radio frequency scenarios.
Implementation Method 1
a first Bragg reflection layer and a first piezoelectric transduction structure that are sequentially stacked on the substrate; a parallel resonator, where the parallel resonator includes a second Bragg reflection layer
Implementation Method 2
a first piezoelectric transduction structure that are sequentially stacked on the substrate; a second piezoelectric transduction structure that are sequentially stacked on the substrate
Data Source
AI summary
The present disclosure relates to filters and preparation methods of the filters. One example filter includes a substrate, a series resonator, a parallel resonator, and a series branch. The series resonator includes a first Bragg reflection layer and a first piezoelectric transduction structure that are sequentially stacked on the substrate. The parallel resonator includes a second Bragg reflection layer and a second piezoelectric transduction structure that are sequentially stacked on the substrate, and a structure of the first Bragg reflection layer is different from a structure of the second Bragg reflection layer. The series branch includes the series resonator, and the series branch is coupled between an input end of the filter and an output end of the filter.