Bulk Acoustic Wave Resonator Cavity Layout for Smaller RF Filters
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Solution Overview
Problem
Conventional filters, such as micro-strip, cavity, dielectric, and IPD filters, fail to meet the requirements of small in-band ripple, large out-of-band rejection, and good rectangularity due to their large size and poor performance characteristics, while existing bulk acoustic wave resonators have fixed resonant frequencies that limit their filtering efficiency.
Innovation Solution
A bulk acoustic wave resonator with a dielectric substrate featuring a first cavity with specific polygonal openings and corresponding openings on both surfaces, formed through laser-induced etching, reduces the inactive region and allows for miniaturization by aligning tangent lines of adjacent sides at intersection points, enhancing the active region and reducing signal transmission loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional filters (micro-strip, cavity, dielectric, IPD) are used, then filtering function is provided, but the filter has large volume and poor performance characteristics (large in-band ripple, small out-of-band rejection, poor rectangularity)
Solution Approach 1:
The patent replaces conventional mechanical filter structures (micro-strip, cavity, dielectric, IPD filters) with a bulk acoustic wave resonator that uses piezoelectric materials to convert electrical signals to acoustic waves and back, achieving superior filtering performance in a compact form factor
Solution Approach 2:
The patent changes the resonant frequency parameter of the bulk acoustic wave resonator by adjusting the thickness of the piezoelectric layer and the dimensions of the cavity, allowing the filter to meet different frequency requirements while maintaining small size and high performance
2Reliability
If existing bulk acoustic wave resonators with fixed resonant frequencies are used, then resonant filtering is achieved, but filtering efficiency is limited due to fixed frequency operation
Solution Approach 1:
The patent makes the resonant frequency of the bulk acoustic wave resonator adjustable by designing the cavity with variable dimensions and the piezoelectric layer with adjustable thickness, enabling the filter to adapt to different frequency requirements and improve filtering efficiency across multiple frequency bands
3Ease of manufacture
If the dielectric substrate has large inactive region, then manufacturing is simplified, but signal transmission loss increases and active region is reduced
Solution Approach 1:
The patent uses an asymmetric cavity design where the cavity dimensions are optimized to minimize the inactive region while maintaining manufacturability, with the cavity extending closer to the edges of the dielectric substrate to reduce signal transmission loss and maximize the active region
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 proposed resonator design effectively minimizes chip size, reduces inactive region area, and shortens routing wire lengths, improving signal transmission efficiency and filter performance by aligning tangent lines at intersection points, thus meeting the requirements of small size and high filtering efficiency.
Implementation Method 1
a radio frequency signal enters into the resonator from an electrode at one end of the resonator, then is converted into an acoustic wave signal of mechanical vibration at an interface of the piezoelectric material and the metal electrode through an inverse piezoelectric effect
Implementation Method 2
the acoustic wave signal is transmitted to the electrode at the other end of the resonator, and is converted into the radio frequency signal at the interface of the metal electrode and the piezoelectric material through a piezoelectric effect
Implementation Method 3
formed through laser-induced etching
Data Source
AI summary
A bulk acoustic wave resonator, a manufacturing method thereof and a filter are provided and belong to the technical field of radio frequency micro-electro-mechanical system. The resonator includes a dielectric substrate, a first electrode, a piezoelectric layer, and a second electrode. The dielectric substrate has a first cavity penetrating through the dielectric substrate in a thickness direction thereof, and the first cavity includes a first opening penetrating through the first surface, and a second opening penetrating through the second surface. The first opening includes first sides sequentially arranged in a clockwise direction, and first connecting sides each connecting two adjacent first sides; the second opening includes second sides sequentially arranged in a clockwise direction, and second connecting sides each connecting two adjacent second sides. The first sides are in one-to-one correspondence with the second sides, and the first connecting sides are in one-to-one correspondence with the second connecting sides.