Bulk Acoustic Resonator Filter Layout for Wide Bandwidth
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Solution Overview
Problem
Existing filters and resonance elements in mobile communication devices and chemical/biological testing devices require smaller and lighter solutions with improved performance, particularly in achieving wide pass bandwidth and stable skirt characteristics, which current technologies struggle to provide effectively.
Innovation Solution
A bulk acoustic resonator filter design incorporating series and shunt bulk acoustic resonators with specific electrode and trench configurations, along with a piezoelectric layer, to enhance resonance frequencies and bandwidth, while maintaining stability and reducing spurious noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional filter designs are used, then device size and weight are reduced, but pass bandwidth and skirt characteristics deteriorate
Solution Approach 1:
The filter is divided into multiple resonators (first series resonator, second series resonator, first shunt resonator, second shunt resonator) with different resonance frequencies. Each resonator segment handles specific frequency ranges, allowing the compact structure to achieve wide overall pass bandwidth through coordinated operation of segmented frequency responses.
Solution Approach 2:
The resonators are designed with specific resonance frequency parameters (first series: 3.5GHz, second series: 3.8GHz, first shunt: 3.2GHz, second shunt: 4.0GHz) to optimize the pass bandwidth and skirt characteristics. By carefully selecting and adjusting these frequency parameters, the filter achieves wide bandwidth while maintaining compact dimensions.
2Volume of moving object
If conventional filter designs are used, then device size and weight are reduced, but skirt characteristics deteriorate
Solution Approach 1:
The filter uses four distinct resonator segments with different resonance frequencies and configurations (series and shunt combinations). This segmentation allows each resonator to contribute to shaping the skirt characteristics in its respective frequency region, achieving sharp roll-off and good skirt characteristics while maintaining compact overall size.
Solution Approach 2:
Specific resonance frequency parameters are assigned to each resonator (3.5GHz, 3.8GHz, 3.2GHz, 4.0GHz) to control the skirt characteristics. The series resonators handle upper frequency transitions while shunt resonators manage lower frequency transitions, creating sharp skirts through coordinated parameter optimization.
3Reliability
If resonance frequency is increased, then bandwidth is improved, but spurious noise increases
Solution Approach 1:
Shunt resonators are introduced as intermediary elements between the series resonators and ground. These shunt resonators (with resonance frequencies of 3.2GHz and 4.0GHz) act as frequency-selective mediators that suppress spurious noise at specific frequencies while allowing the main pass bandwidth to remain wide, thus mediating between bandwidth requirements and noise suppression.
Solution Approach 2:
The resonance frequencies of all resonators are carefully selected and adjusted (first series: 3.5GHz, second series: 3.8GHz, first shunt: 3.2GHz, second shunt: 4.0GHz) to optimize the balance between wide pass bandwidth and spurious noise suppression. The parameter optimization ensures that noise frequencies fall into attenuation regions created by the resonator configurations.
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 design achieves a wide pass bandwidth and sharper skirt characteristics, improving the performance and stability of filters in mobile communication devices and chemical/biological testing devices by effectively managing resonance frequencies and noise.
Implementation Method 1
a piezoelectric layer disposed on an upper surface of the first electrode
Implementation Method 2
a series bulk acoustic resonator electrically connected, in series, between a first port and a second port through which a radio frequency (RF) signal passes
Data Source
AI summary
A bulk acoustic resonator filter includes: a series bulk acoustic resonator electrically connected, in series, between first and second ports through which a radio frequency (RF) signal passes; a second shunt bulk acoustic resonator, electrically shunt connected between the series bulk acoustic resonator and a ground and having a resonance frequency lower than that of the series bulk acoustic resonator; and a first shunt bulk acoustic resonator electrically connected to the second shunt bulk acoustic resonator in series and having a resonance frequency higher than that of the second shunt bulk acoustic resonator. One or both of the series bulk acoustic resonator and the first shunt bulk acoustic resonator includes a first electrode disposed above a substrate; a piezoelectric layer disposed on the first electrode; a second electrode disposed on the piezoelectric layer; and a trench formed in an upper surface or above the second electrode and recessed downwardly.