Bulk Acoustic Resonator Filter Layout for Wide High-Frequency Bands
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Solution Overview
Problem
Existing filters face challenges in achieving a wide pass band with high frequency while maintaining effective electromechanical coupling and filtering characteristics, as reducing the thickness of the resonance part to increase frequency leads to orientation issues and reduced filtering performance.
Innovation Solution
The design incorporates a filter structure with a series part and a shunt part, where the resonant frequency of the shunt bulk-acoustic resonator is higher than that of the series resonator, and inductors are coupled to each other to form a wide pass band with high frequency, using a ladder-type or lattice-type filter structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thickness of the resonance part is reduced to increase frequency, then the frequency is improved, but the electromechanical coupling is reduced and filtering characteristics deteriorate
Solution Approach 1:
The filter is divided into series part and shunt part, each with bulk-acoustic resonators having different resonant frequencies. The series part uses resonators with lower resonant frequency while the shunt part uses resonators with higher resonant frequency, allowing independent optimization of each section to achieve wide passband and high frequency without compromising filtering characteristics
Solution Approach 2:
The resonant frequencies of the bulk-acoustic resonators in the series and shunt parts are set to different values. Specifically, the resonant frequency of the shunt part resonators is higher than that of the series part resonators, creating a frequency differential that enables wide passband while maintaining effective electromechanical coupling and filtering performance
2Speed
If the thickness of the resonance part is reduced to increase frequency, then the frequency is improved, but the electromechanical coupling is reduced
Solution Approach 1:
The filter structure segments the resonators into series and shunt parts with different resonant frequencies. This segmentation allows the series part to operate at frequencies where effective electromechanical coupling is maintained while the shunt part operates at higher frequencies, collectively achieving high frequency response without sacrificing coupling efficiency
Solution Approach 2:
By changing the resonant frequency parameter of the bulk-acoustic resonators between series and shunt parts, the system achieves high operating frequency while maintaining strong electromechanical coupling in the series part. The frequency differential creates complementary operation modes that preserve energy conversion efficiency
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
This configuration allows for the implementation of a filter with a wide pass band and high frequency while maintaining effective electromechanical coupling, enhancing filtering characteristics and reducing the thickness of the resonance part.
Implementation Method 1
an electric field is induced in the piezoelectric layer by electrical energy applied to the first electrode and the second electrode, a piezoelectric phenomenon occurs in a piezoelectric layer due to the induced electric field, and the resonance part vibrates in a predetermined direction. As a result, bulk acoustic waves are generated
Data Source
AI summary
A filter includes: a series part disposed between a signal input terminal and a signal output terminal, and including at least one first bulk-acoustic resonator; an inductor portion including a first inductor disposed between ends of the series part and a second inductor having a first end connected to a connection node of the series part and the first inductor; and a shunt part disposed between a second end of the second inductor and a ground, and including at least one second bulk-acoustic resonator, wherein a resonant frequency of the at least one second bulk-acoustic resonator is higher than a resonant frequency of the at least one first bulk-acoustic resonator.