BAW Resonator Air-Bridge Layout for Second Harmonic Suppression
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Solution Overview
Problem
Bulk acoustic wave resonators exhibit non-linearity at high power levels, leading to unwanted second harmonic emissions that can desensitize receiver paths in wireless communication systems, particularly in filters like film bulk acoustic wave resonator (FBAR) triplexers, where strong second order harmonics are observed and need to be suppressed.
Innovation Solution
The implementation of anti-series connected bulk acoustic wave resonators with an air gap between the conductor and the substrate to reduce parasitic capacitance, which effectively suppresses second harmonic emissions by electrically connecting FBARs in anti-series configuration, utilizing air bridges or cavities to minimize parasitic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If bulk acoustic wave resonators are used at high power levels, then filtering capability is improved, but second harmonic emissions increase causing non-linearity
Solution Approach 1:
The resonator is divided into two separate bulk acoustic wave resonators connected in anti-series configuration. This segmentation allows the harmful second harmonic emissions from one resonator to be canceled by the other resonator operating in opposite phase, while maintaining high power filtering capability
Solution Approach 2:
The invention converts the harmful second harmonic emissions into a beneficial cancellation effect. By connecting two resonators in anti-series, the second harmonic emissions from each resonator are equal in magnitude but opposite in phase, causing them to cancel each other out and transform the harmful effect into a benefit
2Object-generated harmful factors
If resonators are connected in anti-series configuration, then second harmonic suppression is improved, but parasitic capacitance affects performance
Solution Approach 1:
An air gap is introduced as an intermediary element between the two resonators in anti-series connection. This air gap acts as a mediator that minimizes parasitic capacitance between the resonators and the substrate, allowing the anti-series configuration to effectively suppress second harmonic emissions without degrading filtering performance
3Object-generated harmful factors
If air gap is introduced to reduce parasitic capacitance, then second harmonic suppression is improved, but device complexity increases
Solution Approach 1:
The invention uses an air gap (pneumatic approach) to reduce parasitic capacitance between the resonators and substrate. This pneumatic solution is simpler than using complex dielectric structures or additional isolation layers, as it utilizes the natural properties of air as an insulator with minimal dielectric constant
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 achieves significant second harmonic suppression, improving the linearity of filters and meeting stringent harmonic and intermodulation distortion specifications, effectively canceling second harmonic power emissions by approximately 30 decibels, thereby enhancing the performance of multiplexers and filters in wireless communication devices.
Implementation Method 1
an air gap positioned between the conductor and a surface of the substrate
Implementation Method 2
In BAW resonators, acoustic waves propagate in a bulk of a piezoelectric layer
Implementation Method 3
acoustic waves propagate in a bulk of a piezoelectric layer
Implementation Method 4
effectively canceling second harmonic power emissions by approximately 30 decibels
Data Source
AI summary
Embodiments of this disclosure relate to bulk acoustic wave resonators on a substrate. The bulk acoustic wave resonators include a first bulk acoustic wave resonator, a second bulk acoustic wave resonator, a conductor electrically connecting the first bulk acoustic wave resonator to the second bulk acoustic wave resonator, and an air gap positioned between the conductor and a surface of the substrate.