Tunable Acoustic Resonator Circuit Without Integrated Inductors
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Solution Overview
Problem
Conventional acoustic resonators, particularly Bulk Acoustic Resonators (BAW), face challenges in integration with other electronics due to characteristic dispersion, requiring selective sorting or tunable structures, and existing tunable resonator components necessitate expensive silicon substrate space and inductors with low quality factors, leading to performance losses.
Innovation Solution
A tunable resonator circuit is developed without integrated inductors, utilizing a BAW or SAW resonator with an active circuit featuring a negative capacity and adjustable capacitive elements, such as a varactor, to control resonant frequencies without generating parasitic anti-resonance frequencies, allowing for integration on a semiconductor substrate without compromising quality factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an inductor is connected in parallel to the resonator to shift the anti-resonance frequency and enable tuning, then the resonator becomes tunable and filtering capability is improved, but the device complexity increases and parasitic anti-resonance frequencies are generated
Solution Approach 1:
The patent extracts and eliminates the inductor component from the conventional resonator circuit. By removing the inductor that causes complexity and parasitic effects, the invention achieves tuning capability through alternative means (varactor diodes connected in parallel with the resonator) without the harmful side effects of inductor-based tuning.
Solution Approach 2:
The patent replaces the expensive and problematic inductor with simpler, more integrated components (varactor diodes and capacitors) that can be easily fabricated on the same semiconductor substrate as the resonator, reducing overall device complexity and cost.
2Adaptability or versatility
If an inductor is used to shift the anti-resonance frequency away from the series resonance frequency, then the useful band is expanded, but the quality factor decreases due to low quality factor inductors
Solution Approach 1:
The patent removes the inductor from the circuit entirely, eliminating the source of quality factor degradation. The tuning function is achieved through varactor diodes and capacitive elements that do not compromise the high quality factor characteristics of the resonator.
Solution Approach 2:
The patent changes the tuning mechanism from inductive (affecting quality factor) to capacitive (preserving quality factor). By using varactor diodes to vary capacitance rather than using inductors to vary inductance, the resonator maintains its high quality factor while achieving frequency tuning and band expansion.
3Manufacturing precision
If selective sorting is used to keep components that comply with specifications, then manufacturing precision is improved, but productivity decreases due to component rejection
Solution Approach 1:
The patent introduces dynamic tuning capability to static resonator components. By incorporating varactor diodes and control circuits, resonators with slightly varying characteristics can be adjusted to meet specifications, transforming a static selection process into a dynamic adjustment process that increases manufacturing yield.
Solution Approach 2:
The patent enables post-manufacturing parameter adjustment through voltage-controlled tuning. Resonators that initially fall outside specifications can be tuned into compliance by adjusting capacitance values, thereby reducing the need for selective sorting and improving manufacturing productivity.
4Ease of manufacture
If integrated inductors are used on silicon substrate, then the resonator can be integrated with other electronics, but the substrate area increases and costs increase
Solution Approach 1:
The patent extracts and removes the inductor component that occupies significant substrate area. By eliminating the inductor and using only capacitive elements for tuning, the device footprint is dramatically reduced while maintaining integration capability with standard silicon-based electronics.
Solution Approach 2:
The patent uses planar capacitive structures (varactor diodes and metal plates) that can be easily copied and integrated using standard semiconductor fabrication processes, replacing the three-dimensional inductor structures that consume excessive substrate area.
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 solution enables effective frequency tuning and filtering in mobile telecommunications without the need for inductors, reducing substrate costs and maintaining high quality factor performance, while avoiding parasitic frequencies, thus enhancing the integration and functionality of resonators in semiconductor products.
Implementation Method 1
a varactor (45) having a variable capacitance Cv allowing to control the series resonant frequency of the resonator
Implementation Method 2
an acoustic resonator of BAW or SAW type, said resonator having a series resonant frequency and a parallel resonant frequency
Data Source
AI summary
An electronic circuit includes: an acoustic resonator of BAW or SAW type, said resonator having a series resonance frequency and a parallel resonance frequency; an active circuit which is coupled in parallel to said acoustic resonator, said active circuit having a negative capacity acting on the parallel resonance frequency of said resonator.