FBAR-FET Oscillator Using Surface-Charge Gating for 100GHz Output
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Solution Overview
Problem
Current film bulk acoustic resonators face limitations in achieving high-frequency operations beyond a few GHz due to thickness constraints and sensitivity issues, making it challenging to develop resonators for advanced telecommunications technologies.
Innovation Solution
The apparatus comprises a film bulk acoustic resonator and a field effect transistor configured in a feedback loop, where the field effect transistor is gated by the surface charge of the piezoelectric material, enabling the generation of acoustic waves that produce output signals with frequencies up to 100GHz, utilizing graphene or other conductive two-dimensional materials for enhanced conductivity and frequency control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thickness of the piezoelectric material is reduced to achieve higher frequencies, then the frequency increases, but the sensitivity and mechanical strength deteriorate
Solution Approach 1:
The patent changes the material parameter by using graphene or conductive two-dimensional materials instead of conventional metals for the field effect transistor channel. This material substitution enables high-frequency operation (up to 100GHz) while maintaining device sensitivity and mechanical integrity, resolving the contradiction between frequency increase and sensitivity deterioration that would normally require thickness reduction.
2Speed
If the thickness of the piezoelectric material is reduced to achieve higher frequencies, then the frequency increases, but the mechanical strength deteriorates
Solution Approach 1:
The patent employs graphene or conductive two-dimensional materials as the channel material in the field effect transistor, representing a fundamental parameter change from conventional materials. This substitution allows the device to operate at frequencies up to 100GHz while maintaining adequate mechanical strength without requiring reduction of the piezoelectric material thickness.
3Speed
If conventional materials are used in the field effect transistor, then the manufacturing is easier, but the frequency operation is limited to a few GHz
Solution Approach 1:
The patent utilizes graphene or conductive two-dimensional materials which can be deposited using chemical vapor deposition (CVD) techniques. This manufacturing approach, while requiring specialized processes, enables frequency operation up to 100GHz, representing a significant advancement over conventional materials that are limited to a few GHz.
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 higher frequency operations without reducing the thickness of the piezoelectric material, increasing sensitivity and enabling frequencies up to 100GHz, while also allowing for control of the output frequency through voltage and doping adjustments.
Implementation Method 1
the piezoelectric material having first and second regions and being configured such that the application of a potential difference between the first and second electrodes enables the generation of an acoustic wave and associated surface charge in the first and second regions of the piezoelectric material
Implementation Method 2
the field effect transistor being formed on the piezoelectric material of the film bulk acoustic resonator such that the channel is in direct physical contact with the second region of the piezoelectric material and is gated by the surface charge of said second region of the piezoelectric material
Implementation Method 3
the first electrode of the film bulk acoustic resonator comprises electrically connected first and second portions, the second portion capacitively coupled to the channel of the field effect transistor via a dielectric material, and wherein the first portion of the first electrode is capacitively coupled to the first region of the piezoelectric material
Data Source
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Figure 5(a)~6
AI summary
An apparatus comprising a film bulk acoustic resonator and a field effect transistor, the film bulk acoustic resonator comprising first and second electrodes separated by a piezoelectric material, the piezoelectric material configured such that the application of a potential difference between the first and second electrodes enables the generation of an acoustic wave and associated surface charge in the piezoelectric material, the field effect transistor comprising a channel, and source and drain electrodes configured to enable a flow of electrical current through the channel when a potential difference is applied between the source and drain electrodes, wherein the first electrode of the film bulk acoustic resonator comprises electrically connected first and second portions, the second portion capacitively coupled to the channel of the field effect transistor via a dielectric material, and wherein the first portion of the first electrode is capacitively coupled to the piezoelectric material such that the surface charge generated in the piezoelectric material induces a corresponding charge in the first electrode which causes a variation in the electrical current flowing through the channel via the second portion of the first electrode, the variation in electrical current producing an output signal having a frequency which corresponds to that of the acoustic wave.