Anti-Phase Biased Tunable Capacitor for Acoustic Loss Cancellation
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Solution Overview
Problem
Ferroelectric varactors experience significant acoustic losses due to electromechanical coupling, leading to reduced Q-factor and limited frequency range usability, especially above 1 GHz, making them unsuitable for various RF and microwave applications.
Innovation Solution
A multilayered tunable dielectric capacitor design where two tunable dielectric layers are DC biased such that they vibrate in anti-phase, reducing acoustic losses by coupling the vibrations of one layer with another, thereby improving the Q-factor across a wider frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferroelectric varactors are used to achieve high Q and high power handling capacity, then the capacitor performance is improved, but acoustic losses increase at certain frequencies due to electromechanical coupling
Solution Approach 1:
The patent applies anti-phase biasing to convert the harmful acoustic vibrations into beneficial canceling effects. By biasing adjacent dielectric layers in opposite directions, the acoustic vibrations generated in each layer are out of phase and cancel each other, transforming the harmful electromechanical coupling into a useful noise-cancellation mechanism that reduces overall acoustic losses.
Solution Approach 2:
The patent changes the biasing parameters of the dielectric layers, specifically applying opposite polarity DC biases to adjacent layers. This parameter change modifies the operating state of the ferroelectric material, causing the acoustic vibrations to occur in anti-phase and thereby reducing the energy loss through acoustic resonance at problematic frequencies.
2Reliability
If layer thicknesses and materials are optimized to minimize acoustic losses, then Q-factor is improved, but the frequency range is limited due to resonant peaks
Solution Approach 1:
The anti-phase biasing configuration provides universal suppression of acoustic losses across multiple frequency ranges. Instead of optimizing for a single frequency band, the opposite biasing of adjacent layers creates a mechanism that cancels acoustic vibrations broadly, enabling the capacitor to maintain high Q-factor across DC to microwave frequency ranges without being limited by resonant peaks at specific frequencies.
3Adaptability or versatility
If AC signal is applied to achieve voltage tunability, then the capacitance can be adjusted, but acoustic vibrations are generated that increase energy loss
Solution Approach 1:
The patent converts the harmful acoustic vibrations generated during voltage tuning into beneficial canceling effects. By applying opposite DC biases to adjacent dielectric layers, the AC signal-induced acoustic vibrations in each layer are out of phase, causing them to cancel each other and transforming the energy loss mechanism into a useful vibration cancellation system that maintains voltage tunability while reducing overall energy loss.
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 anti-phase biasing significantly reduces acoustic losses and maintains a stable Q-factor from 100 MHz to 3 GHz, eliminating resonant peaks and enhancing the capacitor's performance in frequency ranges previously affected by acoustic vibrations.
Implementation Method 1
The use of barium titanate, strontium titanate, or barium strontium titanate (BST) of any composition including any doped BST formulation to make tunable capacitors relies on the dielectric properties of the ferroelectric material in the paraelectric phase. This means the dielectric constant of the material changes under the applied electric field.
Implementation Method 2
As an electric field is applied, which lowers the dielectric constant, the piezoelectric constant of the material becomes non-zero. As a result, the electric field is converted into a physical change of the lattice constants of the film. Simultaneous application of an AC signal to the material causes acoustic vibrations of atoms in the crystalline lattice and is called electromechanical coupling.
Data Source
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Figure 4B~5
AI summary
An embodiment of the present invention provides a device, comprising a multilayered tunable dielectric capacitor, wherein said multilayers of tunable dielectric are adapted to be DC biased to reduce the dielectric constant; and wherein the DC bias is arranged so that the number of layers of tunable dielectric biased positively is equal to the number of layers of tunable dielectric biased negatively.