Composite RF Power Capacitor for Acoustic Resonance Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing RF power capacitors using ferroelectric ceramic dielectrics, such as barium strontium titanate, degrade severely at certain frequencies when subjected to high bias voltages and high RF powers, leading to unusable devices due to acoustic resonance and limited tunability.
Innovation Solution
Incorporating an acoustic resonance reduction agent (ARRA) into the ceramic material, specifically a composite HDK-NDK ceramic, which includes a majority of barium strontium titanate and a minority of metal oxide like magnesium borate, to eliminate or reduce acoustic resonances without requiring dimension tuning, allowing operation across a wide frequency range with high bias voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ferroelectric ceramic dielectric (barium strontium titanate) is used in RF power capacitors with high bias voltages, then high tunability is achieved, but severe degradation occurs at certain frequencies due to acoustic resonance
Solution Approach 1:
The patent applies composite materials by combining barium strontium titanate (BST) ceramic with an acoustic resonance reduction agent (ARRA) such as magnesium borate or other metal oxides. This composite structure allows the capacitor to maintain high tunability from the BST while the ARRA component suppresses acoustic resonance at specific frequencies, thereby resolving the contradiction between achieving high adaptability and maintaining reliability across the frequency range.
2Adaptability or versatility
If mechanically-actuated variable capacitors are used to achieve high tunability, then capacitance range is improved, but adjustment speed becomes slow (near 1 second)
Solution Approach 1:
The patent replaces the mechanical actuation system with an electrical field-based tuning mechanism. Instead of mechanically moving electrodes to change capacitance, the invention uses an applied electric field to modify the dielectric properties of the ferroelectric ceramic material in real-time. This substitution eliminates mechanical inertia and friction, enabling rapid capacitance adjustment speeds while maintaining high tunability ranges.
Solution Approach 2:
The patent changes the physical parameter being controlled from mechanical position to electric field strength. By varying the applied electric field parameter, the dielectric constant of the ferroelectric material is dynamically adjusted, which in turn modifies the capacitance. This parameter change approach enables fast response times since electric field modulation occurs much faster than mechanical movement, while still achieving wide tunability through the field-dependent dielectric properties.
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 solution enables RF power capacitors to maintain stability and high tunability across the intended frequency range with reduced acoustic resonances, ensuring efficient energy handling and extended operational lifespan.
Implementation Method 1
Incorporating an acoustic resonance reduction agent (ARRA) into the ceramic material, specifically a composite HDK-NDK ceramic, which includes a majority of barium strontium titanate and a minority of metal oxide like magnesium borate, to eliminate or reduce acoustic resonances
Implementation Method 2
it is known from European patent application EP3189538A1, from the same applicant, to use a ferroelectric ceramic material which exhibits paraelectric properties, such as barium strontium titanate, as the dielectric, and to vary the capacitance of the device by applying a varying DC bias voltage of up to 6 kV so as to vary the dielectric constant of the ceramic material
Data Source
AI summary
A radio-frequency (RF) power variable capacitor capable of operating at, at least, 50 watts in the MHz range. The capacitor has a composite HDK-NDK ceramic dielectric. The HDK (high dielectric constant) component comprises an active matrix of barium strontium titanate, for example. Acoustic resonances are reduced or eliminated by the addition of a metal or metalloid oxide such as magnesium borate (NDK—low dielectric constant), which acts as an acoustic resonance reduction agent (ARRA) in the RF power domain. The acoustic resonances which previously occurred under bias voltage 500 V or 1100 V in prior art RF power variable capacitors are eliminated by the addition of the ARRA.