Negative Capacitance Capacitor Design for Wireless Charging
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Solution Overview
Problem
Conventional capacitors do not efficiently utilize AC electric fields due to dielectric materials that increase capacitance, limiting their size and application in devices like wireless charging and energy harvesting.
Innovation Solution
A novel capacitor design that enhances the AC electric field in the same direction as the external field, resulting in a negative dielectric constant and negative capacitance, allowing for a more compact and efficient capacitive reactance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional dielectric materials are used in capacitors, then capacitance increases due to induced dipole moments, but the device size cannot be reduced and AC electric field enhancement is limited
Solution Approach 1:
The patent changes the fundamental parameter of dielectric constant from positive to negative by using a meta-material structure with specific geometric configurations (split-ring resonators and wire structures). This parameter change enables the capacitor to achieve negative capacitance, which provides positive reactance while allowing for significantly reduced device size compared to conventional capacitors.
Solution Approach 2:
The patent employs composite meta-material structures combining conductive elements (wires, split-ring resonators) with specific geometric arrangements to create an artificial material with negative dielectric constant. This composite structure achieves properties not found in natural materials, enabling both high capacitance and compact size.
2Reliability
If inductor is used to provide positive reactance, then the required reactance can be achieved, but the device size becomes large
Solution Approach 1:
The patent substitutes the traditional inductive mechanism (mechanical coil structure) with a capacitive mechanism using negative capacitance. Both inductors and negative-capacitance capacitors provide positive reactance, but the negative-capacitance capacitor achieves the same electrical function in a much more compact form factor, replacing the bulky inductor structure.
3Quantity of substance
If dielectric material is present between conductors, then capacitance increases, but the AC electric field is reduced due to opposing dipole moments
Solution Approach 1:
The patent inverts the traditional dielectric behavior by creating a meta-material with negative dielectric constant. Instead of dipole moments opposing the external field (reducing it), the meta-material structure produces dipole moments that align with and enhance the external AC electric field. This inversion enables both high capacitance and strong electric field enhancement simultaneously.
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
Enables the creation of smaller capacitors with enhanced reactance, improving impedance matching for wireless charging and energy harvesting by maintaining large reactance while accommodating small load resistances, thus efficiently collecting environmental electromagnetic power.
Implementation Method 1
an AC electric field is enhanced (i.e., the additional field is in the same direction as the external field) and the effective dielectric constant becomes less than 1, even less than zero, that is, a negative value. When the effective dielectric constant becomes negative, the capacitance also becomes negative.
Data Source
AI summary
A capacitor includes a first plate and a second plate parallel to the first plate. An RF source includes a first line and a second line through which RF is fed. The first line is electrically connected to the first plate. The second line is passed through the first and second plates and then looped around the first and second plates, and the pass and loop of the second line is repeated at least once. The second line is then passed through the first plate and electrically connected to the second plate to form a capacitor having negative capacitance.