Series Switchable Capacitor Array for Equidistant RF Impedance Steps
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Solution Overview
Problem
Conventional switchable capacitor arrays face challenges in miniaturization without compromising signal quality, particularly in wireless communication devices, where they struggle to provide equidistant impedance steps across a wide frequency range.
Innovation Solution
The proposed solution involves electrically connecting capacitors in series rather than parallel, allowing for equidistant impedance steps by properly choosing the capacitances of individual capacitors, which also simplifies the calculation of total capacitance using binary weighting and offset, enabling a more homogeneous coverage of the impedance domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If capacitors are connected in parallel in conventional switchable capacitor arrays, then the total capacitance is the sum of individual capacitances, but the impedance domain cannot be covered homogeneously and equidistant impedance steps cannot be provided
Solution Approach 1:
The patent inverts the conventional parallel connection approach by using series connection of capacitors. This inversion fundamentally changes the mathematical relationship from additive (parallel) to reciprocal additive (series), enabling equidistant impedance steps when capacitances are properly selected according to the invention's specific formulas.
Solution Approach 2:
The patent changes the connection topology parameter from parallel to series, and simultaneously changes the capacitance value parameters according to specific design formulas. This parameter transformation enables the system to provide equidistant impedance steps across the impedance domain, resolving the non-uniformity issue of conventional parallel connections.
2Adaptability or versatility
If more individual capacitors are used to provide good tuning ability across wide frequency range, then tuning performance improves, but chip size increases and manufacturing costs increase
Solution Approach 1:
By changing the connection topology to series and selecting specific capacitance values according to the patent's formulas, the patent achieves more efficient impedance coverage. This allows fewer capacitors to provide the same or better tuning ability across wide frequency ranges, thereby reducing chip size and manufacturing costs.
Solution Approach 2:
The patent creates a composite capacitor array structure with specific series connection topology and optimized capacitance values. This composite design achieves superior impedance domain coverage efficiency, providing good tuning ability with fewer components compared to conventional parallel connections.
3Device complexity
If conventional parallel connected capacitor arrays are used, then simple capacitance addition is achieved, but impedance states are densely packed in one section while other sections are rarely covered
Solution Approach 1:
The patent inverts the conventional approach by using series connection instead of parallel connection. This inversion transforms the impedance characteristics from non-uniform distribution to equidistant steps, achieving homogeneous coverage of the impedance domain while maintaining manageable device complexity through systematic capacitance selection.
4Area of stationary object
If switchable capacitor arrays are miniaturized, then chip size reduces, but signal quality deteriorates due to increased requirements on switch technology
Solution Approach 1:
By changing to series connection and optimizing capacitance values, the patent reduces the number of capacitors and switches required. This miniaturization is achieved without compromising signal quality because the series topology provides better impedance matching and reduces the burden on switch technology regarding off-voltage handling, off-capacitance value, and off-capacitance Q-factor.
Data Source
AI summary
An improved switchable capacitor array comprises a plurality of n≥2 capacitor units, each comprising a capacitor with a capacitance and a switch unit. The capacitor units are electrically connected in series. Equidistantly spaced impedance values can be obtained if the values of the capacitances are chosen properly.