Variable Inductor Segmentation for Low Series Resistance
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Solution Overview
Problem
Conventional variable inductors face challenges in increasing inductance while maintaining low series resistance, with magnetic field-based inductors limited by increased series resistance and switch-based inductors experiencing increased parasitic capacitance and chip area issues.
Innovation Solution
A variable inductor design featuring two inductors connected between terminals with strategically placed nodes and switch elements that can switch between conductive and non-conductive states, allowing for varying inductance without significant increases in series resistance, achieved through symmetrical and asymmetrical configurations of inductors and switch placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the inductance Ls is increased in a conventional variable inductor, then the gain G of the amplifier is improved, but the series resistance Rs of the inductor increases
Solution Approach 1:
The inductor is divided into multiple segments with different inductance values. Switches connect these segments in series or parallel configurations to achieve variable total inductance. This segmentation allows the circuit to select from discrete inductance values without requiring a single large inductor that would inherently have high series resistance.
Solution Approach 2:
The inductor configuration is made dynamic through switches that can reconfigure the connection topology between inductor segments. By dynamically switching between series and parallel connections, the effective inductance and equivalent series resistance are simultaneously adjusted, allowing optimization of both gain and loss characteristics.
2Adaptability or versatility
If the capacitance Cs is increased to change the resonant frequency to lower frequencies, then the resonant frequency coverage is improved, but the gain G of the amplifier decreases
Solution Approach 1:
The capacitance is divided into multiple segments that can be switched in series or parallel. This segmentation enables the resonant frequency to be adjusted across a wide range by changing the effective capacitance, while the inductor segments provide corresponding inductance values to maintain optimal gain at each frequency point.
Solution Approach 2:
Both inductance and capacitance parameters are made variable through switchable configurations. By coordinating changes in L and C parameters across multiple discrete values, the resonant frequency f0 = 1/(2π√(LC)) can be tuned while maintaining favorable gain characteristics through appropriate L-C pair selection.
3Adaptability or versatility
If switch elements are added to create a variable inductor, then the inductance variability is improved, but the parasitic capacitance and chip area increase
Solution Approach 1:
Multiple inductor segments are merged into a single integrated structure on the chip, sharing common substrates and support infrastructure. Switches are integrated alongside the inductor segments in a compact arrangement, reducing the total chip area compared to discrete components while maintaining full inductance variability functionality.
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 design effectively increases inductance change while minimizing series resistance, enhancing the Q value and reducing parasitic capacitance, thus improving the efficiency and performance of resonant circuits in high-frequency applications.
Implementation Method 1
a switch element that switches between a conductive state and a non-conductive state between the first node and the second node
Data Source
AI summary
A variable inductor includes: a first inductor having two ends connected to a first terminal and a second terminal; a second inductor having two ends connected to the first terminal and the second terminal; a first node provided on the first inductor; a second node provided on the second inductor; and a switch element that switches between a conductive state and a non-conductive state between the first node and the second node.