Parallel Switching Inductor for High-Frequency Oscillator Tuning
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Solution Overview
Problem
Conventional inductive tuning circuits for high frequency oscillators face challenges in providing a significant inductance variation range while maintaining a high quality factor, due to tradeoffs between turned-on resistance and parasitic capacitance, which damages the quality factor.
Innovation Solution
A parallel-based switching inductor device is introduced, comprising a first and second inductor connected in parallel via a switch circuit, allowing for different inductances to be provided in various modes without significantly reducing the quality factor, suitable for high frequency oscillators above 20 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional inductive tuning circuits are used to provide significant inductance variation, then the inductance range is improved, but the quality factor deteriorates due to turned-on resistance and parasitic capacitance
Solution Approach 1:
The inductor is divided into multiple discrete inductive elements (first inductor, second inductor, third inductor) that can be independently switched. This segmentation allows selective combination of inductive elements to achieve different total inductance values while maintaining high quality factor by avoiding the tradeoff of conventional single-inductor tuning circuits
Solution Approach 2:
The switching circuit serves multiple functions: it selects different inductive elements, combines them in series or parallel configurations, and maintains high quality factor across all tuning states. This multi-functionality enables significant inductance variation (超过30% range) while preserving quality factor (variation below 10%)
2Reliability
If the turned-on resistance of MOS transistor switch is reduced, then the quality factor is improved, but the parasitic capacitance increases which damages the quality factor
Solution Approach 1:
The harmful effects of parasitic capacitance are extracted and isolated by placing the switching circuit in a configuration where its parasitic capacitance does not directly load the resonant tank. The switching nodes are positioned such that parasitic capacitances are minimized in the signal path, allowing the use of MOS transistors without severely degrading quality factor
Solution Approach 2:
The inductive elements serve as intermediaries between the switching circuit and the resonant tank. By introducing these inductive elements, the direct connection between the switching circuit's parasitic capacitance and the tank is eliminated, reducing the harmful impact of parasitic capacitance on quality factor
Data Source
AI summary
A switching inductor device having a first port and a second port includes a first inductor and a second inductor with a switch circuit. The first inductor is coupled between the first port and the second port. The second inductor and the switch circuit are connected in series, and are coupled between the first port and the second port; the first inductor and the second inductor are connected in parallel when the switch circuit is turned on.