Multi-Tap LC Oscillator for Wide RF Tuning Without Extra Parasitics
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Solution Overview
Problem
Existing RF/microwave LC oscillators face challenges in achieving a wide frequency tuning range without increasing parasitic capacitance, which limits their performance as operating frequencies increase, and require multiple oscillator cores or LC tanks, complicating design and increasing cost.
Innovation Solution
A system and method utilizing a multi-tap inductor with at least two pairs of taps and a center tap, coupled with capacitors and negative-Gm stages, allowing for extended frequency tuning without additional parasitic capacitance and minimizing silicon footprint, enabling fine tuning adjustments by switching additional inductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple oscillator cores or LC tanks are used to extend tuning range, then frequency tuning range is improved, but device complexity and silicon footprint increase
Solution Approach 1:
The inductor is divided into multiple segments with taps at different positions along the conductor. By selecting different tap pairs, different inductance values are achieved, enabling frequency tuning without requiring multiple complete oscillator cores. The inductor conductor is segmented into multiple sections, each contributing to the overall inductance, allowing selective combination through tap switching.
Solution Approach 2:
A single oscillator core is designed to serve multiple frequency ranges by combining it with different capacitor values selected through the multi-tap inductor configuration. The same oscillator core structure is universally applied across different frequency bands, eliminating the need for separate dedicated oscillator cores for each frequency range.
2Adaptability or versatility
If switches are added to short circuit inductor portions for tuning, then frequency tuning range is improved, but parasitic capacitance increases
Solution Approach 1:
The harmful switching action is extracted and replaced by passive tap connections. Instead of using active switches that introduce parasitic capacitance, the design extracts the tuning function by providing multiple fixed tap points along the inductor conductor. The desired inductance is achieved by selecting appropriate tap pairs, eliminating the need for switching components that would add parasitic effects.
3Measurement precision
If multiple capacitor values are used for fine tuning, then frequency precision is improved, but device complexity increases
Solution Approach 1:
Multiple capacitor values are merged into a single capacitor structure by creating taps at different positions along the inductor conductor. Each tap pair effectively creates a different capacitive division ratio, allowing fine tuning of the frequency without requiring physically separate capacitor components. The single capacitor is combined with the multi-tap inductor to achieve multiple effective capacitance values.
Data Source
AI summary
System and method for increasing the frequency tuning range of a RF/microwave LC oscillator. An electronic communications device includes a controller to regulate the operation of the electronic communications device, a modem coupled to the controller, a radio frequency unit coupled to the controller and to the modem, an oscillator coupled to the controller and to the radio frequency unit, and an amplifier coupled to the radio frequency unit. The oscillator produces a timing and reference signal for the radio frequency unit based on control information from the controller. The oscillator includes a multi-tap inductor that may controllably alter its effective inductance to change the timing and reference signal provided to the radio frequency unit.