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Updated: Aug 7, 2026
10:26
Fabrication and Characterization of Superconducting Resonators
Published on: May 21, 2016
Nonlinear effects in varactor-tuned resonators
1Department of Electronics, University of York, York, YO10 5DD, UK. jkae@ohm.york.ac.uk
Summary
Varactor-tuned resonator circuits exhibit nonlinear effects, like saturation and frequency shifts, even at low radio frequency (RF) power levels. These performance changes depend on circuit design and operating conditions.
Area of Science:
- Electrical Engineering
- Electronic Circuit Design
Background:
- Varactor-tuned resonators are crucial components in oscillators, particularly for achieving low phase noise.
- Understanding their performance under varying radio frequency (RF) power levels is essential for reliable circuit design.
Purpose of the Study:
- To investigate the impact of RF power levels on the performance of various varactor-tuned resonator circuit topologies.
- To analyze the onset and characteristics of nonlinear behavior in these circuits.
Main Methods:
- Development and optimization of S-parameter and PSPICE models for varactors.
- Analysis, simulation, and experimental measurements of series and parallel resonator circuits in unbalanced and balanced modes.
- Systematic variation of RF power levels, bias voltage, and circuit parameters (Q0, QL/Q0).
Main Results:
- Nonlinear operation, including saturation and resonant frequency lowering, observed at low RF power levels (-8 dBm typical).
- Squegging phenomenon noted under specific modified bias conditions.
- Nonlinear effects found to be dependent on unloaded Q (Q0), loaded to unloaded Q ratio (QL/Q0), bias voltage, and circuit configuration.
- Close correlation between analysis, simulation, and measurement results.
Conclusions:
- Varactor-tuned resonator circuits are susceptible to nonlinear effects at unexpectedly low RF power levels.
- The study provides a comprehensive understanding of these nonlinearities, crucial for designing high-performance oscillators.
- Accurate modeling and experimental validation confirm the predicted nonlinear behaviors across different circuit configurations.
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