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Characterizing RF circuits with small-signal S parameters is a well-established practice. However, small-signal S parameters are not sufficient to describe nonlinear circuits with moderate-to-large amplitude signals. So how do you include the nonlinear effects at different amplitudes? You guessed it right! The solution is to use the Large-signal S-parameter (LSSP) analysis.
Large-signal S parameters (LSSPs) are an extension of small-signal S parameters and are defined as the ratio of reflected (or transmitted) waves to incident waves. Since small-signal S parameters are based on the simulation of a linearized circuit, they are independent of the input power. LSSPs include the nonlinear effects at different amplitudes.
The LSSP capability is available for single-tone and multi-tone harmonic balance and PSS Shooting simulations for circuits that translate frequencies.
It is very easy to set up and plot large-signal S parameters. You just need to select the LSSP option available in the hb and pss Choosing Analyses forms. Direct Plot functions are also available to enable plotting of S parameters on a Smith Chart.
For more information on LSSP, you can view the Large-Signal S-Parameter Simulation video on Cadence Online Support. Click the video link now or visit Cadence Online Support and search for the video under Video Library.
Spectre Circuit Simulator and Accelerated Parallel Simulator RF Analysis in ADE Explorer User Guide
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Kamal Kishore Tewari