Specifications

Innovative
Applications
Nonlinear waveform
and X-parameter
characterization
(Options 510, 514, 518,
and 520)
High-power design challenges
• Active devices are commonly driven into nonlinear regions, often by design to increase power
efficiency, information capacity, and output power
• Under large-signal drive conditions, active devices distort time-domain waveforms,
generating harmonics, intermodulation distortion, and spectral regrowth
• Current circuit simulation tools that rely on S-parameters and limited nonlinear
behavioral models are no longer sufficient to fully analyze and predict nonlinear
behavior of devices and systems
• Fewer design iterations are
required to meet current
time-to-market demands
S-parameters in a nonlinear world
In the past, when designing systems with high-power amplifiers (HPAs), designers measured
amplifier S-parameters using a vector network analyzer, loaded the results into an RF simulator,
added other measured or modeled circuit elements, and then ran a simulation to predict system
performance such as gain and power-efficiency under various loads.
Since S-parameters assume that all elements in the system are linear, this approach does not
work well when attempting to simulate performance when the amplifier is in compression or
saturation, as real-world HPAs often are. The errors are particularly apparent when simulating the
combined performance of two cascaded devices that exhibit nonlinear behavior. While engineers
may live with this inaccuracy, it invariably results in extensive and costly empirical-based iterations
of the design, adding substantial time and cost to the design and verification process.
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