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.