85195A IC-CAP Root Diode Model Generator

Note: Model number 85195A has been obsoleted; however, the feature/capability is now included in the W8532EP/ET.

The information below is provided for reference only.

The Keysight Root diode model software is data-based, rather than physical or empirical. It generates a device-specific large-signal model directly from measured DC and small-signal S-parameter data, that accurately represents the terminal characteristics of the device. The model is constructed without circuit simulation or optimization (although simulation may be used in the verification process).

Use of S-parameter as well as DC data results in a model that can accurately predict nonlinear device performance. The Keysight Root diode model predicts device performance as a function of bias, power level, and frequency. It allows circuits to be simulated containing devices for which measured data exists but for which there are no good physical or empirical models. The Keysight Root diode model can be used for varactor and Schottky diodes, in a two-port or one-port configuration.

Based on device compliances you provide in software, the data acquisition system calculates the safe operating range for the device. Within this safe operating range, it takes data adaptively at multiple bias points, depending on the specific nonlinearities of the device under test. Measurements are densely spaced in the most nonlinear regions, such as at the onset of breakdown and forward conduction, and less densely spaced in the reverse-biased region.

The data acquisition system sets the DC bias levels and controls the system hardware to take the DC and S-parameter measurements, based on your inputs. The model generator processes the measured data and generates the lookup table required by a circuit simulator. It produces a data file that is directly readable by the Keysight RF and Microwave Design System (MDS). Both IC-CAP and MDS can be run simultaneously in the X Windows environment. During a simulation, the tabular state-function data from the generated Keysight Root diode model is interpolated using spline functions to emulate the terminal characteristics of the device.

The model includes a link to the MNS microwave nonlinear simulator, to allow verification of the model in IC-CAP