The MultiMatch S-parameter Module can import S-parameters from Touchstone^TM "*.s2p" files. It can also be used to fit equivalent circuits to the small-signal parameters specified for FETs, HEMTs or bipolar transistors.

Models are fitted by initialization and optimization. Package parasitics can be specified and can be included in the optimization. Any of the variables can be specified to be fixed or constrained when the optimization is done.

The model specified or fitted is used in the Device-Modification Module to calculate a set of parameters (power parameters) to map the external transistor voltages to the intrinsic voltages and to map the intrinsic output current to the intrinsic voltages. By using these parameters, the intrinsic load-line of the transistor can be controlled easily and the power performance can be estimated for Class A and, to some degree, also class B stages (Power Options). The effect of any feedback or loading added in the device-modification section can also be determined. Linearity is assumed when the power parameters are calculated.

Power parameters for models not supported by  MultiMatch can be calculated by using the capabilities provided in the Analysis Module (linear models only). The S-parameter module option to use a set of user-specified power parameters are relevant in this case.

Interpolation capabilities (linear, and three or four point spline curve fitting) and editing capabilities are provided. The model fitted should be used to extrapolate the data. It should also be used for interpolation when sufficient data are not provided.

The S-parameters and noise parameters specified or imported can be transformed to those corresponding to different configurations (common source/emitter; common gate/base; common drain/collector). Any power parameters specified are also modified when the configuration is changed.

The default source or load impedance for the amplifier is assumed to be 50 Ohm. Complex terminations can be specified for the input stage and the output stage in the S-parameter Module.

The potential performance of a transistor can be evaluated and s₁₁ , s₂₁ , s₂₂ , 1/s₁₁^* , 1/s₂₂^*, the optimum noise impedance, the noise figure and the VSWRs can be displayed graphically.

Artwork vectors defining the position and orientation of the connections to be made to the transistor must also be defined in the S-parameter module. The defined values are displayed graphically for verification purposes.

If the power performance is of interest, the parameters defining the four boundary lines on the I/V- curves (the pulsed I/V curves measured from the dc operating point of interest should be used) must also be defined in the S-parameter module. The defined boundary lines are also displayed graphically for verification purposes.

A MultiMatch circuit file can be created for the transistor of interest. If a model was fitted or  specified for the transistor, noise parameters can also estimated for the transistor when this is done (Fukui and Cappy equations). The estimated noise parameters are appended to the circuit file created. A nodal description of the model is also written to the file when a model was specified or fitted.

Load-pull data for power transistors can be converted into an equivalent set of unilateral S-parameters in order to allow synthesis of power amplifiers by following the normal MultiMatch synthesis procedures. Feedback should not be used when this is done.