Computer simulation of solid-state amplifiers

Modeling and computer simulation of an L-band class-C transistor amplifier has been performed to determine its AM/AM and AM/PM characteristics. A state-variable representation was developed leading to nonlinear first-order differential equations which were solved by using a standard software subroutine for a single sinusoidal input with various amplitudes. The AM/PM and AM/AM characteristics obtained from the computer model show good agreement with laboratory measurements on a similar amplifier. These nonlinear characteristics were used in the CHAMP time-domain simulation program to determine the spectrum 're-growth' of single, filtered, conventional and offset QPSK and minimum shift keyed (MSK) signals after amplification. A comparison with available laboratory results again shows good agreement between the simulated (computer) and the laboratory (hardware) results.