Analysis of microwave MESFET power amplifiers for digital wireless communications systems

The analysis of microwave MESFET power amplifiers (PAs) for digital wireless communications by using the hybrid Volterra-series method is presented in this paper. Compared with the traditional approach in the pure frequency-domain operation, the hybrid method has the advantage of fast computation for the continuous spectral signals with the same accuracy. The major modification is the equivalent baseband formulations in the time domain for the digital modulation signal, and the frequency-domain treatment with the nonlinear system via Volterra-series expansion. The MESFET two-dimensional current model is utilized and detailed current expressions are given to account for the gate-drain cross-term effects, while the nonlinear capacitors are also considered to describe the MESFET nonlinear characteristics completely. Circuit-level simulation yields the output modulation signal parameters with the measured data confirmation. System performance degradations due to nonlinear distortions of the MESFET PA are also performed for the communication link with the additive white Gaussian noise channel model. These results would be very useful in PA designs for digital wireless communications systems.