Performance of MF-MSK Systems with Pre-distortion Schemes

Efficient RF power amplifiers used in third generation systems require linearization in order to reduce adjacent channel inter-modulation distortion, without sacrificing efficiency. Digital baseband predistortion is a highly cost-effective way to linearize power amplifiers (PAs). New communications services have created a demand for highly linear high power amplifiers (HPA's). Traveling Wave Tubes Amplifiers ( TWTA ) continue to offer the best microwave HPA performance in terms of power efficiency, size and cost, but lag behind Solid State Power Amplifiers ( SSAP's ) in linearity. This paper presents a technique for improving TWTA linearity. The use of predistorter (PD) linearization technique is described to provide TWTA performance comparable or superior to conventional SSPA's. The characteristics of the PD scheme is derived based on the extension of Saleh's model for HPA. The analysis results of Multi-frequency Minimum Shift Keying (MF-MSK) in non-linear channels are presented in this paper. key words : HPA, Nonlinear distortions, Saleh model, AM/AM and AM/PM, Pre-distortion, MF-MSK.