On quantifying the benefits of SSPA linearization in UWC-136 systems

Abstract

A novel comparative analysis of the benefits brought by different degrees of linearization to offset the modulation fidelity (MF) and spectrum regrowth impairments caused by solid-state power amplifier (SSPA) nonlinearity, as measured by error vector magnitude (EVM) and adjacent channel power ratio (ACPR) performance for TIA/EIA Universal Wireless Communication standard UWC-136 signals, are quantified. New results are presented showing the benefits of even modest levels of linearization but also that such benefits may be easily eroded at a receiver by the adjacent channel interference (ACI) in certain circumstances. An equation expressing the incremental MF deterioration experienced by a wanted channel (WC) signal, at its receiver, due to ACI arising from signals in the immediate upper and lower frequency channels, and as a function of adjacent channel (AC) to WC power differential, where signals are subject to different degrees of linearization, is presented. Typical SSPA characteristic values for the equation constants in the cases of one and two immediate AC signals are derived from simulation results. Interesting new results and conclusions relevant to the drafting of harmonious ACPR-EVM specifications and on the advisability of the inclusion of linearization schemes in transmitters, in the context of the UWC-136 system, are presented.