Simple closed-form expression to estimate the ring ratio of 16-APSK to compensate for distortion in nonlinear systems

The aim of this paper is to estimate the BER degradation at different back-off operating points of a commercial SSPA in 16-APSK modulated systems. Recognising that the device tested presents negligible AM/PM distortion, a simple closed form expression to compensate for AM/AM distortion is identified and verified by simulation. The proposed methodology is validated by the use of the Bessel-Fourier behavioural model for the characterization of the PA.