More Practical Intermodulation Distortion in Envelope Elimination and Restoration RF Power Amplifiers

The envelope elimination and restoration (EER) technique used to design RF power amplifiers (PAs) is a dominant method when average efficiency is primary goal for signal with high peak-to-average ratios. The intermodulation distortion (IMD) products of EER RF PA mainly depend on two parameters, which are the finite envelope modulator bandwidth and differential delay between envelope signal and phase signal. This paper derives analytic relationship between IMD levels and above two dependent parameters rather than relationship between IMD levels and each of both parameters, where the latter has been widely cited to this day. By comparison, the expressions derived in this paper are much more close to laboratory measurements than Raab's, and can avoid the ill-condition when the differential delay approaches to zero. Using this paper's contour map in regard to IMD levels, designers can easily choose proper design parameters.