Effects of switching power converter nonidealities in Envelope Elimination and Restoration technique

The Envelope Elimination and Restoration (EER) technique theoretically allows implementation of linear highly efficient RF Power Amplifiers, as required for next generation digital communications. One of the key remaining challenges for a successful implementation of the EER technique is the efficient implementation of the switching power converter in charge of amplifying the baseband envelope signal, since bandwidths in the order of several MHz are expected for the envelopes to be tracked, hence requiring very high switching frequencies and thus compromising efficiency. This work investigates the feasibility of the EER technique by studying the impact of the nonidealities associated to the switching power converter, namely its bandwidth and ripple, upon the overall polar amplification EER scheme. Considering a two-tone test input signal, a design space exploration of the distortion associated to both nonideal effects is evaluated in terms of the output spurious-free dynamic range (SFDR). Design criteria for the optimum filtering characteristic and phase compensation between polar paths are derived. The work concludes by exploring the extension of switching power converter design criteria for an actual CDMA modulation signal.