Optimized envelope tracking power supply for Tetra2 base station RF power amplifier

An ultra-fast tracking power supply (UFTPS) for envelope tracking in a 50 kHz 64-QAM Tetra2 base station power amplification system is demonstrated. A simple method for optimizing the step response of the PID+PD sliding-mode control system is presented and demonstrated, along with a PLL-based scheme for locking the switching frequency to an external clock. High UFTPS efficiency (up to 95%), very low ripple (5 mV_pp) and a fast step response (10 mus) are obtained from a single-phase buck converter with a 4^th-order output filter. This ripple performance is demonstrated to be critical in the considered application. Also demonstrated is the effect of non-zero UFTPS output impedance on envelope tracking performance. At 13 W average (156 W peak) RF output, a reduction of DC input power consumption from 93 W (14% efficiency) to 54 W (24% efficiency) is obtained by moving from a fixed RF power amplifier supply to envelope tracking.