Envelope-Tracking Supply Modulator with Trellis Search-Based Switching and 160MHz Capability

Envelope tracking (ET) is in wide use to raise the efficiencies of PAs. We report on the realization of a new envelope-tracking supply modulator (ETSM). A hybrid amplifier (HA) is commonly used, which, in effect, partitions the envelope bandwidth into a low and high subband. An efficient switching buck converter tracks the low band that contains most of the load current. In parallel, an op amp with a Class-AB output stage supplies the current in the high band. Feedback on the op amp servos the total current to the envelope waveform extracted from the baseband modulator (Fig. 1).