A 200 MHz Bandwidth GaAs Switch-Mode Supply Modulator

Abstract

We report a wide-bandwidth and high-efficiency supply modulator for an envelope tracking power amplifier. We fabricated a GaAs switching power amplifier monolithic microwave integrated circuit (MMIC), the switching frequency of which is 2 GHz, and measured its performance as a supply modulator. A delta-sigma modulation is used to generate digital input signals for the MMIC. To reduce the switching loss, we added an extra feed-back path to a conventional delta-sigma modulator from the output of the comparator to the input of the accumulator. The supply modulator shows a switching efficiency of 66% and an average output power of 30.5 dBm with a 200 MHz bandwidth orthogonal frequency division multiplexing (OFDM) envelope signal.