High-efficiency 400 W power amplifier with dynamic drain voltage control for 6 MHz OFDM signal

In this paper, we present a high-efficiency 400 W power amplifier (PA) for a 6 MHz orthogonal frequency division multiplexing (OFDM) signal with a 10 dB peak-to-average power ratio (PAPR). To improve the efficiency of the PA at a 10 dB backoff from its saturated output power (P_SAT), a dynamic drain voltage control is applied, which supplies two different drain voltages depending on the envelope of the OFDM signal. The PA is fabricated using a 400 W push-pull laterally diffused metal oxide semiconductor (LDMOS) field-effect transistor (FET) for an ultrahigh frequency (UHF) band. The drain current of a single LDMOS FET is 9.5 A at P_SAT. The drain voltages used in the control are set to 40 V and 20 V. Measurement results indicate a power-added efficiency (PAE) in the case of dynamic drain voltage control of 34%, which is 15% higher than PAE at a drain voltage of 40 V. This is the highest output power of a PA with a dynamic drain voltage control to the best of our knowledge.