Envelope Tracking Power Amplifier Using Short-Time Fourier Transform

A new power amplifier (PA) efficiency enhancement technique using short-time Fourier transform (STFT) in envelope tracking (ET) topology is introduced. The proposed technique produced a time-frequency matrix that illustrated the signal spectrum at each time frame. The applied filter was made time variant by setting a threshold for the preserved power percentage at each time frame. The technique gave full control over the tradeoff between bandwidth (BW) reduction and power consumption efficiency and provided a significant BW reduction over pure ET. The proposed method was demonstrated on a 37 dBm, 40-MHz long-term evolution signal at 2.4 GHz, using 65 W 3-dB compression-point GaN PA. The resulting efficiencies were 38.6% [16-quadrature amplitude modulation (QAM)] and 41.9% (64-QAM).