Multi-Octave VHF Transmitter Using Outphasing Modulator and Digital PA

A novel multi-octave VHF transmitter using outphasing modulator and digital power amplfier(P A) is proposed and demonstrated. The digital outphasing signals are generated using a high speed analog comparator and a universal I/Q modulator, and then a pair of digital PAs are adopted to amplify the modulated signal, which reaches about 2.5W with a bandwidth from 20MHz to 225MHz. Finally, a wideband RF transformer is used to combine the two paths digital P A. The prototype achieves - 40.2 adjacent channel leakage ratio (ACLR) and 1.56% error vector magnitude (EVM) for a 64QAM modulated signal with 5.52 dB P APR at 4 MHz bandwidth (BW).