A mobile wireless communications device may include a processor configured to generate a baseband signal, a modulator coupled downstream from the processor, a power amplifier coupled downstream from the modulator, an antenna, and a tunable antenna matching network coupled between the power amplifier and the antenna and configured to match an impedance of the antenna and thereby causing a phase change in an output from the antenna. The processor may be configured to provide upstream phase change compensation in the baseband signal for the phase change in the output from the antenna.