Power Consumption Reduction in RF Transmitter Using PWM Harmonics

A comprehensive power analysis of the recently introduced Sub-Nyquist RF Pulse Width Modulation (RFPWM), which uses a high-order harmonic of the switching frequency as carrier frequency, is presented in this paper. For this purpose, all the processing stages from baseband to radio frequency were implemented in a FPGA, considering the different filters, interpolation and predistortion blocks used to generate the binary waveform. Each implementation was configured to operate with the same carrier frequency but lowering the switching frequency, thus reducing the dynamic power consumption of the all-digital transmitter in the same ratio. The Sub-Nyquist RFPWM was implemented using an outphasing approach, with a 1.4-MHz 64QAM LTE signal as baseband signal and a carrier frequency of 230.4 MHz. Experimental measurements show an excellent performance in all the cases, achieving ACPRI and ACPR2 values below -39 dBc.