Clean Bandwidth Improvement of MPWM Encoding Method for RF All-Digital Transmitter

In radio frequency (RF) all-digital transmitters (ADTs), pulse encoding methods are often used to generate the RF signal of one or several bits, which introduces a large amount of quantization noise (QN). The QN results in a limited clean bandwidth (CBW), which increase the design difficulty of the analog filter significantly. To solve this problem, an optimized mapping pulse width modulation (MPWM) encoding method is presented in this brief. Based on the QN analysis, the concept of noise figure (NF) for MPWM is introduced. Meanwhile, the formulae of the intermedia frequency (IF) and RF QN power in CBW are derived. Then, in the mapping of the IF signal to the RF pulse, the optimized RF pulses are searched by the NF calculation and comparison. Experiments results show that, compared with original MPWM method, the CBW of proposed method is increased by more than 3 times, and it is superior to the other reported approaches.