A Pulse-Modulated Polar Transmitter Using Direct Digital Synthesis for 5G NR Mobile Applications

This brief presents a pulse-modulated polar transmitter using direct digital synthesis (DDS) for 5G NR mobile phone applications. In contrast to the conventional radio-frequency transmitter that requires high-resolution digital-to-analog converters (DACs) to maintain signal fidelity, the proposed transmitter only needs high-speed but low-resolution DACs for DDS. A transmitter prototype was developed and tested with a 5G NR 20-MHz bandwidth signal at the carrier frequency of 836.5 MHz. The transmitter achieved the adjacent channel leakage ratio (ACLR) of −31.9 dBc using the 4 GS/s DACs with resolution of just 4 bits without the use of digital predistortion or other linearization techniques.