An all-digital CMOS 915 MHz ISM band 802.15.4 / ZigBee transmitter with a noise spreading direct quantization algorithm

This paper presents an all-digital CMOS class-D transmitter system for the 915 MHz ISM band using 802.15.2/ZigBee standards. A novel noise spreading quantization algorithm which derives the digitally modulated amplifier input is presented. This new algorithm requires fewer DSP cycles than delta-sigma approaches, while still maintaining high amplifier efficiency and meeting spectral specifications. The entire transmitter is easy to integrate into modern submicron CMOS processes. The power amplifier achieves a peak drain efficiency of 57%, while the overall transmitter system achieves a DC/data-to-RF efficiency of 22%. The CMOS power amplifier is capable of a maximum power output of 18 mW while meeting 802.15.2 specifications.