A 2.4-GHz 18-mW Two-Point Delta-Sigma Modulation Transmitter for IEEE 802.15.4

A 2.4-GHz two-point modulation transmitter (TX), designed for IEEE 802.15.4 (ZigBee) applications, is reported in this paper. The TX is based on a delta-sigma fractional-/V PLL to reduce chip area and power consumption. In addition, the chosen architecture prevents the transmission data rate from being limited by the PLL bandwidth. To alleviate the non-linearity problems of a conventional fractional-N PLL, linearization techniques are adopted. The TX is designed to operate in the 2.4-GHz ISM band, and is capable of delivering a date rate more than 2 Mbps. Implemented in the TSMC 0.18-mum CMOS process, the TX consumes 18 mW under a 1.4-V supply voltage.