A 5.5mA 2.4-GHz two-point modulation Zigbee transmitter with modulation gain calibration

A 2.4-GHz two-point modulation IEEE 802.15.4 (Zigbee) compliant transmitter is presented. This sigma-delta fractional-N PLL based transmitter is optimized for both low-power and low-cost purposes. A novel closed-loop calibration scheme is proposed to minimize the gain mismatch between two modulation points, which is the main source of error in two-point modulation. Fabricated in a 0.15-mum CMOS process, the proposed transmitter achieves EVM less than 8% for 2-Mchips/s MSK modulated signal and consumes 5.5 mA under a 1.55-V regulated power supply. The core area is 0.8 times 1.1 mm².