A 6.5-GHz energy-efficient BFSK modulator for wireless sensor applications

A 6.5-GHz FSK modulator suitable for low power wireless sensor network is presented. The energy efficient modulator employs closed-loop direct VCO modulation to achieve high data rate, multistage variable loop bandwidth technique for fast startup time and /spl Sigma/-/spl Delta/ for reduced power consumption in the synthesizer with fine resolution in frequency channel selection. The modulator, implemented using 0.25-/spl mu/m CMOS, achieves 20-/spl mu/s startup time with an effective data rate of 2.5 Mb/s while consuming 22 mW.