A low-power FSK modulator using fractional-N synthesizer for wireless sensor network application

A low-power fractional-N synthesizer is designed for direct modulation transmitter at 2.40-2.50GHz range using standard 0.18mum CMOS. The synthesizer is fully implemented on-chip for integrated low data rate wireless sensor network (WSN) application. The data rate is as low as 10kbit/s. Phase noise of -93dBc/Hz at 600kHz offset is measured for the synthesizer. The active area is 0.8 times 0.8mm
²
, with total power of 8.0mW from a single 1.8V supply