A 24GHz multi-channel frequency synthesizer in a 0.18µm BiCMOS technology for wireless sensor networks

A 24GHz multi-channel integer-N PLL as part of a 24GHz ISM-band wireless sensor network used for wireless commissioning of light sources (>;1000) in greenhouses is presented. The PLL supports operation across five channels, each at 1Mb/s of datarate in a FSK modulated system. As power consumption is critical for battery lifetime, the synthesizer exhibits a settling time of around 10μs. The PLL contains of a 24GHz LC-VCO, programmable divider, CMOS digital PFD and loop polarity control. The innovative charge pump circuit combines rail-to-rail output range with high output impedance. The IC occupies 2mm² and the power consumption is 21mW from a 1.8/2.5V dual supply voltage.