Sizing of MOS device in LC-tank oscillators

Since previous publications show conflicting results about sizing device, relationship between device size and 1/f
²
phase noise is studied and closed-form equations are derived in order to help designers to size devices in LC-tank oscillators for good phase noise performance. The analysis is divided into two steps. Firstly, periodic noise transfer functions of each VCO noise source to the output of switch FETs are derived, and the impact of sizing on these functions is discussed. Secondly, phase noise equations are derived with these functions. Experiments show that phase noise predicted by the equations agrees with that from simulations.