A C-band GaAs-pHEMT MMIC low phase noise VCO for space applications using a new cyclostationary nonlinear noise model

This paper describes the design of a C-band MMIC VCO for space applications. It exploits a single device with a microstrip resonator coupled with varactors. The technology is a space-qualified GaAs 0.25-um pHEMT process. The MMIC exhibits 350-MHz bandwidth at 7.3 GHz, with 14 dBm output power and −86 dBc/Hz single side-band phase noise (PN) at 100 kHz from the carrier. Performances are in good agreement with simulations. The active device was characterized in terms of low-frequency noise in quiescent operation and its up-conversion into PN under large-signal RF oscillating conditions, using in-house developed measurement setups. A new compact nonlinear noise model was identified and exploited for PN simulations. The model features cyclostationary equivalent noise generators. Comparisons between measurements and simulations show that the nonlinear cyclostationary modeling approach is more accurate rather than conventional noise models in oscillator PN analyses of pHEMT circuits