In this paper, a new cyclostationary nonlinear low-frequency (LF) noise model for field-effect microwave transistors is presented based on the general theory of the technology-independent Charge-Controlled Nonlinear Noise modeling approach. The model definition, experimental extraction, and validation are described. For model parameter identification, the characterization of the device in terms of both LF noise in quiescent operation and its up-conversion into phase noise under large-signal RF oscillating conditions was performed using in-house developed measurement setups. The model is exploited in the design of a C-band monolithic microwave integrated circuit (MMIC) voltage-controlled oscillator (VCO) developed for space applications. The selected technology is a space-qualified GaAs 0.25-μm pseudomorphic HEMT (pHEMT) process. The large-signal technique adopted for the VCO design is also highlighted. Comparisons between measurements and simulations are provided, which show the validity of the design methodology and demonstrate the accuracy of the proposed cyclostationary noise modeling approach for phase-noise large-signal analyses of pHEMT-based circuits. The MMIC exhibits 350-MHz bandwidth at 7.3 GHz, with 14-dBm output power and -86-dBc/Hz single-sideband phase noise at 100 kHz from the carrier.