Design and Simulation of Digitally Tuned Class C Voltage Controlled Oscillator with Enhanced Phase Noise Characteristics

In this paper a novel class C voltage controlled oscillator (VCO) is presented. The presented structure reveals proper starting time characteristics, lower phase noise, higher oscillation amplitude and lower consumption power. Simultaneous application of digitally tuned Varactor diode and 4th order tank circuit improve phase noise characteristics of the VCO. Amplitude feedback mitigates the phase noise and power consumption of the structure. The presented VCO oscillates in 3.2GHz-4.2GHz frequency range with the bais voltage of 0.5V-1V. For robustness analysis of the circuit against process, voltage, and temperature variations (PVT), phase noise comparison for FF@-40°C and SS@85°C technology corners, in addition to TT@25°C, are simulated for offset frequency of 1MHz. Additionally, for estimation of non-ideality effects of the circuit on frequency range variations, Mont Carlo simulations with 50 samples is performed. It is assumed in this simulation that capacitors and inductor have Gaussian distribution with ±5% and ±10% variation range, respectively. The VCO is implemented with 180nm TSMC CMOS technology and is simulated with the ADC commercial software.