Phase Noise comparative analysis of LC oscillators in 28-nm CMOS through the Impulse Sensitivity Function

Comparative Phase Noise (PN) analysis of Hartley, Colpitts and Cross-coupled LC oscillators at 10 GHz in 28-nm CMOS technology is reported. The results of the PN direct plots in the Cadence-SpectreRF design environment are compared with the results obtained by the Impulse Sensitivity Function (ISF). The steps for deriving accurately the ISF are reported and discussed. The results show a very good agreement in a set of conditions, and confirm that the LC cross-coupled differential oscillator exhibits superior PN performance with respect to Colpitts and Hartley, and also that Colpitts exhibits slightly superior performance with respect to Hartley.