(Voltage-Controlled) Oscillators with Ultra-Low Phase Noise

The talk begins with a tutorial-style by introducing different topologies of integrated harmonic oscillators (such as Colpitts, Class-B, Class-C and others) with emphasis on the phase noise generated by thermal noise sources and a comparison on the figure of merit. Then, the fundamental and technological limiting factors to the spectral purity are analyzed and recent circuit solutions to break the phase noise barrier are proposed. Phase noise can be scaled by resorting to the multi-core approach, provided mismatches among oscillators are carefully considered. As an example, a 16-core (voltage-controlled) oscillator demonstrating -130dBc/Hz at 1MHz offset from 20 GHz is presented. A more elegant and efficient approach leverages the series resonance of a tank. The remarkably lower resistance, compared to a parallel resonator, raises considerably the tank’s active power, thus enabling a significant advantage in spectral purity. Two 10GHz BiCMOS VCOs exploiting the concept are showcased. With a minimum phase noise of -138 dBc/Hz at 1-MHz offset from 10GHz frequency, experimental results demonstrate the lowest phase noise ever reported by fully integrated RF oscillators in silicon technology.