NOISE CALCULATIONS AND EXPERIMENTAL RESULTS OF VARACTOR TUNABLE OSCILLATORS WITH SIGNIFICANTLY REDUCED PHASE NOISE

The single-sideband phase noise of varactor tunable GaAs MESFET oscill ators is investigated. Two oscillator circuits with different microstr ip resonator circuits were designed and fabricated, Using a resonator consisting of coupled microstrip lines instead of a single microstrip line, which is a planar monolithically integrable structur, phase nois e is reduced significantly because the quality factor is higher for th e coupled resonator, The phase noise is calculated using a nonlinear t ime domain method, which solves the Langevin equations, describing the deterministic and stochastic behavior of an oscillator by pertubation methods, Calculated and measured phase noise agree within the accurac y of measurements. The very low phase noise of 95 dBc/Hz at 100 kHz of fset frequency is achieved.