High Stability Coplanar Oscillators

The feasibility is demonstrated of various kinds of coplanar oscillator stabilized by a high Q dielectric cavity; their performances are comparable with the ones obtained with microstrip circuits. An X-band coplanar oscillator is described with a frequency vs temperature stability lower than ±.2 ppm/°C over 100°C temperature range; a loaded quality factor QL¿3500; pushing figure of about 8 ppm/V; and noise characteristics particularly appealing. The coplanar approach allows to reduce overall oscillator size, and place directly over the cavity a monolithic chip (including the active portion of the L.O.) avoiding unwanted L.O. couplings anywhere in the circuit.