Active MMW microstrip antenna

Gunn diode oscillators coupled with a log-periodical microstrip antenna, were experimentally studied at frequencies 25-60 GHz. A microstrip antenna was mounted on a dielectric plate with a thickness of about a quarter of wavelength. The backside of the dielectric plate was metalized. Generated power was measured as 5 mW, that was more than 50% of maximum output power generated with the same diode, mounted into the metal waveguide cavity. The oscillation regime varied from single-mode to a noise-like one depending on the dielectric thickness and could be synchronized by an external signal. Such a quasi-optical performance of the Gunn-diode oscillator is feasible for power combining in the open resonator that is essentially promising for applications at millimetre waves.