Effect of cylindrical cavity enclosure on resonance frequency of annular ring microstrip antenna

The effect of cylindrical metallic enclosure on the resonant frequency of a suspended annular ring microstrip antenna (ARMSA) is investigated using HFSS simulation software and theoretically calculated using modal expansion cavity model and circuit theory concept. Theoretical result shows close agreement with simulated results. Variation in resonant frequency with air gap height and inner patch radius is also studied. The patch miniaturization of about 15% is achieved using cavity backed ARMSA.