Input impedance and bandwidth characteristics of a stacked microstrip antenna consisting of an annular slot and a circular patch

The authors present the results of an experimental investigation of the input impedance and bandwidth characteristics of a two-layer element consisting of a resonant annular slot electromagnetically coupled to a circular patch (RASEMCP). The proposed element is smaller than conventional patch radiators; therefore, there is more space on the array free to incorporate supporting microwave circuitry. Contactless electromagnetic coupling is used to couple the element to the feedline, thereby reducing spurious radiation from the feed network. The RASEMCP combines the attractive properties of the resonant annular slot with the well known advantages of stacked configurations, resulting in a wideband, versatile element, most suitable for high-performance array applications.<>