Designing a novel broadband microstrip antenna with capacitive feed

The microstrip antennas have been widely used in recent years for their good characteristics such as electrically thin, lightweight, low cost and so on. However, the electrical performance of the basic microstrip antenna suffers from a number of serious drawbacks; especially its narrow impedance bandwidth restricts the performance of antennas in ultra- wideband (UWB) applications. To overcome the narrow impedance bandwidth associated with probe-fed microstrip antennas, a novel broadband microstrip antenna element is presented. The small antenna comprises a air cavity in the substrate, a capacitively-fed patch which is attached by coaxial probe, and a cut slot on the edge. The analysis of HFSS shows the broadband operation and low VSWR is obtained by adaptable length and width of the cut slot, air cavity, and feed patch. The simulation indicates its bandwidth is 48% under S11≤-10dB, covering 4GHz~6GHz.