Tri-band dual circularly polarized planar antenna with defective ground structure for wireless applications

A novel tri-band asymmetric slot with defective ground structure (DGS) microstrip antenna for dual circular polarization (CP) is proposed. By placing a slot with 45° across diagonally at the center of the patch, excites resonant bands with narrow bandwidth and dual CP operation. The main design challenge is to introduce optimized defected element of circular dumbbell shape to enhance the impedance bandwidth with frequency shift operation at all bands. DGS enabled antenna is practically fabricated and simulated. Antenna is compact in size and shows a good quality of CP at two resonant bands and linearly polarized at one band. Structure displays the impedance bandwidth of 8% (2.26–2.45 GHz), 5.45% (3.41–3.6 GHz) and 3.07% (5.12–5.28 GHz). The design also shows 40 and 11 MHz, 3-dB axial ratio bandwidth at lower and middle bands, respectively. Simulated gain for each band is 4.72, 6.2 and 4 dB. Performance of antenna with and without DGS is also studied and compared. This single probe feed proposed antenna remains consistent with good radiation patterns and sufficient antenna gain over the operating bands. Excellent agreement was obtained between measurements and simulations.