A low profile dual-circularly polarized printed ring-slot
antenna with a small footprint, which radiates above an open cavity
loaded with an artificial magnetic conducting reflector, is presented.
The feed network consists of two T-shaped capacitive feed structures
connected to a miniaturized hybrid branch-line coupler. Experimental
results for a final antenna design (with a size of 0.5λ0 × 0.5λ0 ×
0.057λ0) show a 4% isolation bandwidth between the two ports of the
dual-circularly polarized antenna and a maximum gain of approximately
6.8 dBic. Good front-to-back ratios and low cross-polarization were
achieved. These very compact and low profile antennas are suitable
for 2.4 GHz wireless local area network (WLAN) communication systems.