Multi-band stub loaded square ring microstrip antennas

The square ring microstrip antenna is a compact variation of square microstrip antenna and it is realized by cutting the slot in the center of the patch. The multi-band microstrip antenna is realized by placing the open circuit stub on the edges of the patch. The stub offers capacitive or inductive impedance around the resonance frequency of the patch and realizes dual frequencies. In this paper, the multi-band frequency response of the stub loaded square ring microstrip antennas is studied. Also the multi-port network model for these antennas is proposed, which helps in analyzing the voltage distributions at various frequencies. These voltage distributions are in good agreement with the current distributions generated using the IE3D software.