Multi-Band Configurations of Stub-Loaded Slotted Rectangular Microstrip Antennas

Triple-band rectangular microstrip antennas using combinations of an open-circuit nearly-quarter-wavelength stub, a resonant U-slot, and a pair of rectangular slots are proposed. A new configuration for a tour-band antenna has been realized by cutting two half U-slots inside a stub-loaded rectangular microstrip patch. The multi-port network models for these antennas are also proposed, which help in analyzing the mode distributions at various frequencies. The multi-band response has been experimentally verified, and close agreement was obtained among the simulated, measured, and theoretical results.