The multi-band microstrip antennas are realized by cutting more than one slots at an appropriate position inside the patch or by placing the open circuit stub on the edges of the patch or by using the combination of slots and stub. In this paper, an analysis to study the multi-band response in stub loaded two half U-slot cut rectangular microstrip antenna is presented. The first half U-slot in rectangular patch tunes the spacing between TM10 and TM01 mode frequencies to yield dual frequency response. The second half U-slot further optimizes the spacing between TM10, TM01 and TM11 modes of the patch to yield triple frequency response. The placement of open circuit stub on patch edges further reduces the frequencies of TM11 and TM20 modes of rectangular patch to yield multi-band frequency response. The two half U-slots and open circuit stub re-orients the surface current distributions at first four patch resonant modes, to realize broadside radiation pattern over four frequencies without any variations in the directions of principle planes. The proposed analysis gives an insight into the functioning of slot cut stub loaded multi-band rectangular microstrip antennas and will help to design them at desired frequencies.

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Rectangular Microstrip Antenna Multi-band Microstrip Antenna Rectangular Slot Half U-slot Open Circuit Stub Higher Order Mode