Directly coupled multiple resonator wide-band microstrip antennas

Three new configurations for increasing the impedance bandwidth of the microstrip patch antennas are described. In these configurations, additional resonators are directly coupled through short sections of microstrip line to the radiating edges, nonradiating edges, and all the four edges of the rectangular patch antennas, respectively. Green's function approach and segmentation method are used for the analysis. The experimental results are in reasonable agreement with the analysis and impedance bandwidths of 548 MHz, 605 MHz, and 810 MHz are obtained for these three configurations, respectively in
S
-band (substrate thickness = 0.318 cm and
\epsilon_{r} = 2.55
). The variation in the radiation pattern over this impedance bandwidth is discussed.