Design and Operation of Dual/Triple-Band Asymmetric M-Shaped Microstrip Patch Antennas

Novel designs for compact dual/triple-band microstrip antennas are proposed with an asymmetric M-shaped patch. The designs utilize vias on the longer arm of the patch for the purposes of compactness and separating of the operational bands. As the two resonant frequencies of antenna 1 are related to certain parts of the patch, one resonant frequency can be flexibly tuned with little effect on the other. A prototype of antenna 1 operating at 2.44 and 5.77 GHz is fabricated and measured. It has a low profile of 0.016 λr1, where λr1 is the wavelength of the first resonant frequency fr1 = 2.44 GHz at free space, and a compact patch size of 0.195 λr1 × 0.177 λr1. The antenna also presents low cross polarization and symmetrical patterns in both E- and H-planes. Finally, a triple-band antenna (antenna 2) with enhanced bandwidth is designed.