Research And Design Of Dual-band Microstrip Antennas

Microstrip antennas are widely used due to its small size, light weight, lowprofile, easy to implement multi-frequency and can be integrated with carriers. Withthe development of wireless communication technology, dual-band and widebandmicrostrip antenna technology has been paid more and more attention.The basic theories and dual-band technologies of microstrip antenna areintroduced, and then two kinds of dual-band microstrip antennas applied toWLAN(Wireless Local Area Network) are designed. In the antennas, dual-band isrealized, where the two resonant frequencies are attained through the radiation patch’slength and width, and the coaxial line is used to feed at the diagonal of the rectangularmicrostrip antenna. By adding a capacitive feed patch in the feed circuit, the firstantenna achieved a good impedance match. In the second antenna, a cuboid grooveon the dielectric substrate is carved and the radiation patch fed by coaxial line locatedat the top of the cuboid groove, which reduced the length of the coaxial probeeffectively, thus achieved a good impedance match. Both of two antennas’ impedancebandwidths can cover the frequency range required by the WLAN’s standard IEEE802.11a/b/g/n.A wideband microstrip antenna is designed by utilizing the microstrip antenna’sdual-band characteristics. Based on the coaxial line feed and single frequency’ssimple rectangular microstrip antenna, the antenna attained dual-band function byadding semicircle at the left and right sides of the rectangular radiating patch, andachieved a good impedance match by carving dual rectangular-shaped slot around thefeed point. Two resonant frequencies can be adjusted by changing the radius of thetwo semicircles, the bandwidth of the antenna can be broaden when the two resonantfrequencies are close to each other. Simulation results show that the antenna’sbandwidth is1.1GHz, and the relative bandwidth is28.6%.