Abstract: The author designed a superimposed elliptic ring tri-frequency monopole slot antenna and analyzed the effects of the size 
change of elliptic ring on the antenna performance. The antenna consisted of a superimposed elliptic loop feed terminal, coplanar waveguide feeder and rectangular wide spot floor, and coplanar waveguide was used to feed the antenna. The results show that the designed antenna has trifrequency characteristics, effective working bandwidths are 3.2—3.8 GHz, 5.1—6 GHz and 7.8—12 GHz, the size is 25 mm×25 mm, the radiation characteristics and gain characteristic are good, so it is suitable for small multiband wireless communication system of integrated WiMAX,WLAN and X bands.

Key words: superimposed elliptic ring, tri-band, slot antenna