An Inverted Cavity-Backed Tri-Band Slot Antenna

A compact design for tri-band cavity-backed slot antenna is presented in this paper. The slot antenna is fed at a single port by a microstrip power distributing network printed on the top of one substrate for 900 MHz, 1800 MHz and 2450 MHz bands, respectively. With the use of ridged slots backed by three rectangular cavities recessed in the same conducting plate, a compact design is realized for a tri-band antenna. A prototype is fabricated and tested in an anechoic chamber. The measured 10 dB return loss bandwidth of the slot antenna is 17% for 900 MHz band, 17% for 1800 MHz band and 15% for 2450 MHz band, respectively. The measured gains are 6.27 dBi, 6.7 dBi and 8.7 dBi at 900 MHz, 1800 MHz and 2450 MHz respectively.