Multi-band base station antenna with compact microstrip resonant cell filters

A wide bandwidth multi-band antenna is designed and tested. The design is based on a dual-band patch antenna with the incorporation of microstrip band-stop filters. The antenna consists of two L-shaped probe patch antenna elements operating at different frequency bands. Two compact microstrip resonant cells are connected to the microstrip feed line to stop the transmission of higher frequency signals into the lower frequency detecting patch. As a result, the impedance bandwidths of the elements are wide enough to allow coverage of all the frequency ranges used in mobile communications; namely, five: CDMA800 (824 similar to 896 MHz), GSM900 (870 similar to 960 MHz), GSM 1800 (1710 similar to 1880 MHz), CDMA1900 (1850 similar to 1990 MHz) and UNITS (1920 similar to 2170 MHz).