Broadband, reduced-size monopoles for wireless data communications

Two new compact, monopole antennas for wireless communications have been developed. The first is a reduced-size, double-tuned monopole antenna. By displacing the feed point of the monopole to the top of the stem, it is possible to incorporate impedance transforming and stub tuning elements directly into the antenna structure, thus providing a reduced-size, double-tuned antenna. The double-tuning improves the in-band return loss of the antenna as well as the out-of-band rejection. The second antenna is derived from a dielectric-loaded, partially-folded, bowtie antenna. This antenna exhibits very broad impedance bandwidth with excellent return loss and passband shape. The antenna is 6.93 cm high and exhibits greater than 10 dB return loss over the frequency range of 750 MHz to 1250 MHz thus covering the AMPS, 915 MHz ISM, and European 900 MHz GSM bands. The antenna is intended for use with multi-function handheld data terminals. Details of the both monopole designs as well as experimentally-determined input return loss data are presented.