A multiband microstrip dipole antenna

We have developed a hybrid multiband antenna that integrates a loop antenna into the feed structure of a planar dipole. The planar dipole is tuned to handle GSM and 802.11b WLAN signals while the fundamental and higher order modes of the loop antenna can be used for 802.11a WLAN communications. We first introduce the basic design principles of the planar dipole, and then describe the techniques used to package a loop antenna with a planar dipole using a parallel stripline structure. Measured reflection coefficients comply with simulation predictions and exhibit low return loss in the desired communication bands. Measured radiation patterns reveal an omnidirectional coverage in the lower bands and a wide coverage in the higher band. Such an antenna configuration is suitable for portable devices that integrate multiple wireless communication systems.