A Dual-Band Frequency-Tunable Magnetic Dipole Antenna for WiMAX/WLAN Applications

In this letter, a new dual-band frequency-tunable antenna for Worldwide Interoperability for Microwave Access (WiMAX) and Wireless Local Area Network (WLAN) is proposed. The frequency tuning is realized by the insertion of two varactor diodes into the antenna structure. At the resonant frequencies, the antenna behaves like two magnetic dipoles. The antenna is designed and fabricated. Measurements show that the antenna presents two narrow-band resonant frequencies that can be tuned separately. Either of the two bands can be tuned independently by varying the dc bias of the varactors from 0 to 30 V while keeping the other extremely stable. The antenna can cover 230 MHz of WiMAX frequency band (3.28-3.51 GHz) and 560 MHz of WLAN band (5.47-6.03 GHz). The proposed antenna has a considerable importance in wireless communications because of its planar shape, compact size, simple dc feeding network, and the frequency tuning of one band does not have any effect on the second band.