Dual-Wideband Box-Shaped Antenna with a U-Shaped Slot
In this paper, a study on the dual-frequency box-shaped antenna is presented. With a 5-branch feeding strip and two plates of shorting strips, the antenna shows broadband and compact property. Then a U-shaped slot is etched for dual-band operation. Simulated and measured results all show that this antenna exhibits dual-wideband characteristic, covering several present wireless communication systems, such as GSM800/900 (824--960 MHz), WLAN11b (2.4--2.5 GHz), WiMax802.16 (2.5--2.7 GHz), and Bluetooth band (2.4--2.8 GHz). The simulated impedance bandwidth (2:1 VSWR) is 21.5% and 37.2% in the lower and higher band, ranging from 790MHz-980MHz and 2.3 GHz--3.35 GHz. Then details of the antenna are described and the prototype is fabricated and tested. A measured bandwidth of 19.8% and 38.9% in the two bands, ranging from 820 MHz--1000 MHz and 2.28 GHz--3.38 GHz, is observed, shown good agreement with simulated results. Moreover, the antenna has a coaxial feed with a compact size of 0.27λ×0.22λ×0.036λ (λ is the wavelength referenced to the lowest edge of the operating band 820 MHz).