A miniaturized dual wide-band loop excited quasi-yagi antenna using a defected ground structure

Abstract

A dual wide-band Quasi-Yagi antenna with loop excitation and it's 52% miniaturized model using novel defected ground structure (DGS) is presented, targeting the 2 GHz band. The proposed dual wide-band antenna system has a measured bandwidth of around 1 GHz in both bands that cover 1.45–2.55 GHz and 3.707–4.71 GHz bands including GPS, GSM/EDGE, UMTS/HSDPA, Bluetooth, Wi-Fi, and WiMAX bands. The miniaturized version has a measured bandwidth of 1.5 GHz in the lower band while 620 MHz in the upper band. The size of the antenna without DGS is 78×117.5 mm2. It has a gain of 5.94 dBi, directivity of 6.21 dB, and front-to-back ratio (FBR) of 9.5 dB. The miniaturized antenna has a size of 55×80 mm2. It has a gain of 4.23 dBi, directivity of 4.33 dB, and FBR of 8.5 dB. Both designs have efficiencies around 92%. The superior performance of the antenna without DGS in terms of FBR, gain, and directivity, comes at the cost of 52% larger size.