A Highly Miniaturized Loop Excited Quasi-Yagi Antenna with High Front-to-Back Ratio

A multi-band Quasi-Yagi antenna based on loop excitation is presented with 68% miniaturization, which is achieved using loop meandering and a novel defected ground structure (DGS), targeting the 2 GIlz band. It has a minimum measured -6 dB bandwidth of 249 MHz (0.780-1.029 GHz) in the lower band and 286 MHz (1.932-2.218 GHz) in the upper band covering several LTE bands. The proposed antenna ensures very good Yagi-Uda performance in terms of front-to-back ratio (FBR) and cross-polarization. It has a very high FBR of more than 20 dB with a ground plane width of only 7mm, and has very low cross polarization of -29.3 dB. The gain of the proposed antenna is around 6 dBi, directivity is 8.2 dB, and efficiency is 73%. The size of the miniaturized model is 60 x 50 x 0.8 mm(3).