Gain Augmentation of a Triple Notched Ultra-wideband Antenna using Compact Uniplanar Frequency Selective Surface for Ground Penetrating Radar

A simple structured, compact ultra-wideband (UWB) circular disk monopole antenna of dimension 35 x 30 x 0.8 mm(3) that offers wide bandwidth from 2.64 to 9.36 GHz with sharp triple notch bands at 3.28-3.84, 5.08-5.44, and 5.62-6.06 GHz is integrated to the single-layer UWB frequency selective surface (FSS) that has unit cell dimension of 0.1136 lambda(L) x 0.1136 lambda(L) only where lambda(L) signifies the lower band-edge of UWB. Sharp triple notches are employed by embedding split-ring slot on circular patch and implanting dual circular split-ring resonator pairs at the backside of feed. Addition of FSS layer does not affect the antenna impedance band and offers significant antenna gain improvement by 2-4 dBi in the pass bandwidth with maximum gain of 8 dBi at 8.5 GHz. The antenna also provides high average radiation efficiency of 80%, improved radiation in the broadside direction and consistent group delay response in its pass band when integrated to the FSS layer. Working capability of proposed antenna-FSS structure is evaluated in proximity of soil test bed by keeping thin aluminum sheet at different buried levels. Adequate VSWR profile, linear transfer function response, and consistent group delay response in pass band ensure the eligibility of proposed antenna to work for ground penetrating radar.