Abstract-A new wideband and compact bandstop filter using one dimensional (1-D) mushroom-like electromagnetic bandgap (EBG) structures is proposed in this paper. Although the proposed structure can not be fabricated as easy as defected ground structure (DGS) filters, it has several winning features such as more compactness, better characteristics and no backward radiation. A 5-cell 1-D mushroomlike EBG filter is compared with 5-cell and 9-cell circular DGS filters. The 1-D mushroom-like EBG filter is found to be more compact as it requires fewer cells for the same characteristics and also as it has 0.44 times shorter cell length. The proposed EBG filter has a 10-dB bandwidth of 39% while the 5-cell and 9-cell DGS filters have 10-dB bandwidth of 20% and 27%, respectively. Also, the 1-D mushroom-like EBG filter is studied for various number of cells and compared with a two dimensional (2-D) structure. The simulated and measured results are found to be in good agreement.

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Abstract:In this paper, a wideband dual rectangular loop antenna over an EBG surface is proposed for low profile wireless applications. A low frequency mushroom-like EBG surface is used as the antenna ground plane. In comparison with a PEC ground plane, design of antenna above an EBG ground plane results in 60% reduction of the structure thickness. The investigated antenna is designed for circular polarization. It is shown that the axial ratio bandwidth (< 3 dB) and return loss bandwidth (< 10 dB) of the dual rectangular loop antenna above the designed EBG surface are 18% and 14%, respectively. The simulated and measured results are in good agreement.

The removal of ground surface influence from ground penetrating radar (GPR) signals in shallowly-buried objects is of great importance. The ultra-wideband (UWB) radar is a solution which uses short pulse to distinguish ground surface from shallowly-buried objects. In this paper, a novel method optimizes bandwidth based on designing a Gaussian signal. Experimental results confirm the proposed method efficiency.

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