This paper presents the design of compact Tapered Slot Antennas (TSAs) for application in an Ultra Wide Band (UWB) microwave imaging system. In the initial step, a conventional size-reduced TSA with an exponential taper for 3.1-10.6 GHz band is designed. From the radiation pattern analysis, it is found that this antenna exhibits poor directivity in the lower part of UWB. To overcome this shortfall, two modifications are investigated. One includes corrugations and the other one elliptical cuts on sides of the initial TSA. It is shown that the modified TSAs feature improved directivity while their UWB impedance characteristics are similar to the original TSA. The TSA with corrugations exhibits an almost constant directive radiation pattern across UWB. However, its gain oscillates with frequency leading to a pulse distortion. Therefore the size-reduced TSA with elliptical cuts in conducting sides looks to be the most attractive choice with respect to both directive properties and distortionless pulse transmission.
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