An integrated eight-element antenna array has been proposed for ultra-wideband (UWB) applications. It consists of eight UWB antenna elements and an eight-way binary-tree modified Wilkinson power divider. Any two adjacent elements in the array are connected to each other and share a common side, thus leading to a connected antenna array. Moreover, this arrangement can be utilized to avoid grating lobe level at higher frequencies. Each antenna element comprises a square ring patch and is excited by a tapered balun to achieve low cross-polarization levels. In order to validate the design, a prototype has been fabricated and measured. Both simulated and measured results confirm that the proposed integrated antenna array achieves a good performance of a reflection coefficient below -10 dB from 2.9 GHz to 10.8 GHz, including stable radiation patterns with low side lobe and cross-polarization levels, thus the antenna is promising for applications in UWB imaging systems.
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