On the use of spiral antenna arrays for short-pulse ultra-wideband applications

Seven-element hexagonal arrays based on two- and four-arm spiral elements are introduced and analyzed in frequency and time domains. Full-wave modeling based on CST Microwave Studio verifies that these arrays can work over 4:1 bandwidth with VSWR<;2.1:1, side lobe level (SLL)<; -10dB, broadside axial ratio <; 2 dB over the most operating bandwidth, appealing scanning capability over wide scan angles, and fidelity factor (FF)> 90% indicating simultaneously good time and frequency domain performances. The benefits of using the four-arm spiral antenna to achieve an array with dual-circular polarization operation and better axial ratio are demonstrated. Also, arrays´ efficiency and the complexity of the feed network of the multi-arm spiral antenna array are investigated and possible solutions are successfully demonstrated.