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 fourarm 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.