Four-Arm 2nd Mode Equiangular Slot Spiral Antenna with Infinite Balun Feed

N.A. Stutzke and D. Filipovic (USA)


Antennas and antenna arrays, microstrip antenna, slot antenna, spiral antenna.


The design and performance of a 4-arm slot spiral antenna operated in the 2nd (split-beam) mode is presented. The antenna combines Archimedean and equiangular spiral geometries to allow fabrication of a dual-Dyson balun feed with relatively short cables. The required feed network for 2nd mode operation is much simpler than for a 4-arm printed strip or wire spiral antenna and the number of ports is cut in half. The proposed antenna is simulated with a Finite-Element Boundary-Integral (FE-BI) code and the results are verified experimentally. In general there is good agreement between numerical and measured results. During fabrication the coax to slotline transitions at the feed points were offset from the geometric center. The main effect is deteriorated omnidirectionality. Reasonable performance over a 3:1 bandwidth is achieved, but could be improved by better fabrication of the feed region.

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