Travelling Wave Mechanism and Novel Analysis of the Planar Archimedean Spiral Antenna in Free Space

While Archimedean spiral antennas were invented a half-century ago, only self-complementary impedance can be evaluated directly from the Babinet’s principle. This paper examines the effects of metal width and arm spacing on printed spiral’s input impedance. A model is proposed based on examination by decomposition of planar spiral. A closed-form expression for the input impedance of Archimedean spiral antenna is obtained by evaluating the proposed model with conformal mapping techniques. Full-wave numerical simulations, Babinet’s principle and a fabricated antenna demonstrate the accuracy of the proposed model.

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