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An inward-fed two-arm Archimedean spiral antenna is proposed, which integrates a stripline feed network into one of the spiral arms. A broadband stripline tapered impedance transformer conformal to the spiral's winding provides a novel matching network between the input impedance of the spiral and the characteristic impedance of the stripline. The Dyson-style balun at the spiral's center converts the guided stripline mode to the radiating spiral mode. The transformation from a gap-fed design to a stripline-fed design is provided to illustrate the design process. Measured and simulated results for a probe-fed design operating from 2 to over 20 GHz are provided to illustrate the synthesis and performance of a demonstration antenna.

Abstract-This paper presents an analytical formula to evaluate even-and odd-mode characteristics of infinitely parallel coplanar waveguides (CPW) with the same dimensions in each CPW, given name as periodic coplanar waveguides (PCPW). The analysis yields a closed-form expression based on the quasi-TEM assumption and conformal mapping transformation. Calculated results show that both the even-and odd-mode characteristic impedances are in good agreements with the results generated by numerical solvers and available experimental data. The results are important especially for highly demand on miniaturization of circuit design to place multiple CPWs in parallel.

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