Design of spiral antenna using a Vivaldi-shaped balun

Abstract

This paper proposes a design of a spiral antenna using a Vivaldi-shaped balun for broadband matching characteristic with high tolerance to fabrication error and low geometrical complexity. The proposed antenna consists of spiral arms, a Vivaldi-shaped balun, and a ground with a cavity-backed structure. The Vivaldi-shaped balun is connected to the spiral two arms to obtain broad matching characteristics, and the cavity-backed structure is employed to achieve a high directivity. To verify proposed antenna performance, such as reflection coefficients, bore-sight gains, and radiation patterns, the antenna is measured in a full anechoic chamber. The results confirm that the proposed antenna is suitable for broadband spiral antennas with high tolerance to fabrication error and low design complexity.