Design of a compact broadband planar spiral antenna backed by an absorbing cavity

This paper presents a compact and unidirectional spiral antenna for broadband and circularly polarized operation. First, size reduction of the radiator using antenna miniaturization techniques is considered and explored through the application of meandering lines and resistive loading. Then in order to achieve a unidirectional radiation, the spiral antenna is backed by an absorbing cavity. The constitutive parameters of the absorbing material in the cavity are obtained via the measurement of the transmission coefficient of the material. The designed antenna was implemented and measured. The measurement results demonstrate validation of the design and realization of 50% size reduction.