A circular HIS reflector with a symmetric fan-shape patch array applied to a spiral antenna

This paper presents the antenna characteristics of a spiral antenna backed by a circular high-impedance surface reflector (CirHISR) composed of a fan-shaped patch element. The fan-shaped patch element is arrayed symmetrically. The antenna height between the spiral antenna and the bottom surface of the CirHISR is 0.09 wavelength (9.0 mm) at the lowest operating frequency of 3 GHz. Input impedance and axial ratio are analyzed using FEKO based on the method of moment and compared to that of a spiral antenna with a CirHISR asymmetric array using a fan-shaped patch element. It is found that good antenna characteristics are obtained across a frequency range of 3 GHz to 10 GHz (a fractional bandwidth of 108%). Similar antenna characteristics are also found between the spiral with the CirHISR symmetric patch array and that of the asymmetric one.