Design of composite spiral antenna loaded with a new type reflector in Ku-band

In this paper, we proposed a composite structure spiral antenna whose working band covers the entire Ku band. The design of the antenna is the composite of equiangular spiral and Archimedes spiral: The internal of antenna element is with equiangular spiral, and the external of is with Archimedes spiral. So the size of antenna plane is reduced effectively. Furthermore, in order to suppress the back forward radiation of the antenna and to achieve the balanced feed, we designed the improved reflector cavity structure and exponential gradient Balun. Simulation results show that the far-field gain of the antenna is higher than 5dB, and the VSWR is less than 2.5dB in the Ku band.