This paper presents, for the first time, the hybrid use of loading techniques (which involve terminating the spiral arms with different structures to give a resistive or capacitive effect) and a novel technique of cavity groove in order to enhance the performance of two-arm, cavity-backed, 2–18 GHz spiral antenna. The antenna is made on Duroid 5880 and has the smallest form factor (50 mm diameter), meeting all the performance metrics, which are targeted for efficient performance of a spiral antenna for ultra-wideband (UWB) applications. Measured results match the simulated results and show that by the utilization of hybrid loading and cavity groove, the gain is increased by a factor of 3.65 dBi and the axial ratio is improved by 2.73 dB at (2 GHz) as compared to a simple Archimedean antenna made on Duroid 5880, without increasing the size. The proposed antenna shows 2.25 dB more gain and improved axial ratio performance as compared to a simple Archimedean spiral antenna made on Tmm4, without the utilization of the hybrid techniques proposed earlier in the literature.
Axial Ratio Improvement of Spiral Antenna with Resistive Loading
