Design of an Ultra-Wideband Low-Profile Archimedes Spiral Antenna

This paper proposed an ultra-wideband(UWB) and lowlow-profile Archimedes spiral antenna loaded with EBG structure. The primary structure of the antenna includes a spiral radiator, a microstrip balun, an Electromagnetic Bandgap (EBG) structure, and a back cavity. The spiral arms are designed to be self-complementary, and they are short-circuited to the back cavity at their ends, which serves to lower the antenna's cut-off frequency.The central spiral arm, which is connected to the microstrip feeding balun and varies exponentially, serves to effectively lower the input impedance. This design not only shortens the length of the balun but also significantly reduces the overall size of the antenna.Loaded with two-step spur-type two-finger EBGs(Electromagnetic bandgap), realizing a new type of reflector structure. The proposed antenna has a compact size of 12.5 X 61 X 61mm³• Simulation results indicate that the VSWR bandwidth can extend up to 180%, covering the range from IGHz to 20GHz with a VSWR that is less than 2.5. Additionally, the AR is fundamentally kept below 3dB across the frequency range. The antenna's gain is greater than $5dB$ over the 4GHz-20GHz band and 1 dB over 2-3GHz. The simulation results show good circular polarization performance and ultra-wideband performance.