Gain and bandwidth enhancement of low-profile unidirectional radiation spiral slot antenna

摘要

A novel simple antenna based on substrate integrated coaxial-like waveguide (SICW) is presented to enhance the gain and bandwidth of circularly polarized (CP) antenna with unidirectional radiation. The stepped inner metal strip is introduced in SICW, which results in a stronger radiation gain and wider axial ratio bandwidth. In addition, unlike traditional spiral antennas, the slot spiral antenna can be directly fed by a coaxial line at the inner port of the waveguide. As SICW can make the antenna directly realize unidirectional radiation, the extra reflector is not needed, and the antenna has a low profile of 0.1λ (λ is the free space wavelength at the lowest frequency). The simulation and measurement results show that by using SICW with a stepped inner metal strip, the overlapping bandwidth of CP antenna can be increased significantly from 57.3% (2.7-4.85 GHz) to 71.6% (2.6-5.5 GHz) and the boresight gain of the antenna is improved 2 dBi over the entire frequency band.