Ultra-wideband low-profile circularly-polarized two-arm spiral antenna

The invention belongs to the technical field of antennas, provides an ultra-wideband low-profile circularly-polarized two-arm spiral antenna, and aims at solving the contradiction of consideration of ultra-wideband, low profile, circular polarization and high gain development of an existing spiral antenna. The spiral antenna comprises a back cavity, a radiator dielectric substrate, an antenna spiral arm, a balun and a coaxial joint, wherein a feeding port is formed in the center of the radiator dielectric substrate; the antenna spiral arm is located on the upper surface of the radiator dielectric substrate and is connected with the upper end of the balun through the feeding port; the balun is located in the back cavity; the lower end of the balun is connected with the coaxial joint; the back cavity comprises a cylinder and a slope; the cylinder is arranged at the center of the back cavity; the slope is connected with the cylinder; the cylinder and the slope jointly form a circular truncated cone; an annular groove and a window are formed in the cylinder; and the window is used for arranging the balun. By the spiral antenna provided by the invention, the performance requirements of the wide band, low profile, circular polarization and high gain of the spiral antenna are well considered; and meanwhile, the frequency band bandwidth of the antenna is greatly improved.