A novel compact circularly polarized horn antenna

A novel circularly polarized horn antenna with wide bandwidth and compact size is presented. The antenna is composed of an ellipse-aperture horn antenna, circular-to-square transition and novel circularly polarizer. The polarizer consists of five-step septum in a square waveguide, coaxial-waveguide converter and reflecting back-cavity. The antenna achieves an impedance bandwidth (S11<;-10dB) of 22.1% and a 3-dB AR (Axial Ratio) bandwidth of 18.3%, with the 3dB-AR beam width of about 138°, and the antenna gain is over 10.5dBi in the operation band.