Simple generation of orbital angular momentum modes with azimuthally deformed Cassegrain subreflector

A parabolic reflector antenna with an azimuthally deformed Cassegrain subreflector is proposed to effectively generate arbitrary orbital angular momentum (OAM) modes. The Cassegrain dual-reflector antenna was fabricated for 18 GHz and measured in the near-field range. The near-field to far-field transformed radiation phase around a full azimuth shows that the proposed antenna generates fields with the l = 1 OAM mode. Simulated and measured feed reflection coefficients are below −10 dB for 15.1–21.2 GHz, even though the distance between a horn feed and a deformed subreflector is 15.6 mm, thus it is expected that the proposed structure can be used for a broadband low-profile antenna.