A Compact Ultrawideband Reflector Antenna: Using a Wide-Band Omnidirectional Antenna with a Mechanically Steerable Endfire Beam to Illuminate a Half-Cut Paraboloid Reflector

An ultrawideband, compact, paraboloid reflector antenna with a mechanically steerable endfire beam is presented, with its performance evaluated in frequency, time, and power domains. A fixed, omnidirectional monocone feed, engineered to maintain the same illumination of the reflector during its rotation, is used to facilitate scanning. Moreover, the omnidirectional mode of the antenna system can be enabled by recessing the reflector. A monocone feed is designed using the spherical mode expansion (SME) technique to achieve consistent monopole-like patterns over a wide bandwidth. To achieve the small group delay variation at a reduced size, the reflector is placed close to the monocone. The nearfield paraboloid can still produce a planar wavefront without destructive interference despite this proximity; therefore, the destructive interference is avoided. The reflector is designed based on a multidimensional parametric study to accomplish a reduced size and reasonable performance in both frequency and time domains.