Rotationally Symmetric Lens Antenna with Biconical Feed for Broadband Measurement Applications

We present a body of revolution (BoR) lens antenna with biconical feed. Due to the rotationally symmetric structure, the numerical optimization is carried out in a very efficient manner by 2D FEM simulation. The overall design is decomposed into several steps: Initially, the geometry of the biconical feeding structure out of brass is optimized for a broadband matching to the lens material, neglecting its finite size. Next, the shape of the polyethylene (PE) lens has been optimized for a broadband highly directive radiation towards the horizon. The three parts of the BoR antenna, namely the PE lens and the brass top and bottom cones used for feeding, have been fabricated by CNC milling. The assembly process of the antenna, which operates between 700 MHz and 12 GHz, is outlined as well. A very good agreement between the measured and FEM-simulated $S_{11}$ is demonstrated. The radiation measurement results show that the proposed antenna has a stable omnidirectional pattern, and features a moderate to high gain (up to 10.5 dBi) with increased frequency.