By Marcus C. Walden
Abstract: The design of a 16-element waveguide array employing radiating T-junctions that operates in the Ku band is described.
Amplitude weighting results in low elevation sidelobe levels, while impedance matching provides a satisfactory VSWR, that are both achieved over a wide bandwidth (15.7-17.2 GHz). Simulation and measurement results, that agree very well, are presented. The design forms part of a 16 x 40 element waveguide array that achieves high gain and narrow beamwidths for use in an electronic-scanning radar system.
I. INTRODUCTION: Design equations for optimum horn antennas have long been established . This concept has been employed in an electronic-scanning ground surveillance radar system for nominal elevation beamwidths of 10° and 20°. Unfortunately, for narrower beamwidths, the optimum horn becomes impractically long for a man-portable system (e.g. for a desired 5° beamwidth, the length is ~1.5 m).
Because the antenna forms part of a 40-element array that defines the azimuth beamwidth, a 16-element waveguide array with a corporatefeed structure was selected to achieve the desired 5° elevation beamwidth with a short physical length.