First Order Design of a Quadruple-Ridged Flared Horn for the ngVLA Band 1

The design of an all-metal quadruple-ridged flared horn (QRFH) feed antenna for the ngVLA optics is presented. The feed is required to operate over the 1.2 GHz - 3.5 GHz frequency band with an optimization goal of maximizing the receiving sensitivity
$(A_{\mathrm{e}}/T_{\text{sys}})$
at an elevation angle of 45° and minimizing the fundamental waveguide mode reflection coefficient over the specified frequency band. The initial optimization was done on an analytically defined profile for both the horn and ridges, which provided a good starting point for optimizing horns with spline-defined profiles. In the final optimizations, the maximum ridge length was constrained to be about three-quarters of the total horn's length to allow for the addition of thermal and vacuum breaks. The final design has an average sensitivity of 13.4 m
²
/K over frequency and tipping angles.