Experimental comparison of fabrication-driven performance in corrugated feed horns for the ngVLA

This letter presents the design, fabrication, and experimental validation of a corrugated feed horn for the Next Generation Very Large Array (ngVLA) Band-5 receiver operating over the 30–50 GHz frequency range. The proposed horn employs an axially corrugated circular waveguide with a flared throat, logarithmic spiral opening, and tapered groove geometry, optimized using full two-dimensional field integration to maximize aperture efficiency while accounting for phase, amplitude, taper, and cross-polarization effects. To evaluate the impact of fabrication method and material, three feed horns with identical electromagnetic designs were made: a CNC-machined tellurium copper, a CNC-machined aluminum, and a tellurium copper horn using metal additive manufacturing. All three feed horns were characterized for return loss and radiation patterns under identical conditions at the Communications Research Centre (CRC) in Ottawa Canada using their compact antenna test range (CATR) anechoic chamber. Measured results show excellent agreement with simulations for the CNC-machined feeds, achieving a return loss better than 23 dB across the operating band. The additively manufactured feed shows larger deviations primarily in cross-polarization response, highlighting the direct impact of fabrication-induced geometric deviations on cross-polarization performance at millimeter-wave frequencies.