A chemically etched corrugated feedhorn array for D-band CMB observations

We present the design, manufacturing, and testing of a 37-element array corrugated feedhorns for Cosmic Microwave Background (CMB) measurements between $140$ $170$ GHz. The was designed to be coupled Kinetic Inductance Detector arrays, either directly (for total power measurements) or through an orthomode transducer polarization measurements). manufactured in platelets by chemically etching aluminum plates $0.3$ mm $0.4$ thickness. process is fast, low-cost, scalable, yields high-performance antennas compared other techniques same frequency range. Room temperature electromagnetic show excellent repeatability with average cross level about $-20$ dB, return loss $-25$ first sidelobes below dB far $-35$ dB. Our results qualify this as valid candidate state-of-the-art CMB experiments, where large detector arrays high sensitivity purity are paramount importance quest discovery $B$-modes.