W-band prototype of platelet feed-horn array for CMB polarisation measurements

TL;DR

This paper reports on a scalable, low-cost W-band prototype of a platelet feed-horn array with excellent reflection, beam pattern, and polarization characteristics, suitable for future CMB polarization experiments.

Contribution

It introduces a novel platelet fabrication technique for high-performance, scalable corrugated feed-horn arrays for CMB measurements.

Findings

Reflection below -30 dB over 30% bandwidth

Good beam pattern repeatability with low sidelobes

Suitable for large cryogenic detector arrays

Abstract

We present the design and performance of a 2x2 prototype array of corrugated feed-horns in W-band. The module is fabricated using a so-called "platelet" technique by milling Aluminum plates. This technique is suitable for low-cost and scalable high performance applications. Room temperature Return Loss measurements show a low (<-30 dB) reflection over a 30% bandwidth with a maximum matching of -42 dB at 100 GHz for all four antennas. Beam pattern measurements indicate good repeatability and a low (-25 dB) sidelobe and crosspolarisation levels. This work is particularly relevant for future Cosmic Microwave Background polarisation measurements, which require large microwave cryogenic detector arrays coupled to high performance corrugated feed horns.