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

Abstract

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

Development of a 70–110 GHz silicon corrugated horn for cosmic microwave background experiment

“…19 It is demonstrated that the misalignment between the different layers of the horn also causes higher cross-polarization. 20 The cross-polarization at 70 GHz has the similar beam shape to the main lobe, which indicates that the polarization of the AUT is not orthogonal to the polarization of the standard gain antenna when measuring the polarization. The asymmetry of cross-polarization is most likely a result from the defect in the horn.…”

“…The higher level of cross‐polarization is related to the manufacturing error of wave‐guide transition, which cause the leakage of the co‐polar beam patterns at the measurement plane of the cross‐polarization 19 . It is demonstrated that the misalignment between the different layers of the horn also causes higher cross‐polarization 20 . The cross‐polarization at 70 GHz has the similar beam shape to the main lobe, which indicates that the polarization of the AUT is not orthogonal to the polarization of the standard gain antenna when measuring the polarization.…”

“…This simplified the fabrication process but increase the difficulty of design. A 37‐element array was fabricated by Mandelli et al 20 This array was made by aluminum using chemical etching and computer numerical control (CNC) milling technology. The return loss of chemically etched corrugated feedhorn is below −25 dB, and the cross‐polarization is below −20 dB.…”

Total power horn-coupled 150 GHz LEKID array for space applications

“…The corrugated feed-horn array, completed with the single-mode circular waveguide array, has been described and fully characterised in [55], where it is possible to find all the information about the design, size and performance. The aperture of the feed-horns and the distance between them constrain the number of LEKIDs to be hosted on a 3 substrate to 37.…”

“…In the lumped element configuration [54], the absorption of the radiation happens in the inductor of the resonator and then the breaking of Cooper-pairs produces a change of the resonant frequency and the quality factor of the resonator, which can be measured by measuring the amplitude and phase of the bias signal transmitted past the resonator. The goal of the ASI/KIDS project concerns the development of two LEKID arrays: one sensitive to the total power and the other sensitive to the radiation polarisation, both coupled to the radiation via corrugate feed-horns [55]. In the polarisation sensitive array, the polarisation is separated in the two components by single-mode orthomode transducer.…”