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Multiple flare-angle horn feeds for sub-mm astronomy and cosmic microwave background experiments

Leech, J. and Tan, B. K. and Yassin, G. and Kittara, P. and Wangsuya, S. and Treuttel, J. and Henry, M. and Oldfield, M. L. and Huggard, P. G. (2011) Multiple flare-angle horn feeds for sub-mm astronomy and cosmic microwave background experiments. Astronomy & Astrophysics, 532 . Art. No. A61. ISSN 0004-6361. doi:10.1051/0004-6361/201117124.

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The use of large-format focal plane imaging arrays employing multiple feed horns is becoming increasingly important for the next generation of single dish sub-mm telescopes and cosmology experiments. Such receivers are being commissioned on both general purpose, common user telescopes and telescopes specifically designed for mapping intensity and polarisation anisotropies in the cosmic microwave background (CMB). Telescopes are currently being constructed to map the CMB polarisation that employ hundreds of feeds and the cost of manufacturing these feeds has become a significant fraction of the total cost of the telescope. Aims. We have developed and manufactured low-cost easy-to-machine smooth-walled horns that have a performance comparable to the more traditional corrugated feed horns that are often used in focal plane arrays. Our horns are much easier to fabricate than corrugated horns enabling the rapid construction of arrays with a large number of horns at a very low cost. Methods. Our smooth walled horns use multiple changes in flare angle to excite higher order waveguide modes. They are designed using a genetic algorithm to optimise the positions and magnitudes of these flare angle discontinuities. We have developed a fully parallelised software suite for the optimisation of these horns. We have manufactured prototype horns by traditional electroforming and also by a new direct drilling technique and we have measured their beam patterns using a far-field antenna test range at 230 GHz. Results. We present simulated and measured far-field beam patterns for one of our horn designs. They exhibit low sidelobe levels, good beam circularity and low cross-polarisation levels over a fractional bandwidth of 20%. These results offer experimental confirmation of our design technique, allowing us to proceed confidently in the optimisation of horns with a wider operational bandwidth. The results also show that the new manufacturing technique using drilling is successful, enabling the fabrication of large format arrays by repeatedly drilling into a single aluminium plate. This will enable the construction of focal plane arrays at a very low cost per horn. Conclusions. We have developed a new type of high performance feed horn that is fast and easy to fabricate. Having demonstrated the efficacy of our horn designs experimentally, we are building and testing a prototype focal plane array of 37 hexagonally close packed horns. This prototype array will be an important step towards building a complete CMB mapping receiver using these feed horns.

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Additional Information:© ESO, 2011. Article published by EDP Sciences. Received 21 April 2011 / Accepted 14 June 2011 The construction and testing of the horn array prototypes, and horn software development work was supported using an STFC follow-on fund grant and support from the Keck Institute for Space Studies, at the California Institute of Technology. The authors would like to thank Bertrand Thomas for his assistance in setting up and using the ABmm vector network analyser and 230 GHz antenna test range at the Rutherford Appleton Laboratories. We are now pursuing the commercialisation of this technology, both for sub-mm and longer wavelengths, in collaboration with ISIS Innovation Ltd, the technology transfer company of the University of Oxford.
Group:Keck Institute for Space Studies
Funding AgencyGrant Number
Keck Institute for Space Studies (KISS)UNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords: instrumentation: detectors / instrumentation: photometers / instrumentation: spectrographs / instrumentation: polarimeters / submillimeter: general / cosmic background radiation
Record Number:CaltechAUTHORS:20160302-152124713
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64968
Deposited By: Colette Connor
Deposited On:03 Mar 2016 03:30
Last Modified:10 Nov 2021 23:38

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