Dielectrically Loaded Quad-ridge Flared Horns for Ultra Wideband Reflector Feed Applications in Radio Astronomy
Doctoral thesis, 2022

Reflector-based radio telescopes are used as tools for observations in both radio astronomy and space geodesy. To observe the weak sources in space, highly sensitive receivers, fronted by optimized reflector feeds, are therefore needed. Wideband and ultra-wideband (UWB) systems enable large continuous frequency bandwidth and reduce the number of receivers that are needed to cover the radio spectrum. Therefore, they are attractive for existing and next generation of reflector arrays such as the Square Kilometre Array (SKA), Allen Telescope Array (ATA), Deep Synoptic Array (DSA), and the Next Generation Very Large Array (ngVLA). To achieve sensitive wideband and UWB performance with reflector feeds, a near-constant beamwidth and good impedance match are required over large frequency bands. The quad-ridge flared horn (QRFH) is a robust and compact UWB feed technology for this purpose, and is easily designed with single-ended excitation for 50-Ohm ports. The QRFH is dual-linear polarized and can typically achieve good performance up to 6:1 bandwidth with high band-average aperture efficiency and good impedance match. A drawback in existing state-of-the-art QRFH designs, is that they suffer from gradually narrowing beamwidth and increasing cross-polarization in the upper part of the frequency band. This is especially challenging for QRFHs that are designed to illuminate deep reflector geometries. The narrowing beamwidth leads to reduced aperture efficiency, and therefore also reduced sensitivity. To meet the demand for high sensitivity observations over large bandwidths, these challenges need to be addressed.
This thesis introduces and investigates low-loss, dielectric loading of the QRFH design to achieve ultra-wideband performance that reaches beyond decade bandwidth exemplified with 20:1 bandwidth in one single QRFH. The dielectric load is homogeneous, with a small and non-intrusive footprint and improves the beamwidth performance over the frequency band, while keeping the complexity low and the QRFH footprint compact. Keeping the QRFH robustness and compact footprint is favorable for practical receiver installation in real-world applications for radio observations. Three quad-ridge designs with dielectric loading are investigated, both for room temperature and cryogenic applications, and are shown to be highly suitable for wideband operation in existing and future reflector arrays.

dielectric loaded antennas

dielectric materials

reflector antenna feeds

radio astronomy

ultra wideband antennas

quad-ridge flared horn (qrfh)

radio receivers

horn antennas

broadband antennas

aperture antennas.

HC2, Hörsalsvägen 14, Campus Johanneberg
Opponent: Prof. Dirk I. L. de Villiers, Stellenbosch University, South Africa


Jonas Flygare

Chalmers, Space, Earth and Environment, Onsala Space Observatory

Dielectrically Loaded Quad-Ridge Flared Horn for Beamwidth Control Over Decade Bandwidth-Optimization, Manufacture, and Measurement

IEEE Transactions on Antennas and Propagation,; Vol. 68(2020)p. 207-216

Journal article

Strategy and Overview for Development of Beyond-Decade-Bandwidth Quad-ridge Flared Horns for Radio Astronomy

15th European Conference on Antennas and Propagation, EuCAP 2021,; (2021)

Paper in proceeding

Beyond-Decade Ultrawideband Quad-Ridge Flared Horn With Dielectric Load From 1 to 20 GHz

IEEE Transactions on Antennas and Propagation,; Vol. 71(2023)p. 2110-2125

Journal article

J. Flygare, S. Weinreb, D. P. Woody, Quad-ridge Choke Horn with Dielectric Load as a Wideband Feed for Non-cryogenic Reflector Arrays in Radio Astronomy

Bredbandiga antenner för radioastronomi

När vi tittar på science fiction-film ser vi kanske stora parabolantenner som vi antar är sändare och mottagare av radiosignaler till och från satelliter eller våra rymdfärjor. Ibland stämmer det i verkligheten, men ibland är de stora parabolerna inga sändare, utan enbart mottagare som inte letar efter starka radiovågor från satelliter utan istället svaga radiovågor från universum. Vi kallar dessa paraboler för radioteleskop. Radioteleskopet kom till av en slump år 1928, när Karl Jansky letade signalstörningar med en stor radioantenn. Han upptäckte samtidigt att radiovågor oväntat nog också kom från mitten av vår galax. Sedan Janskys upptäckt har radioastronomin blivit ett viktigt verktyg för astronomer att studera universum med, och kunna se sådant som vi inte kan se med kikarteleskop. Osynligt ljus från stjärnor på radiovåglängder, eller radiofrekvenser, kan färdas genom saker som synligt ljus inte kan göra obehindrat, till exempel moln i vår atmosfär. Desto mer radiofrekvenser vi kan studera från universum samtidigt, desto mer bredd på frekvensbandets information får vi – mer bandbredd. Denna avhandling behandlar hur man ökar bandbredden i radioteleskop genom att använda speciella material i mottagarens första komponent - mataren.

Wideband antennas for radio astronomy

When we watch a science fiction movie, we might see large parabolic antennas that we assume are transmitters and receivers of radio signals to and from satellites or our space shuttles. Sometimes in reality this is the case, but sometimes those large parabolas are not transmitters, only receivers and they are not looking for strong radio waves from satellites, but weak radio waves from the universe. We call these parabolas radio telescopes. The radio telescope came about by chance in the year 1928 when Karl Jansky was looking for signal interference with a large radio antenna. He discovered at the same time that radio waves were also coming from the center of our galaxy. Since Jansky’s discovery, radio astronomy has become an important tool for astronomers to study the universe with, and be able to see things we cannot see with binocular-type telescopes. Invisible light from stars at radio wavelengths, or radio frequencies, can travel through things unaffected in a way visible light cannot, for example through clouds in our atmosphere. The more radio frequencies we can study from the universe simultaneously, the more width of the frequency band’s information we get – more bandwidth. This thesis explains how to increase bandwidth of radio telescopes by using special material in the receiver's first component - the feed.

RadioNet 4

European Commission (EC) (EC/H2020/730562), 2017-01-01 -- 2020-12-31.


Onsala Space Observatory

Subject Categories

Electrical Engineering, Electronic Engineering, Information Engineering



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5115



HC2, Hörsalsvägen 14, Campus Johanneberg

Opponent: Prof. Dirk I. L. de Villiers, Stellenbosch University, South Africa

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