Ultra-wideband feed design and characterization for next generation radio telescopes
Licentiatavhandling, 2018

Radio telescopes are used as tools for observations in both radio astronomy and geodesy. To observe the weak sources in space, highly sensitive receivers headed by optimized reflector feeds are needed. Wideband and ultra-wideband (UWB) receiver systems enable large continuous frequency bandwidth and reduce the number of receivers that are needed. Therefore, they are attractive for the next generation of large reflector arrays such as the Square Kilometre Array (SKA) and the Next Generation Very Large Array (ngVLA). To achieve highly 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 popular UWB feed technology for this purpose. Typically, the QRFH achieve good performance up to 6:1 bandwidth and are designed for high aperture efficiency. However, due to the very small noise contributions of today's low-noise amplifiers (LNA), it is becoming more relevant to design specifically for high sensitivity. A drawback in existing state-of-the-art QRFH designs, is that they suffer from narrowing beamwidth as the frequency increases over the bandwidth. To meet the demand for high sensitivity observations over large bandwidths, these challenges need to be addressed.
In this thesis, the spline-defined QRFH design for the room temperature SKA Band 1 feed package over 350-1050 MHz is presented. The QRFH spline-profile is optimized for high sensitivity over the 3:1 bandwidth for the SKA reflector dish.
The thesis also introduces a low-profiled dielectric load at the center of a QRFH design for 10:1 bandwidth for the BRAND project. The dielectric load improves the beamwidth performance over the 1.5-15.5GHz frequency band, while keeping the complexity of the QRFH concept low. Both of the approaches that are introduced here are applicable for any future QRFH design, and are therefore relevant for the community in the hunt for high sensitivity observations.

reflector feed

geodesy

radio astronomy

quad-ridge flared horn

square kilometre array

dielectric loading

spline-defined

decade bandwidth

Ultra-wideband antennas

ED, Hörsalsvägen 11, Campus Johanneberg
Opponent: Prof. Dirk I. L. de Villiers, Stellenbosch University, Stellenbosch, South Africa

Författare

Jonas Flygare

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium, Rymdgeodesi och geodynamik

Styrkeområden

Informations- och kommunikationsteknik

Infrastruktur

Onsala rymdobservatorium

Ämneskategorier

Kommunikationssystem

Annan elektroteknik och elektronik

Utgivare

Chalmers tekniska högskola

ED, Hörsalsvägen 11, Campus Johanneberg

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

Mer information

Senast uppdaterat

2018-11-23