Abstract
We present the design, manufacture, and measured performance of a dielectrically loaded quad-ridge flared horn (QRFH) feed for decade bandwidth radio astronomy application. The introduction of the dielectric load improves the QRFH beamwidth control in H-plane at the mid and upper frequency range. Consequently on the reflector, illumination efficiency, phase efficiency, and the intrinsic cross-polarization ratio (IXR) have been improved. The dielectric load is made from homogeneous low-loss polytetrafluoroethylene and has a low profile with a cylinder shape for simple installation at the center of the QRFH. The dielectrically loaded QRFH presented here covers 1.5–15.5 GHz with a calculated average aperture efficiency above 50% on a f/D = 0.3 prime-focus reflector. We present a calculation of system noise temperature and sensitivity for the QRFH on a 100 m prime-focus reflector. Measured beam patterns of the QRFH are in good agreement with the simulations over the full frequency band. The input reflection coefficient was predicted to be below −10 dB across the bandwidth. We present a tolerance analysis that explains why the measured one deviates.
Highlights
U LTRA wideband (UWB) systems enable science projects in radio astronomy to have a large continuous bandwidth
In this article we have presented the design, manufacture and performance of a dielectrically loaded quad-ridge flared horn (QRFH) over 1.5–15.5 GHz for radio astronomy application over decade bandwidth
The low profile of the dielectric load keeps the QRFH compact which is important when integrated in a cryostat dewar
Summary
U LTRA wideband (UWB) systems enable science projects in radio astronomy to have a large continuous bandwidth. UWB systems can reduce the number of receivers needed to cover a large frequency band. The current state-of-the-art LNA technology can achieve low noise temperatures over wide bandwidths [7], [8]. The QRFH robustness, singleended interface and compact design leads to simple integration in a cryostat dewar together with the LNAs for low-noise applications. In this article we demonstrate how the QRFH beamwidth control can be improved over 10:1 bandwidth with a dielectric load. This technique has achieved good beam pattern symmetry over 6:1 bandwidth with a three-layered dielectric [15].
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