The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
We analyse signal and noise in receiving connected array antennas with equal low-noise amplifiers (LNAs) and constrained beamforming. An equivalent two-port circuit is derived for the receiver noise figure. Compared to the actual LNAs, the equivalent IAA is shown to have the same noise-match admittance but generally larger minimum noise figure and coefficient of source mismatch. The increased parameters...
We have measured the aperture-array noise temperature of the first Mk. II phased array feed that CSIRO has built for the Australian Square Kilometre Array Pathfinder telescope. As an aperture array, the Mk. II phased array feed achieves a beam equivalent noise temperature less than 40 K from 0.78 GHz to 1.7 GHz and less than 50 K from 0.7 GHz to 1.8 GHz for a boresight beam directed at the zenith...
We describe recent developments in measuring both signal and noise in phased array feeds for radio astronomy at CSIRO. We introduce new techniques including aperture array noise measurements with beamforming weights matched to a reflector's focal field. Weights are calculated via antenna-range and in-reflector measurements. We also describe the separation of system temperature and aperture efficiency...
This paper presents the measured sensitivity of CSIRO's first Mk. II phased array feed (PAF) on an ASKAP antenna. The Mk. II achieves a minimum system-temperature-over-efficiency Tsys/η of 78 K at 1.23 GHz and is 95 K or better from 835 MHz to 1.8 GHz. This PAF was designed for the Australian SKA Pathfinder telescope to demonstrate fast astronomical surveys with a wide field of view for the Square...
Noise parameter measurements of six candidate transistors for a Square Kilometer Array (SKA) low-noise amplifier (LNA) are presented. They provide reliable data in the frequency range where some low-noise transistors are inadequately characterized. The results of these measurements inform the design of an LNA for SKA1-Survey Band 2 with measured minimum noise temperature of 21 K.
Wideband electromagnetic band gap resonator antennas that can provide gains from 15 dBi in extremely small physical areas are proposed. It is shown that strongly truncated circular superstructures and ground planes with identical areas can be used to significantly improve the aperture efficiency of these antennas. An example antenna design with a maximum aperture efficiency of 121% is described. The...
We describe the development of a low-noise active balun for a dual-polarized planar connected array antenna operating in the 0.71.8GHz frequency range. The device consists of two single-ended low-noise amplifiers (LNAs) operating at ambient temperature with a passive output-side balun. Issues of device characterization, matching and stability are discussed and techniques for measuring the signal and...
In this paper we demonstrate the gain enhancement of a semicircular slot antenna using a multilayer frequency-selective surface (FSS). A theoretical analysis of the FSS with a UWB semicircular slot antenna is presented. The multilayer FSS provides an appropriate reflection phase to act as a reflector and is able to enhance the gain of the slot antenna. Simulations show a linear phase response from...
A method is proposed to extract the phase constant β and attenuation constant α of bounded waves in a finite periodic structure using scattering parameters. The proposed method accounts for the mutual coupling between the unitcells when computing the wavenumbers of the propagating modes. It is useful when the unit cell configuration is complex and typical eigen-mode solvers fail.
The characteristic basis function method (CBFM) is extended to apply to efficient analysis of dual-polarized connected-patch arrays where neighboring patches are connected via two-wire transmission lines and a groundplane. Comparison with a reference solution shows that the use of tertiary basis functions can significantly improve the CBFM approximation to the array currents and radiation patterns...
We analyse the sensitivity of a dual-polarized planar connected array with single-ended low noise amplifier (LNA) loading and differential beamforming of the outputs of LNA pairs. Sensitivity is found to depend on the LNA minimum noise figure source admittance and input admittance, with the dependence on the input admittance being relatively weak. Good performance is obtained if these admittances...
Placing a phased array at the focus of a paraboloidal reflector increases the area of sky a radio telescope can observe. For a 9×10 chequerboard phased array on a 12 m parabolic dish the available field of view increase from 1 to 36 square degrees at 1.4 GHz. To access this field of view multiple beams are formed. It is impractical to form enough beams to recover all the energy incident on the phased...
We analyze the efficiency of a connected checkerboard phased array feed (PAF) being investigated in the Australian Square Kilometer Array (SKA) Pathfinder. Both rotationally symmetric and offset-fed reflectors are considered. The array is assumed to be loaded with single-ended amplifiers and we compare single-ended and differential beamforming of the amplifier outputs. The results provide information...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.