Improved sensitivity of a low noise aperture array tile for the SKA
Recent experimental results for the sensitivity of aperture arrays at room temperature show 40 K array noise temperatures over the frequency range from 1000 MHz to 1500 MHz. Further reduction of array noise temperature is important to comply with the SKA sensitivity requirements at affordable cost. Furthermore the frequency range should be extended to a lowest frequency of 500 MHz, in order to meet the bandwidth specification for the future SKA Mid Frequency Aperture Array. The work presented here builds on our earlier published results, obtained with aperture arrays for the frequency range from 1000 MHz to 1500 MHz. Noise measurements with a 2×2 array using newly designed broadband antenna/LNA modules, show a further reduction in noise temperature to 35 K and below for this frequency range. At the same time the new design has a much broader frequency response, down to 600 MHz, with an array noise temperature near 40 K. These noise measurements could be done despite the harsh RFI environment, of which the influence on the design will be discussed. The results of the presented noise measurements are state-of-the-art for a room temperature system in the 600-1500 MHz frequency range.