Analysis of sky contributions to system temperature for low frequency SKA aperture array geometries
Analysis of sky contributions to system temperature for low frequency SKA aperture array geometries
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DOI：
10.1007/s10686-011-9278-6
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发表时间：
2012-03
影响因子：
3
通讯作者：
N. Razavi-Ghods;E. D. L. Acedo;A. El-Makadema;P. Alexander;A. Brown
中科院分区：
文献类型：
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作者：
N. Razavi-Ghods;E. D. L. Acedo;A. El-Makadema;P. Alexander;A. Brown
新一代射电望远镜，例如拟议的平方公里阵列 (SKA) 和低频阵列 (LOFAR)，在很大程度上依赖于使用非常大的相控孔径阵列，这些阵列在高达约 1.4 GHz 的频率范围内工作在宽带宽上。 SKA 特别包括孔径阵列，每个站由数千个元件组成，提供无与伦比的测量速度。目前正在研究两种不同的阵列（标称频率为 70 MHz 至 450 MHz 和 400 MHz 至 1.4 GHz），以便将其纳入整体 SKA 配置中。在本文中，我们旨在分析许多规则和不规则平面天线阵列配置对系统温度的影响，这些配置是低频 SKA（稀疏断开阵列）的可能几何形状。我们重点关注 500 MHz 以下频段，其中真实天空对系统温度 (Tsys) 的贡献非常显着，并且主导整个系统噪声温度。我们通过模拟多个 SKA 站的远场响应来计算天空噪声对 Tsys 的贡献，然后将其与 Haslam 408 MHz 调查的天空亮度温度分布进行卷积，然后将其缩放到 100 MHz 的观测结果。我们对阵列温度的分析是通过假设对银河平面上方和下方的三个寒冷区域进行观测来进行的。结果显示了规则阵列在以奈奎斯特速率采样时的优点，以及与非规则阵列相比在欠采样时以栅瓣形式出现的缺点。
The new generation of radio telescopes, such as the proposed Square Kilometer Array (SKA) and the Low-Frequency Array (LOFAR) rely heavily on the use of very large phased aperture arrays operating over wide band-widths at frequency ranges up to approximately 1.4 GHz. The SKA in particular will include aperture arrays consisting of many thousands of elements per station providing un-paralleled survey speeds. Currently two different arrays (from nominally 70 MHz to 450 MHz and from 400 MHz to 1.4 GHz) are being studied for inclusion within the overall SKA configuration. In this paper we aim to analyze the array contribution to system temperature for a number of regular and irregular planar antenna array configurations which are possible geometries for the low-frequency SKA (sparse disconnected arrays). We focus on the sub-500 MHz band where the real sky contribution to system temperature (Tsys) is highly significant and dominants the overall system noise temperature. We compute the sky noise contribution to Tsysby simulating the far field response of a number of SKA stations and then convolve that with the sky brightness temperature distribution from the Haslam 408 MHz survey which is then scaled to observations at 100 MHz. Our analysis of array temperature is carried out by assuming observations of three cold regions above and below the Galactic plane. The results show the advantages of regular arrays when sampled at the Nyquist rate as well as their disadvantages in the form of grating lobes when under-sampled in comparison to non-regular arrays.