Main beam modeling for large irregular arrays The SKA1-LOW telescope case
Main beam modeling for large irregular arrays The SKA1-LOW telescope case
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大型不规则阵列的主光束建模 SKA1-LOW 望远镜案例
DOI：
10.1007/s10686-017-9565-y
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发表时间：
2017
影响因子：
3
通讯作者：
Bui-Van H
中科院分区：
文献类型：
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作者：
Bui-Van H
21世纪的大型射电望远镜，如低频阵列(LOFAR)或Murchison Widefield阵列(MWA)，利用天线的相控孔径阵列来实现极高的探测速度。平方公里阵列低频仪器(SKA1-LOW)将由一组非常规相控阵系统组成。利用几个系数来预测这些阵列的主光束对于望远镜的定标是至关重要的。提出了一种对大型非规则阵列的主波束和前几个副瓣进行建模的有效方法。该方法利用Zernike多项式来表示阵列方向图。从定义在阵列上方的等价面上定义的电流出发，将方向图表示为不同阶的Zernike函数的傅里叶变换和。Zernike多项式的系数由两种不同的方法得到：最小二乘法和解析法。分析表明，这两种方法对于表示主波束和前几个副瓣具有相似的性能。此外，还给出了不同阵型的数值结果，验证了该方法的有效性，并对远离圆形的阵型也是如此。
Large radio telescopes in the 21stcentury such as the Low-Frequency Array (LOFAR) or the Murchison Widefield Array (MWA) make use of phased aperture arrays of antennas to achieve superb survey speeds. The Square Kilometer Array low frequency instrument (SKA1-LOW) will consist of a collection of non-regular phased array systems. The prediction of the main beam of these arrays using a few coefficients is crucial for the calibration of the telescope. An effective approach to model the main beam and first few sidelobes for large non-regular arrays is presented. The approach exploits Zernike polynomials to represent the array pattern. Starting from the current defined on an equivalence plane located just above the array, the pattern is expressed as a sum of Fourier transforms of Zernike functions of different orders. The coefficients for Zernike polynomials are derived by two different means: least-squares and analytical approaches. The analysis shows that both approaches provide a similar performance for representing the main beam and first few sidelobes. Moreover, numerical results for different array configurations are provided, which demonstrate the performance of the proposed method, also for arrays with shapes far from circular.