论文标题
在存在射频干扰的情况下,多频阵列校准
Multifrequency Array Calibration in Presence of Radio Frequency Interferences
论文作者
论文摘要
无线电干涉仪是分阶段阵列,从测量的协方差矩阵产生高分辨率图像。这种仪器的校准是必要的,并且是一项关键任务。这就是通过引用的天体来源的知识来进行工具错误的估计。但是,在现代无线电干涉仪(Lofar,SKA)中使用高灵敏天线会带来射电天文学的新挑战,因为对射频干扰(RFI)更敏感。在校准过程中,RFI的存在通常会引起最先进的解决方案的偏见。本文的目的是提出一种减轻RFI影响的替代方法。为此,我们首先提出了一个模型,以考虑到较低的结构噪声,考虑到多个频道中的数据中存在RFI。然后,我们使用空间交替的广义期望最大化(SAGE)算法实现校准参数的最大似然估计,我们最初得出两组完整的数据,允许更新的近距离表达式表达式。与一些更古典的方法相比,数值模拟显示RFI损坏数据的性能有了显着增长。
Radio interferometers are phased arrays producing high-resolution images from the covariance matrix of measurements. Calibration of such instruments is necessary and is a critical task. This is how the estimation of instrumental errors is usually done thanks to the knowledge of referenced celestial sources. However, the use of high sensitive antennas in modern radio interferometers (LOFAR, SKA) brings a new challenge in radio astronomy because there are more sensitive to Radio Frequency Interferences (RFI). The presence of RFI during the calibration process generally induces biases in state-of-the-art solutions. The purpose of this paper is to propose an alternative to alleviate the effects of RFI. For that, we first propose a model to take into account the presence of RFI in the data across multiple frequency channels thanks to a low-rank structured noise. We then achieve maximum likelihood estimation of the calibration parameters with a Space Alternating Generalized Expectation-Maximization (SAGE) algorithm for which we derive originally two sets of complete data allowing close form expressions for the updates. Numerical simulations show a significant gain in performance for RFI corrupted data in comparison with some more classical methods.