射电天文学中用于改进的射频干扰消除的替代自适应滤波器结构
Alternative Adaptive Filter Structures for Improved Radio Frequency Interference Cancellation in Radio Astronomy
摘要：
在射电天文学中，来自仅接收射频干扰（RFI）的辅助天线的参考信号可以被修改以在天文学接收器处模拟RFI环境。然后可以从天文信号路径中消除RFI。然而，天文学家通常只需要信号统计。如果RFI统计变化缓慢，则可以以比标准自适应滤波器所需的速率低得多的速率将消除应用于信号相关性。在本文中，我们描述了五个抵消器设置;预相关和后相关抵消器，使用一个或两个参考信号以不同的方式。理论上的残余RFI和增加的噪声水平进行检查，并证明使用微波电视RFI在澳大利亚望远镜紧凑阵列。RFI被衰减到低于系统噪声，至少降低20 dB。虽然双参考消除器比单参考消除器增加更多的参考噪声，但这种噪声是零均值的，只会增加系统噪声，从而降低灵敏度。残留在单参考消除器（但不是双参考消除器）输出中的残余RFI设置非零噪声基底，其不像随机系统噪声那样起作用，并且可能限制可实现的灵敏度。因此，双参考消除器通常会导致更好的消除。双参考前相关抵消器需要双抵消器设置才有用，并给出与双参考后相关抵消器等效的结果。
英文摘要：
In radio astronomy, reference signals from auxiliary antennas that receive only the radio frequency interference (RFI) can be modified to model the RFI environment at the astronomy receivers. The RFI can then be canceled from the astronomy signal paths. However, astronomers typically only require signal statistics. If the RFI statistics are changing slowly, the cancellation can be applied to the signal correlations at a much lower rate than is required for standard adaptive filters. In this paper we describe five canceler setups; precorrelation and postcorrelation cancelers that use one or two reference signals in different ways. The theoretical residual RFI and added noise levels are examined and are demonstrated using microwave television RFI at the Australia Telescope Compact Array. The RFI is attenuated to below the system noise, a reduction of at least 20 dB. While dual-reference cancelers add more reference noise than single-reference cancelers, this noise is zero-mean and only adds to the system noise, decreasing the sensitivity. The residual RFI that remains in the output of single-reference cancelers (but not dual-reference cancelers) sets a nonzero noise floor that does not act like random system noise and may limit the achievable sensitivity. Thus, dual-reference cancelers often result in superior cancellation. Dual-reference precorrelation cancelers require a double-canceler setup to be useful and to give equivalent results to dual-reference postcorrelation cancelers.
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