Astronomical Verification of a Stabilized Frequency Reference Transfer System for the Square Kilometer Array
Astronomical Verification of a Stabilized Frequency Reference Transfer System for the Square Kilometer Array
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DOI：
10.3847/1538-3881/aa6db1
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发表时间：
2017-04
期刊：
影响因子：
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通讯作者：
D. Gozzard;S. Schediwy;R. Dodson;M. Rioja;Mike Hill;Brett Lennon;John K. McFee;P. Mirtschin
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文献类型：
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作者：
D. Gozzard;S. Schediwy;R. Dodson;M. Rioja;Mike Hill;Brett Lennon;John K. McFee;P. Mirtschin
为了满足其尖端的科学目标，平方公里阵列(SKA)望远镜需要向其每个天线分配高精度的频率基准。频率基准通过光纤链路分布，必须进行主动稳定，以补偿链路上的环境扰动对信号施加的相位噪声。SKA的工程要求要求任何拟议的频率参考分配系统都必须在“天文验证”测试中得到验证。给出了对SKA-MID提出的稳频基准传输系统进行天文验证的结果。利用澳大利亚望远镜紧凑型阵列的双接收器结构，从数据中减去天空信号的相位噪声，从而可以直接比较使用标准频率基准进行的观测的相位噪声，以及传输超过77公里光纤电缆的稳定频率基准传输系统。给出了用于5 GHz和25 GHz天文定标器观测的稳频基准传输系统的分数频率稳定度和相位漂移的结果。这些观测加上166公里城域光纤链路上传输信号稳定性的附加实验室结果被用来表明，测试中的稳定传输系统在广泛的观测条件范围内超过了所有SKA的相位稳定性要求。此外，我们已经证明，使用多个合成器向阵列的子部分提供参考信号的替代参考传播系统可能会限制望远镜的成像能力。
In order to meet its cutting-edge scientific objectives, the Square Kilometre Array (SKA) telescope requires high-precision frequency references to be distributed to each of its antennas. The frequency references are distributed via fiber-optic links and must be actively stabilized to compensate for phase noise imposed on the signals by environmental perturbations on the links. SKA engineering requirements demand that any proposed frequency reference distribution system be proved in “astronomical verification” tests. We present results of the astronomical verification of a stabilized frequency reference transfer system proposed for SKA-mid. The dual-receiver architecture of the Australia Telescope Compact Array was exploited to subtract the phase noise of the sky signal from the data, allowing the phase noise of observations performed using a standard frequency reference, as well as the stabilized frequency reference transfer system transmitting over 77 km of fiber-optic cable, to be directly compared. Results are presented for the fractional frequency stability and phase drift of the stabilized frequency reference transfer system for celestial calibrator observations at 5 and 25 GHz. These observations plus additional laboratory results for the transferred signal stability over a 166 km metropolitan fiber-optic link are used to show that the stabilized transfer system under test exceeds all SKA phase-stability requirements within a broad range of observing conditions. Furthermore, we have shown that alternative reference dissemination systems that use multiple synthesizers to supply reference signals to sub-sections of an array may limit the imaging capability of the telescope.