A programmable, real-time, digital signal processing (DSP), least-mean-squares (LMS) interference canceler was developed and demonstrated as a successful method of excising the GLONASS satellite L-band downlink signals from the 100 m Green Bank Telescope (GBT). This canceler has the potential for aiding the observation of redshifted OH lines near 1600 MHz in the presence of GLONASS signals. Our canceler approach is similar to experiments reported by Barnbaum and Bradley, Baan et al., and Kesteven et al. for mitigating ground-based radio frequency interference (RFI), but we add the new features of a tracking dish antenna to follow the satellite for improved cancellation performance, complex adaptive filter coefficients that reduce the required filter length, and a programmable delay line for bulk time delay correction. An analysis of LMS tracking performance for moving satellites is presented, and effective use of a reference antenna distantly located from the telescope is demonstrated. As is expected from the known properties of LMS cancelers, larger filter orders are shown to yield more reliable cancellation and are less sensitive to data time misalignment. GLONASS interference seen by the GBT was suppressed below the noise floor without corrupting a signal that simulated an astronomical source, even with rapid orbital transits and long integration times.
展开▼
机译：开发了一种可编程的实时数字信号处理（DSP），最小均方（LMS）干扰消除器，并将其作为从100 m Green Bank望远镜中切除GLONASS卫星L波段下行链路信号的成功方法进行了演示（ GBT）。该消除器有可能在存在GLONASS信号的情况下帮助观察1600 MHz附近的红移OH线。我们的消除方法类似于Barnbaum和Bradley，Baan等人和Kesteven等人所报道的实验。用于减轻基于地面的射频干扰（RFI），但我们增加了跟踪碟形天线的新功能来跟随卫星，以提高抵消性能，减少所需滤波器长度的复杂自适应滤波器系数，以及用于批量处理的可编程延迟线延时校正。对移动卫星的LMS跟踪性能进行了分析，并证明了远离望远镜的参考天线的有效使用。从LMS抵消器的已知特性可以预期，较大的滤波器阶数显示出更可靠的抵消，并且对数据时间未对准的敏感性较小。由GBT观测到的GLONASS干扰被抑制在本底噪声以下，而不会破坏模拟天文来源的信号，即使轨道快速穿越和积分时间较长也是如此。
展开▼
