Characterization of L-band RFI and implications for mitigation techniques
Characterization of L-band RFI and implications for mitigation techniques
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L 频段 RFI 的特征及其对缓解技术的影响
DOI：
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发表时间：
2003
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通讯作者：
J. Johnson
中科院分区：
文献类型：
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作者：
S. Ellingson;G. Hampson;J. Johnson
我们描述了在1200-1800 MHz频段内的射频干扰（RFI）的测量结果，这些测量结果是从美国宇航局的P-3研究飞机在沿着美国大西洋中部海岸飞行期间在2，000和20，000英尺高度上观测到的。获得了功率谱和相干采样波形数据。我们的研究结果表明，低于1400 MHz的频谱通常由地面雷达的脉冲主导，这些脉冲虽然非常强，但各自的发射占空比为0.1%。我们检测到，但无法确定一些相对较弱的间歇性RFI内的20 MHz的保护频带为中心的1413 MHz。在1420 MHz以上，我们没有检测到明显的RFI，但是这个特定实验的有限灵敏度使得不可能排除RFI在损害总功率辐射测量的水平上的存在。辐射计设计的implications，包括可能的积极对策，RFI缓解，进行了讨论。I.射频干扰（RFI）会影响在L波段工作的辐射计的操作，即使是在1413 MHz左右的受保护的26 MHz频段工作的系统也是如此。虽然在L波段的带宽为100 MHz的顺序是理想的，以提高灵敏度，在土壤水分和海洋盐度的应用，使用主动RFI缓解技术，需要实现这些带宽。为了有效，这种技术必须考虑RFI的频谱和时间特性。本文介绍了在机载平台上对1200-1800 MHz频段的射频干扰进行初步调查的结果。这些数据是使用被称为L波段干涉测量仪/分析仪（丽莎）的便携式仪器收集的，该仪器是俄亥俄州州立大学电子科学实验室于2002年开发的。丽莎包括两个互补的子系统：一个现成的计算机控制的频谱分析仪和一个定制的宽带高动态范围相干采样接收器。前者有助于理解RFI在大频率跨度和长时间段上的分布，而后者提供了具有高时间分辨率的波形捕获能力。我们对在美国大西洋中部海岸上空的初始试飞期间捕获的数据进行的分析揭示了RFI的一些特性，这些特性有助于了解新的机载和天基辐射计的设计，特别是减缓技术的发展。
We describe measurements of radio frequency interference (RFI) in the 1200-1800 MHz band as observed from NASA's P-3 research aircraft during a flight along the Mid-Atlantic coast of the U.S. at altitudes of 2,000 and 20,000 ft. Both power spectra and coherently-sampled waveform data were obtained. Our results indicate that the spectrum below 1400 MHz is typically dominated by pulses from ground based radars, which, while very strong, individually have transmit duty cycles of on the order of 0.1%. We detect but are unable to identify some relatively weak intermittent RFI inside the 20 MHz protected band centered at 1413 MHz. We detect no significant RFI above 1420 MHz, but the limited sensitivity of this particular ex- periment makes it impossible to rule out the presense of RFI at levels damaging to total power radiometry. Im- plications for radiometer design, including possible active countermeasures for RFI mitigation, are discussed. I. Introduction Radio frequency interference (RFI) can impair the op- eration of radiometers operating at L-Band, even for sys- tems that operate in the protected 26 MHz frequency band around 1413 MHz. While bandwidths on the order of 100 MHz at L-Band are desirable for improving sensitiv- ity in soil moisture and ocean salinity applications, the use of active RFI mitigation techniques is required to achieve these bandwidths. To be effective, such techniques must take into account the spectral and temporal properties of the RFI. This paper presents some findings from an initial sur- vey of RFI in the frequency range 1200-1800 MHz, as ob- served from an airborne platform. The data were collected using a portable instrument known as the L-Band Inter- ference Surveyor/Analyzer (LISA), which was developed at the Ohio State University ElectroScience Laboratory in 2002. LISA includes two complementary subsystems: an off-the-shelf computer-controlled spectrum analyzer and a custom wideband high-dynamic-range coherent-sampling receiver. The former is useful for understanding the dis- tribution of RFI over large frequency spans and long time periods, whereas the latter provides waveform capture ca- pability with high temporal resolution. Our analysis of data captured during an initial test flight above the mid- Atlantic coast of the U.S. reveals some properties of the RFI which are helpful to know in the design of new air- borne and space-based radiometers, and especially in the development of mitigation techniques.