SP: Development of an Interference Temperature Monitor

智能优势：射频干扰（RFI）监测是频段分配和减少用户之间有害干扰的重要工具。过去，人为干扰的一个主要来源是汽车点火。现在，人为干扰的主要来源是电子设备、数字答录机、计算机等。像蜂窝电话和无线计算机网络这样的通信设备相对来说是新出现的，它们利用带有功率控制的码分多址（CDMA）有效地利用频谱，以最小的发射机功率最大化容量。这些设备产生的扩频，如果不知道去扩频信号的编码，就不能很容易地与高斯噪声区分开来。噪声信号的另一个来源来自新的数字电视发射机。为了避免有害干扰并尽量减少环境中噪声水平的提升，监测这种噪声的水平是很重要的。频率在500 MHz ~ 20 ghz之间的自然环境噪声主要由来自地面的约300 K、来自宇宙背景的约3K和来自大气的约5 ~ 30 K组成。在射电天文波段和其他在线接收波段，重要的是要防止噪声温度的任何增加，而在其他波段的噪声温度的测量可以是有效利用频谱的各种应用，包括射电天文和无线通信所需的有用信息。麻省理工学院干草堆天文台建议开发一种监测器，以测量频率范围为30至1500兆赫的干扰水平，校准以提供以开尔文度为单位的输出度量，并具有足够的灵敏度，能够量化到几开尔文的水平，在受保护的仅接收波段（如射电天文学，遥感和深空波段）中不需要的噪声。这支持了NSF和FCC的联合倡议。在第一阶段，提案人计划研究提供灵敏度和精度所需的接收器和校准设计，而不会产生显着的内部互调，杂散响应和杂散信号。在这个阶段，他们还将根据麻省理工学院干草堆天文台（位于马萨诸塞州韦斯特福德）现有设备的RFI环境的初步测量，为设计设定规范。在第二阶段，我们提出了干扰温度监测器的原型，并在干草堆测试设计。在第三阶段，我们建议在马萨诸塞州和新罕布什尔州南部地区的几个地点对该系统进行测试。在未来，根据结果，这样的监测系统可以在其他地方复制，以收集数据集，以表征其他地点的RFI环境。更广泛的影响：通过这个项目，提案人旨在提高对无线电波技术特性及其各种应用的认识，如射电天文学和无线通信，以及射频干扰环境。因此，将开发一个简单的射频监测系统，用于大学预科教育环境，以使学生和教师熟悉无线电波信号的测量技术以及学校和城镇周围的环境。这些数据可以通过互联网进行相互比较，干草堆天文台将开发基于网络的教育材料，介绍无线电波的研究及其各种应用。建议者尤其会安排在天文台附近的本地学校部署简易的商用无线电接收器和天线，让学生参与射频测量。作为澳大利亚SEARFE项目的一部分，将促进与澳大利亚学生和教师的合作，以加强关于这一主题的国际网络。作为美国国家科学基金会在干草堆天文台的“教师研究经验”项目的一部分，一个与当地教师合作的项目将于2003年夏季启动。

Intellectual Merit: Radio Frequency Interference (RFI) monitoring is an important tool in theassignment of frequency bands and in the reduction of harmful interference between users. In thepast, a major source of man-made interference was from automobile ignition. Now a majorsource of man-made interference is from electronic devices, digital answering machines,computers etc. Communication devices like cellular phones, and wireless computer networks arerelative new comers and are making efficient use of the spectrum using Code Division MultipleAccess (CDMA) with power control to maximize capacity with the minimum transmitter power.These devices generate a spread spectrum which cannot be easily distinguished from Gaussiannoise without knowledge of the code to de-spread the signal. Another source of noise-like signalscomes from the new digital television transmitters. In order to avoid harmful interference andminimize the elevation of the noise level in the environment, it is important to monitor the levelof this noise. The natural environmental noise for frequencies between 500 MHz and 20 GHzconsists mainly of about 300 K from the ground, 3K from the cosmic background, and about 5 to30 K from the atmosphere. In the radio astronomy bands and other itreceive onlyle bands, it isimportant to prevent any increase in the noise temperature while measurement of the noisetemperature in other bands can be useful information needed to optimize the efficient use of thespectrum for various applications including radio astronomy and wireless communications.MIT Haystack Observatory proposes to develop a monitor to measure the interference levels inthe frequency range 30 to 1500 MHz, calibrated to provide the output metric in units of degreesKelvin, and with sufficient sensitivity to be able to quantify, to a level of a few degrees Kelvin,the unwanted noise in the protected receive-only bands like those for radio astronomy, remotesensing, and deep space bands. This supports the joint initiative between the NSF and the FCC.In phase 1, the proposers plan to study receiver and calibration designs needed to provide the sensitivityand accuracy without significant internal inter-modulation, spurious responses and spurioussignals. In this phase they will also set specifications for the design based upon preliminarymeasurements, using currently available equipment, of the RFI environment at the MIT HaystackObservatory, in Westford, MA. In phase 2 we propose to prototype the interference temperaturemonitor and test the design at Haystack. In phase 3 we propose to conduct tests of the system at afew locations in the Massachusetts and Southern New Hampshire area. In the future, dependingon the results, such a monitoring system could be replicated elsewhere to gather a data set tocharacterize the RFI environment at other locations.Broader Impact: Through this project, the proposers aim to enhance the awareness of the properties ofradio wave technology and its various applications such as radio astronomy and wirelesscommunications, as well as the radio frequency interference environment. Thus, a simple RFImonitoring system will be developed for use in pre-college educational settings to acquaintstudents and teachers with the measurement techniques of radio wave signals and theenvironment around their schools and towns. Such data could be inter-compared using theInternet, and Haystack Observatory will develop web-based educational materials to introduce thestudy of radio waves and their various applications. In particular, the proposers will arrange for thedeployment of simple radio receivers and antennas, available commercially, to local area schoolsaround the Observatory to engage students in RFI measurements. A collaboration with studentsand teachers in Australia, as part of the Australian SEARFE project will be promoted to enhanceinternational networking on this topic. A project with local area teachers as part of NSF'sprogram 'Research Experiences for Teachers (RET)' at Haystack Observatory is starting insummer 2003 to initiate this activity.