Waveform Measurements of Radars Operating in the 3.5 GHz Band

Summary

The focus of this NASCTN project is to develop test methods and perform measurements necessary to characterize the waveforms of radars that operate in the 3.5 GHz band.

This NASCTN effort is coordinated with the Department of Defense (DOD), and the results of this project will support the spectrum regulators as they develop a certification process for Spectrum Access Systems (SAS) and the associated Environmental Sensing Capability (ESC) that may be deployed in this frequency band.

The National Advanced Spectrum and Communications Test Network (NASCTN) has completed its reports of two measurement campaigns of radars operating in the 3.5 GHz band. These projects focused on collecting and analyzing digital waveforms of navy radars in Point Loma, located in San Diego, CA, and Fort Story, located in Virginia Beach, VA, test sites to promote a broader effort of spectrum-sharing with commercial users.  The results included observation of active radar tuning across a range of frequencies, two radars operating simultaneously in the same or different frequency channels, adjacent-band emissions, and frequency-hopping narrowband emissions from an unknown source.   

The projects’ objectives are to create results that will inform the development, testing and certification of Environmental Sensing Capability (ESC) nodes in coastal areas which facilitate prioritization and coordination of frequencies managed by Spectrum Access Sharing (SAS) systems.  The 3.5 GHz spectrum-sharing initiative is an ongoing effort to develop systems for managing three tiers of priority data traffic – navy radar as the primary incumbent, followed by licensed commercial users, and general access of remaining capacity. 
Data collection in Point Loma spanned from March to April and in Fort Story from August to October 2016.  NASCTN collected a library of high quality In-Phase and Quadrature (I/Q) waveform data covering the entire band in question and portions of adjacent bands. The digital waveforms were retained if energy was detected above a predefined threshold in the band of interest, a metric which can be further useful in triggering data acquisition and diagnostics in subsequent signal analysis studies. 

These findings help guide the development of ESC capability to receive waveforms of different radar equipment, including a class of more sophisticated radars yet to be deployed in this band, as well as their testing by a certification body.  Measurements of key parameters, including the antenna rotation period, pulse repetition interval, pulse duration, and center frequency offset, will aid the development of robust ESC detectors of radar.  The study also facilitates understanding of waveform deviations due to the effects of dispersion, multipath fading and loss in the propagation channel resulting from environmental conditions, including variations in temperature, humidity, barometric pressure and wind speed. 

Throughout the timeline of the project, NASCTN also engaged in community outreach and awareness by holding briefings and workshops on the collection efforts at Point Loma and Fort Story in order to bring together Federal, Industry, and Academia stakeholders to share research, information, and activities to overcome challenges, discuss solutions, and measurements collected in the 3.5 GHz band. The Fort Story report will be released soon.

The reports may be found at the following links: 

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Created December 29, 2016, Updated January 30, 2018