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Publication Number: FHWA-HRT-10-037
Date: October 2010

Step Frequency Ground Penetrating Radar Characterization and Federal Evaluation Tests

Summary

SF GPR emissions characterization testing has been performed to measure emissions of FHWA/USDOT technology relative to criteria established by the NTIA. Testing was conducted using standardized equipment at the FAA Technical Center in New Jersey. Measurements were carried out in a standardized GPR test geometry. Results show that the SF GPR was largely compliant with the proposed emissions mask when notches were implemented (with exceptions noted in the results section of this report). In the few frequency ranges where FAA Technical Center measurement data indicated that there were compliance issues, emissions were reduced to meet NTIA criteria by adjusting the system attenuation to frequencies above 140 MHz during follow-up measurements at an FCC-certified laboratory. Below 140 MHz, an MMIC switching device in the SF GPR produced emissions that exceeded NTIA criteria during measurements and during follow-up measurements at an FCC-certified laboratory. There was no practical method for reducing the unintentional SF GPR emissions below 140 MHz, but it was notable that NTIA emissions criteria were substantially below typical ambient signal levels in this range.

As described above, emission measurement data were collected for SF GPR emissions over a broad range of frequencies at and around the operating frequencies of the SF GPR equipment being tested. In addition, detailed emissions data were collected over significantly narrower bandwidths corresponding to critical Federal systems. The general data were analyzed and described in this report, while the detailed Federal system data will be provided to appropriate agencies in electronic form (along with this report).

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United States Department of Transportation - Federal Highway Administration