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

Step Frequency Ground Penetrating Radar Characterization and Federal Evaluation Tests

Executive Summary

Step frequency ground penetrating radar (SF GPR) technology offers unprecedented subsurface three-dimensional (3D) imaging capabilities. Subsurface material deterioration, void imaging, and precise material and geometry measurements of civil infrastructure are all accurately and efficiently carried out using this specialized technology. Through previous evaluations and reports, the Federal Highway Administration (FHWA) has determined that SF GPR can be applied to subsurface infrastructure evaluation problems to meet needs in the national interest.(1,2) In addition to infrastructure applications described in these reports, it is notable that land mines, runway pavements, and buried historic sites can be imaged using SF GPR technology.

Due to SF GPR operating principles, system emissions testing is required to support an FHWA/United States Department of Transportation (FHWA/USDOT) application for a National Telecommunications and Information Administration (NTIA) Stage 3 (developmental) and NTIA Stage 4 (operational) certificate of spectrum support under NTIA rules for out-of-band operations. This testing is described in this report along with a proposed coordination procedure between NTIA and system users to ensure appropriate system operation. Results of the emissions testing indicate that the system can operate safely without violating emissions criteria in Annex K of the Manual of Regulations and Procedures for Federal Radio Frequency Management.(3)

SF GPR emissions tests were conducted by Federal Aviation Administration (FAA) staff at the FAA Technical Center in New Jersey during the week of March 9, 2009. The emissions tests used a standardized test configuration across a measurement spectrum from 50 MHz to 6 GHz. These tests characterized SF GPR emissions relative to an emissions mask defined by NTIA rules (described in detail in the background section of this report). Tests included general measurements that covered the full range of operating frequencies of the SF GPR and detailed emission measurements in narrow frequency ranges corresponding to specific Federal systems identified by NTIA. Based on initial results from these SF GPR emissions tests, needs for follow-up testing were defined. Follow-up data are included in appendix C of this report. The data were collected by a Federal Communications Commission (FCC)-certified emissions test laboratory after final tuning changes were made to reduce emissions at specific frequencies. This test laboratory also produced a test report based on collected emissions data (see appendix E).

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