GPS World, January 2017

0 10 20 30 40 50 60 2 0 2 North error meters 0 10 20 30 40 50 60 2 0 2 East error meters 0 10 20 30 40 50 60 5 0 MORE ONLINE JANUARY 2017 WWW GPSWORLD COM GPS WORLD 63 beamforming GNSS receiver applications that can significantly benefit from this technology include stationary GNSS monitoring installations such as those used in satellite based and ground based augmentation systems and GNSS receivers for autonomous vehicles and UAVs in high multipath areas such as urban canyons The application of more rigorous calibration techniques will likely improve correlator beamforming performance in a GNSS receiver even further Moreover combining this technique with more advanced gatedcorrelator approaches such as the double delta correlator could improve multipath mitigation performance further still The credible advantages that correlator beamforming affords GNSS receivers in terms of size weight power and cost and full beamforminglevel multipath mitigation performance is worthy of additional investigation and technology development especially for emerging applications such as autonomous vehicles and UAVs that have a requirement to operate frequently in severe multipath environments such as cities DISCLAIMERS The views expressed in this article are those of the authors and do not reflect the official policy or position of the United States Air Force Department of Defense or the United States Government ACKNOWLEDGMENTS This article is based in part on the paper Correlator Beamforming for Multipath Mitigation at Relatively Low Cost Initial Performance Results presented at ION GNSS 2016 the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation held Sept 12 16 2016 in Portland Oregon The authors thank all those who helped and supported the work presented in this article Specifically we thank Lt Col Phillip Corbell Ph D AFIT professor for his review and valuable feedback of the correlator beamforming section of this article We also thank Rick Patton ANT Center coordinator for supporting equipment installation and data collection efforts The authors would also like to acknowledge and thank Locata Corporation for the excellent support and assistance provided throughout all CRADA activities SANJEEV GUNAWARDENA is a research assistant professor of electrical engineering with the Autonomy and Navigation Technology ANT Center at the Air Force Institute of Technology AFIT Wright Patterson AFB Ohio His research interests include RF design digital systems design high performance computing software defined radio SDR and all aspects of GNSS receivers and associated signal processing JOHN RAQUET is a professor of electrical engineering and the director of the ANT Center at AFIT He has been involved in navigation related research for more than 25 years MARK CARROLL is a research engineer with AFITs ANT Center He received his B S and M S in computer engineering from Miami University Oxford Ohio in 2012 and 2014 respectively His current research includes multi GNSS algorithms SDRs and other GNSSrelated research and development in support of the Air Force Research Laboratory Time minutes 5 Down error meters FIGURE 15 3 D position error as a function of time same color key as Figure 14 Further Reading For references related to this article go to gpsworld com and click on More in the navigation bar then on Innovation Method North Error East Error Down Error RMS m i RMS m i RMS m i Singleelement reference 229 134 641 Correlator beamforming 058 75 056 58 144 78 Traditional beamforming 040 83 039 71 089 86 TABLE 3 3D RMS position error and percent error reduction with respect to single element antenna