Overcoming Antenna-Induced Biases in GPS Measurements

  • Published
  • By Maria Callier
  • Air Force Office of Scientific Research
ARLINGTON, Va. --  An Ohio State University research team has developed very efficient approaches vital to the growth of global navigation satellite systems. 

Air Force Office of Scientific Research-funded scientist, Dr. Inder J. Gupta, led the team and conducted both the theoretical and practical work that has enabled techniques to estimate and mitigate antenna-caused biases in GPS (Global Positioning System) receivers equipped with anti-jam antennas or adaptive antennas. 

Military GPS receivers use adaptive antennas to operate in hostile electromagnetic environments (jamming). An adaptive antenna will adjust its pattern in real-time to minimize the effect of jamming on the GPS receiver. This will be accomplished by steering the radiation pattern in the jammer direction while maintaining the desired response in the GPS satellite direction. 

Dr. Gupta noted, "GPS has become increasingly significant to the military for precision navigation and timing and is the most widely used source to obtain this information. A GPS receiver determines its locations by measuring the distance from multiple GPS satellites in view." The approaches are very significant because previously the receiver's antenna and associated electronics introduced distortion into the satellite signals that resulted in biases in the distance measurements and affected the accuracy of position and time solution. 

He has also designed and built a new ground plane for the testing of the antennas and studied the effects of antenna elements on the performance of GPS anti-jam antennas. 

For his many efforts, Dr. Gupta was elected a Fellow of the IEEE in 2000. In 2007 the Antenna Measurement Techniques Association awarded him their Distinguished Achievement Award and the Edmond S. Gillespie Fellowship. He has also received the Ohio State University College of Engineering Lumley Research Award. Recently, Dr. Gupta was awarded an Institute of Navigation Fellowship with the citation, "For contributions to the theory and development of adaptive antennas for satellite navigation."