A Real-Time Software Receiver for the GPS and Galileo L1 Signals

Galileo L1 Signals B. M. Ledvina, Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University M. L. Psiaki, T. E. Humphreys, Sibley School of Mechanical and Aerospace Engineering, Cornell University S. P. Powell, and P. M. Kintner Jr., School of Electrical and Computer Engineering, Cornell University BIOGRAPHY Brent M. Ledvina will be an Assistant Professor in the Electrical and Computer Engineering Department at Virginia Tech in Spring 2007. He received a B.S. in Electrical and Computer Engineering from the University of Wisconsin at Madison and a Ph.D. in Electrical and Computer Engineering from Cornell University. His research interests are in the areas of ionospheric physics, space weather, estimation and ltering, and GPS/GNSS technology and applications. Mark L. Psiaki is a Professor of Mechanical and Aerospace Engineering at Cornell University. He received a B.A. in Physics and M.A. and Ph.D. degrees in Mechanical and Aerospace Engineering from Princeton University. His research interests are in the areas of estimation and ltering, spacecraft attitude and orbit determination, and GNSS technology and applications. Todd E. Humphreys is a graduate student in the Sibley School of Mechanical and Aerospace Engineering. He received his B.S. and M.S. in Electrical and Computer Engineering from Utah State University. His research interests are in estimation and ltering, spacecraft attitude determination, GNSS technology, and GNSSbased study of the ionosphere and neutral atmosphere. Steven P. Powell is a Senior Engineer with the Space Plasma Physics Group in the School of Electrical and Computer Engineering at Cornell University. He has M.S. and B.S. degrees in Electrical Engineering from Cornell University. He has been involved with the design, fabrication, and testing of several GNSS receivers. Paul M. Kintner, Jr. is a Professor of Electrical and Computer Engineering at Cornell University. He received a B.S. in Physics from the University of Rochester and a Ph.D. in Physics from the University of Minnesota. His research interests include the electrical properties of upper atmospheres, space weather, and developing GNSS instruments for space science. He is a Fellow of the APS. ABSTRACT A real-time interoperable GPS and Galileo L1 software receiver has been developed and tested. The receiver has 12 channels for tracking GPS satellites and 12 channels for tracking Galileo satellites. The receiver consists of a GPS L1 RF front end, data parallelizing and acquisition hardware, and software routines running on a 3.4-GHz Pentium processor. The software is composed of bit-wise parallel correlation routines, code and carrier tracking loops, data demodulation routines, and navigation solution code. The main contributions of this work are the demonstration of a GPS L1 C/A code RF front end being used with the Galileo L1 binary-o set-carrier(1,1) (BOC(1,1)) signals and the demonstration of an interoperable GPS and Galileo real-time software receiver. This RF front end uses a commercial o -theshelf (COTS) GPS RF front end designed for the L1 C/A code signal. To accommodate the Galileo L1-B BOC(1,1) signal, modi cations to the delay-locked-loop (DLL) were required. The downside to the approach is that this particular RF front end induces a 4.6 dB loss in carrier-to-noise in the Galileo signals, because of the narrow ltering intended for the narrower GPS L1 C/A code signal. The successful live tracking of GPS and Galileo satellites using this RF front end demonstrates the feasibility of using RF front ends designed for the GPS L1 C/A code signals in interoperable GPS and Galileo receivers or Galileo receivers. The GPS and Galileo L1 software receiver tracks 24 channels in real time. It requires 46% of the processing capabilities of a 3.4 GHz Intel Pentium 4 PC.