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Development And Test of A Digitally Steered Antenna Array for The Navigator GPS ReceiverGlobal Positioning System (GPS)-based navigation has become common for low-Earth orbit spacecraft as the signal environment is similar to that on the Earth s surface. The situation changes abruptly, however, for spacecraft whose orbital altitudes exceed that of the GPS constellation. Visibility is dramatically reduced and signals that are present may be very weak and more susceptible to interference. GPS receivers effective at these altitudes require increased sensitivity, which often requires a high-gain antenna. Pointing such an antenna can pose a challenge. One efficient approach to mitigate these problems is the use of a digitally steered antenna array. Such an antenna can optimally allocate gain toward desired signal sources and away from interferers. This paper presents preliminary results in the development and test of a digitally steered antenna array for the Navigator GPS research program at NASA s Goddard Space Flight Center. In particular, this paper highlights the development of an array and front-end electronics, the development and test of a real-time software GPS receiver, and implementation of three beamforming methods for combining the signals from the array. Additionally, this paper discusses the development of a GPS signal simulator which produces digital samples of the GPS L1C/A signals as they would be received by an arbitrary antenna array configuration. The simulator models transmitter and receiver dynamics, near-far and multipath interference, and has been a critical component in both the development and test of the GPS receiver. The GPS receiver system was tested with real and simulated GPS signals. Preliminary results show that performance improvement was achieved in both the weak signal and interference environments, matching analytical predictions. This paper summarizes our initial findings and discusses the advantages and limitations of the antenna array and the various beamforming methods.
Document ID
20120016323
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Pinto, Heitor David (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Valdez, Jennifer E. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Winternitz, Luke M. B. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Hassouneh, Munther A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Price, Samuel R. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 26, 2013
Publication Date
November 5, 2012
Subject Category
Communications And Radar
Report/Patent Number
GSFC.CP.7477.2012
GSFC.CPR.7484.2012
Meeting Information
Meeting: 27th Space Simulation Conference
Location: Annapolis, MD
Country: United States
Start Date: November 5, 2012
End Date: November 8, 2012
Sponsors: American Inst. of Aeronautics and Astronautics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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