Performance and Jamming Test Results of a Digital Beamforming GPS Receiver

NAVSYS High Gain Advanced GPS Receiver (HAGR) uses a digital beamsteering antenna array to track up to twelve GPS satellites on L1 and L2, each with up to 10 dBi of additional antenna gain over a conventional receiver solution. This digital, reprogrammable architecture provides a costeffective solution for military applications where precision GPS measurements are needed. The additional gain provided on the satellite signals by the HAGR significantly increases the precision of the observed P(Y) code pseudo-ranges and carrier phase. The HAGR digital beamforming receiver maintains the digital beams directed at each satellite using the receiver’s navigation solution, using aiding information from an inertial navigator or attitude reference and the satellite position derived from the ephemeris data. This directivity also improves the Anti-Jamming rejection of the GPS receiver. This paper describes the operation of the HAGR digital beam steering array and presents test results showing the precision navigation capability. Test results from the HAGR at the Electronic Proving Grounds, Fort Huachuca, during jamming tests are also presented that demonstrate the anti-jam performance of a beamsteering receiver. INTRODUCTION A key requirement for aircraft precision approach and landing systems is to provide high quality GPS pseudo-range and carrier phase observations in both the ground reference station and the aircraft making the approach. For military applications, such as the Joint Precision Approach and Landing System (JPALS) and the Navy’s Shipboard Relative GPS (SRGPS) carrier landing system, the measurement precision must be maintained in a hostile environment, where GPS jamming may occur, and also using GPS reference stations installed in less than ideal locations, for example on the mast of a ship where significant signal multipath can corrupt the measurement performance. NAVSYS has developed a digital beam-steering GPS receiver which processes the GPS data from a multielement phased array antenna. This has significant performance advantages over previous GPS reference station architectures which used a single reference antenna. In particular, the digital beam-steering approach has the following benefits in meeting the military JPALS or SRGPS key requirements. 1. Must provide high accuracy pseudo-range and carrier –phase observations The beamsteering provides gain in the direction of the GPS satellites increasing their effective C/N0Gain from beam-forming The increase in C/N0 on the GPS satellites reduces the pseudo-range and carrier-phase measurement noise improving the navigation solution accuracy. 2. Must be able to maintain precision in the presence of close-in multipath The digital beam-steering optimizes the adaptive antenna pattern for each satellite tracked. This provides gain in the direction of the desired satellite signal and will attenuate signals arriving from other directions, such as close-in multipath. This allows the GPS signal integrity to be maintained even under non-ideal antenna installation scenarios. 3. Must be able to maintain performance in a jamming environment. With conventional Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE MAY 2002 2. REPORT TYPE 3. DATES COVERED 00-00-2002 to 00-00-2002 4. TITLE AND SUBTITLE Performance and Jamming Test Results of a Digital Beamforming GPS Receiver 5a. CONTRACT NUMBER