Simulation and validation of a GPS antenna array concept for JPALS application

Abstract : The goal of Joint Precision Approach and Landing System (JPALS) is to provide navigation to support automatic shipboard landings in zero visibility conditions. The accuracy, integrity and availability requirements for this system are extremely stringent. In order to meet such demanding navigation performance, a dual-frequency carrier phase differential GPS solution is being pursued. In addition, both the shipboard reference station and the airborne user may be subject to multiple hostile jamming sources. The system must be able to continuously provide service with little or no drop in integrity and availability. In order to achieve such stringent performance goals in the difficult operating environment of JPALS, advanced technology will likely be required. One likely element will be the use of an antenna array with digital beam/null steering capabilities to help mitigate jamming and multi-path errors. This paper will present an initial feasibility study for the use of controlled reception pattern antennas (CRPAs) in the JPALS environment. It will present the benefits and the potential difficulties in the implementation of CRPA algorithms for JPALS use. Due to the motion of the ship and the flexure in the antenna mast arm, there may be some uncertainty in the knowledge of the orientation of the shipboard reference antenna array. This uncertainty leads to errors in the carrier phase output of the CRPA. A simple beam-forming algorithm is presented, and its potential effectiveness for use in JPALS will be presented. The paper concludes by outlining the deficiency associated with the classical beam-forming algorithm implementation for JPALS.