Navigation warfare - Final report

This report describes the activities of the project TK mot GNSS which have been carried out between 2004 and 2006. Selected results are also presented. The project can be divided into three main activities: development of anti-jam demonstrator system, evaluation of adaptive beamforming for GPS, and scenario-based development of NAVWAR. The development of the anti-jam demonstrator has required most of the resources. Two adaptive beamforming algorithms were implemented and evaluated by using the anti-jam demonstrator and live GPS-signals. Of the two beamforming methods parallel optimization of each satellite signal combined with suppression of jamming signals, also denoted MT-LCMV, was proven to be the most effective. Depending on the choice of beamforming algorithm and the relative placement of the jammers there is a difference in how well the anti-jam system can suppress jamming signals and also how many satellite signals the GPS receiver can lock onto. To jam an adaptive antenna system (AJ) multiple jammers geomterically spread out, and preferably elevated, are required. By employing more jammers than the number of minimas the beamforming system can generate, and separate them sufficiently, the jamming suppression capability of the AJ-system can be destroyed. Elevated jammers block the sky for the beamforming system and cause GPS-receiver to lock onto fewer satellite signals. To implement NAVWAR a well thought out jamming strategy is required in order not to jam blue forces use of GNSS.