GPS Anti-Jam Technology (GAJT): Safe monitoring of cargo despite GPS interference.

GPS interference has long been known in the military sector, which is why extensive research into countermeasures has been conducted – with success. Technical solutions are now available that are increasingly being used for civilian purposes, especially in the field of logistics. GPS anti-jamming technology, or GAJT for short, is an effective tool for protecting satellite navigation systems from interference signals so that they are not affected by jamming or spoofing. The technology was developed by Novatel from Hexagon, a company specializing in the collection, analysis and use of geospatial data.

To distinguish between real GPS signals and interference signals, GAJT antennas analyze the signal movement: GPS signals are emitted by satellites moving through space at a speed of about four kilometers per second. Conversely, jammers are usually placed stationary on the ground. The signal strength can also be an indicator of GPS jamming. This jammer is located close to the GPS receiver, so its signal is much stronger than that of navigation satellites located at an altitude of 20,000 to 26,000 kilometers in space. As a result, the jammer overcomes the weak GPS signals and saturates the electronics on the front end of the GPS receiver. This situation is similar to trying to have a conversation in a room where a stereo is playing. If the volume exceeds a certain level, it becomes difficult to understand the other person. GAJT antennas automatically detect interference signals and create a digital image of them. An integrated algorithm analyzes this image and effectively removes the interference signal.

The physical principle behind this is similar, if greatly simplified, to that of antiphonal sound generation, where two opposing sound waves cancel each other out. Modern noise-canceling headphones (ANC headphones) work on the same concept: once the microphones in the headphones detect ambient noise, such as the roar of a construction machine, an onboard chip calculates the exact antiphonal sound. Ideally, this allows the external sound source to be completely compensated for. The result is silence or – in the case of GAJT antennas – undisturbed GPS reception.