Technique for improving the immunity of a satellite navigation receiver to intended jamming

Modern unmanned air vehicles (UAV) are equipped with satellite navigation receivers to provide stability in space and maintain the desired track. The satellite navigation receivers feature low noise immunity that can result in loss of satellite signals and, hence, in deviation from the desired track or control loss. The paper presents a technique for improving the immunity of a satellite navigation receiver under wide- and narrow-band interference as well as deceptive interference. The technique was implemented through the analysis of NMEA output data of a satellite navigation receiver. The main advantage of the proposed technique is the use of relatively small computational power of the onboard computer. The proposed technique is based on the analysis of the signal/noise ratio, the number of navigation satellites used as well as the integrity of the output coordinates of an UAV receiver. The proposed technique allowed developing an algorithm for detecting the interference which consists of two stages. At the first stage, presence of interference is identified, the second stage implies the comparison of the output coordinates of the receiver with the desired ones making it possible to assess the effects of deceptive interference. The algorithm is implemented in the G programming language in the LabVIEW environment. The technique and the algorithm for identifying the interference were tested by conducting a series of semi-natural experiments with the CH-3803M signal simulator which allowed estimating the threshold values of signal levels from navigation satellites in the presence of interference. As a test sample the ATGM336H multisystem satellite navigation receiver was used that provides a possibility to select a satellite navigation system (GLONASS, GPS or BeiDou) or to use their combination for solving an UAV navigation problem. The authors conducted a series of experiments for assessing the effects of different interference on the performance of the ATGM336H satellite navigation receiver.