Inkarbaieva O. Optimization of signal processing method in radio engineering systems of terrain mapping from the helicopter

The dissertation research focuses on the development and study of a signal processing method in helicopter radio-electronic systems for measuring the terrain relief of the area selected by the pilot for a safe landing, under any weather conditions and using its sensor signals. These systems are proposed to be used as a complement to the classical onboard systems installed in the cockpit to estimate the surface height during landing. Thus, the aim of the research is to improve the accuracy of terrain assessment when selecting a safe landing platform under adverse meteorological conditions using optimal signal processing onboard radar. The object of research is the process of signal processing of the reflected surface to estimate the relief. The subject of the research is methods and algorithms for processing radar signals to solve problems of terrain mapping in helicopter radars. This research was prompted by the fact that helicopter operations require landing on an unprepared airfield under hazardous conditions. In addition, during landing, dusty vortices can occur, which prevent the pilot from navigating in space and making the right decisions regarding the control. These increases the risk to the crew and passengers. A perspective solution to the problem is the development of safe landing systems with preliminary terrain detection. At present, research on the development of such systems are carried out all over the world, but most of them are based on heuristic approaches using ready-made technological solutions, and further data processing is based on generalized engineering experience. Moreover, their effectiveness in low visibility conditions is limited. This limitation is to be solved using a dual-antenna direction finder with end-to-end signal processing in the radio wavelength range, as this will allow measurements with increased accuracy and will ensure operation in all weather conditions, day and night. To achieve the goal of the dissertation research, some tasks are solved. First, the mathematical models of spatio-temporal stochastic radio signals and the likelihood functions for the observation equations for a dual-antenna helicopter radar are developed. According to the criterion of the maximum likelihood function, an optimal algorithm is synthesized for the processing of spatio-temporal stochastic signals in an amplitude sum-and-difference radar system for measuring terrain that located onboard a helicopter. The peculiarity of the synthesized algorithm is that it can estimate the distance to each surface point and its angular position, which allows for recovery of the surface relief along the flight direction within the overlapping radiation patterns. The resulting algorithms for surface height measurement are tested on two simulation models: under ideal measurement conditions and considering the scattering of signals by a rough surface. As a result, their overall performance and the effectiveness of the resulting terrain restoration algorithm are demonstrated. However, it is shown that the error of the terrain height measurement system is determined by the resolution and geometry of the radar sensor.