The Research Of Key Satellite Communications Technology For Helicopter Anti-rotor Obstructs

With the continuous development of helicopter manufacturing technology,its capabilities in flight performance have been continuously improved,and due to its fast and flexible characteristics,It has been widely used in the public industry such as battlefield support,armed reconnaissance,and medical rescue,fire fighting,emergency rescue,and traffic management,so researching satellite communications for helicopters has important value.Aiming at the deep signal fading caused by the rotor passing by the antenna during the flight of the helicopter,to realize the uninterrupted communication between the helicopter and the ground,it is necessary to conduct in-depth research on helicopter channel characteristics,transmission system,demodulation synchronization in a large dynamic environment and other related technologies.In view of the above-mentioned characteristics of helicopters,this paper proposes a satellite communication transmission scheme with anti-rotor occlusion,and analyzes and simulates related technologies in the scheme.The main content and results of this article include:1.The basic composition and characteristics of the helicopter satellite communication system are analyzed.Based on this,the channel characteristics in the Ku and Ka frequency bands are modeled and simulated by FEKO geometric modeling / electromagnetic simulation.2.Study the slot communication technology under the helicopter rotor occlusion channel.Based on this,a slot communication transmission system suitable for this subject is proposed.The forward link adopts the transmission system based on the physical layer coding.After adaptively designing the frame format,,Has the advantage of being insensitive to aircraft models.The return link adopts the physical layer coding + fountain coding transmission scheme,which can adapt to multiple models and support multiple modulation and coding methods with high efficiency.3.Analyze and study the effect of Doppler frequency and Doppler frequency change rate on demodulation caused by helicopter flight speed and flight acceleration.The effects of algorithm modules such as tracking are simulated and analyzed.Based on this,a maximum likelihood estimation algorithm + Kalman filter algorithm frequency estimation and tracking algorithm are proposed.The simulation results show its correctness and feasibility.4.For the characteristic that the signal will be blocked by the helicopter rotor periodically,and the signal power and signal-to-noise ratio at the receiver end of the demodulator will change in a large dynamic range,the timing error detection algorithm uses a normalized error detection algorithm.Timing phase error,the best sampling point is directly interpolated through the interpolation circuit,the error detection accuracy has nothing to do with the signal amplitude.The open-loop carrier recovery circuit estimates the carrier phase by frame-by-frame processing,and recovers the data carrier frame-by-frame by phase interpolation.Since the phase detection algorithm extracts the absolute phase of the data,it has nothing to do with the signal amplitude.Therefore,it is suitable for application environments with large dynamic changes in signal levels.5.A software implementation plan and a hardware implementation plan are given for the helicopter satellite communication system,and tests are performed on the implemented hardware platform according to the test plan,and the test results meet the requirements of relevant indicators.