"blackout" Monitoring And Control Of Transmission Systems Research

"Blackout", one of the barriers faced by human being in the development space industry, is another key problem after overcoming "sound barrier ", "thermal barrier" in high-speed flight research. The plasma is generated when the spacecraft rubs against the surrounding air intensely in reentry atmosphere process, and the amplitude and phase effects of the plasma on radio frequency electromagnetic wave will result in the interrupt of communication -" blackout ".Researchers from the late 1950's begin seeking for the effective approaches to reduce the problem of interruption during the reentry communication. It is hoped through the theoretical study to fully understand the electromagnetic properties of the "Blackout" area to ensure the smooth communication between the ground station and the spacecraft. Therefore, experts home and abroad have conducted a great deal of studies and made great progress in the theoretical research, numerical simulation, indoor experiment and the flight test.This paper analyzes the characteristics of the "Blackout" emerged when the spacecraft of the different speeds, of the different frequency bands and of different reentry height, and computes and makes a comparison to the information transmission bit error rate between the different modulation and demodulation systems,then compares the advantages and disadvantages of the three modulation systems. Finally it proposes the feasible engineering measures to eliminate the "Blackout", and that helps to build a solid theoretical and practical foundation to the application of the manned space flight communication-system.First of all, this paper refers to the electromagnetic characteristics of the "Blackout", and studies on the theoretical analysis, formula deduction and simulation calculation of the spreading characteristics of electromagnetic wave in "Blackout" Area. And then, based on the principles of digital communication, a channel simulation model is established in a "Blackout" plasma environment. The bit error rate calculation flow charts of the three modulation systems namely 2ASK,2FSK and 2PSK are made in coherent and incoherent demodulation mode, then deduces the respective bit error rate calculation formula, and calculated the band RF electromagnetic wave at different height of various modulation and demodulation system bit error rate, whereby the analysis summed up the advantages and disadvantages of the three modulation systems. Finally, this paper analyzes the feasibility and effectiveness of the various approaches and measures to reduce the "Blackout".