Research On Angle Tracking Technology Of Telemetry System In Wireless Fading Channel

In order to evaluate the performance of telemetry receiving system more objectively,accurately,quickly and economically,a comprehensive simulation platform of digital telemetry system can be established,which transmits telemetry signals from the target,propagates through space wireless channel,and reaches the ground station.Then the ground station receives and demodulates telemetry signals.It can replace the traditional means of field test and flight calibration,and thus saves a lot of money,time,manpower,material and financial resources.Taking the PCM-FM telemetry signal and the single channel mono-pulse system as an example,firstly,starting from the telemetry signal source,the mathematical modeling and simulation analysis of the single channel mono-pulse angle tracking system of the PCM-FM telemetry signal under the condition of no interference are carried out.A more comprehensive and realistic antenna pattern modeling method is put forward,and its rationality and accuracy are illustrated.Next,taking multipath fading in wireless fading channel as an example,the mathematical model of the process of single channel mono-pulse angle error demodulation under multipath and two-path interference conditions is established,and the reflection coefficients under the conditions of “ground clutter model” and “dry ground reflection model” are simulated compared respectively.The angle tracking performance of telemetry system under static conditions is studied.The simulation results and analysis of the influence of multipath effect on the differential beam pattern,the process of the angle error signal generation,modulation and demodulation are given,and the rules are summarized.The simulation results are compared,analyzed and summarized with field experiments.Then,the dynamic angle tracking mathematical model under the condition of multipath effect is established,and the angle tracking performance is simulated and analyzed under different target distances,heights and velocities.The measures and suggestions of anti-multipath interference are put forward from the aspects of field test and system design.Based on the analysis of the formation mechanism of multi-path angle measurement error,a “single information source” model is established to study the anti-multipath interference effect under different forgetting factor parameters,and the simulation results are analyzed and summarized.Finally,field experiments are used to verify and analyze the method of improving the tracking performance of the system by modifying the forgetting factor in the tracking algorithm of the servo system.Based on the brief introduction of the adjustment principle and verification conditions of forgetting factor,the effect of modified forgetting factor on angle tracking performance of telemetry system is analyzed from two aspects of tracking jitter and tracking lag respectively according to the field test results,and the related suggestions are summarized.