COMPENSATION OF THE DOPPLER SHIFT OF THE RADIO ALTIMETER ON A HIGH-SPEED CARRIER
Background . One of the main error sources of a continuous-wave radar altimeter is the Doppler shift due to high vertical velocity. This kind of error dominates when altimeter is placed on a high-speed vehicle. The common way which compensate Doppler shift with the dynamic delay in output averaging filter results with inappropriate value of the filter time constant. So this paper aims in improvement of the height filtering algorithm. Matherials and methods . Height filtering algorithm is expanded with the procedure of vertical velocity estimation. Velocity estimates are used for current height data correction. Derived filtering equations are variant of nonlinear sigma-point Kalman filter where observed values are time periods of altimeter modulation. Results . Obtained filtering algorithm was verified with altimeter simulation model included stochastic differential equation of the dynamic tracking loop. The simulation model accounts for main sources of altimeter errors. Conclusions . Obtained filtering algorithm correctly eliminates Doppler shift of a continuous-wave radar altimeter readings which is one of the main error sources in high vertical velocity scenarios.