Power management for radar altimeter with double-phase-coded continuous wave modulation

Determination of altitude information for the safety of aircraft is a very important issue. Although the Linear Frequency Modulated Continuous Wave (LFMCW) was the most commonly used modulation in radar altimeter, the shortcomings of LFMCW that its signal form is simple and it can be easily detected by time-frequency analysis were exposed with the development of the detecting technique. Due to the complicated signal form and lower transmitting power, the Phase-coded signal like Binary Phase Shift Keying (BPSK) signal modulated by m sequence has the better property of Low Probability of Intercept (LPI) and has now gained considerable attention. Although power-management can further reduce the transmitting power and improve the stealthy performance, it has not been studied in altitude estimation for radar altimeter. In this paper, we propose a novel algorithm for altitude estimation in radar altimeter. Since the proposed algorithm combines the advantages of both Phase-coded modulation and power-management, it has the better stealthy performance on the premise of keeping sufficient accuracy of altitude estimation. Moreover, we also present an analysis on the effects of Doppler shift and power update step size. The simulation results verify the proposed approach.