Radioaltimeters with frequency modulation of the probing signal

Mathematical models of radiated, reflected and differential radio signals used in radio altimeters in the time and frequency domains based on the analytical Gabor method in quadrature form are presented. Symmetric and asymmetric types of linear frequency-modulated radio signals and limitations used in their analytical application, as well as signals using a sinusoidal type of modulating voltage, are considered. The time, frequency, correlation and zero counting methods of construction are given. Each of the methods corresponds to the same principle of construction. Detailed structures of radio altimeters are given, their advantages and disadvantages are considered, and recommendations for their use are given.