This study is concerned with the problem of increasing the accuracy of a low-altitude altimeter employing the frequency modulation principle. A way to suppress the "discrete error" of the altimeter by employing additional «slow» frequency modulation of the carrier wave and averaging the resulting counts is considered. The benefit of such approach is simplicity of technical implementation manifesting in minimal changes in the microwave path and the recording device, which needs to run in averaging count mode. It is shown that, given a limited frequency band, the linear modulation form is not optimal. Results of error calculations presented are obtained via mathematical modelling of the altimeter’s operation for different shapes of the additional prequency modulation. It is shown that using complex shapes of the «slow» modulation with positive third derivative and optimizing for a given altitude range allows to reduce the average measurement error 2–3 times additionally relatively to the linear modulation form without expanding the occupied frequency band.

This study is concerned with the problem of increasing the accuracy of a low-altitude altimeter employing the frequency modulation principle. A way to suppress the “discrete error” of the altimeter by employing additional frequency modulation of the carrier wave and averaging the resulting counts is considered. The benefit of such approach is simplicity of technical implementation manifesting in minimal changes in the microwave path and the recording device, which needsto run in averaging count mode. This work presents a genetic algorithm for computing the array of additional modulation frequencies which can be used to reduce the mean square of the discrete error given a limited frequency band. Results of error calculations presented are obtained via mathematical modeling of the altimeter’s operation. It is shown that using additional modulation frequencies obtained by the genetic algorithm allows to reduce the average measurement error two times relatively to the linear modulation form without expanding the occupied frequency band.