THE QUALITY OF ESTIMATION OF PARAMETERS OF A BROADBAND SIGNAL WITH NON-OPTIMAL RECEPTION UNDER CONDITIONS OF DISPERSION DISTORTIONS IN THE EARTH'S IONOSPHERE

Abstract

In the article, analytical expressions are obtained that make it possible to calculate the variance of the estimates of the initial phase, frequency and delay of the signal, as well as the covariance functions of pairs of estimates under the conditions of dispersion distortions. At the same time, the evaluating device does not know exactly or does not know the level of dispersion distortions at all and does not try to evaluate them. Therefore, the estimation of the parameters is carried out by a non-optimal algorithm. The described conditions arise in practice, for example, when trying to estimate the above parameters of a broadband signal by a classical estimator that does not take into account dispersion distortions. The described conditions also occur when the true value of the slope of the dispersion characteristic of the channel deviates from the previously measured value over time or due to the use of inaccurate measurement results or an inaccurate prediction of the value of the slope of the dispersion characteristic of the channel. The article presents analytically obtained graphs for the root-mean-square deviations of the obtained phase, delay and frequency estimates for the case of complete absence of dispersion distortion compensation and the case of incomplete dispersion distortion compensation. In particular, it is shown that the degradation of the quality of delay estimation is due to two factors: a value decrease and an expansion of the correlation peak. In terms of energy, this degradation exceeds the acquisition or demodulation loss. The results of the obtained calculations are confirmed by simulation modeling.