Evaluation of accuracy of radiometric correlation-extreme navigation systems

Abstract

Background: The use of passive matrix radiometric sensors of the millimeter wave range in aircraft navigation systems, which make it possible to form a radiometric image of a ground navigation object under conditions of high-speed flight of aircraft, is one of the effective ways to ensure high accuracy in measuring the coordinates of objects and, ultimately, leads to an increase in the probability of positioning aircraft [1]. In work [2], analytical relationships were obtained and quantitative estimates of the accuracy of positioning of aircraft equipped with a matrix radiometric navigation system were made. It is shown that the use of matrix radiometric sensors makes it possible to realize the required high (up to units - tens of meters) positioning accuracy of high-speed aircraft.

Objectives: The purpose of this article is to develop a method for increasing the accuracy of a radiometric correlation - extreme system based on the use of a matrix radiometric millimeter-wave receiver with channel compaction.

Materials and methods: In this paper, we used the method of linear multiplexing with channel separation according to the waveform using orthogonal Walsh functions. In this case, the sensitivity for each channel corresponds to the sensitivity of the modulation radiometer, and in comparison with the sensitivity of the compensation radiometer, it decreases by about two times. Taking into account the orthonormality of the Walsh functions, the signal at the output of each channel is proportional to the intensity (power) of the signal at the input of this channel.

Results: In this work, it is shown that the optimal number of combined channels is a multiple . The analysis of the results of the calculations shows that the combination of 64 channels into one amplifier-conversion path leads to an increase in inter-channel interference and, as a consequence, to a deterioration in the sensitivity of each channel.

Conclusions: In this case, it is expedient to limit the number of channels to be sealed per one amplifying-converting path. So, when 16 channels are combined into one path, the sensitivity of each channel remains quite high: about 1 K – for a super heterodyne radiometric receiver, and less than 1 K – for a direct amplification radiometric receiver. In this case, the number of amplifying-conversion paths with the total number of channels in the matrix 64 is equal to four.