Spatial Filtering when Determining the Position of Radio Sources

Introduction. The angular method of locating overlapping spectrum radio sources (RS) is supplemented by spatial filtering (SPF) of their multipath signals. The cross-correlation function (CCF) between the estimates of signals at the reception point (RP) allows extraction of RS signals with a minimum delay corresponding to the true position of RS under a certain configuration of the multi-position receiving system. The CCF between the estimates of signals in different points allows matching the position lines defined by the estimates of azimuth and elevation angle corresponding to the same RS thus avoiding the formation of false points and areas of location.

Aim. Development and investigation of a method for matching position lines based on RS signal estimates obtained by spatial filtering in different receiving points.

Materials and methods. The MUSIC method was used to estimate the direction of arrival of overlapping spectrum signals in different RPs. Based on these estimates, the coefficients of the spatial filter for RS signal selection were calculated using the least squares criterion. Calculating the CCF estimates of signals at a fixed RP eliminates the reflected signals from further analysis. The quality of SPF is improved with an inaccurately specified amplitude–phase distribution (APD) of the antenna array (AA) by rejecting non-suppressed interfering signals. The study was carried out by statistical simulation in the MATLAB environment.

Results. Under an accurate APD definition of the AA the probability of locating RS with signals of any intensity reaches 100 %. The worst results are achieved when one strong RS signal dominates in all reception points under inaccurate definition of the APD of AA. In such a case, the application of additional rejection increases the probability of correct location of weak RS from 40 to 90 %.

Conclusion. Depending on different propagation conditions and signal levels, the accuracy of _АА calibration and the probability of location of weak signal sources exceeds 90 %.

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