V.B. Bakeev, S.S. Telegin, A.P. Trofimov
The use of antenna arrays for space radiomonitoring has several advantages compared to mirror antennas. For example, systems with antenna arrays overwhelm mirror antenna systems in spatial search speed.
However due to the broadbandness limits (frequency ratio over 5) circular antenna arrays are unable to form direction pattern with width enough to perform classical direction finding methods. In lower part of bandwidth antenna arrays are too dense, while being sparse in upper part of bandwidth. That impacts the minor lobes size dramatically.
The problem of acquiring the direction finding accuracy needed is solved by using one of superresolution methods (MUSIC, Capon).
This gives us solution to the first part of the problem – finding satellite’s coordinates. However, the second part – radiotechnical analysis of satellite emission is not that easy. For example that would be nearly impossible if there is another satellite that has emission spread close to ours and fitting into minor or even major lobe.
Solution of that problem is using algorithms of spurious signal suppression. The idea is to create optimum conditions for the signal while maintaining worst possible conditions for spurious signals. That maximizes Signal/(noise+spurious signals) ratio.
Evaluation of a known method of forming optimal direction pattern showed that in certain cases (especially when one considers emitters coupling, ground, etc) it is not effective enough.
Despite the fact that we can find satellite direction in broadband antenna arrays using one of superresolution methods, the problem of identification satellite’s emission requires serious research to build effective algorithms to form optimal direction patterns.