Simultaneous Resolving of Frequency Separated Narrow Band Terrestrial Radio Sources by Multi Antenna Spectrum Monitoring Systems Assisting Radio Astronomy

Abstract

Radio telescope sites require regular surveys of terrestrial radio information, viz. spectrum, flux density and radio direction. Terrestrial wireless radio sources may interfere in the radio telescope signals. Such signals received through wide band antennas in the VHF/UHF bands are amplified, integrated and spectrum-frame averaged. The radio direction of these sources can be resolved if they are steady over the time of observation, unique in frequency and if the system consists of two or more stationary antennas possessing low side-lobe levels, positioned on the perimeter of a circle parallel to but above the ground plane, with their major lobes directed opposite to the center of the circle. The maximum side-lobe level determines the maximum extent to which the antennas may be separated in angle in relation to the center of the circle. To resolve the sources, the signal is processed and then they are related to the radiation patterns with some algorithm. The overall observation angle can be made complete omni-directional by adding more number of antennas to the system, or by repositioning the two-antenna system on other sections of the arc. The generalized theory with mathematical modeling and error analysis are briefly described. Supporting experimental results obtained from a fully functional multi-antenna system with omni-directional coverage in the horizontal polarization are also presented.