disclosed is an radio frequency volumetric direction finding methodology , utilizing an half maxwell fish - eye lens having a semi - spherical shape , a focal plane with a feed structure composed of near - equally spaced frequency - independent antenna elements disposed uniformly to form a 2 - dimentional feed array ; and rf power splitters for each element and combiners for combining the rf energy received by the elements ; forming rows and columns ; thereby reducing the number of required rf receiver channels for subsequent processing , where the maximum row / column and differential amplitude comparison is used for deriving df estimation of intercepted signals ; as part of a robust signal detection and direction - finding system ; for detecting and processing a plurality of signals emanating from navigation , radar and communication equipment on surface and airborne platforms .