Monopulse errors reduction using increased AM-PM conversion receivers

Monopulse detectors constitute the most accurate technique in radar to obtain target direction so they are widely used in ATC applications and in active guidance systems. In the second case, their main interest is their immunity against ECMs due to the fact that they extract the information from the quotient Δ/Σ, and then. external modulation does not affect the measure. However, in E.W. environments, receivers must handle high input powers and nonlinear effects, as saturation of input stages, causes channels desequillibriums and then errors. In ATC applications, the enormous dynamic range of the received signals also causes error due to nonlinear phenomena. In this paper, a simple method is described to reduce errors produced because of input stages saturation. This method, based in an artificial increase of AM to PM conversion has application in the two-channel monopulse processor first proposed by Selenia (the most used in ATC SSR sensors) and the one utilized in active guidance systems (used in E.W. environments). Experimental results agree quite well with theory.