Abstract: The invention relates to an ASDE radar to supply information on airport surface traffic. A well-known ASDE radar comprises an antenna having an elevation-depending gain factor ##EQU1## for .omega..sub.1 .ltoreq..omega.<.omega..sub.2, where .omega..sub.1, .omega. and .omega..sub.2 represent angles of depression. In such a radar, the echo power of an airport surface target is independent of the distance, whereas the echo power of rain clutter is inversely proportional to the square of the distance. Consequently, a remote surface target still projected on the radar screen above the rain clutter, is likely to disappear in the rain clutter when approaching the radar; this may result in fatal consequences. To solve the above problem, the ASDE radar of the invention comprises a combination of an antenna having a gain factor ##EQU2## and a sensitivity time control circuit in its receiver.

Abstract: The invention relates to monopulse radar for automatic angle tracking of a moving target, which prevents angle tracking errors from occurring when the polarization of the received signals is orthogonal to the polarization of the radar receiver. The monopulse radar comprises two monopulse clusters (4, 5) tuned to the same frequency band and arranged to receive mutually orthogonal polarizations; only one of these clusters lends itself for the transmission of r.f. signals. When supplied sum and difference signals by the two clusters (4, 5), the receiver (8) produces the angular error signals required to keep the radar directed at the target. The error signals are determined by the amplitude ratio between the difference signals and the sum signal from the first cluster or by the amplitude ratio between the difference signals and the sum signal from the second cluster, depending on the ratio between the sum signals from the two clusters.