Low probability of intercept - Definition and Overview

A low probabililty of intercept radar has the characteristic that it is unlikely to be detected by passive radar detection equipment (such as a radar warning receiver - RWR) while it is searching for or tracking a target. This characteristic is desirable because it allows you to find and track an opponent without them realising that you are doing so.

One of the major characteristics of an LPI radar is that is has small side lobes. These occur because the radio energy emitted by a radar doesn't all go in the direction that it is pointed - some leaks out in other directions. This energy allows the radar to be detected even when it isn't pointing at the detector. It also means that the radar has to be made more powerful than would otherwise be necessary, increasing the chance of detection. Other ways of reducing the profile of a radar include using wider frequency bandwidth (wideband), frequency hopping, using a frequency-modulated continuous-wave signal and using only the minimal amount of power required for the task.

Modern phased array radars not only control their side lobes, they also use very thin, fast moving beams of energy. These beams are less likely to be noticed when sweeping over a vehicle or aircraft equipped with radar warning equipment. Fighter aircraft, bombers and surface-to-air missile systems all desire reduced electro-magnetic profiles for improved stealth.

Systems which feature LPI include modern AESA radars such as that on the F/A-18E/F 'Super Hornet' and the electronically steered phased array on the S-300PMU-2.

References

• [1] (http://www.dtic.mil/matris/sbir/sbir032/sbir101.html)