RADAR TRANSPONDERS AND RADAR TARGET ENHANCERS

Radar transponders and radar target enhancers have been in use in a variety of applications for many years. Perhaps the most widely-known applications of radar transponders are in Identification Friend or Foe (IFF) and its civilian counterpart, secondary surveillance radar for air traffic control, and as racons in marine navigation and, most recently, as Search And Rescue Transponders (SART) in the Global Marine Distress and Safety System (GMDSS). Radar target enhancers may be less familiar, since their uses hitherto have been limited to military applications, especially the enhancement of the effective radar cross-sections of missile test range drone aircraft and missiles. With the significant reductions recently, in the cost of microwave semiconductors, it has become possible to apply both techniques to an increasing range of civil applications. While transponders and radar target enhancers have some aspects in common, they differ in many important ways and it is the purpose of this paper to explain the operation of each, illustrated by means of practical examples.