Principles of Modern Radar - Volume 2 1891121537

554 CHAPTER 12 Electronic Protectionoptimal performance under natural conditions, and is consequently used only when needed.In addition, responsive EP may require some form of detection, characterization, and assessmentof the EW environment to determine whether to initiate or terminate the selectedEP. The inherent time lag associated with the environment sensing and EP decision logicmay lead to improper EP implementation in a dynamically changing EW environment.Radar performance may actually suffer more due to the sluggish EP switching than itwould without any EP.Numerous EP techniques and designs have been developed over the decades. The onespresented in this chapter provide at best a small sampling of the wide variety of approachesthat have been conceived and implemented. The radar system engineer’s selection of anappropriate suite of EP techniques must take into consideration a wide variety of factors,such as EW environment severity and likelihood; EP technology maturity; EP designimpacts on radar performance under natural environments; radar size, weight, cooling,and power limitations; and program schedule and funding constraints.The reactive nature of EW makes it critical to continually understand and anticipatean adversary’s capabilities in order to successfully counter them. The terms robust anddurable are sometimes used to describe an EP capability that provides consistently goodperformance over a wide range of EA conditions and cannot be quickly defeated by aredesigned or reprogrammed EW threat once its existence and characteristics are revealed.In contrast, the terms fragile and perishable are sometimes used to describe an EP capabilitywhose performance breaks down when specific threat assumptions are not met or that canreadily be countered once it has been exposed.Electronic warfare concerns are at times given secondary priority in radar developmentefforts. This might be attributable to a lack of understanding of the wide range ofpotential EW environments and the ease with which reactive EW threats may emerge.In some cases, addressing EP requirements might be deferred until after a baseline radardevelopment is under way or even completed to avoid compromising a program’s survivalthrough the revelation of potential performance shortfalls. Generally, however, modernradar development identifies and incorporates critical EP requirements from the earlieststages of the design to best ensure that the final system is properly equipped to performits mission under any anticipated electromagnetic environment.The EP techniques described in the subsequent sections are organized into categoriescorresponding to major radar functional subsystems: antenna, receiver, transmitter, exciter,signal processor, and data processor. Many of the EP techniques obviously have designimplications across multiple subsystems; in such cases we pick the subsystem that seemsto be most central to conveying the EP concept. The actual division between the categoriesthemselves may be somewhat blurred in modern radars. For example, radars may incorporateparts of the transmitter and receiver in the antenna array or may digitally implementtraditional analog receiver functions in the signal processor. Therefore, the categories areintended primarily in a functional sense rather than an actual physical implementation.12.5 ANTENNA-BASED EPThe antenna is the radar’s first line of defense against jamming. Electronic protection isaccomplished through pattern attenuation and blanking of EA interference as well as angletracking approaches that help counter angle deception EA.