简介:Duringthepastfewyears,theterahertz(THz)frequencyregimehashadrenewedscientificandtechnologicalinterestbecauseofrecentbreakthroughsintheareasofhighpowersources,sensitivedetectors,novelmaterials,andhighresolutionvideoimaging.Becauseitliesbetweentheradiofrequenciesandinfraredwavelengths,theterahertzelectromagneticregionwasthoughttobepromisingforpracticalapplications(300micrometerswavelengthcorrespondsto1THzfrequency),butitsufferedfromveryhighattenuationthroughtheatmosphere(above1dB/meter),andwasfoundtobedifficulttogenerate,modulate,anddetect.Ontheotherhand,manynon-polardielectricmaterialsaretransparenttoTHzwaves,allowingthedetectionofinclusions,internalinhomogeneities,ormaterialsbehinddielectricobstaclesfor
简介:Thispaperstudiesthedevelopmentonthefirstorderseacluttercrosssectionforbistatichighfrequencysurfacewaveradar(HFSWR).Basedonthereceivedfirstorderelectricfieldexpression,aclosed-formofcrosssectionsisderivedtoaccountforthecaseofreceivingantennaarraybeingmountedontheshipborneplatform.Theuniformlinearmotionandswaymotioncomponentsareassumedtoberesponsiblefortheobserveddifferencesincomparisonwiththebistaticfixedantennacase.Correspondingly,simulationsareconductedtostudytheseaclutterspectralcharacteristicsforthesetwocasesversusdifferentsystemparametersandseastateconditions.ItisshownnumericallythattheforwardmotioncomponentwillspreadtheBragglinesseverelyandtheinfluencetriggeredbytheswaymotioncanbeexplainedastheBesselfunctionmodulationoftheordinaryseaclutterspectra.TheobtainedresultshaveimportantimplicationsintheapplicationofshipborneHFSWRtechnologytooceanremotesensingandtargetdetection.
简介:介绍了演进中的ISO/IEC18000系列标准,分析了ISO/IEC18000标准的局限性,诸如标准的可用性可能受到损伤,造成产品性能标识模糊,对工程设计带来不便,影响引入通信技术新成就以改进RFID空中接口设计等。