به كارگيري آشكارساز GLR در رادارهاي غير فعال مبتني بر سيگنال ديجيتال تلوزيوني

چكيده انگليسي :

Employment of GLR detector in DVBT Based Passive Radar Fatemeh Majed f majed@ec iut ac ir Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Dr Mahmmod Modarres Hashemi modarres@cc iut ac irAbstractPassive bistatic radar PBR is a specific case of bistatic radars that exploits the existing non radartransmitters of opportunity in the environment Since there is no dedicated transmitter in these they havelower costs of procurement operation and maintenance Also they are physically small difficult to belocated resistent to anti radiation missiles and they do not need frequency allocations Besides bistaticnature of these radars protects them against intentional interference and makes them capable for detection oflow observable targets In contrast passive radars have some disadvantages as well Opportunity waveformsare not originally designed for radar operation and are no longer under the control of the radar designer Inaddition PBR systems do not have the information of such waveforms directly and hence must use adedicated receiver channel known as reference channel Therefore all the PBR system receivers includetwo receiving channels denoted by reference channel and target channel In low radio frequency bands suchas UHF and VHF achievable gain of the antenna is limited so the antenna s beam is relatively wide Hencethe target channel antenna will receive the transmitter s direct signal as well As a result signal processingoperation is much more complex in passive radars than in active radars Among broadcast andcommunication signals that have been considered and analyzed as possible passive radar sources thethumbtack ambiguity function of the Digital Video Broadcasting Terrestrial DVB T signal in addition tobeing stationary over time makes such a signal a good candidate for passive applications However DVB Tsignal has some deterministic components that cause certain ambiguities in its ambiguity function at non zerodelay and varying Doppler offsets These ambiguities reduce the effectiveness of the radar system as theymask targets at these offsets and or contribute to false alarms in the radar system In this thesis after studyingthe origins of these ambiguities proposed methods for side peaks suppression are reviewed Side peakssuppression in DVB T signal has been studied widely however its effect on the target detection performanceis not considered In this thesis we have shown that the conventional peak suppression methods are not ableto eliminate the whole peaks and therefore the remained peaks degrade the detection performance Inaddition if the target s signal power levels are significantly different side peaks of the stronger targetsincrease the detector s threshold Therefore the weaker targets which are located at these peak s positions can not be detected Moreover we employed the GLR detector for detecting target echoes in DVB T basedpassive radars which does not need to eliminate the ambiguity peaks and is able to detect the targets with lowSNRs We compare the performance of GLR detector with the performance of the method which applys CA CFAR detector after peak suppression methods as preprocessing and show the superiority of our proposeddetector Keywords Bistatic Radar Passive Radar DVB T GLR Detector شش

ماجد، فاطمه

به كارگيري آشكارساز GLR در رادارهاي غير فعال مبتني بر سيگنال ديجيتال تلوزيوني

رادار دو پايه