TAILIEUCHUNG - Digital Video_2

Tham khảo sách 'digital video_2', công nghệ thông tin, đồ họa - thiết kế - flash phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 11 Passive Radar using COFDM DAB or DVB-T Broadcasters as Opportunistic Illuminators Poullin Dominique ONERA France 1. Introduction This chapter is not dedicated to improve DVB-T Digital Video Broadcasters-Terrestrial reception in critical broadcasting conditions. Our purpose is to explain and illustrate the potential benefits related to the COFDM Coded Orthogonal Frequency Division Multiplex waveform for passive radar application. As we ll describe most of the benefits related to COFDM modulation with guard interval for communication purpose could be derived as advantages for passive radar application. The radar situation considered is the following the receiver is a fixed terrestrial one using COFDM civilian transmitters as illuminators of opportunity for detecting and tracking flying targets. The opportunity COFDM broadcasters could be either DAB as well as DVB-T ones even in SFN Single Frequency Network mode for which all the broadcasters are transmitting exactly the same signal. Such application is known in the literature as PCL Passive Coherent Location application Howland et al 2005 Baker Griffiths 2005 . This chapter will be divided into three main parts. The first ones have to be considered as simple and short overviews on COFDM modulation and on radar basis. These paragraphs will introduce our notations and should be sufficient in order to fully understand this chapter. If not it is still possible to consider a classical radar book as well as some articles on COFDM like Alard et al 1987 . More specifically the COFDM description will outline the properties that will be used in radar detection processing and the radar basis will schematically illustrate the compulsory rejection of the zero-Doppler paths received directly from the transmitter or after some reflection on the ground. Then the most important part will detail and compare two cancellation filters adapted to COFDM waveform. These two filters could be applied against multipaths reflection on ground

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