ﮐﺎﻫﺶ ﮐﻼﺗﺮ ﺑﺮد- دوﭘﻠﺮ ﺑﺎ ﻓﯿﻠﺘﺮ ﻓﺸﺮدهﺳﺎزي ﭘﺎﻟﺲ وﻓﻘﯽ ﺑﻪوﺳﯿﻠﻪ ﺷﮑﻞﻣﻮج ﻓﺮﮐﺎﻧﺲ ﭘﻠﻪاي ﺗﺼﺎدﻓﯽ

Range-Doppler Clutter Suppression with Adaptive Pulse Compression by Randomized Stepped Frequency Waveform

ﺩﺭ ﺭﺍﺩﺍﺭﻫﺎﻱ ﭘﺎﻟﺲ ﺩﻭﭘﻠﺮ ﻣﻌﻤﻮﻻً ﺍﺯ ﻓﺸﺮﺩﻩﺳﺎﺯﻱ ﭘﺎﻟﺲ ﻭ ﺭﻭﺵ ﭘﺮﺩﺍﺯﺵ ﺩﻭﭘﻠﺮ ﺑﺮﺍﻱ ﺁﺷﮑﺎﺭﺳﺎﺯﻱ ﻫﺪﻑ ﻣﺘﺤﺮﮎ ﺍﺯ ﻃﺮﻳﻖ ﺗﺒﺪﻳﻞ ﻓﻮﺭﻳــﻪ ﺳــﺮﻳﻊ ﺍﺳﺘﻔﺎﺩﻩ ﻣﻲﮐﻨﻨﺪ. ﺭﻭﺵ ﻓﺸﺮﺩﻩﺳﺎﺯﻱ ﭘﺎﻟﺲ ﻣﺘﻌﺎﺭﻑ ﻭ ﺧﺮﻭﺟﻲ ﻓﻴﻠﺘﺮ ﻣﻨﻄﺒﻖ ﺍﺳﺘﺎﻧﺪﺍﺭﺩ ﺑﺮﺍﻱ ﺁﺷﮑﺎﺭﺳﺎﺯﻱ ﺍﻫﺪﺍﻑ ﮐﻮﭼﮏ ﻧﺰﺩﻳﮏ ﺑــﻪ ﻳــﮏ ﻫــﺪﻑ ﺑــﺰﺭﮒ ﮐﺎﺭﺍﻳﻲ ﻣﻨﺎﺳﺒﻲ ﻧﺪﺍﺭﺩ، ﺯﻳﺮﺍ ﮔﻠﺒﺮﮒﻫﺎﻱ ﺟﺎﻧﺒﻲ ﺧﺮﻭﺟﻲ ﻓﻴﻠﺘﺮ ﻣﻨﻄﺒﻖِ ﻫﺪﻑ ﺑﺰﺭﮒ، ﺑﺎﻋﺚ ﻣﺎﺳﮏﺷﺪﮔﻲ ﺍﻫــﺪﺍﻑ ﮐﻮﭼــﮏ ﻣﻲﺷــﻮﺩ. ﻓﺸﺮﺩﻩﺳــﺎﺯﻱ ﭘــﺎﻟﺲ ﻭﻓﻘﻲ ﺍﻳﻦ ﻣﺸﮑﻞ ﺭﺍ ﺑﻪﻃﻮﺭ ﻗﺎﺑﻞﺗﻮﺟﻬﻲ ﺭﻓﻊ ﻣﻲﮐﻨﺪ. ﺍﻣﺎ ﻫﺪﻑ ﺳﺮﻳﻊ ﻳﮏ ﺷﻴﻔﺖ ﻓﺎﺯ ﺩﻭﭘﻠﺮ ﺑﻪ ﻓﺮﮐﺎﻧﺲ ﺳﻴﮕﻨﺎﻝ ﺩﺭﻳﺎﻓﺘﻲ ﺍﻟﻘﺎء ﻣﻲﮐﻨــﺪ ﮐــﻪ ﺑﺎﻋــﺚ ﻋــﺪﻡ ﺗﻄﺎﺑﻖ ﺳﻴﮕﻨﺎﻝ ﺍﺭﺳﺎﻟﻲ ﻭ ﺩﺭﻳﺎﻓﺘﻲ ﻣﻲﺷﻮﺩ؛ ﺩﺭﻧﺘﻴﺠﻪ ﻧﺴﺒﺖ ﺗﻮﺍﻥ ﺳﻴﮕﻨﺎﻝ ﺑﻪ ﻧﻮﻳﺰ ﮐﺎﻫﺶ ﻣﻲﻳﺎﺑﺪ. ﺍﺯﺁﻥﺟﺎﻳﻲﮐﻪ ﻓﻴﻠﺘﺮ ﻣﻨﻄﺒﻖ ﺩﺭ ﮔﻴﺮﻧــﺪﻩ ﺭﺍﺩﺍﺭ ﻓﻘــﻂ ﺑــﺎ ﻧﺴﺨﻪ ﺳﻴﮕﻨﺎﻝ ﺍﺭﺳﺎﻟﻲ ﺗﻄﺒﻴﻖ ﺩﺍﺭﺩ، ﺑﻪﺩﻟﻴﻞ ﻋﺪﻡ ﺗﻄﺒﻴﻖ ﺑﺎ ﺳﻴﮕﻨﺎﻝ ﺩﺭﻳﺎﻓﺘﻲ ﺍﺯ ﻣﺤﻴﻂ، ﺧﺮﻭﺟﻲ ﺁﻥ ﺩﭼﺎﺭ ﺗﻠﻒ ﻣــﻲﺷــﻮﺩ. ﻣﻌﻤــﻮﻻً ﻓﺸﺮﺩﻩﺳــﺎﺯﻱ ﭘــﺎﻟﺲ ﻭﻓﻘﻲ ﺩﺭ ﻣﺤﻴﻂ ﺻﺮﻓﴼ ﻧﻮﻳﺰﻱ ﺑﺎ ﻳﮏ ﺗﮏ ﭘﺎﻟﺲ ﻗﺎﺑﻞﺍﺟﺮﺍ ﺍﺳﺖ ﺍﻣﺎ ﺩﺭ ﺣﻀﻮﺭ ﮐﻼﺗﺮ ﻗﻮﻱ ﺑﻪ ﭼﻨﺪ ﭘﺎﻟﺲ ﺑﺮﮔﺸﺘﻲ ﺍﺯ ﻫﺪﻑ ﻧﻴــﺎﺯ ﺩﺍﺭﺩ. ﺩﺭ ﺍﻳــﻦ ﻣﻘﺎﻟــﻪ ﺑــﺮﺍﻱ ﺗﺄﻣﻴﻦ ﺍﻳﻦ ﭘﺎﻟﺲﻫﺎ، ﺩﺭ ﻓﺮﺳﺘﻨﺪﻩ ﺭﺍﺩﺍﺭ ﻣﺠﻬﺰ ﺑﻪ ﻓﺸﺮﺩﻩﺳﺎﺯﻱ ﭘﺎﻟﺲ ﻭﻓﻘﻲ، ﺷﮑﻞﻣﻮﺝﻫﺎﻱ ﻣﺘﻨﻮﻉ ﺑﻪﻭﺳﻴﻠﻪ ﭘﺮﺵ ﻓﺮﮐﺎﻧﺴﻲ ﺗﺼﺎﺩﻓﻲ ﺩﺭ ﺷﮑﻞﻣﻮﺝ ﻓﺮﮐﺎﻧﺲ ﭘﻠﻪﺍﻱ ﺗﻮﻟﻴﺪ ﻣﻲﺷﻮﺩ. ﺑﺎ ﺍﻳﻦ ﺭﻭﺵ ﺍﻫﺪﺍﻑ ﻣﺎﺳﮏ ﺷﺪﻩ ﺩﺭ ﻣﺠﺎﻭﺭﺕ ﻳﮏ ﻫﺪﻑ ﻗﻮﻱ ﻭ ﮐﻼﺗــﺮ ﺑــﺎ ﺭﻭﺵ ﭘﻴﺸــﻨﻬﺎﺩﻱ ﺁﺷــﮑﺎﺭ ﻣﻲﺷــﻮﺩ. ﻧﺘــﺎﻳﺞ ﺷــﺒﻴﻪﺳــﺎﺯﻱ ﺁﺷﮑﺎﺭﺳﺎﺯﻱ ﺍﻫﺪﺍﻑ ﻣﺘﺤﺮﮎ ﻣﺎﺳﮏﺷﺪﻩ ﺑﺎ ﺳﺎﻳﺮ ﺭﻭﺵﻫﺎﻱ ﻣﺘﺪﺍﻭﻝ ﻣﻘﺎﻳﺴﻪ ﻭ ﺑﺮﺭﺳﻲ ﻣﻲﮔﺮﺩﺩ.

Pulse-Doppler radars typically use pulse compression and Doppler processing to detect moving targets through fast Fourier transforms. The conventional pulse compression method and the standard matched filter output for detection of small targets close to a large target do not work well, since the sidelobes of the match filter output by a large target could mask the smaller targets. Adaptive pulse compression resolves this issue significantly in noise. However, the fast targets induce Doppler phase shift in the received signal frequency, in which cause mismatch between the received signal and the transmitted signal. Consequently, the Signal to Noise Ratio is reduced. Whereas the matched filter in the radar receiver is only adapted to the transmitted signal version and its output will be wasted due to non-matching with the received signal from the environment. Adaptive pulse compression is generally applied with a single pulse in alone noise environment, but in the presence of strong clutter it is required to several return pulses. In this paper, to supply these pulses, in a radar transmitter equipped with adaptive pulse compression, waveforms diversity are generated by random frequency hopping in step frequency waveform. The simulation results of the detection of masked moving targets are compared with other conventional methods.