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Proceedings with Extended Abstracts (single PDF file) - Radio ...

Proceedings with Extended Abstracts (single PDF file) - Radio ...

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In the case of commercial FM, stations emitting 100 kW ERP are ubiquitous;this power level is comparable to that of incoherent scatter radars! Of coursethe broadcast antenna directivity is much lower than that of ISR or MSTsystems. The second feature is subtle; it is highly likely that efficient communicationsand broadcast signals have excellent range-Doppler ambiguity.Thus it is possible to fully resolve the range of targets consistent <strong>with</strong> thetransmitter bandwidth (as in conventional radar waveforms). It is also possibleto estimate the Doppler power spectrum. For non periodic waveforms(such as FM, and the newer digital modulations used in wireless communicationsand broadcast), these data can be estimated <strong>with</strong>out suffering anyrange or Doppler aliasing. The mathematical basis for these statements hasbeen demonstrated by Sahr and Lind [1997]. Similar efforts using randomwaveforms in active radars were undertaken by Hagfors and Kofman [1991]and Sulzer [1986]. .1.1 Technology AdvancesPassive radar detection algorithms are computationally intensive comparedto those of most conventional radars. Fortunately, recent progress in computinghardware has effectively eliminated this challenge for illuminators <strong>with</strong>effective bandwidth less than about 250 kHz. Morabito and Sahr [2004] arepreparing a report which describes efficient numerical schemes for evaluatingthe range-Doppler pro<strong>file</strong>s.The MRR uses a “distributed” topology, which requires two synchronizationof two receivers separated by 150 km, as well as transport of the datafrom each receiver to the computational detection engine. The former problemhas been solved inexpensively <strong>with</strong> GPS clocks, and the data transportis achieved <strong>with</strong> internet connectivity. A distributed receiver is necessary forMST applications, which will be described below.Although not strictly necessary, modern digital receivers offer very highperformance as well as convenience in synchronization. Their use is stronglyrecommended.1.2 Practical Benefits of Passive RadarBy ceding the operation of a transmitter to others, a number of benefitsaccrue.472

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