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

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

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scatteringvolumeTXRXFigure 3: Sketch of the forward scattering geometry for passive bistatic MSToperation.Conventional TV broadcasts are ordinarily of little use for atmosphericsounding because the high amplitude sync pulse appears about every 63 µs,resulting in a backscatter range ambiguity of 9.5 km. However the GDOPfactor applies to this, too. Taking a typical GDOP of 10 we observe thatthe altitude ambiguity increases to about 100 km. Although analog TV is“less interesting” as a waveform, it more resembles a simple periodic pulsewaveform, and will be quite simple to detect and proces.The GDOP factor also applies to the effective wavelength sampled (for aBragg-like scattering process). In a conventional backscatter radar, operatingat a frequency of 50 MHz, radio waves are strongly scattered from irregularitieswhose wavelength is about 3 m. However, in a forward scatter system<strong>with</strong> GDOP of 10, the sampled wavelength would be 30 m. Thus, relativelyhigh transmitter frequencies can sample scatterers associated <strong>with</strong> relativelylarge wavelength/small ⃗ k, for which the scattering cross section is still large.Also, it is simpler to build high gain antennas at UHF than VHF, whichmakes it more possible to exclude undesired signals (from ground clutter, orother interferors at other azimuths).476

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