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

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Figure 2: Example of range-azimuth interferometry from Melissa Meyer’sMaster’s thesis [2003]. By computing the passive radar extention to otherwiseconventional interferometric cross-spectra, the scatterer can be located inazimuth and range. In this figure, dark blue is the noise background, <strong>with</strong>light blue, yellow, and red indicating progressively stronger signals. Theresolution in this imate is 1.5 km in range and 1.0 km in azimuth. At 1000km range this corresponds to 0.001 radian, about 0.2 ◦ .plot the additional propagation delay for targets at MST altitude, for severaltransmitter–receiver separation distances.There is an additional challenge. The strong forward scatter path causes“geometric dilution of precision” in range (altitude), as illustrated in Fig. 5.A dilution of precision factor of 10 means that, if the range resolution ofa backscatter radar is 1 km, then in the forward scatter application therange (altitude) resolution would be 10 km. This means that analog FMwaveforms, <strong>with</strong> a bandwidth of 150 kHz and an intrinsic range resolutionof about 1 km, provide little altitude discrimination, and strong coincidence<strong>with</strong> ground clutter. Therefore, much higher bandwidth illuminators wouldbe useful.Digital television, has a bandwidth of about 6 MHz, and an intrinsicrange resolution of about 25 m. Thus a GDOP of 10 produces an altituderesolution of about 250 m, which is quite acceptable.475

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