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The Bandwidth and Anti-Jam Capability of the Integrated FLL/INS BOC


A.Y. Shatilov

In earlier works the anti-jam capability (J/S) calculation techniques for tracking systems did not state that the system is kept optimal in the presence of jammer (from the optimal filtration theory’s pont). The J/S estimates din not guarantee that system’s optimally tuned for the maximum jammer level and there’s no possibiliry for futher lowering errors and getting goal in anti-jam capability. In this article the special design techinique for trackin loop synthesis and bandwith determination is presented. The technique keeps FLL optimal at maximum jammer power and guarantees top estimate of antijam capability at given limitations for tracking error. The necessity of giving limitation for tracking error turned out to be a feature for FLL in opposite, for instance, to PLL and DLL. In PLL or DLL tracking error is limited by discriminator’s aperture. In FLL discriminator’s aperture could be made infinite due to reducing of correlator’s accumulation time. So the doppler error is theoretically unlimited by aperture and hence anti-jam capability can grow to infinity. But it’s not the way the developer would like. It’s more reasonable to arrange a compromise between anti-jam capability, and precision and the developed technique allows to do so for FLL. The curves ‘J/S vs. doppler error’ has been presented. These curves allow quick finding of compromise solution for anti-jam navigation receiver development. It is shown that in the case of aiding, anti-jam capability does not depend on user dynamics but only does depend on the dy-namics of INS velocity error and the dynamics of oscillator frequency drift. Both latter processes can be merged into one summarized dynamic disturbance input. The dynamic model both for INS velocity error and the oscillator frequency drift is suggested as random walk. The way to find random walk’s forming noise spectral density by given Allan deviations for oscillator drift and INS velocity error is given.

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