Signal Amplitude-Based Multipath Envelope Fitting: A Promising Method for Short-Delay Multipath Mitigation in Space Applications

摘要

Multipath is one of most unpredictable error sources inrnprecise positioning and navigation. Its geometrydependentrnproperty makes it difficult to be mitigatedrnusing a single technique for all the possible geometricrnmultipath delays. The state-of-the-art mitigationrntechniques have proven efficient against multipath havingrna medium (30 m to 250 m) or large delay (> 250 m), butrnineffective to short-delay (< 30 m) delay multipath.rnHowever, in practice, most of the multipath signals enterrnthe receiver with short delays. In space applications, thernreceivers on the space vehicles even suffer from veryshort-rndelay multipath (< 5 m) that is reflected from thernvehicle itself or from other vehicles during the operationsrnof rendezvous and docking.rnThis paper proposed a new multipath mitigation method,rncalled Signal Amplitude-based Multipath EnvelopernFitting (SAMEF), which is capable of mitigating shortdelayrnand very-short-delay multipath by up to 50%. It alsornexhibits a promising performance for medium or largerndelays as compared to other state-of-the-art methods.rnSAMEF is based on the fact that the signal quality valuesrn(e.g. signal amplitude) mainly contain multipathrninformation. This information will be used to modify therncorrelator outputs in such a way that multiple weightedrnmodified-correlators can be linearly combined forrnmultipath estimation by the process of curve fitting. Arnsimple implementation strategy for SAMEF is alsornproposed that operates in-conjunction with the trackingrnloop and has a very low computational load. Therndemonstration using a typical scenario in space verifiesrnthe feasibility of SAMEF and shows that SAMEF canrnprovide a good multipath immunity for almost allrngeometric multipath delays larger than 1 m.