Disquisition On Multipath Mitigation Algorithm In Spread-Spectrum Ranging Systems

This thesis studies the multipath mitigation techniques in the background of developing receivers of certain important national defence pre-research project . It consists of three main parts:In the first part, we analyse the effect of multipath on code-tracking loops of receivers in Spread-Spectrum Ranging Systems. First, we establish the model of received signals with the present of multipath through the presentation of multipath's characters. Then, we analyse the theory of Delay Lock Loop(DLL), based on which we derive the tracking error of DLL caused by multipath.In the second part, some of the multipath mitigation techniques widely used presently are analysed and compared with each other, from which we select the MEDLL(Multipath Estimating Delay Lock Loop)technique as the multipath mitigation algorithm in scope of signal processing in the receivers. First, we classify the multipath mitigation techniques into four categories, And then the presentation of principles and simulation of performances are done of three widely-used techniques of multipath mitigation, which are based on the code tracking loop with the name of Narrow-Correlator-Spacing technique,ELS(Early late Slope) technique and MEDLL technique. From the presentation and simulation, the MEDLL technique is selected as the multipath mitigation algorithm in signal processing's scope..In the third part, aimed at the implement of MEDLL technique in the receivers, we analysis in detail its algorithm flow,parameter selecting and implement on hardware.