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Adaptive Anti-Jamming Technologies In IF Digitalized Spread Spectrum Receiver

Posted on:2006-01-24Degree:DoctorType:Dissertation
Country:ChinaCandidate:S J LuFull Text:PDF
GTID:1118360185963774Subject:Information and Communication Engineering
Abstract/Summary:PDF Full Text Request
According to the ideology of software radio theory, the realization of intermediate frequency (IF) digitalized direct sequence spread spectrum (DSSS) receiver is one of the focuses in DSSS communications study. It is of great value to deploy narrowband interference (NBI) suppression techniques in IF digitalized DSSS receiver for commercial and military applications. The NBI suppression studys based on single antenna have bring out lots of schemes and techniques, but only a few of them have been deployed in practice. In this dissertation, the deployment of NBI suppression theory and techniques in digitalized DSSS receivers is studied intensively, the improvement on adaptive algorithms and NBI suppression techniques are performed to make them feasible for practical realization.Most of the lectures on NBI suppression assume that the spread spectrum signal and the background noise are white. This assumption cannot stand up in digitalized receiver because of the IF oversampling and digital low pass filtering in digitalized receiver. The code-aided optimal filtering is studied extensively in the circumstance of oversampling and colored background noise. The output SINR limitations of MMSE and constrained MMOE optimal filter are derived in the cirsumstance aforementioned. These limitations constitute the base of the code-aided optimal filtering and NBI estimate-subtract filtering.This dissertation summarize the recursive least squares (RLS) algorithm, blind recursive least squares algorithm and the QR decomposing for these two algorithms. Since the filtering vector is needed in QRD-RLS and QRD-BRLS, the parallelism of QR decomposing will be impeded slightly. The Inverse QR decomposion (IQRD) scheme for BRLS algorithm is proposed in this dissertation to enhance the parallelism, the systolic array structure for IQRD is proposed to calculate the algorithm in parallel. The square-root-free and division-free calculation scheme is proposed to simplify the hardware complicacy.The nonlinear filtering for NBI estimate-subtract assumes that the prediction error is dominated by spread spectrum signal and the background noise power is far below spread spectrum chip power, this assumption promises the low error ratio of chip decision but may not be attainable to digitalized DSSS receiver in military communication environment, and does not coincide with the principle of DSSS communication that decreases bit error ratio (BER) depending on spread spectrum gain, not on chip power. According to this principle, a novel filtering scheme named partly despread nonlinear filtering (PDNF) is proposed which makes chip decision after partly despreading the filtered sequence and recovering information bit...
Keywords/Search Tags:Digitalized Receiver, Narrowband Interference Suppression, Direct Sequence-Minimum Shift Keying (DS-MSK), adaptive filtering, Partly Despread Nonlinear Filtering (PDNF), Fast Refreshed Subband Adaptive Filtering (FRSAF)
PDF Full Text Request
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