Modeling And Simulation Of Land-ship HF Hybrid Sky-surface Wave Radar

This dissertation presents Land-ship HF Hybrid Sky-Surface Wave Radar based onexisting OTH radar research. Research for this radar system is still blank. Thisdissertation includes signal modeling of radar, the channel characteristics, positioningalgorithm, radar signal processing and sea clutter. The main work is summarized asfollows:To begin with, this dissertation has established the basic mathematical model of theLand-ship HF hybrid sky-surface wave radar, outlined each module, and derived itsradar equation. Then, the radar transmitter and receiver system, the reasons why theradar signal waveform selection is LFMCW, and the principle of selecting parameters ofLFMCW has been introduced.Secondly, the channel characteristics of the radar signal have been discussed,among which the channel characteristics of the ionosphere got in-depth analysis. Thenthe three basic theorems of ionosphere have been analyzed, on the basis of which somerelevant derivations and Radar beam coverage have been made, so that some law ofelectromagnetic wave propagation path in the ionosphere has been got. In addition, toexplore the effects of the ionosphere on the radar signal, a simple modeling of radarsignals through the ionosphere has been built. Taking account of interference, the jointdistribution of the radar signal amplitude and magnitude of interference has beenderived, through which we gain the conclusions that to increase the signal energy caneliminate the signal amplitude fluctuation effects on signal detection. Finally, a generalmodel of ionospheric radar signal phase pollution function has been presented, and thecharacteristics of ionospheric phase contamination has been introduced.Third, this dissertation studies the positioning algorithm and the basic methods ofradar signal processing via Land-ship HF Hybrid Sky-Surface Wave Radar. Firstly, thisdissertation studies the existing ground-based positioning method and analyze theshortcomings of the method; taking into account the curvature of the Earth, presents aspherical positioning algorithm, on the basis of which Geometrical Dilution ofPrecision(GDOP) were analyzed. The results showed that this radar system cancomplete objectives in a certain positioning accuracy requirement; then themeasurement of speed and angle was analyzed in far field; the above basis, Range-Azimuth-Doppler algorithm were derived under the signal model. The results of radarsignal processing simulation show that under a large signal to noise ratio, targetdetection of this radar system is feasible, while under the strong noise background, theeco signal will be covered, which means that the basic radar signal processing methodsfail.Finally, this dissertation examines the strong sea clutter background, in which Land-ship HF Hybrid Sky-Surface Wave Radar works. First, this dissertation describesthe mechanism of sea clutter generated, discusses its Bragg resonance condition, andobtains a first-order expression of sea clutter Doppler frequency. On this basis,combining the features of this radar system, this dissertation analyzes the spread of the1st-order sea clutter, get the spatial distribution of spread of sea clutter and the law thatshipborne platforms impact on sprectrum spread. Taking account of the relevantgeometric characteristics, space-time distribution of1st-order sea clutter have beenobtained. Finally, the power spectrum of1st-order sea clutter was explored using Gillderive results under narrow beam conditions. Combined with the wide beamcharacteristics under the new system, the method to get subdivision beam has beenmade to simulate the power spectrum1st-order sea clutter. On this basis, the use ofmatlab simulation has been produced based on the principle of first-order sea clutter seaclutter spectrum, and the simulation results confirmed the analysis in this dissertationabout the first-order sea clutter characteristics.