The Research On Super Resolution Angle Measurement In VHF And Phased Array Radar

VHF and phased array radar becomes an important equipment in the area ofanti-stealth because of its natural advantages in anti-stealth and resisting anti-radiationmissiles. It works on VHF and makes general absorbing material and coating invalid.However, compared with microwave radar with a same aperture, meter-band radar hasbad elevation resolution and serious multipath effect. Its wave beam is wide and easy tohit ground. All the above disadvantages makes target position information easy todestroy.This project focus on the measurement of elevation angle when facing multipath.Main tasks are summarized as follows.First of all, to simulate and analyze the effects on reflection coefficient by signalpolarization mode, ground roughness, terrain undulation and earth curvature, models ofphased array measuring angle and multipath reflection are built by the ways of arraysignal processing.Secondly,as a classic algorithm of measuring angle, the substance of maximumvalue method is generating a few spatial filters to match with one target respectively.But the accuracy of this method is limited by sweeping spaces. The monopulsemeasuring angle method measures angle by dealing with the amplitude or phase of twoadjacent wave beams in just one single pulse, which makes its high real-time.Simulation is performed to analyze the reason for using two beams’ overlappingposition at their half power beam width in engineering, and it shows the monopulsemeasuring angle method can meet requirements of both accuracy and range at the sametime. On the other hand, the resolution of measuring angle with monopulse is one wavebeam width. And it is only suitable for one single target. As for two targets in the mainlobe, the measuring value will be the weighted barycenter value of the angles of thattwo targets.Thirdly, to introduce the mathematical model of coherent source and classic superresolution algorithm MUSIC and ESPRIT principles.But for strongly coherent sourcewith multipath effect, the rank of signal covariance matrix shows negative, which makesMUSIC algorithm and ESPRIT algorithm invalid. Hence, preprocessing for signalcovariance matrix should be done to recover its rank. After that super-resolutionalgorithm would be applied. For decorrelation algorithm, spatial smoothing algorithm(forward smoothing, backward smoothing and two-sides smoothing), matrixreconstruction algorithm (matrix decomposition algorithm, modified matrixdecomposition algorithm and matrix decomposition algorithm based on spatialsmoothing) and Toeplitz algorithm (Toeplitz approaching method) are studied in theproject. The measurement accuracy, resolution capability and influenceing factors of these methods are simulated. In addition,parameters chosen in engineering are alsoanalyzed in this project. The result shows that matrix decomposition algorithm based onspatial smoothing takes less calculation and is more suitable in engineering application.The elevation measuring algorithm based on beam split is introduced in the end,for the reason that super-resolution algorithm takes large calculation.This algorithmutilized characteristics of reflected wave. They are amplitude with sinusoidal variationand contrary phase in adjacent split lobes. The measurement would be accurate ifelevation coding region and error curve matches environment well. If not, largemeasurement error occurs.