Research On W-band Full Polarimetricradar Target Characteristics Measurement Algorithms

The development of stealth technology and anti-stealth technology relies on theresearch of targets electromagnetic scattering characteristics. The electromagneticscattering characteristics of complex targets vary from different electromagneticenvironment. Broad band and variable polarization technology are combined in this paperto obtain more detailed information of the targets, including high resolution range profile,two-dimensional image and polarization decomposition information based on fullpolarimetric scattering matrix. This combination has great research value in the field oftarget identification, radar imaging, precision guided and so on.Firstly, the construction theory and detection method of W-band variable polarizationradar system are studied. Based on four-submatrix antenna feeder and the virtualpolarization synthesis technology, this system can transmit and receive the signals with allkinds of polarization model to get the full polarimetric scattering matrix. Using digitalweighted amplitude-phase techonology, multichannel amplitude-phase error calibration isachived; the insertion loss introduced by the traditional beamforming network is reducedthrough digital beam forming method; the EIRP of transmitter and the sensitivity ofreceiver are improved. This system can also transmit multi-mode emission signals and hasgreat potential in the target recognition and classification, according with current trends inradar techonology.Secondly, the methods to extract target scattering characteristics are emphasizedlyresearched, including the algorithms to extract target scattering matrix and to get highresolution range profile. Furthermore, two decomposition methods (Freemandecomposition and Cloudede compositon) are used to extract the full polarimetricscattering matrix to get more information. The processing results based on simulation andtesting data are given. The more detailed range profile informations is received and thetypical radial targets are identified and successfully. The results show that the algorithmsused have the capacity for target identification and classification.Finally, two-dimension imaging methods of the target are deeply researched. Takingadvantage of the turn-table system outside, tank model data is collected. After applyingRange-Doppler algorithm to tank model data, two-dimension high resolution far-fieldimages are received and the results are satisfactory. However, it is often impossible for thelarge complex groud targets to meet the far-field conditions, electromagnetic wave in the irradiation area can not be regarded as plane wave like in the far-field, or the terriblemeasuring errors will occur. Therefore, two near-field imaging algorithms are proposedincluding spherical back-projection (SBP) algorithm and the algorithm which combinesnear-field to far-field projiection and the extended coherent processing method. These twoalgorithms deal with spherical wave model directly to get accurateimagings, avoidingfar-field approximation. The former is of low efficiency due to a large number ofinterpolation and superposition, but the latter can achieve high efficiency owing to FFT andcan improve the signal-noise ratio because of coherent superposition. Numerical simulationresults proved that these methods are very effective. The comparision of the two methodsshows that the second algorithm is more effective.