Instantaneous measurement for radar target polarization scattering matrix

Adopting ＂simultaneous transmitting, simultaneous receiving＂ operational scheme, instantaneous polarization radar （IPR） can measure target polarization scattering matrix （PSM） using only once target echoes in two orthogonal polarization channels. Firstly, signal model and signal process are advanced under narrowband condition. Secondly, measurement performances of two typical IPR waveforms are analyzed in detail. At last, field experiments are carried out using X-band IPR system designed by National University of Defense Technology （NUDT）, China. Compared with results obtained by alternative polarization measurement scheme, following results can be obtained： the difference of relative amplitude measurement results is smaller than 2 dB and that of relative phase measurement results is smaller than 10？, verifying the validity of instantaneous polarization measurement scheme.

Orthogonal matrix of polarization combinations:concept and application to multichannel holographic recording

Orthogonal matrices have become a vital means for coding and signal processing owing to their unique distributional properties.Although orthogonal matrices based on amplitude or phase combinations have been extensively explored,the orthogonal matrix of polarization combinations(OMPC)is a novel,relatively unexplored concept.Herein,we propose a method for constructing OMPCs of any dimension encompassing 4n(where n is 1,2,4,8,…)mutually orthogonal 2ncomponent polarization combinations.In the field of holography,the integration of polarization multiplexing techniques with polarization-sensitive materials is expected to emerge as a groundbreaking approach for multichannel hologram multiplexing,offering considerable enhancements in data storage capacity and security.A multidimensional OMPC enables the realization of multichannel multiplexing and dynamical modulation of information in polarization holographic recording.Despite consolidating all information into a single position within the material,we effectively avoided extraneous crosstalk during the reconstruction process.Our results show that achieving four distinct holographic images individually and simultaneously depends on the polarization combination represented by the incident wave.This discovery opens up a new avenue for achieving highly holographic information storage and dynamically displayed information,harnessing the potential of OMPC to expand the heretofore limited dimensionality of orthogonal polarization.

Novel polarization filter design for wideband radar

Usually the polarization of the interference and the target backscattering may vary constantly, so the optimal receiving polarization of the polarization filter should be recalculated, which makes the filter realization very difficult. Also the predict method of the necessary parameters is not explained in most papers, which makes the polarization filter realization impossible. A novel modi- fied interference suppression （MIS） polarization filter is proposed, which resolves these problems by a new polarization designed strategy. The computation of this polarization filter is easy in most conditions, and the necessary parameters estimation method in real time is introduced, which makes polarization filter design possible.

Practical calibration method for instantaneous polarization radar systems utilizing a metal sphere

A practical calibration method is proposed for instantaneous polarization radar systems.The method only needs one measurement by using a metal sphere.The distortions of system and the actual polarization scattering matrix（PSM）of target can be obtained.First,an instantaneous polarization radar system is presented.The system can obtain PSM by a single pulse echo.The dual-polarization antenna can transmit and receive two orthogonal polarization waves.The multilayer micro-strip patch antenna is adopted for this kind of radar system.Second,based on the multi-port network theory,the operation and system errors of instantaneous polarization radar system are analyzed.By making assumption on the cross-talk factors of antenna,distortion matrices of R and Tare derived.Finally,the calibration method based on instantaneous polarization measurement is introduced.Simulation results show the performance of this calibration method.The values of calibrated PSM are in agreement with the actual ones after calibration.

Structural polarization properties of vector Gaussian beam in the far field

Based on the vector angular spectrum representation of optical beam and the method of stationary phase, the analytical TE and TM terms of vector Gaussian beam have been presented in the far field. By using the local polarization matrix, the polarization properties of the TE and TM terms in the far field are investigated, and it is found that the degree of their polarization is only determined by the spatial location. When the source is completely polarized, the TE and TM terms are both completely polarized in the far field. When the source is completely unpolarized, the TE and TM terms in the far field are partially polarized. The whole beam is also partially polarized except on the propagating axis. Moreover, the degrees of polarization of TE and TM terms are both larger than that of the whole beam.

Dynamic modulation performance of ferroelectric liquid crystal polarization rotators and Mueller matrix polarimeter optimization

A ferroelectric liquid crystal polarization rotator(FLCPR)has been widely used in polarization measurement due to its fast and stable modulation characteristics.The accurate characterization of the modulation performance of FLCPR directly affects the measurement accuracy of the instrument based on liquid crystal modulation.In this study,FLCPR is accurately characterized using a self-developed high-speed Stokes polarimeter.Strong linear and weak circular birefringence are observed during modulation processes,and all the optical parameters of FLCPR are dependent on driving voltage.A dual FLCPR-based Mueller matrix polarimeter is designed on the basis of the Stokes polarimeter.The designed polarimeter combines the advantages of the high modulation frequency of FLCPR and the ultrahigh temporal resolution of the fast polarization measurement system in the Stokes polarimeter.The optimal configuration of the designed polarizer is predicted in accordance with singular value decomposition.A simulated thickness measurement of a 24 nm standard SiO2 thin film is performed using the optimal configuration.Results show that the relative error in thickness measurement caused by using the unsatisfactory modulation characteristics of FLCPR reaches up to−4.34%.This finding demonstrates the importance of the accurate characterization of FLCPR in developing a Mueller matrix polarizer.

The signal selection and processing method for polarization measurement radar

Based on the ambiguity function, a novel signal processing method for the polarization measurement radar is developed. One advantage of this method is that the two orthogonal polarized signals do not have to be perpendicular to each other, which is required by traditional methods. The error due to the correlation of the two transmitting signals in the traditional method, can be reduced by this new approach. A concept called ambiguity function matrix （AFM） is introduced based on this method. AFM is a promising tool for the signal selection and design in the polarization scattering matrix measurement. The waveforms of the polarimetric radar are categorized and analyzed based on AFM in this paper. The signal processing flow of this method is explained. And the polarization scattering matrix measurement performance is testified by simulation. Furthermore, this signal processing method can be used in the inter-pulse interval measurement technique as well as in the instantaneous measurement technique.