Polarimetric Radar Cross Section Research Articles

A Novel Target Detection and Identifying Approach Using Polarimetric Radar Cross-Section and Matrix Correlation Coefficient

This paper presents a novel target detection and identifying approach using polarimetric radar cross-section and matrix correlation coefficient. We have adopted a polarimetric radar cross-section matrix correlation strategy (PRMC) algorithm using a matrix correlation approach based on the polarimetric radar cross-section. It is projected as an inverse scattering problem under the electromagnetic scattering model using polarimetric Physical Optics approximation. The experimental measurements using canonical targets carried out under semicontrolled conditions verify the performance of the developed procedures. Finally, the identification strategies' effectiveness is demonstrated in free-space conditions and a scene with a brick and autoclaved aerated concrete wall.

Comprehensive analysis of polarimetric radar cross-section parameters for insect body width and length estimation

The length and width of insect body are critical parameters for entomological radar species identification. However, the body width is not measurable in entomological radar currently. In this study, the scattering matrices (SM) of 159 insect specimens were measured using an X-band fully polarimetric laboratory rig in a microwave anechoic chamber. The relationships between the polarimetric radar cross-section (RCS) parameters extracted from the SM and the insect body width were studied. It was found that all these parameters have good correlations with the body width and can be used to estimate it. The mopping relationships between the polarimetric RCS parameters and the body width are built, and can be used as empirical formulas for insect body width estimation. In addition, based on these parameters, two new body length estimation methods were proposed. The performance of the proposed body width and length estimation methods when the echo signals were noisy was analyzed. It was found that the parameter that represents the product of the RCSs when the polarization direction is parallel and perpendicular to the insect body axis has the best performance for both the estimation of body width and length.

Insect Multifrequency Polarimetric Radar Cross Section: Experimental Results and Analysis

The measurement of insect radar cross section (RCS) is a prerequisite for the studies such as the quantitative estimation of insect population density and the identification of insects using entomological radar. In this article, we established a multiband polarimetric RCS measurement system in the microwave anechoic chamber. The targets’ range profile at different frequencies can be obtained based on the step frequency continuous wave, and meanwhile the clutter elimination and polarimetric calibration were applied to reduce the measuring error. The multifrequency (X-/Ku-/Ka-bands) polarimetric RCSs of 169 insects belonging to 21 species were measured and reported, which is the first time to systematically present the multifrequency polarimetric RCSs of insects. The mass of all specimens range from 25.6 to 964 mg, and their ventral-aspect RCSs range from −57.47 to −32.17 dBsm at X-band, from −48.27 to −33.87 dBsm at Ku-band and from −69.76 to −36.40 dBsm at Ka-band. For small insects less than 300 mg, the HH polarization RCS increases rapidly with frequency at X-band and fluctuates with the frequency at Ku-band, while the VV polarization RCS increases monotonically with frequency at X- and Ku-band. For larger insects, the HH polarization RCS decreased slowly with frequency at X-band and fluctuates with the frequency at Ku-band, while the VV polarization RCS increases with the frequency, then reaches the maximum, finally fluctuates with the frequency. At Ka-band, the measured polarization RCS versus frequency curves are smooth and all show similar variation. The measurement results verify the effectiveness and accuracy of the established system.

SimRadar: A Polarimetric Radar Time-Series Simulator for Tornadic Debris Studies

In an effort to study and characterize scattering mechanisms of debris particles in tornadoes, a numerical polarimetric radar emulator was developed. This paper is primarily motivated by attempts to explain radar observations near tornadoes. One such observation is the regions of negative differential reflectivity, which have been found near tornadoes but they are yet to be explained physically. There are hypotheses that suggest common debris alignment and/or dominant scattering from objects with high radar-cross-section (RCS) values that cause negative $Z_{DR}$ , but they are extremely challenging to verify due to the inherent danger near the vicinity of tornadoes. It is, however, possible to numerically construct the scenes through representative simulations to verify the plausible causes. This serves as our primary motivation to develop the radar emulator. The novel aspects of this paper are the realistic trajectory derivation, which is based on a physical air-drag model, and the representative diversity of RCS contributions from each debris object, developed through realistic polarimetric RCS modeling and anechoic chamber measurements.

Solution for polarimetric radar cross section measurement and calibration

The exact radar cross-section (RCS) measurement is difficult when the scattering of targets is low. Full polarimetric calibration is one technique that offers the potential for improving the accuracy of RCS measurements. There are numerous polarimetric calibration algorithms. Some complex expressions in these algorithms cannot be easily used in an engineering practice. A radar polarimetric coefficients matrix (RPCM) with a simpler expression is presented for the monostatic radar polarization scattering matrix (PSM) measurement. Using a rhombic dihedral corner reflector and a metallic sphere, the RPCM can be obtained by solving a set of equations, which can be used to find the true PSM for any target. An example for the PSM of a metallic dish shows that the proposed method obviously improves the accuracy of cross-polarized RCS measurements.

Nonlinear Calibration of Polarimetric Radar Cross Section Measurement Systems

Polarimetric radar cross section measurement systems are characterized by polarimetric system parameters eh and ev. These parameters can be measured by use of rotating dihedrals. The full polarimetric dataset as a function of the angle of rotation can be analyzed with a nonlinear set of calibration equations to yield the system-parameter complex constants and the four polarimetric-calibration amplitudes. These amplitudes appropriately reproduce the system's drift, and very accurately satisfy a drift-free system-configuration criterion. The results indicate that the nonlinear approach is better than the previously studied linear approach, which yielded system parameters that were seriously distorted by system drift.

X-밴드 완전 편파 Scatterometer 시스템 보정에 관한 연구

A study on the calibration of an X-band HPS(Hongik Polarimetric Scatterometer) system for ground-based operation is presented in this paper. In order to calibrate the scatterometer system, the degree of its distortions are analyzed by comparison between theoretical- and measured-values using the theoretically well-known calibration targets such as a metal sphere, a trihedral corner reflector(CR) and a metal cylinder. The calibration works in the field conditions depend on the precise and stable measurements of those calibration target. we present a measurement technique, so-called, an automatic 2-D target-scanning technique, using the incidence-angle( and directions) control of HPS system. Then, we used STCT(Single-Target Calibration Technique) and GCT(General Calibration Technique) to calibrate a distortion of the scatterometer system, and measured the polarimetric RCS(Radar Cross Section) and phase-difference of a trihedral-CR as a test-target to verify the accuracy of the calibration technique. Then, three different types(i.e., 10, 20, 30 cm) of trihedral-CR were used. we obtained the error ranges about dB, dB in a polarimetric RCS and about and in the co-polarized phase-difference by using the GCT and STCT, respectively.

A Scatterometer System for Laboratory Study of Polarimetric Electromagnetic Signatures of Icy Hydrometeors

Radar sensors with dual-polarization capability allow a better understanding and characterization of weather hazards, particularly hydrometeor particles. The knowledge of natural polarimetric hydrometeor scattering signatures, on the other hand, has been limited in theoretical calculations, simulations, and radar measurements. In this paper, an experimental approach was designed with the assistance of a controlled laboratory environment. An advanced vector network analyzer-based scatterometer system has been developed in harmony with an environmentally monitored anechoic chamber with special configurations for hydrometeor measurements. The polarimetric radar cross section (RCS) of various natural and man-made icy hydrometeor samples is measured across wide X-band frequencies and compared with theoretical modeling results. The dual-polarization radar variables and hydrometeor melting parameters are derived from the RCS measurements with interesting observations obtained. The described technology and results serve as the basis of a new hydrometer microphysics knowledge base for hydrometeor classification processing in the next-generation multichannel dual-polarized hazard monitoring radars.

X-밴드용 완전 편파 Scatterometer 설계

A full-polarimetric scatterometer(HPS: Hongik Polarimetric Scatterometer) for X-band is designed, fabricated, and verified using the theoretically well-known point-targets in this paper. The X-band full-polarimetric scatterometer consists of an OMT(Orthogonal-Mode Transducer)+horn antenna, the angle control part for the OMT+horn antenna, a transmitter/receiver with a network analyzer and a frequency-conversion circuitry, and a movable support of these parts. We use an inclinometer sensor to control the vertical and horizontal incidence angles. The full polarimetric data can be obtained because of the polarization switches and the OMT. The accuracy of the scatterometer system is verified by measuring the polarimetric RCS(Radar Cross Section) of one of the theoretically well-known point-targets, i.e., a corner reflector.

Polarimetric RCS Calibration using Reference Reflectors

A new polarimetric radar cross section (RCS) calibration technique using two reference reflectors is developed and verified experimentally in the anechoic chamber of Multimedia University. The antenna system and the two orthogonal channels are modeled as a two-port network. The technique utilizes two electrically large reflectors, namely a rectangular flat plate and a 45° rotated dihedral corner reflector as the calibration targets to provide large reflections for co-polarization and cross-polarization returns, respectively. The orientation of the reflectors is not critical, and their theoretical RCS are not required in the calibration process. Therefore the alignment problem and uncertainties in the computation of the theoretical responses are eliminated. A metallic sphere with known theoretical RCS is used to verify the calibration accuracy and determine the correction factor for absolute RCS measurement. Scattering measurements are performed using a Vector Network Analyzer (VNA). Raw data are acquired and stored in the PC for further processing. Time domain gating technique is applied to remove the target-chamber coupling effect in the measurements.

Wide-band multiport antenna characterization by polarimetric RCS measurements

A theoretical description of the scattering of multiport antennas is derived in accordance with the polarimetric radar target characterization. For two-port antennas with dual linear orthogonal polarization, a procedure for the determination of the antenna mode scattering parameters and the structural scattering parameters of the complete polarimetric antenna scattering matrix [S] is given. A measurement setup and experimental results of wide-band polarimetric radar cross section (RCS) antenna measurements are presented. For two-port antennas, in total, 24 unknowns have to be determined. The load variation method is used. The polarimetric RCS antenna measurement is especially advantageous over a wide bandwidth; for example 2-40 GHz with only one single calibration. From the antenna scattering matrix [S], the antenna parameters like polarimetric gain, optimum gain, gain bandwidth, wave admittance, structural scattering, etc., are derived. Results are shown for an X-band horn antenna and a 2-18-GHz dual linearly polarized horn. The measurement technique and evaluation gives the most complete and very accurate information about antenna radiation, antenna characteristics, and scattering obtainable with one single measurement setup. Some quantities determined here, like the maximum available gain and the polarization characteristics, are difficult to access with standard transmission measurements. No cable from the antenna to the receiver is necessary. This helps avoid some difficulties usually experienced at low signal levels.

Single reference, three target calibration and error correction for monostatic, polarimetric free space measurements

The authors present a scheme for absolute calibration of a polarimetric scattering range. All free-space polarimetric radar cross section (RCS) and antenna measurements are subject to errors like coupling and residual reflections. The modeling of these errors results in a 12-term error correction. The procedure for the error correction with three linear independent calibration targets and an isolation measurement is shown. Based on network analysis, a single reference calibration is introduced. This single reference calibration requires the precise calculation of only one reference target. As single references, spheres or flat plates are used. The references of the other targets are determined by the calibration procedure. The single reference calibration is suitable for all narrow and wideband, complex, polarimetric RCS, and antenna measurements. Measurements are shown for different targets which demonstrate the benefits of the single reference calibration. >