Comprehensive Characterization of an Ellipsoidal Cylinder Calibrator for Radar Cross Section Measurement

Abstract

Currently, a set of scaled squat circular cylinders (SCCs) have been widely used for co-polarimetric radar cross section (RCS) calibration in various test ranges where low RCS metal pylons are used. The major drawback of a circular cylinder (CC) is its high sensitivity to elevation angle, as well as the frequency-dispersive theoretical RCS. In this work, we propose a new RCS calibrator, the metal ellipsoidal cylinder (EC), whose RCS characteristics are similar to a metal sphere, while it can be mounted on a metal pylon with little electromagnetic (EM) interactions as a CC does. A high-frequency RCS expression is derived using geometrical optics (GO) for the new calibrator. The scattering mechanisms are analyzed to establish the accurate parametric representation of the theoretical RCS. Based on surface current analysis and numerical calculation, the calibrator-pylon interaction (CPI), the angular sensitivity, and the bistatic RCS characteristics are discussed, enabling the calibration uncertainty evaluation for applying the proposed calibrator in the ground-plane range (GPR). Numerical and experimental results of a manufactured squat EC (SEC) are presented to demonstrate the excellent performance of the proposed EC calibrator for co-polarimetric RCS calibration.

Calibration of Polarimetric Millimeter MIMO Radar for Near-Field Ultrawideband Imaging Measurement

“…According the selected parameters in Table I, the maximal blurred range is 30 m involving the equivalent cable length of about 6.3 m. To alleviate the impacts of the intensive scattering from unexpected objects, the calibrators are placed at the area with relatively low background level, where a range gate is set to prevent the radiation leakage from other intensive objects, such as the walls of the yard. The background data is measured for the implementation of the constant clutter cancellation to A SEC with the diameter of 38.1 cm (1500 mils) and the height of 17.78 cm [35], a cylinder with the diameter of 22.86 cm (900 mils) and the height of 10.67 cm, and a cylinder with the diameter of 19.05 cm (750 mils) and the height of 8.89cm are selected as the calibrators for the HH and the VV polarizations, whereas a plate dihedral with the plate size of 10cm×7.5cm is adopted for the VH and the HV polarizations. The RCS value of the SEC and the 750-cylinder can be used in quantitative analysis on the calibration effectiveness.…”

“…For the system calibration, the rotatable double-antenna polarimetric active radar calibrator (RODAPARC) used in our previous polarimetric calibration [29] [34] is not available in this case, because of distinct operating frequency bands. Metal cylinders and a Short Ellipsoidal Cylinder (SEC) [35] are used in the calibration HH and VV channels, whereas a plate dihedral with a specific rotation angle is selected as the calibrator for cross-polarization (HV and VH) channels. Regarding the bistatic scattering characteristics of the plate dihedral in near-field condition, the theoretical RCSs varying with frequency and azimuth angle are calculated for each element via the method of moments (MOM) [36].…”

A New Quarter Concave Cylinder Linked Dihedral Reflector for Fully Polarimetric Calibration of Wideband Nonreciprocal Radar Systems

“…2. To suppress the interference of undesirable components, a CE model based parametric representation approach [20]- [23] is used to extract the main SC.…”

“…In addition, the theoretical PSM varying with rotation angle along the radar line of sight (LOS) is derived based on physical optics (PO). A novel polarimetric calibration procedure based on parametric representation using complex exponential (CE) model [20]- [23] is presented to suppress the interference of undesirable scattering components for enhanced accuracy. Finally, experimental results are presented to validate the usefulness of the QCCLD polarimetric passive calibrator.…”