IEEE 1502:2020 pdf free download – IEEE Recommended Practice for Radar Cross-Section Test Procedures
4.1 Introduction
Radar scattering is typically represented as the RCS of the test object. The term RCS evolved from thebasic metric for radar scattering: the ratio of the power scattered from an object in units of power per solidangle (steradians) normalized to the plane-wave illumination in units of power per unit area. The RCS isthus given in units of area (or effective cross-sectional area of the target, hence the name). Note that theRCS of the test object is a property of the test object alone; it is neither a function of the radar system northe distance between the radar and the test object, as long as the object is in the far field. Because the RCSof a target can have large amplitude variation in frequency and angle, it is expressed in units of decibelswith respect to a square meter and is abbreviated as dBsm (sometimes DBSM or dBm2). In terms of thisdefinition, the RCS of a radar target is a scalar ratio of powers. If the effects of polarization and phase areincluded,the RCS can be characterized by the complex polarimetric scattering(CPS)matrix,which isbased on one-half the real part of the complex Poynting vector. The CPS is proportional to a Hadamardproduct of a 2×2 matrix of the real-valued RCSs corresponding to each of the four combinations oftransmit-receive polarizations and a 2×2 matrix of the complex exponentials associated with the phases ofthe scattered fields for the same combinations of both polarizations (Bhattacharyya, Sengupta [B6], Ruck[B64]).
4.2.1 Measurement history
Radar reflectivity measurements go back to the earliest days of radar. What are now known as RCSmeasurements began to be more openly discussed in the literature in the late 1950s and early 1960s(Bachman [B3], Cummings [B13],Currie, Curie [B15], Johnson et al. [B38],Kennedy [B40], Proceedingsof the IEEE [B60]), although much of that work was under the auspices of the military and thus not readilyavailable. This situation began to change with the 1965 publication of a Special Issue of the Proceedings ofthe IEEE [B61 ], which concentrated on topics associated with radar reflectivity. Several of the 1965 papersin this issue specifically focused on the requirements of RCS measurements,including an overview of thestate of the art in RCS measurements (Blacksmith et al. [B7],[B8]). In addition, this issue included paperson range requirements (Kouyoumjian，Peters [B50]),target support issues (Freeny [B26]), measurementtechniques (Bachman [B3], Huynen [B29]), and discussions of typical facilities, both static(Marlow et al.[B54]) and dynamic (olin，Qucen [B59]). With the publication of this issue,a growing open-sourceliterature base on RCS measurements became available to practitioners in the field.
The ensuing period marked the beginnings of two measurement trends: the rapid development of newapproaches to making measurements, and measuring targets with low RCS. There was a major push toreduce significantly the radar scattering from military vehicles.Along with the objective to producevehicles with reduced RCS came the requirement to measure these smaller signal levels accurately. Inaddition，many applications required the full complex polarimetric scattering matrix. Thus，significantefforts were made to improve the technology of RCs measurements，including increasing the dynamicrange of the measurement system and adding complex phasor measurements.
During this same time period,significant research was being conducted on the theory of electromagneticscattering. Universities such as Syracuse University，the University of Michigan，The Ohio StateUniversity, and the Georgia Institute of Technology were engaged in understanding the foundations ofscattering,with the objectives of taking better measurements and being able to predict analytically andnumerically the scattering from increasingly complex objects. During this period,increased computationalpower allowed tools like the method of moments (MOM) (Harrington [B28]), the geometrical theory ofdiffraction(GTD)(Keller [B39]), physical optics (PO) ) (Ufimtsev, Senior [B69]), and the physical theoryof diffraction (PTD)(Ufimtsev [B68]) to be used for realistic scenarios.