N-Port Theory Applied to Backscatter Polarimetry and Depolarization in Foliage Penetration
Abstract
This tutorial paper on polarimetric definitions uses N-port network theory to prove results that are frequently stated without proof in the literature, including the symmetry of the polarization scattering matrix in backscattering, the equation for received voltage, and the equations defining Stokes vectors and backscatter Mueller matrices. Appropriate N-port networks are defined for a single-polarized antenna, a dual-polarized antenna, and a backscattering target. An important result is demonstrated: reciprocity (symmetry of the polarization scattering matrix) is meaningful only in the context of the monostatic convention, for which the coordinate system is the same for both transmit and receive. This, in turn, implies a change in the handedness of the coordinate system, so that scattered fields and Stokes vectors are expressed in opposite handedness from incident fields and Stokes vectors. These results are used as tools in the derivation of a new technique for measuring depolarization in foliage penetration (FOPEN). Four polarimetric active radar calibrators (PARCs) are used with an algorithm to completely measure the Mueller matrices describing downward-going and upward-going foliage penetration. Keywords: Polarization scattering matrix; Stokes vector; Mueller matrix; Foliage penetration; Depolarization; Polarimetric calibration; N port theory.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1989
- Accession Number
- ADA213437
Entities
People
- R. M. Barnes
Organizations
- Massachusetts Institute of Technology