J. C. da S. Lacava

From Maxwell's Equations to Polarimetric SAR Images: A Simulation Approach

A new electromagnetic approach for the simulation of polarimetric SAR images is proposed. It starts from Maxwells equations, employs the spectral domain full-wave technique, the moment method, and the stationary phase method to compute the far electromagnetic fields scattered by multilayer structures. A multilayer structure is located at each selected position of a regular rectangular grid of coordinates, which defines the scene area under imaging. The grid is determined taking into account the elementary scatter size and SAR operational parameters, such as spatial resolution, pixel spacing, look angle and platform altitude. A two-dimensional separable “sinc” function to represent the SAR spread point function is also considered. Multifrequency sets of single-look polarimetric SAR images are generated, in L-, C- and X-bands and the images are evaluated using several measurements commonly employed in SAR data analysis. The evaluation shows that the proposed simulation process is working properly, since the obtained results are in accordance with those presented in the literature. Therefore, this new approach becomes suitable for carrying out theoretical and practical studies using polarimetric SAR images.

Closed form expressions for scattering matrix of simple targets in multilayer structures

Scattering matrix of a simple target embedded in multilayer planar structure is derived. The structure is excited by an elliptically polarized plane wave incident at an oblique angle. The calculation of the electromagnetic fields is performed in spectral domain. The scattering matrix of a planar electric dipole printed on upper interface and surrounding by free-space is evaluated. The obtained results agree with those existing on the literature for normal incidence case.

Probe-Fed Linearly-Polarized Electrically-Equivalent Microstrip Antennas on FR4 Substrates

This paper describes a simple but efficient procedure for designing electrically-equivalent microstrip antennas on FR4 sub-strates. Radiation patterns, reflection coefficient magnitude ( |Γ| ), mutual coupling and cross-polarization level of probe-fed linearly-polarized antennas are calculated and discussed. Experimental results of |Γ| and radiation patterns of rectangular, elliptical and triangular patches validate the proposed procedure.

Flush-mounted telemetry antenna design for a sounding rocket competition

In this paper a flush-mounted circumferential microstrip array, designed as a sounding rocket telemetry antenna, is reported. The purpose is to comply with the requirements of an international competition for engineering students. Experimental results validate the design approach.

Cavity-backed hybrid microstrip antenna on FR4 substrate

A novel cavity-backed probe-fed linearly-polarized microstrip antenna is proposed and implemented. The resulting flush-mounted radiator exhibits symmetrical bandwidth, low cross-polarization - due to its hybrid patch - and low-cost, if built on FR4 material. Substrate integrated waveguide (SIW) technology is used in the cavity-backed antenna fabrication.

An alternative formulation for guided electromagnetic fields in grounded chiral slabs - Summary

An alternative formulation for guided electromagnetic fields in grounded chiral slabs is presented. This formulation is formally equivalent to the double Fourier transform method used by the authors to calculate the spectral fields in open chirostrip structures. In this paper, we have addressed the behavior of the electromagnetic fields in the vicinity of the ground plane and at the interface between the chiral substrate and the free space region. It was found that the boundary conditions for the magnetic field, valid for achiral media, are not completely satisfied when we deal with chiral material. Effects of chirality on electromagnetic field distributions and on surface wave dispersion curves were also analyzed.

Design of flush-mounted hybrid microstrip antennas

A novel cavity-backed probe-fed linearly-polarized microstrip antenna is proposed in this paper. The resulting flush-mounted radiator exhibits symmetrical bandwidth, high radiation efficiency, and low cross-polarization. Substrate integrated waveguide technology is used for the antenna fabrication. Experimental results are in excellent agreement with simulated data.

Electromagnetic characteristics of simple targets embedded in chiral multilayer structures

The scattering properties of a chiral stratified multilayer structure having an printed planar electric dipole are addressed in this paper. In order to obtain the scattered fields the method of moments in spectral domain is applied. The dipole scattering is characterized by the radar cross section (RCS), the polarimetric response, the α-angle from Cloude-Pottiers target decomposition theorem and the directivity function. The results point out that all parameters are sensible to variations on the chiral layer admittance. The chiral layer impinges a rotation on the polarization plane of linearly incident wave for all frequency analyzed.

Closed-form dyadic spectral Green functions for microstrip structures with ferromagnetic substrates

This paper presents a full-wave analysis method for microstrip structures with magnetic anisotropy. Working in the Fourier domain, dyadic spectral Green functions in compact and closed form are derived. Special attention is dedicated to the cross-polarization analysis of a short dipole printed on a biased ferrite substrate.

Analysis and Design of Cavity-Backed Probe-Fed Hybrid Microstrip Antennas on FR4 Substrate

A novel cavity-backed probe-fed linearly polarized microstrip antenna based on the concept of hybrid radiators is proposed and implemented. The resulting flush-mounted antenna exhibits symmetrical bandwidth, low cross-polarization radiation in the H-plane, due to its hybrid patch, and low cost, since it can be built on a FR4 laminate. Substrate integrated waveguide technology is used in the fabrication of the metallic cavity. The effect of mutual coupling is analyzed for two classical arrangements: the side-by-side and the collinear configurations.