ECE 458

• Electromagnetics, Optics and Remote Sensing

This course examines the propagation characteristics of radiowaves in ionized and magnetized gases and applications of radiowaves in Earth’s near space environment. Propagation effects and applications examined include dispersion and attenuation, reflections and refractions (in plane and spherical stratified geometries), skywave communication links, backscatter radar remote sensing, and magneto-ionic propagation effects in the ionosphere/magnetosphere system.

ECE 458 is a follow-on course to ECE 350 concerned with the complexities of EM wave propagation on and around our planet with a special focus on near-Earth space environment including the neutral (un-ionized) atmosphere, ionosphere, magnetosphere, and solar wind. Topics include

• Multipath — in mobile communications in urban areas as well as in ionospheric sky-wave links,
• Dispersion — in isotropic and anisotropic propagation media,
• Absorption — in weakly collisional plasmas occupying the lower ionosphere,
• Refraction, reflection, guidance — in media with slowly varying refractive indices in plane and spherical stratified geometries,
• Scattering and scintillations — why the sky is blue and stars twinkle - stochastic phenomena not covered in ECE 329 and 350,
• Depolarization — of crucial importance in anisotropic propagation media not covered in ECE 329 and 350,

with a focus on the underlying physics of near-Earth space environment giving rise to these propagation effects.

Homework assignments will require the use of scientific computing tools (e.g., MATLAB, Python) for signal processing and data visualization.

• Maxwell's equations and boundary conditions
• Plane wave propagation
• Reflection and refraction from a plane interface
• Interaction between electromagnetic energy and materials

Class notes.

Elective

Engineering Science: 2 credits or 67%
Engineering Design: 1 credit or 33%

This course examines the propagation characteristics of radiowaves in ionized and magnetized gases and applications of radiowaves in Earth’s near space environment. Propagation effects and applications examined include dispersion and attenuation, reflections and refractions (in plane and spherical stratified geometries), skywave communication links, backscatter radar remote sensing, and magneto-ionic propagation effects in the ionosphere/magnetosphere system.

A. By the time of Exam No. 1 (after 19 lectures), the students should be able to do the following:

• Recognize and represent monochromatic uniform and non-uniform plane TEM waves in phasor notation, and use a refractive index parameter to relate wave properties in material media (isotropic) to wave properties in free space (1).
• Recognize orthogonal polarized wave pairs, synthesize arbitrarily polarized wavesand perform Poynting flux calculations in terms of linear and circular orthogonal pair components (1).
• Derive the refractive index for a collisionless plasma and recognize propagation and evanescence conditions in ionospheric plasma in terms of plasma and radiowave frequencies (1).
• Calculate phase and group velocities from specified dispersion relations and/or refractive index formulae, and perform group path and phase path calculations in homogeneous dispersive media (1,6).
• Understand WKB and full-wave theory of reflection for radiowaves propagating in the direction of a plane stratified inhomogeneity (1,6).
• Understand the damping effect of electron collisions in the D-region ionosphere on radiowave propagation of radiowaves (1,6).
• Understand the basic principles of ionospheric sounding measurements and calculate virtual height versus frequency curves (ionograms) given an ionospheric electron density profile. Also understand the average morphology and causes of formation of the ionosphere (1,2,6).
• Perform ray tracing calculations based on Snell’s Law and Bouguer’s rule in plane and spherical stratified media (1,6).
• Perform ionospheric ray tracing calculations using the secant Law, Breit and Tuve Theorem, Martyn’s Theorem to determine skywave link parameters including the skip zone and maximum usable frequency (MUF) (1,2,6).

B. By the time of Exam No. 2 (after 36 lectures), the students should be able to do all of the items listed under A, plus the following:

• Understand radiation fields of line antennas and calculate the effective length and pattern vector of line antennas with given current distributions (1).
• Understand the reciprocal relation between antenna transmission and reception and calculate the voltage response of antennas to incident plane waves in terms of the antenna pattern vector (1).
• Understand antenna system parameters including the radiation resistance, antenna gain and directivity, and effective area, and construct the power budget equations for communication systems (Friis transmission formula) including surface reflections (space wave links) and surface waves. (1,2,6).
• Calculate the radiation patterns for 1- and 2-D antenna arrays and understand the applications of antenna arrays (in hardware and software) in radio imaging applications pertinent to radio astronomy and radio remote sensing. (1,2,6)
• Understand the relationship between aperture plane fields and plane wave spectrum of fields radiated from an aperture and how the concept of diffraction relate to both (1).
• Use the Fresnel diffraction formula to understand the scintillation of radiowaves propagating through a weakly perturbed ionosphere (1,4,6)
• Understand the first Born-approximation formulation of radiowave scattering from a weakly inhomogeneous ionosphere and develop the notion of Bragg scattering central to the operation of ionospheric/atmospheric backscatter radars (1,6).
• Understand the fundamentals of parameter estimation with backscattered radar signals returned from ionospheric and/or atmospheric refractive index irregularities (1,2,6).

C. By the time of the Final Exam (after 41 lectures), the students should be able to do all the items listed under A and B, plus the following:

• Derive refractive indices for normal modes of propagation in a collisionless but magnetized plasma neglecting the heavy ion effects (for parallel and perpendicular propagation), and perform phase and group velocity as well as phase and group path calculations associated with the normal modes (1).
• Identify the conditions when quasi-longitudinal approximation is applicable and perform Faraday rotation computations, and design simple remote sensing experiments exploiting the Faraday rotation phenomenon (1,2,6).