Learn More
An electromagnetic feasible adjoint sensitivity technique (EM-FAST) has been proposed recently for use with frequency-domain solvers . It makes the implementation of the adjoint variable approach to design sensitivity analysis straightforward while preserving the accuracy at a level comparable to that of the exact sensitivities. The overhead computations(More)
In a dispersive medium, the appearance of the steady-state part of the signal is preceded by oscillations known as precursors. These early oscillations are the product of the interrelated effects of phase dispersion and frequency dependent attenuation. Inside water, the attenuation rate of the Brillouin precursor is sub-exponential, following the inverse(More)
The design, simulation and performance enhancement of a new structure for X-band high-power, low-loss, low-bias, triangularferrite waveguide circulator are presented. Dual circulation property is obtained by triangular shape of ferrite post. The effects of circulator’s structure parameters, such as ferrite parameters and magnetic DC bias, on isolation,(More)
The relationship between the phase of the reflection coefficient and the surface-wave bandgap in planar artificial magnetic conductors (AMCs) is investigated. The periodic surface of the AMC is modeled as a surface impedance and the plane-wave reflection coefficients and the supported surface waves are obtained by this model. Next, the connection between(More)
In a causally dispersive medium the signal arrival appears in the dynamical field evolution as an increase in the field amplitude from that of the precursor fields to that of the steady-state signal. The interrelated effects of phase dispersion and frequency dependent attenuation and/or amplification alter the pulse in such a fundamental way that results in(More)
Time reversal techniques are based on the time reversal invariance of the wave equation. They use time-reversed fields recollected by an array antenna to perform imaging and focusing on the source of received signals. Two widely used time reversal techniques are DORT and time reversal MUSIC which are based on eigenvalue decomposition of the time reversal(More)
Superluminal group velocities, defined as group velocities exceeding the speed of light in vacuum, c, have been theoretically predicted and experimentally observed in various types of dispersive media, such as passive and active Lorentzian media, one-dimensional photonic crystals, and undersized waveguides. Though superluminal group velocities have been(More)
The appearance of precursor fields in a causally dispersive dielectric is due to the interrelated effects of phase dispersion and frequency dependent attenuation of the medium. Until now, rigorous studies of these transient fields have been performed showing the evolution of the precursors and their unique penetrating features that can be used in imaging(More)
Superluminal group velocities, defined as group velocities exceeding the speed of light in vacuum, c, have been theoretically predicted and experimentally observed in various types of dispersive media, such as passive and active Lorentzian media, one-dimensional photonic crystals, and undersized waveguides. Though the group velocity was found to be(More)