In this paper, a new family of Cassinian wave-guides
is proposed, simulating and calculation are finished with CST
Microwave Studio that based on Finite Integral Technique (FIT),
and some results are given. electromagnetic field mode type of it
is TE, electromagnetic field is stronger near neck region, and
some resonance frequencies appear. The new Cassinian curve
wave-guides will possess higher power than ones of the
rectangular and elliptic wave-guides because the height at the
position where maximal electric field occurs is smaller.
It was proposed that perfect invisibility cloaks can be constructed for hiding objects from electromagnetic
illumination (Pendry et al., Science 312, p. 1780). The cylindrical cloaks experimentally
demonstrated (Schurig et al., Science 314, p. 997) and theoretically proposed (Cai et al., Nat. Photon.
1, p. 224) have however simplified material parameters in order to facilitate easier realization
as well as to avoid infinities in optical constants. Here we show that the cylindrical cloaks with
simplified material parameters inherently allow the zeroth-order cylindrical wave to pass through
the cloak as if the cloak is made of a homogeneous isotropic medium, and thus visible. To all
high-order cylindrical waves, our numerical simulation suggests that the simplified cloak inherits
some properties of the ideal cloak, but finite scatterings exist.
We analyze, both analytically and numerically, the effectiveness
of cloaking an infinite cylinder from observations by electromagnetic
waves in three dimensions. We show that, as truncated approximations
of the ideal permittivity and permeability tensors tend towards
the singular ideal cloaking fields, so that the anisotropy ratio tends to
infinity, the D and B fields blow up near the cloaking surface. Since
the metamaterials used to implement cloaking are based on effective
medium theory, the resulting large variation in D and B will pose a
challenge to the suitability of the field averaged characterization of "
and 碌. We also consider cloaking with and without the SHS (softand-
hard surface) lining, shown in [6] to be theoretically necessary
for cloaking in the cylindrical geometry. We demonstrate numerically
that cloaking is significantly improved by the SHS lining, with both
the far field of the scattered wave significantly reduced and the blow
up of D and B prevented.
Feeding antennas with proper signals can be difficult. The signal is often described as a voltage, and voltages are not well defined in electromagnetic wave formulations. There are several tricks to model voltage generators in such situations, and one is the magnetic frill. This model shows the basic steps of defining a magnetic frill voltage generator for a dipole antenna, and it also compares the resulting antenna impedance with known results.
The Schumann resonance frequencies are a set of eigenmodes in the extremely low frequency (ELF) portion of the electromagnetic field spectrum. These frequencies are only present for planetary-like bodies with a substantial ionosphere acting as a perfect electric conductor, thus forming a resonance cavity with the surface. In this example, the Schumann resonance frequencies for the Earth are calculated.
Feeding antennas with proper signals can be difficult. The signal is often described as a voltage, and voltages are not well defined in electromagnetic wave formulations. There are several tricks to model voltage generators in such situations, and one is the magnetic frill. This model shows the basic steps of defining a magnetic frill voltage generator for a dipole antenna, and it also compares the resulting antenna impedance with known results.
This book provides the reader with the basics in radio engineering,
the techniques needed to generate, control, detect, and use radio waves. The
text approaches the relevant problems both from the electromagnetic theory
based on Maxwell抯 equations and from the circuit theory based on Kirchoff
and Ohm抯 laws. Brief introductions to the electromagnetic theory as well
as to the circuit theory are provided. Besides passive transmission lines and
components, active RF circuits are also addressed.
DDSCAT 7.3 is a freely available open-source Fortran-90 software package applying the “discrete
dipole approximation” (DDA) to calculate scattering and absorption of electromagnetic waves by targets
with arbitrary geometries and complex refractive index. The targets may be isolated entities (e.g., dust
particles), but may also be 1-d or 2-d periodic arrays of “target unit cells”, which can be used to study
absorption, scattering, and electric ?elds around arrays of nanostructures.
