148 research outputs found
On Artificial Magneto-Dielectric Loading for Improving the Impedance Bandwidth Properties of Microstrip Antennas
In the present paper we discuss the effect of artificial magneto-dielectric
substrates on the impedance bandwidth properties of microstrip antennas. The
results found in the literature for antenna miniaturization using magnetic or
magneto-dielectric substrates are revised, and discussion is addressed to the
practically realizable artificial magnetic media operating in the microwave
regime. Using a transmission-line model we, first, reproduce the known results
for antenna miniaturization with non-dispersive material fillings. Next, a
realistic dispersive behavior of a practically realizable artificial substrate
is embedded into the model, and we show that frequency dispersion of the
substrate plays a very important role in the impedance bandwidth
characteristics of the loaded antenna. The impedance bandwidths of reduced size
patch antennas loaded with dispersive magneto-dielectric substrates and
high-permittivity substrates are compared. It is shown that unlike substrates
with dispersion-free permeability, practically realizable artificial substrates
with dispersive magnetic permeability are not advantageous in antenna
miniaturization. This conclusion is experimentally validated.Comment: 22 pages, 14 figures, 5 tables, submitted to IEEE Trans. Antennas
Propaga
Frequency range and explicit expressions for negative permittivity and permeability for an isotropic medium formed by a lattice of perfectly conducting particles
An analytical model is presented for a rectangular lattice of isotropic
scatterers with electric and magnetic resonances. Each isotropic scatterer is
formed by putting appropriately 6 -shaped perfectly conducting
particles on the faces of a cubic unit cell. A self-consistent dispersion
equation is derived and then used to calculate correctly the effective
permittivity and permeability in the frequency band where the lattice can be
homogenized. The frequency range in which both the effective permittivity and
permeability are negative corresponds to the mini-band of backward waves within
the resonant band of the individual isotropic scatterer.Comment: 25 pages, 6 figure
Enhancement of perovskite solar cells by plasmonic nanoparticles
Synthetic perovskites with photovoltaic properties open a new era in solar
photovoltaics. Due to high optical absorption perovskite-based thin-film solar
cells are usually considered as fully absorbing solar radiation on condition of
ideal blooming. However, is it really so? The analysis of the literature data
has shown that the absorbance of all photovoltaic pervoskites has the spectral
hole at infrared frequencies where the solar radiation spectrum has a small
local peak. This absorption dip results in the decrease of the optical
efficiency of thin-film pervoskite solar cells by nearly 3% and close the ways
of utilise them at this range for any other applications. In our work we show
that to cure this shortage is possible complementing the basic structure by an
inexpensive plasmonic array.Comment: 6 pages 6 picture
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