92 research outputs found
Nonorthogonality relations between complex hybrid modes: an application for the leaky-wave analysis of laterally shielded top-open planar transmission lines
In this paper, the orthogonality relations between
complex modes are investigated to demonstrate the coupling effect
that exists along a transverse direction ( -axis) between TE and
TM hybrid modes when power storage, loss, or leakage occur
in the longitudinal direction ( -axis) of a transmission line. As an
example, the parallel-plate waveguide modes are used to study
a laterally shielded top-open microstrip line. The study of leaky
waves is a very interesting application of the novel orthogonality
relations derived in this paper. This study is carried out using the
correct and incorrect orthogonality formulations, showing that
physically valid results are obtained only when the orthogonality
relations derived in this paper are properly introduced in the
formulation. A physical explanation of this novel coupling effect
between TE andTM hybrid modes with respect to the -direction
is given in terms of inhomogeneous plane waves. Comparisons
with previous results for a laterally shielded slot-line antenna are
presented to confirm the accuracy and usefulness of this novel
proposed method
Leaky and Surface Waves in Multi-Layered Laterally Shielded Microstrip Transmission Lines
In this paper the leakage effects in open laterally-
shielded multilayered microstrip transmission lines are investigated. Po-
tential solutions are often reported to be difficult to find, since they are
located in the complex propagating factor plane. To overcome this
problem, a novel iterative algorithm is implemented to relate the solu-
tions in the real axis of closed transmission lines with their correspond-
ing complex open structure modes. The problem of modeling the leaky
behavior of the open top wall is introduced, and a mathematical and
physical explanation of the solutions is proposed. The advantage of this
new technique is that it allows us to easily track the leaky solutions to
their final location in the complex plane. Results are presented, includ-
ing the field and power patterns associated to leaky waves, showing that
the derived technique is indeed effective for the study of the complex
modes excited in this type of structures.Universidad Politécnica de Cartagen
Ciudad y confort ambiental: estado de la cuestión y aportaciones recientes
This paper analyses the relationships between urban climate, environmental comfort and urban
planning, from the point of view of the concepts and fundamental ideas evolution, from the basic
methodological contributions and from recent year’s reviews, especially in the topic of the environmental
comfort indexes. The paper gives a review with highlights in the more recent contributions.En este trabajo se analizan las relaciones entre clima urbano, confort ambiental y planificación
urbana desde el punto de vista de la evolución de los conceptos e ideas fundamentales, de las aportaciones
metodológicas básicas realizadas y de las aplicaciones y revisiones de los últimos años, en
particular en el campo de los índices de confort. Se traza, con ello, un estado de la cuestión y se destacan
las aportaciones recientes más destacadas
Numerical evaluation of the Green's functions for arbitrarily shaped cylindrical enclosures and their optimization by a new spatial images method
IIn this paper, a spatial image technique is used to efficiently calculate the mixed potential Green’s functions associated with electric sources, when they are placed inside arbitrarily shaped cylindrical cavities. The technique is based on placing electric dipole images and charges outside the cavity region. Their strength and orientation are thencalculated by imposing the appropriate boundary conditions for the fields at discrete points on the metallic wall. A method for the assessment of the potentials accuracy is proposed, and several optimization techniques are presented. Three cavities are analyzed to demonstrate the usefulness of the techniques. The cutoff frequencies and potentials patterns are compared to those obtained by a standard finite elements technique, showing excellent agreement. Finally, a band-pass filter based on coupled lines is analyzed, demonstrating the practical value of the technique.This work has been developed with support from the Spanish National Project (CICYT) with reference TEC2004-04313-C02-02/TCM, and the Regional Seneca Project with reference 02972/PI/0
Microstrip leaky-wave antenna with control of leakage rate and only one main beam in the azimuthal plane
An original leaky-wave antenna (LWA), conceived
from a microstrip line which is laterally shielded by parallel plates,
is presented in this paper. This structure shows, for the first time,
that the leakage rate of a microstrip leaky-mode can be easily
controlled while negligibly affecting the pointing direction. The
antenna is based on the radiation from the second higher order
mode of the microstrip line, which is perturbed by the addition
of the two conductor walls to control the level of the leakage
rate. The parallel-plates also serve as a mechanism to obtain a
single main beam in the azimuthal plane, therefore improving the
radiation pattern compared to common dual-beam second-higher
order mode microstrip LWAs. The proposed antenna is analyzed
by obtaining the corresponding leaky-mode complex propagation
constant, which is calculated by a specific method of moments
approach. The modal results obtained from the leaky-mode
dispersion curves are validated with analysis performed on a
three-dimensional structure using commercial finite element
method solver. Also, a prototype is fabricated to experimentally
confirm the advantages of this novel leaky-wave line source.This work
was supported in part by the Spanish National project TEC2004-04313-C02-02/
TCM, in part by the Regional Seneca project 02972/PI/05, and in part by Regional
Scholarship PMPDI-UPCT-2007
A novel leaky-wave antenna combining an image NRD guide and a strip circuit
This letter presents a novel leaky-wave antenna which
combines an image NRD (nonradiative dielectric) guide and a
printed strip circuit. The proposed structure allows for an easier,
cheaper and more flexible tapering mechanism than all previous
leaky-wave antennas in NRD technology. The working mechanism
is explained, and two different tapering strip-circuit topologies
are proposed. Cosine tapered illuminations are designed using a
two-dimensional leaky-mode analysis technique. Simulations with
high-frequency structure simulator (HFSS) three-dimensional
analysis are presented for validation purposes. Also, the influence
of the feeding transitions for each printed-circuit design is studied.
Results show the feasibility of one of the proposed designs, leading
to a tapered radiation pattern with sidelobes level below 20 dB.This work was
supported by Spanish National Projects ESP2001-4546-PE and TIC2000-0591-
C03-03, and Regional Seneca Project 2002 PB/4/FS/02
Printed-circuit leaky-wave antenna with pointing and illumination flexibility
A novel leaky-wave antenna, based on a periodic set
of slots printed on a rectangular dielectric waveguide is conceived
in this work. The antenna presents the ability to independently
control the aperture illumination and the pointing direction,
by only modifying the photoetched printed-circuit layout. The
working mechanism is described using a leaky-mode dispersion
analysis, and cosine-tapered designs are performed at 50 GHz.
The radiation patterns are obtained using HFSS analysis to check
the reduction of sidelobes levels, and the capacity to tune the
pointing direction over a wide range of elevation angles.This work was supported by Spanish National Projects ESP2001-4546-PE,
TEC2004-04313-C0202-TCM, Regional Seneca Project 2002 PB/4/FS/02,
and the EPSON-Ibérica Foundation
Simple analysis and design of a new leaky-wave directional coupler in hybrid dielectric-waveguide printed-circuit technology
This paper presents a new theory to analyze and design a novel leaky-wave coupler based on a hybrid dielectric-waveguide printed-circuit technology. The analysis theory is based on a combined method of moments (MoM) geometrical optics (GO) technique, which makes use of the leaky mode complex propagation constant. This MoM-GO approach allows to easily obtain the response of the coupler, and to illustratively understand the working mechanism of the proposed structure. A coupler is designed to work at 5.5 GHz. Leaky mode results are compared with three-dimensional finite-element method simulations, showing the validity and accuracy of the new theory developed. This novel directional coupler presents interesting advantages when compared to previous wave couplersThis work was supported in part under Spanish National Project ESP2001-4546-PE and Spanish National Project TEC2004-04313-C02-02-TCM and under the Regional Séneca Project 2002PB/4/FS/02
Application of the high-gain substrate-superstrate configuration to dielectric leaky-wave antennas
The high-gain substrate-superstrate configuration,
which was proposed to increase the gain in printed circuit antennas,
is applied to dielectric leaky-wave antennas (LWAs) to
improve its frequency response. Analysis of a slitted suspended
dielectric rectangular waveguide is carried out using a full-wave
method. It is proved that the minimum values of the leakage
constant of the leaky-wave mode for the suspended configuration
are related to the high-gain resonance conditions. Moreover, it is
found that the suspended LWA exhibits very small beamwidth
variations in a large frequency bandwidth. It is well-known that
inhomogeneous filled LWAs suffer from variation of beamwidth
as the angle of maximum radiation is scanned with frequency.
The proposed topology can be adjusted so that a flat response of
the beamwidth can be obtained in a large frequency band, while
maintaining the frequency-scanning behavior of the LWA.This work was
supported by Spanish National Projects ESP2001-4546-PE and TIC2000-0591-
C03-03, by Regional Seneca Projects 2002 PB/4/FS/02 and PMPDI-UPCT-
2004, and by the EPSON-Ibérica Foundation
Analysis and design of periodic leaky-wave antennas for the millimeter waveband in hybrid waveguide-planar technology
This work presents a full-wave integral equation
approach specifically conceived for the analysis and design of
laterally-shielded rectangular dielectric waveguides, periodically
loaded with planar perturbations of rectangular shape.
This type of open periodic waveguide supports the propagation
of leaky-wave modes, which can be used to build leaky-wave
antennas which exhibit many desirable features for millimeter
waveband applications. The particularities of the leaky-mode
analysis theory are described in this paper, and comparisons with
other methods are presented for validation purposes. Using this
leaky-mode analysis method, a novel periodic leaky-wave antenna
is presented and designed. This novel antenna shows some important
improvements with respect to the features of previously
proposed antennas. The results of the designed radiation patterns
are validated with three-dimensional electromagnetic analysis
using commercial software.This
work was supported by Spanish National projects ESP2001-4546-PE and
TEC2004-04313-C02-02/TCM and Regional Séneca projects 2002 PB/4/FS/02. The authors would like to thank the EPSON-Ibérica Foundation
for its stimulating support.
and PMPDI-UPCT-2004.
The authors would like to thank the EPSON-Ibérica Foundation
for its stimulating support
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