265 research outputs found
Microstrip patch antennas with 3-dimensional substrates
This paper investigates the concept of replacing conventional flat 2-D patch antennas with 3-D versions where the substrate height is not uniform. The hypothesis of this work is that the electric fields are not evenly distributed under the patch and hence increasing the height in specific locations can be beneficial in terms of size of performance
Manipulating microsized coupling gaps for reconfigurable antenna applications
Synthetically arranged microlines (width ≤ 1mm) have been considered for antennas and radiating structures at microwave frequencies. Finite-difference time-domain simulations show how the electrical size of the structure and multiple resonances can be controlled by carefully introducing microsized gaps
Antenna emblems reshaped as icons and esthetic logos (aerial)
This paper introduces the concept of designing microstrip patch antennas to take the form of aesthetic arbitrary shapes or logos. Various intermediate shapes have been examined to analyze the behavior of asymmetric, curved, angular and disconnected sections
Capacitive coupling of discrete micro-sized gaps for RF applications
This paper investigates the performance of a passive thin metallic object
containing micro-sized gaps exposed to a plane wave excitation. This work has potential
applications for emerging antenna fabrication techniques where the conducting sections are
made from discrete metallic sections. This includes antennas composed from nanomaterials
and conventional inkjet printed antennas. Electromagnetic simulations showed metallic
sections separated by a micro-sized gap were found to capacitively couple. The coupling
can be enhanced by reducing the size of the gap, increasing the width of the metallic object
or by filling the gap with a permittivity greater than unity. It should be noted that the DC value
of parallel plate capacitor is not strictly valid at radiofrequencies – however, this paper shows
that the DC value of capacitance is a reasonable approximation and is useful to understand
the behavior
3D printing, inkjet printing and embroidery techniques for wearable antennas
This paper will review techniques of manufacturing wearable antennas. 3D printing can be used to create flexible substrates. 3D shapes can be created which can be used to reduce the antenna size. Embroidery will also be discussed. The technique naturally lends itself to linear antennas
On specific absorption rates in the human mucous membrane with conducting spectacles at mobile phone frequencies by FDTD simulation
An anatomically correct FDTD head phantom was used to
study SAR levels in the mucous membrane found in the
lining of the nose, sinuses and ears. The membrane is
found to absorb significant levels of energy when
illuminated by a plane wave from the front of the head.
The frequency range considered is 0.8 to 2.6GHz.
Metallic spectacles were found to significantly change the
SAR in the eyes and mucous membrane
A study of changes to specific absorption rates in the human eye close to perfectly conducting spectacles within the radio frequency range 1.5 to 3.0 GHz
This paper investigates relative changes in specific
absorption rates due to perturbing metallic spectacles in proximity
to the face. A representative electrical property biological
matter model with 25 distinct tissue types based on magnetic resonance
imaging data is used with the finite-difference time-domain
method. Both plane wave and dipole stimuli are investigated and
are used to represent an excitation from the front of the head. The
frequency range investigated is 1.5 to 3.0 GHz. Results show that
metallic spectacles may significantly alter SAR level distributions
within the head. Specific attention is given to energy interactions
with the eyes. Results are given for several common spectacle
frame shapes
A study of changes to specific absorption rates in the mucous membrane close to perfectly conducting spectacles within the radio frequency range 0.8 to 2.6 GHz.
Abstract—this paper investigates the effects of metallic spectacles on the Specific Absorption Rates (SAR) in
the mucous membrane in the human head, using the FDTD method. The excitation is a vertically polarised plane
wave traveling from the front of the face to the back of the head. The frequency range considered is 0.8 to
2.6GHz. Metallic spectacles were found to significantly change the SAR in the mucous membrane
Miniaturization of circular patch microstrip antenna using an arc projection
A semi-circle arc projection is introduced to miniaturize the patch in circular patch microstrip antennas. The idea has been inspired from the effectiveness of a cuboid ridge in size reduction of a rectangular patch microstrip antenna. A prototype of the proposed antenna together with a prototype of a conventional circular patch antenna have been fabricated and measured. The two antennas are compared and the results are presented and discussed. A parametric study is also carried out on the characteristics of the arc projection
Specific absorption rate perturbations in the eyes and head by metallic spectacles at personal radio communication frequencies.
The research in this thesis involves the absorption in the human head of microwaves
in the frequency range 0.5 to 3GHz with the excitation positioned in front of the face.
It is hypothesised that metallic spectacles can significantly affect the absorption in the
head.
The effects of metallic spectacles have been primarily investigated using computer
modelling. The finite-difference time-domain (FDTD) is the most common
computational tool used in bioelectromagnetics. For this research an independent,
specially written FDTD code has been used. The accuracy of the code was carefully
validated against controls. Two anatomically accurate heads were implemented into the
FDTD code.
Different shapes and sizes of metallic spectacles were modelled. The materials that the
spectacles were made of were also investigated. Realistic and geometric spectacles were
considered. Vertically and horizontally polarised plane waves as well as vertically and
horizontally orientated dipoles are used as sources. A genetic algorithm (GA) was
employed as a search technique to optimise the spectacles for the specific absorption
rates (SAR) in the eyes and the head.
Measurements were also made of a phantom with metallic spectacles. Results showed
good agreement with the FDTD code. Results confirmed the hypothesis that metallic
spectacles can significantly affect the SAR in the head and particularly in the eyes
- …