01-11-2012, 04:48 PM
DESIGN OF LINEARLY POLARIZED RECTANGULAR MICROSTRIP PATCH ANTENNA USING IE3D/PSO
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ABSTRACT
In this project, a novel particle swarm optimization method based on IE3D is used to design
an Inset Feed Linearly Polarized Rectangular Microstrip Patch Antenna. The aim of the thesis is to
Design and fabricate an inset fed rectangular Microstrip Antenna and study the effect of antenna
dimensions Length (L) , Width (W) and substrate parameters relative Dielectric constant (εr) , substrate
thickness on Radiation parameters of Band width. Low dielectric constant substrates are generally
preferred for maximum radiation. The conducting patch can take any shape but rectangular and
circular configurations are the most commonly used configuration. Other configurations are complex
to analyze and require heavy numerical computations.
The length of the antenna is nearly half wavelength in the dielectric; it is a very critical
parameter, which governs the resonant frequency of the antenna. In view of design, selection of the
patch width and length are the major parameters along with the feed line depth. Desired Patch
antenna design is initially simulated by using IE3D simulator. And Patch antenna is realized as per
design requirements.
INTRODUCTION
Communication between humans was first by sound through voice. With the desire for
slightly more distance communication came, devices such as drums, then, visual methods such as
signal flags and smoke signals were used. These optical communication devices, of course, utilized
the light portion of the electromagnetic spectrum. It has been only very recent in human history that
the electromagnetic spectrum, outside the visible region, has been employed for communication,
through the use of radio. One of humankind’s greatest natural resources is the electromagnetic
spectrum and the antenna has been instrumental in harnessing this resource.
Overview of Microstrip Antennae
A microstrip antenna consists of conducting patch on a ground plane separated by
dielectric substrate. This concept was undeveloped until the revolution in electronic circuit
miniaturization and large-scale integration in 1970. After that many authors have described the
radiation from the ground plane by a dielectric substrate for different configurations. The early work
of Munson on micro strip antennas for use as a low profile flush mounted antennas on rockets and
missiles showed that this was a practical concept for use in many antenna system problems. Various
mathematical models were developed for this antenna and its applications were extended to many
other fields. The number of papers, articles published in the journals for the last ten years, on these
antennas shows the importance gained by them. The micro strip antennas are the present day antenna
designer’s choice.
Waves on Microstrip
The mechanisms of transmission and radiation in a microstrip can be understood by
considering a point current source (Hertz dipole) located on top of the grounded dielectric substrate
(fig. 1.1) This source radiates electromagnetic waves. Depending on the direction toward which
waves are transmitted, they fall within three distinct categories, each of which exhibits different
behaviors.
Surface Waves
The waves transmitted slightly downward, having elevation angles θ between π/2and π -
arcsin (1/√εr), meet the ground plane, which reflects them, and then meet the dielectric-to-air
boundary, which also reflects them (total reflection condition). The magnitude of the field
amplitudes builds up for some particular incidence angles that leads to the excitation of a discrete set
of surface wave modes; which are similar to the modes in metallic waveguide.
The fields remain mostly trapped within the dielectric, decaying exponentially above the
interface (fig1.2). The vector α, pointing upward, indicates the direction of largest attenuation. The
wave propagates horizontally along β, with little absorption in good quality dielectric. With two
directions of α and β orthogonal to each other, the wave is a non-uniform plane wave. Surface waves
spread out in cylindrical fashion around the excitation point, with field amplitudes decreasing with
distance ®, say1/r, more slowly than space waves. The same guiding mechanism provides
propagation within optical fibers.
MICROSTRIP PATCH ANTENNA
Microstrip antennas are attractive due to their light weight, conformability and low cost.
These antennas can be integrated with printed strip-line feed networks and active devices. This is a
relatively new area of antenna engineering. The radiation properties of micro strip structures have
been known since the mid 1950’s.
The application of this type of antennas started in early 1970’s when conformal antennas
were required for missiles. Rectangular and circular micro strip resonant patches have been used
extensively in a variety of array configurations. A major contributing factor for recent advances of
microstrip antennas is the current revolution in electronic circuit miniaturization brought about by
developments in large scale integration. As conventional antennas are often bulky and costly part of
an electronic system, micro strip antennas based on photolithographic technology are seen as an
engineering breakthrough.