DIELECTRIC RESONATOR ANTENNA

Report
THIS PRESENTATION CONSISTS OF
1.Introduction
2.Purpose of DRA
3.Structure of DRA
4.Excitation methods
5.Radiation patterns
6.Factors effecting the Resonant frequency
7.Challenges
8.Conclusions
9.References
INTRODUCTION
 The field of wireless communication has been under
going a revolutionary growth in the last decade.
2G-cellular communication (portable mobile phones)
3G- Bluetooth, LAN
 The crucial component of a wireless network is the
‘Antenna’.
 In the last two decades the classes of antennas
investigated and extensively reported are
1.Microstrip patch antenna
2.Dielectric Resonator Antenna
INTRODUCTION TO DRA
Since the frequency range of interest has gradually
progressed upward and the frequencies in millimeter
region(100-300Ghz) are employed, the conduction
losses in metallic antennas increase to such a level
that efficient operation of the systems is impaired.
So an idea to use dielectric material as a radiator was
conceived.
Dielectric resonators were used as energy storage
devices but if the cavity is not enclosed by metallic
walls the EM fields exist beyond the geometrical
boundary of the cavity.
INTRODUCTION TO DRA
 The use of dielectric resonator as a resonant antenna
was proposed by S.A LONG in early nineteen eighties.
 Dielectric resonator antennas offer advantages like
small size, low cost and most importantly freedom
from metallic loss.
 Therefore dielectric resonator antenna have a lot of
applications in millimeter band where the conductor
loss of a metallic antenna becomes severe.
PURPOSE OF DRA
 As the frequency increases conductor losses
increases and antenna efficiency will decreases.
 Conversly only losses present in the DRA are due
to imperfections in the Dielectrics which are very
small compared to conductor losses.
 Dielectric resonators which we are using in
microwave applications are having (ɛ > 20) and
Q(50-500).
 By choosing a dielectric material (5<€<20)
properly the radiation fields can be enhanced.
 The dimension of a DRA is of the order of λo/√(ε). Thus by
choosing high value of ε, the size of DRA can be significantly
reduced.
 High Radiation efficiency(=95%)due to absence
of conductor losses.
 High ɛr tolerance (1-5%)
 Wide frequency range: f = 0.7 -35GHz
COMPARISION WITH MICROSTRIP
ANTENNA
 In Micro strip radiation occurs due to narrow slots
where as in DRA radiation occurs due to whole DRA
surface.
COMPARISION WITH MICROSTRIP
ANTENNA
 In Micro strip radiation occurs due to narrow slots
where as in DRA radiation due to whole DRA surface.
 DRA has wider impedance bandwidth than micro
strip
DRA avoids surface waves
STRUCTURE OF DRA
 The DRA consists of a ground plane and over it a
dielectric resonator is placed as shown in the figure.
 The dielectric resonator can be of various shapes like
rectangular ,cylindrical , hemispherical, triangular
,spherical cap, circular ring etc
STRUCTURE OF DRA
Shapes of DRA
Some examples of Dielectric materials
Ref::1
 An important parameter for DRA is its resonant
frequency
The Resonance frequency of a dielectric resonator depends on
dimensions of resonator and dielectric constant.
Ref::1
 DRA size decreases as the dielectric constant increases
 Wavelength of the dielectric resonator is important
because from this wave length the dimensions of
Micro strip circuit can be designed.
The dielectric resonator antenna is a resonant circuit
that is able to store electromagnetic fields with a
minimum loss of energy within the resonator i.e. a
cavity with a high-unloaded quality factor, QU.
Simple design of DRA using Disk shape
dielectric
The dielectric resonator antenna (DRA) consists of high
dielectric constant materials, high quality factors and
mounted on a grounded dielectric
substrate of lower
permittivity.
The selected dielectric disk
is operating at frequency of 2.4 GHz
with dielectric constant of 34.73.
The micro strip transmission line has been used as a
feeding line for the resonator.
The magnetic fields inside a DRA
THE ELECTRIC FIELDS INSIDE A DRA
FIELDS INSIDE A RECTANGULAR
DRA
The Hx component of magnetic field is dominant along the centre of
DRA , while E-fields (Ey and Ez) circulate around the Hx component.
Showing 2-D image of fields inside
DRA
Excitation Methods
 APERTURE COUPLING
 PROBE COUPLING
 MICROSTRIP LINE COUPLING
Aperture coupling
This method of exciting DRA is through an aperture in
the ground plane upon which the DRA is placed.
The various types of apertures are shown
Showing aperture coupling
 Micro strip line COUPLING is preferred over the
coaxial cable because it offers good impedance
matching compared to the coaxial line.
 The length of the slot is chosen large enough so that
sufficient coupling exists but small enough so that it
does not resonate within the band of operation.
Aperture coupling to rectangular
DRA
Aperture coupling to cylindrical
DRA
PROBE COUPLING
 This type of coupling employs a probe in order to
couple a DRA.
 The probe consists of a centre pin that extends
through the ground plane.
 This probe can also be soldered to a flat metal strip
which is placed adjacent to DRA.
 This flat metal strip can also be modeled so that
impedance matching is achieved.
SHOWING PROBE COUPLING
COUPLING THROUGH A METAL
PLATE
PROBE COUPLING TO RECTANGULAR DRA
MICROSTRIP LINE COUPLING
 A DRA can be coupled with the help of micro strip line
in two ways
1)Direct-coupling
2)side-coupling
SHOWING DIRECT COUPLING
SHOWING SIDE COUPLING
THE MULTISEGMENT DRA(MSDRA)
 QU
refers to the Internal energy dissipation where as
the External quality factor QE refers to energy
dissipation outside .
The loaded Q,QL takes into account all causes of energy
dissipation and is given by
The experimental results[1]
The radiation patterns for different a/d
ratios
The radiation patterns for different €r
values
Radiation Pattern[1]
The HPBW for Hplane is 77.72° greater
than measurement,
which are 72°.
The HPBW for Eplane is 46.61° for
measurement and 45
°for simulation
respectively.
Ref:;1
There are a few factors affecting the Resonance
frequency.
1 Adhesives for Dielectric
Resonator.
2. Environment.
3. Equipment.
4. Fabrication process.
Challenges
In order to be suitable for GSM and PCS antenna,
applications εr needs to be <30
DRAs with ε r <30 at frequencies below 3GHz are
generally too large to be used for handsets
REFERENCES
[1] S.A Long ,M.W.McAllister and L.C.Shen ,“The resonant
cylindrical dielectric cavity antenna ,”IEEE Transactions on
Antennas & Propagation,Vol.31,pp.406-412,May 1983.
[2]Collin,R.E. ,Foundations for Microwave Engineering, New
York: McGraw Hill,1966.
[3]A.Petosa, Dielectric Resonator Antenna Handbook,
Norwood, MA:Artech House,2007.
[4]K.M.Luk and K.W.Leung, Dielectric Resonator Antennas,
Baldock,U.K. : Research Studies,2003.
WEBSITES:
www.wikipedia.com
www.antena-theory.com
Thank you….....
Any queries…….

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