Review Article
Defected Ground Structure: Fundamentals, Analysis, and
Applications in Modern Wireless Trends
Mukesh Kumar Khandelwal,
1
Binod Kumar Kanaujia,
2
and Sachin Kumar
3
1
Department of Electronics & Comm un ica tion Engineering, Bhagwan Pa rshur a m Institute of Technology, Sector 17,
Rohi ni 110089, India
2
School of Computational and In tegrative Sciences, Jawaharlal Nehru Uni versity, Delhi 110067, India
3
Department of Electron ics & Commun ication Engineerin g, ABES Engineering College, Ghazia bad 201009, I nd ia
Correspondence should be addressed to Mukesh Kumar Khandelwal; mukesh.khandelwal@gmail.com
Received September ; Revised December ; Accepted December ; Published February
AcademicEditor:IkmoPark
Copyright © Mukesh Kumar Khandelwal et al. is is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
Slots or defects integrated on the ground plane of microwave planar circuits are referred to as Defected Ground Structure. DGS is
adopted as an emerging technique for improving the various parameters of microwave circuits, that is, narrow bandwidth, cross-
polarization, low gain, and so forth. is paper presents an introduction and evolut ion of DGS and how DGS is dierent from
former technologies: PBG and EBG. A basic concept b ehind the DGS technolog y and several theoretical techniques for analysing
the Defected Ground Structure are discussed. Several applications of DGS in the eld of lters, planar waveguides, ampliers, and
antennas are presented.
1. Introduction
Conventional microstrip antennas had some limitations, that
is, single operating frequency, low impedance bandwidth,
low gain, larger size, and polarization problems. ere are
number of techniques which have been reported for enhanc-
ing the parameters of conven tional microstrip antennas, tha t
is, using st acking, dierent feeding techniques, Frequenc y
Selective Surfaces (FSS), Electromagnetic Band Gap (EBG),
Photonic Band Gap (PBG), Metamaterial, and so forth.
Microwave component with Defected Ground Structure
(DGS) has been gained popularity among a ll the techniques
reported for enhancing the parameters due to its simple
structural design. Etched slots or defects on the ground plane
of microstrip circuits are referred to as Defected Ground
Structure. Single or multiple defects on the ground plane
may be considered as DGS. Initially DGS was reported
for lters underneath the microstrip line. DGS has been
used underneath the microstrip line to achieve band-stop
characteristics and to suppress higher mode harmonics and
mutual coupling. Aer successful implementation of DGS in
the eld of lters, nowadays DGS is in demand extensively
for various applications. is paper presents the evolution
and development of DGS. e basic concepts, working
principles, and equivalent models of dierent shapes of DGS
are presented. DGS has been used in the eld of microstrip
antennas for enhancing the bandwidth and gain o f microstrip
antenna and to suppress the higher mode harmonics, mutual
coupling between adjacent element, and cross-polar ization
for improving the radiation characteristics of the microstrip
antenna. Applications of DGS in microwave technology are
summarized in this paper and the applications of DGS in the
eld of antennas are discussed.
Low cost, high performance, compact size, wideband, and
low prole antennas oen meet the stringent requirements of
modern wireless communication systems. Modern commu-
nication demands the availability of ecient, compact, and
portable devices that can be operated at high data-rates and
at low signal powers. Researchers have been working towards
the development and advancement of RF front ends to meet
Hindawi
International Journal of Antennas and Propagation
Volume 2017, Article ID 2018527, 22 pages
https://doi.org/10.1155/2017/2018527
International Journal of Antennas and Propagation
the latest requirements. Various novel approaches have been
reported to improve the performance of microwave com-
ponent. PBG has been proposed by John and Yablonovitch
proposed [, ]. For providing a rejection band of certain
frequency PBG is used. Periodic structure on the ground
plane provides a rejection band . However, the modelling of
PBG structure for microwave and millimeter-wave compo-
nents is very dicult. Radiation from perio dic etched defects,
number of lattice, lattice shapes, lattice spacing and relative
volume fraction are some parameters that eects the band gap
properties of PBG. ere is another ground plane aperture
(GPA) technique, which simply incorporates the microstrip
line embedded with a centred slot at the ground plane.
GPA has been reported for dB edge coupler and bandpass
lters [–]. Width of the GPA creates a signicant eect
on the characteristic impedance of the microstrip line, hence
controlling the return loss level.
In order to alleviate these problems, Park et al. []
proposed Defected Ground Structure (DGS) rstly and used
the term “DGS” in describing a single dumbbell shaped
defect. e DGS can be regarded as a simplied form of EBG
structure, which also exhibits a band-stop property []. DGS
opens a door to microwave researchers of a w ide range of
applications. Various novel DGSs have been proposed and lot
of applications have been explored extensively in microwave
circuits. e development of DGS is thoroughly discussed
in []. Subsequently, three books [–] have addressed the
microstrip antennas with DGS. DGS has become an alterna-
tive of EBG for modern applications due to its simplicity and
low cost. Dumbbell shaped DGS was initially used to realize
a lter [], and other shapes were reported subsequently to
realize dierent microwave circuits such as lters [–],
ampliers [], rat race couplers [], branch line couplers,
and Wilkinson power dividers [, ]. In [], the DGS is
integrated with a MPA. Deferent DGS printed antennas have
been investigated in [].
In this paper, an overview and evolution of DGS are pre-
sented in detail. e working principles and basic concepts of
DGSunitsareintroducedandtheequivalentcircuitmodels
of DGS units available in literature are also presented. In
the last sect i on, the applications of DGS in modern wireless
communication are presented and the evolution trend of DGS
is given.
2. Photonic Band Gap
Photonic Band Gap (PBG) structures are periodic structures
etchedonthegroundplaneandhavetheabilitytocontrolthe
propagation of electromagnetic waves. Periodic structures
eects the current distribution of the structure. e periodic
structures can inuence on the propagation of electromag-
netic waves and radiation characteristics. e PBG have the
perio dic defects, which can be treated as a resonant cavity
and aect the propagation of the electromagnetic waves.
PBG forms free mode inside the forbidden band gap and
provides a stopband at certain frequency. PBG has been
reported for improving the directivity of antennas, surface
wave’s suppression, and harmonics suppression [].
3. Electromagnetic Band Gap (EBG) Structure
eEBGtechniqueisbasedonthePBGphenomenaand
also realized by periodical structures. In [], EBG has been
introduced as high-impedance surface or PBG surface. ese
structures are compact and result in high gain, low prole and
high eciency antennas. EBG has been created an interest in
the eld of an tenna. EBG structures suppress the surface wave
current hence increase the antenna eciency. e surface
wavesdecreasetheantennaeciency.Surfacewavesuppres-
sion using EBG technique impro ves the antenna performance
by increasing the antenna eciency and antenna gain [].
4. Defected Ground Structure
e compact geometrical slots embedded on the ground
plane of microwave circuits are referred to as Defected
Ground Structure (DGS). A single defect (unit cell) or a
number of periodic and aperiodic defects congurations may
be comprise d in DGS. us, periodic and/or aperiodic defects
etched on the ground plane of planar microwave circuits
are referred to as DGS. Earlier Photonic Band Gap (PBG)
[] and Electromagnetic Band Gap (EBG) [, ] have
been reported with irregular ground planes. e comparison
between PBG, EBG, and DGS is depicted in Table .
4.1. Working Principle. DGS has been integrated on the
ground plane with planar transmission line, that is, micro-
strip line, coplanar waveguide, and conductor backed copla-
nar wave guide [–]. e defects on the ground plane
disturb the current distributio n of the ground plane; this
disturbance changes the characteristics of a transmission
line (or any structure) by including some parameters (slot
resistance, slot capacitance, and slot inductance) to the line
parameters (line resistance, line capacitance, and line induc-
tance). In other words, any defect etched in the ground plane
underthemicrostriplinechangestheeectivecapacitance
and inductance of microstrip line by adding slot resistance,
capacitance, and inductance.
4.2. Unit DGS. e rst DGS model has been reported as
a dumbbell shaped defect embedded on the ground plane
underneath the microstrip as shown in Figure []. e
response of its return loss is also shown in the gure.
DGS has some advantages over PBG. (1)In PBG, periodic
structures occupy a large area on the circuit board. On
the other hand a few DGS elements may create similar
typical properties. Hence, circuit size becomes compact by
introducing DGS. (2) DGSiscomparablyeasytodesign
and fabricate and its equivalent circuit is easy to realize. (3)
Higher precisions are achieved in comparison to other defect
embedded structures.
Two aspects for utilizing the performance of DGS are
DGS unit and periodic DGS. A variety of deferent shapes
of geometries embedded on the ground plane under the
microstrip line have been reported in the literature [–
]. ese shapes include rect angular dumbbell [], circular
dumbbell [], spiral [], “U” [], “V” [], “H” [], cross
[], and concentric rings []. Some complex shapes have
International Journal of Antennas and Propagation
T:ComparisonofPBG,EBG,andDGS.
PBG EBG DGS
Denition
Photonic Band Gap (PBG)
structures are periodic structures
etched on the ground plane and
have the ability to control the
propagation of electromagnetic
waves
e EBG technique is based on
the PBG phenomena and also
realized by periodical structures
but compact in size
Single or few com pact
geometrical slots embedded on
the ground plane of microwave
circuits are referred to as
Defected Ground Structure
(DGS)
Geometry Periodic etched str ucture Periodic etched stru cture One or few etched structures
Parameter ext raction Very dicult Very dicult Relatively simple
Size Large
Smaller than PBG and larger
than DGS
Much more compact than PBG
and EBG
Fabrication Dicult Dicult Easy
Examples [] [, ] [–]
Microstrip line
Dumbbell DGS
(a)
Frequency (GHz)
S-Parameters (dB)
0
−5
−10
−15
−20
−25
−30
02468
S
11
S
21
(b)
F : e rst DGS unit: (a) dumbbell DGS unit; (b) simulated -parameters for dumbbell DGS unit [].
also been studied which include meander lines [], split
ring resonators [, ], and fractals []. Some of them are
discussed in this paper along with the modelling techniques
for them.
Other DGSs units have more advantages than dumbbell
DGS:
() e slow wave factor is increased and a better degree
of compactness is achieved. A miniaturization of
.% has been achieved by using “H” shaped DGS
in comparison to dumbbell DGS [].
() Stopband is with an improved bandwidth and better
return loss level [, , ].
() An improved -factor is achieved. -shaped DGS
gives higher than spiral shaped DGS. While com-
paring the transfer characteristics of the -shaped
DGS with the conventional DGS and the spiral
shaped DGS at same resonance frequency it is found
that -factorofthespiralDGSisabout.,while
the -shaped DGS provides a higher -factor of
. [].
4.3. Periodic DGS. Periodic DGSs for planar microwave cir-
cuits are earning major attraction of microwave researchers.
Microstrip lines with a periodic DGS have been presented:
bandpass and low pass planar lters [, , ]. By using
periodic structure phenomena higher slow wa ve rate with
greater degree of miniaturizat ion is achieved. Repetition of
single defect with a nite spacing is referred to as periodic
structure. By cascading the defects (resonant cells) in the
ground plane the return loss level and bandwidth is impr oved
depending on the number of periods. Shape of DGS unit,
distance between two DGS units and the distribution of
the dierent DGSs are the main parameters that aect t he
performance of periodic DGS. Two periodic DGS shapes are
shown in Figure ; horizontally periodic DGS (HPDGS) and
vertically periodic DGS (VPDGS) are shown in Figures (a)
and (b), respectively [, ].
International Journal of Antennas and Propagation
Microstrip line
Dumbbell DGS
(a) (b)
F : Periodic DGS: (a) HPDGS; (b) VPDGS [, ].
T : Applications, advantages, and disadvantages of dierent type of DGS.
S. number Shape Reference Advantage Disadvantage Applications
Dumbbell []
Simple structure, easy to design and
analyse
Single stop band Band-stop lter
HPDGS [] .% s ize reduction
Larger size than VPDGS,
dispersion problem
Matching network of amplier
VPDGS [] .% size reduction Dispersion problem Matching network of amplier
-slot [] Improved -factor Single stop band Band-stop lter
-slot [] Improved -factor Single stop band Band-stop lter
CrossDGS[]
Sharp rejection, ultra-wide stop
band
— Low pass lter
Fractal
DGS
[] Wide stop band No sharp cut-o frequency Band-stop lter
Spiral
DGS
[] Multistop band Complex analysis Band-stop lter
Application, advant ages, and disadvantages of dierent
shapes of DGS are summarized in Table .
5. Equivalent Circuit Models of DGS
Each metallic part of microstrip antenna is a combination
of distribu ted resistance, capacitance, and inductance. Hence
each model may be represented by its equivalent circuit
model. By Babinate’s principle each slot is reciprocal to
its metallic structure and also may be represented by its
equivalent resistance, capacitance and inductance model.
Full-wave analysis is used for analysing the responses of DGS
and to nd the equivalent circuit model. However, Full-wave
analysis fails to describe about the physical dimensions and
position of the DGS. Conventional methods for analysing
the DGS were based on trial and error iterative methods
so they were time consuming and there was a possib ili ty
for not getting the optimum results [, , , –].
Figure shows the conventional design and analysis methods
of DGSs.
Equivalent circuit of DGS can be extracted by four
types and comparisons of all types of parameter extraction
methods are summarized in Table .
() LC and RLC equivalent circuits.
() shaped equivalent circuit.
() Quasi-static e quivalent circuit.
() Using ideal transformer.
5.1. LC and RLC Equivalent Circuits. e LC equivalent
circuitmodeloftheDGSisshowninFigure.Anequivalent
circuit model of one-pole Butterworth low pass lter is shown
in Figure (b). e current path is increased due to the
rectangular parts of dumbbell DGS; thus eective inductance
and eective capacitance of microstrip line are changed. e
two rectangular slots of dumbbell DGS are responsible for
adding a capacitive eect and a thin rectangular defected
slot which connects both the rectangular shaped defects
accounts for adding the inductance to the total impedance.
Due to this LC circuit, a resonance is occurred at a certain
International Journal of Antennas and Propagation
T : Comparison of parameter extraction methods.
S. N Method Advantage Disadvantage Summary
LC and RLC []
DGS which have similar shape
like dumbbell DGS have almost
same characteristics like
dumbbell DGS and could be
analysed
Complex and cannot
determine the
location of DGS
An equivalent circuit
model of one-pole
Butterworth low pass
lter
shaped []
More accurate results in
comparison with LC and RLC
circuits
Complex and cannot
determine the
location of DGS
Explains both
amplitude versus
frequency and phase
versus frequency
characteristics
Quasi-static[]
e limitations of full-wave
analysis can be overcome by
developing the equivalent circuit
model depending upon
quasi-static technique
Complex and cannot
determine the
location of DGS
Role of dimensions of
the DGS is explained
for creating the stop
band characteristics
Using ideal
transformer []
Can determine the location of
DGS
—
A simple and accurate
circuit model for the
slotted ground plane
with microstrip line
Start
Guess dimensions of
DGS
Select dielectric
material & thickness
Perform full-wave
analysis
1
1
Extract S-parameters versus
frequency
Is the frequency
response
acceptable?
Change dimensions
iteratively
Stop
No
Ye s
F : Flowchart of design and analysis of conventional dumb-
bell DGS [].
frequency. e slotted area of the DGS is pro portional to
the eective inductance and inversely pro portional to the
eective capacitance. An increment in slotted DGS area gives
rise to the eective inductance thus results in a lower cut-o
frequency. A decrement in the D GS area reduces the eective
capacitance, thereby increasing the resonant frequency.
e reactance of Butterworth low pass lter can be
obtained as
𝐿𝐶
=
1
0
0
−
0
,
()
where
0
is the resonance angular frequency. and of the
circuit are calculated as
=
𝑐
0
1
⋅
1
2
0
−
2
𝑐
,
=
1
4
2
2
0
,
()
Z
0
L
C
Z
0
jX
LC
(a)
g
0
g
1
g
2
jX
1
(b)
F : equivalent circuit: (a) equivalent circuit of the
dumbbell DGS circuit; (b) Butterworth-type one-pole prototype low
pass lter circuit [].
where
0
and
𝑐
are resonant frequency and cut-o frequency,
respectively. DGSs which have similar shape like dumbbell
DGS have almost same characteristics like dumbbell DGS;
thus they could be analysed like Butterworth low pass lter as
discussed above. Furthermore, DGS unit can be analysed also
by a parallel , ,andresonant circuit more eciently. e
, ,andresonant circuit is shown in Figure . A resistance
is added to the circuit to model the radiation, conductor,
and dielectric losses.
e capacitance , inductance , and resistance can be
calculated as []
=
𝑐
2
0
2
0
−
2
𝑐
,