Defected Ground Structure: Fundamentals, Analysis, and Applications in Modern Wireless Trends
International Journal of Antennas and Propagation
Defected Ground Structure: Fundamentals, Analysis, and Applications in Modern Wireless Trends
Mukesh Kumar Khandelwal 0
Binod Kumar Kanaujia 1
Sachin Kumar 2
0 Department of Electronics & Communication Engineering, Bhagwan Parshuram Institute of Technology , Sector 17, Rohini 110089 , India
1 School of Computational and Integrative Sciences, Jawaharlal Nehru University , Delhi 110067 , India
2 Department of Electronics & Communication Engineering, ABES Engineering College , Ghaziabad 201009 , India
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, crosspolarization, low gain, and so forth. This paper presents an introduction and evolution of DGS and how DGS is different from former technologies: PBG and EBG. A basic concept behind the DGS technology and several theoretical techniques for analysing the Defected Ground Structure are discussed. Several applications of DGS in the field of filters, planar waveguides, amplifiers, and antennas are presented.
Conventional microstrip antennas had some limitations, that
is, single operating frequency, low impedance bandwidth,
low gain, larger size, and polarization problems. There are
number of techniques which have been reported for
enhancing the parameters of conventional microstrip antennas, that
is, using stacking, different feeding techniques, Frequency
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 all 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 filters 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. After successful implementation of DGS in
the field of filters, nowadays DGS is in demand extensively
for various applications. This paper presents the evolution
and development of DGS. The basic concepts, working
principles, and equivalent models of different shapes of DGS
are presented. DGS has been used in the field of microstrip
antennas for enhancing the bandwidth and gain of microstrip
antenna and to suppress the higher mode harmonics, mutual
coupling between adjacent element, and cross-polarization
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
field of antennas are discussed.
Low cost, high performance, compact size, wideband, and
low profile antennas often meet the stringent requirements of
modern wireless communication systems. Modern
communication demands the availability of efficient, 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
the latest requirements. Various novel approaches have been
reported to improve the performance of microwave
component. PBG has been proposed by John and Yablonovitch
]. 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
components is very difficult. Radiation from periodic etched defects,
number of lattice, lattice shapes, lattice spacing and relative
volume fraction are some parameters that effects the band gap
properties of PBG. There 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 3 dB edge coupler and bandpass
]. Width of the GPA creates a significant effect
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) firstly and used
the term ?DGS? in describing a single dumbbell shaped
defect. The DGS can be regarded as a simplified form of EBG
structure, which also exhibits a band-stop property [
opens a door to microwave researchers of a wide range of
applications. Various novel DGSs have been proposed and lot
of applications have been explored extensively in microwave
circuits. The development of DGS is thoroughly discussed
]. Subsequently, three books [
] have addressed the
microstrip antennas with DGS. DGS has become an
alternative of EBG for modern applications due to its simplicity and
low cost. Dumbbell shaped DGS was initially used to realize
a filter [
], and other shapes were reported subsequently to
realize different microwave circuits such as filters [
amplifiers , 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
presented in detail. The working principles and basic concepts of
DGS units are introduced and the equivalent circuit models
of DGS units available in literature are also presented. In
the last section, the applications of DGS in modern wireless
communication are presented and the evolution trend of DGS
2. Photonic Band Gap
Photonic Band Gap (PBG) structures are periodic structures
etched on the ground plane and have the ability to control the
propagation of electromagnetic waves. Periodic structures
effects the current distribution of the structure. The periodic
structures can influence on the propagation of
electromagnetic waves and radiation characteristics. The PBG have the
periodic defects, which can be treated as a resonant cavity
and affect 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
T he EBG technique is based on the PBG phenomena and
also realized by periodical structures. In [
], EBG has been
introduced as high-impedance surface or PBG surface. These
structures are compact and result in high gain, low profile and
high efficiency antennas. EBG has been created an interest in
the field of antenna. EBG structures suppress the surface wave
current hence increase the antenna efficiency. The surface
waves decrease the antenna ef f iciency. Surface wave
suppression using EBG technique improves the antenna performance
by increasing the antenna efficiency and antenna gain [
4. Defected Ground Structure
The 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 configurations may
be comprised in DGS. Thus, 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) [
been reported with irregular ground planes. The comparison
between PBG, EBG, and DGS is depicted in Table 1.
4.1. Working Principle. DGS has been integrated on the
ground plane with planar transmission line, that is,
microstrip line, coplanar waveguide, and conductor backed
coplanar wave guide [
]. The defects on the ground plane
disturb the current distribution 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
inductance). In other words, any defect etched in the ground plane
under the microstrip line changes the ef fective capacitance
and inductance of microstrip line by adding slot resistance,
capacitance, and inductance.
4.2. Unit DGS. The first DGS model has been reported as
a dumbbell shaped defect embedded on the ground plane
underneath the microstrip as shown in Figure 1 . The
response of its return loss is also shown in the figure.
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) DGS is comparably easy to design
and fabricate and its equivalent circuit is easy to realize. (3)
Higher precisions are achieved in comparison to other defect
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 [
]. These shapes include rectangular dumbbell , circular
], spiral [
], ?U? [
], ?V? [
], ?H? [
], and concentric rings [
]. Some complex shapes have
also been studied which include meander lines [
ring resonators [
], and fractals . Some of them are
discussed in this paper along with the modelling techniques
Other DGSs units have more advantages than dumbbell
(1) The slow wave factor is increased and a better degree
of compactness is achieved. A miniaturization of
26.3% has been achieved by using ?H? shaped DGS
in comparison to dumbbell DGS [
(2) Stopband is with an improved bandwidth and better
return loss level [
37, 41, 45
(3) An improved -factor is achieved. -shaped DGS
gives higher than spiral shaped DGS. While
comparing the transfer characteristics of the -shaped
DGS with the conventional DGS and the spiral
shaped DGS at same resonance frequency it is found
that -factor of the spiral DGS is about 7.478, while
the -shaped DGS provides a higher
4.3. Periodic DGS. Periodic DGSs for planar microwave
circuits are earning major attraction of microwave researchers.
Microstrip lines with a periodic DGS have been presented:
bandpass and low pass planar filters [
37, 44, 45
]. By using
periodic structure phenomena higher slow wave rate with
greater degree of miniaturization is achieved. Repetition of
single defect with a finite spacing is referred to as periodic
structure. By cascading the defects (resonant cells) in the
ground plane the return loss level and bandwidth is improved
depending on the number of periods. Shape of DGS unit,
distance between two DGS units and the distribution of
the different DGSs are the main parameters that affect the
performance of periodic DGS. Two periodic DGS shapes are
shown in Figure 2; horizontally periodic DGS (HPDGS) and
vertically periodic DGS (VPDGS) are shown in Figures 2(a)
and 2(b), respectively [
Application, advantages, and disadvantages of different
shapes of DGS are summarized in Table 2.
5. Equivalent Circuit Models of DGS
Each metallic part of microstrip antenna is a combination
of distributed 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 find 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 possibility
for not getting the optimum results [
6, 31, 44, 103?106
Figure 3 shows the conventional design and analysis methods
Equivalent circuit of DGS can be extracted by four
types and comparisons of all types of parameter extraction
methods are summarized in Table 3.
(1) LC and RLC equivalent circuits.
shaped equivalent circuit.
(3) Quasi-static equivalent circuit.
(4) Using ideal transformer.
5.1. LC and RLC Equivalent Circuits. The LC equivalent
circuit model of the DGS is shown in Figure 4. An equivalent
circuit model of one-pole Butterworth low pass filter is shown
in Figure 4(b). The current path is increased due to the
rectangular parts of dumbbell DGS; thus effective inductance
and effective capacitance of microstrip line are changed. The
two rectangular slots of dumbbell DGS are responsible for
adding a capacitive effect 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
frequency. The slotted area of the DGS is proportional to
the effective inductance and inversely proportional to the
effective capacitance. An increment in slotted DGS area gives
rise to the effective inductance thus results in a lower cut-off
frequency. A decrement in the DGS area reduces the effective
capacitance, thereby increasing the resonant frequency.
The reactance of Butterworth low pass filter can be
where 0 is the resonance angular frequency.
circuit are calculated as
where 0 and are resonant frequency and cut-off 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 filter as
discussed above. Furthermore, DGS unit can be analysed also
by a parallel , , and resonant circuit more efficiently. The
, , and resonant circuit is shown in Figure 5. A resistance
is added to the circuit to model the radiation, conductor,
and dielectric losses.
The capacitance , inductance , and resistance can be
calculated as [
An equivalent circuit model of one-pole Butterworth low pass filter
frequency and phase
Role of dimensions of the DGS is explained for creating the stop band characteristics
A simple and accurate circuit model for the slotted ground plane with microstrip line
GLC + jBLC
5.2. Shaped Equivalent Circuits. The shaped equivalent
circuit model shown in Figure 6 was proposed after and
equivalent circuit [
]. The shaped equivalent circuit
gives more accurate results in comparison with and
Park proposed shaped equivalent circuit model, which
explains both amplitude versus frequency and phase versus
frequency characteristics. The shaped equivalent circuit is
more complex and it is difficult to extract all the parameters
of the model. However, shaped equivalent circuit gives
more accurate results. The ABCD parameters of the shaped
equivalent circuit for the unit cell DGS can be calculated as
6. Applications of DGS in
The limitations of full-wave analysis can be overcome
by developing the equivalent circuit model depending upon
quasi-static technique. Basic principle of DGS is included
in this approach and the role of dimensions of the DGS
is explained for creating the stopband characteristics.
Optimization technique is used to evaluate the deferent structures
of DGS because deferent shapes have different characteristics.
5.4. Using Ideal Transformer. A simple and accurate circuit
model for the slotted ground plane with microstrip line has
been presented by Caloz et al. [
]. Figures 8 and 9 show the
proposed structure by Caloz et al. and its equivalent circuit
model, respectively. and represent the intrinsic series
inductance and shunt capacitance, of the microstrip line and
represents the turn?s ratio of the ideal transformer. An ideal
transformer is used for modelling the coupling between the
microstrip line and the slots embedded on the ground plane.
The microstrip line is modelled by an ideal transmission line
of electrical length . The location of slot integrated on the
ground plane divides the microstrip line into two parts of
lengths 1 and 2, where 1 + 2 = . The microstrip line is
modelled by the periodic repetition of a shunt capacitance
and a series inductance , given by
where is the length of the line and is the number of
unit cells, corresponding to the number of slots. The slots
are modelled by ideal transmission lines, characterized by the
An equivalent circuit model for antenna also has been
presented using ideal transformer [
]. A circular slot is
embedded in the ground plane underneath an open ended
microstrip line. Equivalent circuit model of the proposed
DGS antenna is shown in Figure 10. Distributed parameters
are used in the equivalent circuit.
DGS is widely used nowadays in active and passive devices.
Each DGS shape has its own characteristics and creates effect
on the performance of the device according to its geometry
and size. DGS has been used in filters, coplanar waveguides,
microwave amplifiers, and antennas to improve their
performance. DGS is used for miniaturizing the size of component,
enhancing the operating bandwidth and gain, reducing the
mutual coupling between two networks, suppressing the
higher order harmonics and unwanted cross-polarization,
and also producing notched band to stop interference with
any band. Several applications of DGS available in literature
are discussed further.
6.1. Filters. Numerous DGS shapes have been reported to
design planar circuits. Different shapes of DGS have been
5.3. Quasi-Static Equivalent Circuit. A quasi-static equivalent
circuit model was presented by Karmakar et al. for a dumbbell
shaped DGS [
]. Physical dimensions of dumbbell DGS play
a vital role for determining the equivalent circuit model. This
model is different from the two types of equivalent circuits
mentioned above (LC or RLC model, and shaped equivalent
circuit) and depicted in Figure 7.
Develop 2-port network model of DGS
Select dielectric material and approximate DGS dimensions
Vary one design
parameter at a time
in a do loop to get
C+ C+ L1 C+
shaped equivalent circuit for unit DGS: (a) equivalent circuit; (b) shaped circuit [
Ideal transformer: coupling
Series inductance: intrinsic L
Shunt capacitance: intrinsic C
explored to design bandpass and band-stop planar filters.
Initially, a dumbbell shaped DGS was embedded in the
ground plane underneath a microstrip line for creating a filter
response. It perturbs the electromagnetic fields around the
defect and trapped electric fields give rise to the capacitive
effect, while the surface currents around a defect cause an
inductive effect. This, in turn, results in resonant
characteristics of a DGS, causing an effect of filters.
6.1.1. Low Pass Filter. Single and cascaded dumbbell shaped
DGSs were used with microstrip line and T-junction of
microstrip line to design a low pass filter [
]. Two DGS units
were integrated with a microstrip line as shown in Figure 11.
The -parameters shown in Figure 11(b) clearly explain their
low pass response.
A new -pole LPF design method using the DGS has
been proposed [
] and depicted in Figure 12. The DGS-LPF
neither has open stubs, nor high-impedance lines because
a very wide microstrip line has been adopted to realize
the shunt capacitors. An equivalent circuit also has been
proposed to calculate the resonant frequency of LPF. The
parameter response is shown in Figure 12(b).
Different shapes of DGS shown in Figure 13 have been
presented by MK Mandal for LPF response [
dumbbell shaped DGS was presented with an equivalent
circuit model. A quasi-static analysis approach has been
reported for DGS filters by Karmakar et al. [
?I,? ?H,? and ?cross? shaped DGSs have been
introduced with their equivalent circuit model for LPF [
? ? ?
k = Ns
elliptical function response has been obtained using both
dumbbell shaped and spiral shaped DGS under the single
wide microstrip line [
]. A triangular dumbbell DGS has
been used to synthesize microstrip DGS low pass filter [
-equivalent circuit was presented to analyse the structure
] as shown in Figure 14.
Complementary Square Ring Resonator (CSRR) has been
used periodically to design the LPF [
]. Fractal dumbbell
shaped DGS also has been reported for achieving the low
pass filter response [
]. The circuit area of a LPF has been
minimized with wide stop band characteristics [
6.1.2. Band-Stop Filter. By embedding a defect on the metallic
ground plane a certain band of frequency can be rejected and
a planar band-stop filter can be realized. Surface wave and
other leakage transmission are suppressed at this stopband.
A square patch has been inserted inside the conventional
dumbbell shaped DGS to modify its frequency response and
to allow the control of the rejected frequency [
]. Low, high,
or even multiple frequencies can now be rejected by the
proper choice of the positions of the short circuits that can
be placed along the circumference of the square patch. The
varactor diode was used between the square patch and CPW
ground to make it tuneable as shown in Figure 15.
Semicomplimentary Split Ring Resonator (SCSRR) has
been used for realizing the band-stop filter [
equivalent circuit model was presented using an ideal transformer.
Both single cell and double cell structures were proposed as
shown in Figure 16.
A wideband band-stop filter has been introduced using
stepped impedance resonator and Defected Ground
]. A fabricated prototype of band-stop filter has
approximately 139% 20-dB rejection bandwidth. Substrate
Integrated Waveguide (SIW) also has been reported with
DGS as a band-stop filter [
]. The complex eigen value
problems of the SIW cavity have been studied with an FDFD
method and it has been shown that the SIW cavities can
easily achieve high -factors . It has been found that
the proposed DGS SIW cavity filters present very promising
performances with low insertion loss and high stopband
rejection. Such types of filters are valuable in the design
Measured Microstrip line Dumbbell shaped DGS
DGS-LPF section (W1)
Unit = mm
and realization of low cost microwave and millimeter-wave
systems. Compactness has been achieved using a SIW filter
with DGS resonators [
], with better frequency selectivity
and wide stopband. In these designs, the DGS is etched on
the ground plane of SIW cavity.
6.1.3. Bandpass Filter. DGS also has been used for bandpass
filter (BPF) response. Several researches have been reported
for BPF with DGS. A wide stop band bandpass filter based on
dual-plane interdigital DGS slot structure has been presented
]. An equivalent circuit model also has been presented as
shown in Figure 17. The filter has the merits of high selectivity
and wide upper stopband.
The bandpass filters with ultra-wideband (UWB)
characteristics also have been proposed [
]. A notch is
implemented in UWB bandpass filter using open circuited
line and DGS ; an equivalent circuit model also presented
for analysing the structure theoretically. The schematics of
open circuited line DGS BPF and its equivalent circuit model
are shown in Figures 18 and 19, respectively.
Dual-band bandpass filters also have been implemented
using Defected Ground Structure [
bandpass filter stacked with spiral shaped CPW Defected Ground
Structure and back-side coupled strip lines have been
proposed with quasi-elliptic function [
]. The filter shown in
Figure 20, allows two transmission paths to RF signals, has
3 4 5
Coupling planes of DGS
a dual-band response and proposed for a WLAN
application. The two quasi-elliptic function structures on different
layers generate respective passband, and can change the
operating frequency of each of them. Four poles in the
stopbands are realized to improve the selectivity of the
filter and the isolation between the two passbands.
Dualband BPF response has been achieved by using Defected
Ground Structure waveguide [
]. A dual-band BPF with
controllable second passband using a variable characteristic
impedance transmission line in the stub loaded resonator
has been reported [
]. The characteristic impedance of the
transmission line can be controlled with the help of the
Defected Ground Structure and the varactor diodes located
in the ground plane. It was demonstrated that the second
passband can be adjusted while keeping the first passband
constant. The proposed filter provides low insertion losses
throughout the entire tuning range of the second
An ultra-wideband differential bandpass filter has been
]. A narrow notched band is introduced and
common-mode suppression is achieved using DGS. Using
the slot-line DGS, the interference of notch structure is
cancelled out for common-mode. Compared with former UWB
differential filter structures, the proposed filter provides
interference rejection function, wider bandwidth and
simpler design theory and good common-mode performance,
indicating potential applications in the UWB communication
systems. Dual-notched compactness has been achieved using
DGS in Ultra-Wideband Bandpass Filter [
]. The schematic
diagram is shown in Figure 21. A compact Ultra-Wideband
Bandpass Filter (UWB BPF) has been proposed using
coupled lines incorporating arrow shape and -slot Defected
Ground Structures (DGSs) [
]. The input and output feeding
lines are connected to the coupled lines on one side of the
substrate while the -slot DGS is etched in the other side of
the substrate below the coupled lines as shown in Figure 22.
Reference plane Reference plane
S11 in CST microwave
S21 in CST microwave
S21 in measurement results
S11 in measurement results
6.2. Coplanar Waveguide. Recently, a great trend towards the
implementation of a reconfigurable DGS, where the location
of the transmission zeros can be controlled and tuned, may
be seen from a number of recent publications. In addition to
this, DGS unit cell has been proposed on coplanar waveguide.
Several studies have been reported in this regard [
55, 56, 66?
]. Coplanar waveguides having band-stop performance
have been proposed with DGS using SIW technique [
]. Figure 23 shows the model of SIW embedded with
A reconfigurable DGS resonator on CPW has been
proposed, which was capable of yielding arbitrary transmission
zeros over the band 1?11 GHz [
]. Reconfigurability of the
structure was achieved by using PIN diodes. Spiral DGS has
been implemented on the top and bottom ground plane of the
grounded CPW to produces the highest band-stop rejection
and two independent band-stop resonances [
]. A compact
reconfigurable band-stop resonator has been realized using
DGS on CPW [
6.3. Amplifier. DGS also has been employed with planar
microwave amplifiers. Lim et al. (2001) improved the
efficiency of power amplifier using DGS [
]. As shown in
Figure 24, a series of dumbbell DGS has been embedded on
the ground plane underneath the microstrip line to improve
the efficiency and to tune the harmonics of power amplifier.
Further, Lim et al. (2002) proposed DGS to reduce the size
of matching networks of microwave amplifiers using the slow
wave characteristics of microstrip [
]. In order to reduce the
size, while keeping the same electrical length, two and three
DGS patterns were adopted in matching networks. DGS has
been reported to suppress the harmonics of power amplifier
with /4 bias line [
]. A DGS-based Doherty power amplifier
has been proposed with suppressed harmonics [
6.4. Antenna. In the early phases of the development of DGS,
a majority of DGS shapes were explored to design microstrip
filters, and these applications inspired the antenna engineers
to realize planar antenna with stopband characteristics by
integrating DGS on their ground plane. DGS has been used
for improving the various parameters of the conventional
planar antenna. Different configurations have been explored
since 1999 to achieve various goal as discussed below.
Open circuited metal lines
5 6 7
lines; (b) -parameter response [
6.4.1. Circularly Polarized DGS Antenna. The latest
communication devices should be compact, lightweight, inexpensive,
and versatile and thus require circularly polarized microstrip
antennas. Circular polarized microstrip antennas have been
widely used for mobile communication, global positioning
system (GPS), radio frequency identification (RFID)
readers, and wireless local area network (WLAN) applications.
They also provide a powerful modulation scheme in active
read/write microwave tagging systems. DGS also has been
integrated on the ground plane of the microstrip antennas
for achieving the circular polarization (CP) [
]. Kuo and
Hsieh achieved the CP using triangular shaped DGS
coinciding with the corners of equilateral triangle , as shown in
Figure 25. CP has been achieved in aperture coupled annular
ring microstrip antenna using DGS [
]. A design approach
for the circular polarization of the microstrip antenna has
been implemented with the concept of unbalanced DGS feed
]. A dual-band asymmetric slits loaded microstrip
patch antenna has been proposed and CP was achieved using
DGS in both bands of operation [
]. Deferent shapes of DGS
used in [
] are shown in Figure 26.
6.4.2. Multiband Antenna. Multiband also can be achieved by
using DGS. Several studies have been reported in this regard
]. Dual broadband antenna with rectangular slot has
been analysed for wireless applications . A switchable
single and multifrequency antenna depicted in Figure 27 is
proposed with triple slot on the ground plane [
A microstrip-fed antenna design based on the patch
monopole for a triple-frequency operation has been
presented with DGS [
]. A triple band microstrip antenna has
been realized and miniaturization was achieved using DGS
]. A compact, DGS monopole antenna has been presented
], which employs a single L-shaped slot in the ground
plane of a conventional circular disc monopole antenna
in order to achieve multiband performance. A low profile
multifrequency-band printed antenna module has been
presented. The radiator was a crescent-shaped microstrip patch
with DGS [
]. A triple band microstrip patch antenna is
proposed with DGS [
]; circular polarization is achieved by
embedding the slots on ground.
6.4.3. Wideband Antenna. DGS also has been employed
for wideband and ultra-wideband microstrip antennas. As
shown in Figure 28(a), a square shaped defect has been
integrated on the ground plane with an open ended microstrip
line for enhancing the bandwidth of the microstrip antenna
]. Further, a parasitic square element was used at the centre
of the square defect on the ground plane underneath the open
ended microstrip line as shown in the Figure 28(b) [
impedance bandwidth of about 80% was achieved by using
parasitic element at the centre of square DGS.
A double -shaped DGS has been used to broaden
the impedance bandwidth of a conventional microstrip-fed
monopole antenna [
]. DGS has been integrated with probe
fed rectangular microstrip patch antenna for improving
DGS patterns etched off from the ground plane (bottom side)
polarization (co- to cross-polarized isolation) with enhanced
]. A pair of L-shaped slots and parasitic
structures on the ground plane has been presented for enhancing
the bandwidth of a square radiating patch [
6.4.4. Antenna with Notched Band. A simple and compact
ultra-wideband microstrip-fed planar antenna with
dualband-stop characteristic has been presented [
]. A notch
band of 600 MHz for band rejection of WLAN has been
created by using a -slot shaped DGS embedded underneath
the microstrip line. A novel compact printed monopole
antenna with dual-band-notched characteristics used for
UWB applications has been presented and investigated [
Dual band-notched characteristic was achieved using a G-slot
DGS in the ground of the feeding line and a pair of E-shaped
stubs in the radiating patch. A printed monopole antenna
with desired band-rejection characteristic, in the frequency
band of DSRC systems and WLAN, has been proposed for
UWB applications [
]. A compact UWB planar antenna with
Via hole for feed
dual-notched bands has been presented and discussed [
The band notches were realized by I-shaped DGS as well
as a L-shaped arm with shorting pin on the ground plane.
For enhancing the impedance bandwidth novel techniques
on the ground plane were used. A microstrip-fed printed
monopole antenna with dual-band-notched characteristics
has been proposed for UWB applications [
]. By using an
arc-shaped stub on the back of the substrate, which was
connected to the top patch through a cylindrical via pin,
the lower notched band was achieved. To realize the wide
notch band from 5.1 GHz to 5.9 GHz, a couple of stepped CLL
elements were placed near the feeding line, and an arc-shaped
slot was etched on the radiating patch. A log periodic dipole
antenna has been proposed for UWB applications [
monopoles on the ground plane and half on the signal plane
are placed for achieving the UWB response. And a -shaped
slot is introduced to achieve a notch band. A notch band is
achieved at 4.6 GHz in an UWB antenna [
6.4.5. Size Reduction of Antenna with DGS. Effective
capacitance and effective inductance of the model are changed by
embedding the slots on the ground plane, resulting in shifting
(b) Dumbbell shaped DGS
(c) DGS without truncated corners
(d) Defected Ground Structure
of resonance frequency to its lower side. Thus, compactness
is achieved by using DGS. Several researches have been
reported in this regard [
33, 94, 95
]. A compactness of 30%
is achieved by using meandering slots in the ground plane
]. A ? ? shaped slot integrated in the ground plane to
achieve the miniaturization and compactness of 80% has
been achieved [
6.4.6. Cross-Polarization Suppression of Antenna with DGS.
DGS has been reported for suppressing the cross-polarization
level of the antenna. The cross-polarized radiation was
theoretically studied in [
]. A suppression of 5 dB in
crosspolarization level has been achieved by using dot shaped
defects . The suppression in cross-polarized radiations
is improved to the value of 10?12 dB by using arc-shaped
]. A 35 dB of isolation is achieved between copolar
and cross-polarization level by using circular shaped DGS
]. Fabricated prototypes of proposed antenna in [
shown in Figure 29. The cross-polarization level of the value
of ?36 dB is achieved in stacked microstrip antenna using
]. Minimum cross-polarization level of ?42 dB is
achieved by using DGS in UWB antenna shown in Figure 30
6.5. Negative Group Delay Circuits (NGDC). A negative
group delay circuit (NGDC) is used for time advancement for
wave propagation and has been applied for various wireless
applications. Chaudhary et al. have proposed miniaturization
technique for NGDC using -shaped DGS [
characteristics of DGS and external resistor were used to
achieve the desired amount of group delay at operating
frequency. Two-stage NGDC was also designed and fabricated
to enhance the group delay [
6.6. Variable Characteristics Impedance Line. DGS also
has been used for designing the variable characteristics
impedance line for power divider [
]. An unequal 1 : N
Wilkinson power divider with variable power dividing ratio
has been reported with DGS [
]. A fixed 1 : 6 divider
with rectangular DGS and island was fabricated first; then
unequal dividing ratio of divider was adjusted by varying the
equivalent capacitance of varactor diode [
In this paper, the evolution of DGS is presented. The basic
ideas behind the working principle are discussed. Circuit
model and characteristics of deferent shapes of DGS are
discussed. Deferent techniques are presented for analysing
the DGS. T he role of DGS in the f ield of microwave and
microstrip antennas is presented with various applications of
DGS, that is, miniaturization, multiband performance,
bandwidth enhancement, gain enhancement, mutual coupling
suppression between two elements, higher mode harmonics
suppression, cross-polarization suppression, notched band
creation, and circular polarization achievement. Applications
with parasitic centre patch [
Ground plane Metal strip
of DGS in the field of Microwave Engineering are
summarized in Table 4.
The authors declare that they have no competing interests.
International Journal of
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International Journal of
International Journal of
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