design and characterization of optimized progressive ... · the low profile patch antenna...

Abstract— In this paper, two new Electromagnetic Band Gap

structures arranged in stacked configuration are proposed.

Named as Stacked Electromagnetic Band Gap (SEBG) and

Progressive Stacked Electromagnetic Band Gap (PSEBG)

structures. Its surface properties such as Artificial Magnetic

Conductor (AMC) and Forbidden band gap (FBG) are

determined by using Finite element method (FEM) based 3D

electromagnetic (EM) simulator and obtained results are

compared with classical mushroom type electromagnetic band

gap (MEBG) structure. The proposed unit cell of SEBG and

PSEBG structures consist of two layers above the conducting

ground plane; a lower layer, contains array of MEBGs with

small square patches and an upper layer contains planar

MEBG structure. These structures are used as ground plane for

low profile microstrip patch antennas. A comparative study is

performed to optimize the best electromagnetic band gap

reflecting ground, which can enhance the radiation

characteristics of operating antenna lying over its surface and

exhibit compact ground structure with less wastage in back

side. In order to complete the study, return loss and radiation

pattern of a rectangular microstrip patch antenna placed above

the proposed SEBG and PSEBG as well as reference MEBG

ground surfaces are analyzed and compared.

I. INTRODUCTION

he immense development in antenna engineering

facilitates design of compact antenna [2] structures with

improved performance characteristics. Numerous

techniques [3-5] have been proposed for miniaturization of

radiating antennas such as use of high permittivity substrates

or meandering paths and fractal shapes antennas. However,

they are suffering with narrow antenna band-width and

ohmic losses (fractal shapes antennas). The unique properties

of EBGs, showing solution to problems, hence antennas are

loaded by EBG surfaces [5-9]. EBGs are the periodic array

of electromagnetic structures printed on metal backed

dielectric substrate. The periodicity of an array is electrically

small, as well as the dimensions of the individual particles in

the unit cell(UC). Shape and dimensions of the individual

patch elements play key role for designing of EBGs and

synthesis of its frequency response. Generally patch elements

exhibit in squared [10], hexagonal [11] and rectangular [12]

shapes. The EBG surfaces may show the two interesting

behaviours: one is artificial magnetic conductor (AMC), in

which reflection phase is near or equal zero. Another is

forbidden frequency band gap (FBG), in which no surface

wave can propagate along the surface. The AMC behaviour

occurs because of very high impedance in a specific

frequency range, during which the tangential electric field

components is small, leading to several interesting

applications in the antenna field [10-15]. Moreover,

depending on the geometry of the UC, both behaviours may

appear in the same frequency range [16,17]. The AMC

property helps in designing of low profile antennas, as the

image currents appear in phase, and so, antennas can be

placed parallel and close to the EBG grounds [18]. The FBG

property can be useful in improving antenna radiation

patterns [10,11]. In order to reduce the aperture of printed

antennas and improving the performances in terms of

efficiency and gain, it is possible to use the concept of

electromagnetic band gap[10].Various experimental methods

of characterizing the electromagnetic band gap structures is

considered [19,20].

The objective is to propose two new models of stacked

EBG structures and characterize its properties. To minimize

ground plane size along with profile of radiating antenna

without increasing back radiation of antenna. Also to study

the low profile patch antenna performance in the presence of

proposed SEBG and PSEBG ground surfaces.

The idea of stacked EBG surface has been introduced in

[10], where the author used three layer structure for size

reduction of unit cell. Suppression of noise in parallel plate

waveguide was done by using stacked EBG structures in

[21]. The investigation of band gap properties in double

layered dipole and triple arrays is done in [22].

The basic electromagnetic band gap structure consists of

periodic array of dielectric or metallic patches in one, two or

three dimensions, printed on one side of dielectric where

other side contains metallic ground. This controlls the

propagation of electromagnetic waves at certain angles of

incidence at some frequencies. Such frequencies are called

partial band gap, if the propagation is not allowed in all the

directions and this frequency region is called universal band

gap[23,24]. In this paper, MEBG surface is chosen as a base

Design and Characterization of Optimized Progressive Stacked

Electromagnetic Band Gap (PSEBG) ground for low profile patch

antennas

K. Praveen Kumar*, Dr, Habibullah Khan

Lecturer, Dept., of Electrical and Electronics Engineering, Eritrea Institute of Tech., Mainafhi, State

of Eritrea, East Africa. E-mail: [email protected]

Professor, Dept., of ECE, KL Deemed to be University, Vaddeswaram, A.P, India.

.

T

International Journal of Pure and Applied MathematicsVolume 118 No. 20 2018, 4765-4776ISSN: 1314-3395 (on-line version)url: http://www.ijpam.euSpecial Issue ijpam.eu

4765

of designing new SEBG and PSEBG surfaces, because it has

been studied extensively in literature. The proposed models

are developed by placing a planar MEBG structure over an

array of compact MEBG structures. The FBG and AMC

properties of proposed models depend on respective UC

parameters. The FBG is influenced with the parameters of

both the lower and upper MEBGs, where as the in-phase

reflection property depends primarily on the parameters of

the upper planar MEBG, especially the size of the metallic

patch[25].

II. UNIT CELL DESIGN

Figure 1 to 3 showing the schematic diagrams of MEBG,

SEBG and PSEBG. The MEBG is considered here as

reference structure. All EBG models are designed on FR4

substrate, relative permittivity of 4.4, permeability of 1 and

loss tangent of 0.02 with a thickness (height) 'H' of 3.2mm

(124mil). The lattice in Figure 1 consists of square metal

patch of 17.5X17.5 mm2

printed on one top side of FR4

substrate backed continuous ground plane. A vertical

conducting stub (via) of radius 0.475mm, is used to short

the square metal patch with conducting ground through

substrate from their center. The lattice in figure 2 consists of

square metal patches arranged in layers (stacked), where

lower layer contains array of four compact square metal

patches having a dimension of 3.4X3.4mm2 mounted at a

height H/2 of 1.6mm (62mil), placed at four corners of UC,

top layer contains planar square metal patch of size

17.5X17.5 mm2, placed at a height of 3.2mm. All these

patches are connected to ground plane lying on the other side

of substrate by a vertical conducting stub of radius of

0.475mm from their center. The lattice in figure 3 consists of

vertically stacked arrangement of patches, where lower layer

contains progressive array of compact square metal patches,

the array of square patches placed at four corners of a UC

having dimensions of 3.4X3.4mm2. Next array of square

patches placed diagonally with a size of 3.075X3.075mm2.

All these patches are placed at a height H/2 of 1.6mm

(62mil), connected to ground plane lying on the other side of

substrate by a conducting vertical stub of radius 0.475mm

from their center. Top layer is similar to what is explained in

figure 2. In this study, to minimize EBG cell size, the

researcher has chosen FR4 with thickness 3.2mm otherwise,

the AMC metallization will get excited by the feed line

similar to an antenna if EBG UC size is equal or greater than

the radiating patches. The summery of complete dimensions

of all three (MEBG, SEBG and PSEBG) models are listed in

table I.

(a) Top view (b) Side view

Fig. 1. Schematic of MEBG unit cell printed on FR4

substrate contains square patch on top face, vertical

conducting stub and ground conductor on back face.


Fig. 2. Schematic of SEBG unit cell printed on FR4 substrate

contains planar square patch on top face, array of square

patches in the middle layer ground conductor on back face

and vertical conducting stubs passing through the substrate

shorting all square patches in both the layers to ground

conductor.

(a) Top view (b) Side view Fig. 3. Schematic of PSEBG unit cell printed on FR4

substrate contains planar square patch on top face, array of

square patches in the middle layer ground conductor on back

face and vertical conducting stubs passing through the

substrate shorting all square patches in both the layers to

ground conductor.

TABLE I

DIMENSIONS OF ALL THREE UCS OF ELECTROMAGNETIC BAND GAP

STRUCTURES.

Parameter

Name Symbol MEBG

SEBG

PSEBG

Square

patches

W X W 17.5X17.

5 mm2

17.5X17.

5 mm2

17.5X17.5

mm2

W1 X W1 3.4X3.4

mm2

3.4X3.4 mm2

W2 X W2 3.075X3.075

mm2

Gap G 1mm 1mm 1mm

Stub

radius

R 0.475mm 0.475mm 0.475mm

Dielectric

substrate

height

H 3.2mm 3.2mm 3.3mm

g

W

H

g

W

W1

Lower MEBG Array

Top MEBG

H

g

W

W1

W2

Top MEBG

H

2nd array of MEBG

1st array of MEBGs

International Journal of Pure and Applied Mathematics Special Issue

4766

The MEBG, SEBG and PSEBG UC dimensions such as

height of substrate, patch size, gap between adjacent patches

and substrate material are considered identical, so that their

resonance frequency will be remain constant and equal and

other important properties such as AMC and FBG can be

easily compared.

III. ANALYSIS OF EBG STRUCTURES

Numerous methodologies are available in literature for the

analysis of EBG UC. They are broadly classified into four

categories [26]: 1)Lumped element circuit model [10], 2)

Transmission line model [27], 3) Computational

electromagnetic modeling using of full wave solvers. Due to

the complexity of the electromagnetic band gap structures, it

is usually difficult to characterize them with above specified

two analytical methods. Full wave electromagnetic

simulators that are based on advanced numerical methods are

popularly used in analysis of electromagnetic band gap

structures. In this paper reflection phase, high impedance

region and dispersion features of MEBG, SEBG and PSEBG

are determined by using FEM based 3D-EM simulator.

A. AMC behavior analysis

AMC is one of the unusual but important properties of the

electromagnetic band gap structures. To determine the AMC

property of three models, FEM simulation based on the

Bloch-Floquet theory (High Frequency Structure simulator

(HFSS) from Ansoft) is considered. In the FEM simulator, to

determine the coefficient of reflection phase, the UC should

be applied with perfect magnetic conductor (PMC) and

perfect electric conductor (PEC) boundaries periodically on

its four sides. To model the effect of periodic replication in

an infinite array structure, the wave port on the top face of

UC is de-embedded, the complete simulation setup is shown

in Figure 4.

(a) Simulation setup for MEBG unit cell.

(b) Simulation setup for SEBG unit cell.

(c) Simulation setup of PSEBG unit cell.

Fig. 4. AMC and High impedance properties measurement setup of

MEBG, SEBG and PSEBG unit cells in FEM based 3D-EM simulator

contains periodic boundaries on its four sides with topped wave port.

Fig. 5. Reflection phase diagram, represents the in-phase band gap and

resonating frequency of respective unit cell.

Figure 5 shows the coefficient of reflection phase for the

normal incident plane waves for MEBG, SEBG and PSEBG

structures. It varies continuously from +1800 to -180

0 relative

to the frequency. The frequency where the reflection phase is

zero is the resonant frequency of structure. At and around the

resonance frequency, in a specific range, the surface

impedance of respective structure is higher than or equal to


4767

characteristic impedance of free space, then reflection

coefficient is +1, and hence the reflection phase is zero. The

range lies between +900 to - 90

0 region, where reflected

waves interfere with the incident waves in-phase, so the

respective electromagnetic band gap structure behave like an

AMC in this region. In the lower and higher frequency

regions, this structure exhibits similar reflection phase

characteristics as those of a conventional perfect electric

conductor (PEC) surface. Hence, any antenna element

operating within AMC range can be directly placed over the

proposed design without being shorted. This enhances the

radiation characteristics of the mounted antenna. The

frequency of operation, AMC band width of three structures

are extracted from reflection phase diagram shown in figure

5, and are depicted in Table II. The SEBG structure is

exhibiting 1.22%, PSEBG is exhibiting 1.59%, less AMC

band gap compared to MEBG model.

TABLE II

COMPARISON OF AMC BAND GAP OF MEBG, SEBG AND PSEBG UNIT

CELLS.

Parameter

Name MEBG

SEBG

PSEBG

Resonant

frequency

2.5GHz 2.5GHz 2.5GHz

AMC

band gap

404.2MHz 373.8MH

z

364.4MHz

Fractiona

l band

gap

16.17% 14.95% 14.58%

B. High impedance region

High impedance region can be defined as a low loss reactive surface. At

and around the resonance frequency, the impedance of MEBG, SEBG and

PSEBG structures are exhibiting very high surface impedance as shown in

figure 4. This property helps in development of low volume radiating

antennas.

Fig. 6. High impedance nature of MEBG, SEBG and PSEBG unit cells.

C. FBG behavior analysis

Under normal incidence, the EBG designs cannot be

differentiated fully by their surface properties, so the FBG

property of any EBG UC is obtained from its dispersion

diagram. The simulation setup for measurement of FBG of

electromagnetic band gap structure in FEM based simulator

consists of a perfect matched layer (PML) boundary defined

on the top of the UC model to intimate free space above the

surface. Perfect magnetic conductors (PMC) and perfect

electric conductors (PEC) boundaries are applied on four

sides of the UC periodically [44,45]. The complete

measurement setup for all three UC models are shown figure

7. In this paper -X direction of propagation [28] is

considered. The dispersion diagram (wave number verses

frequency) contains first dispersion mode (maximum value

of mode 1 determines the lower frequency limit of band gap

or TM mode) and second dispersion mode (mode 2 or TE

mode). The intersection of mode 2 with the light line

determines the upper limit of frequency band gap. By

examining the area between the lower and upper limits of

band gap, forbidden band gap is obtained where surface

propagation is inhibited.

(a) Unit cell of MEBG applied with periodic boundaries topped PML.

(b) Unit cell of SEBG applied with periodic boundaries topped PML.


4768

(c) Unit cell of PSEBG applied with periodic boundaries topped PML.

Fig. 7. FBG property measurement setup of MEBG, SEBG and PSEBG

unit cells in FEM based simulator.

(a) Dispersion diagram of MEBG, represents FBG of 2.45GHz and leaky

wave starting point of 3.66GHz.

(b) Dispersion diagram of SEBG, represents FBG of 2.13GHz and leaky


(c) Dispersion diagram of PSEBG, represents FBG of 1.95GHz and leaky


Fig. 8. Dispersion diagram for three EBG models.

Figure 8 shows the dispersion diagrams of the three

electromagnetic band gap architectures (MEBG, SEBG and

PSEBG). This helps to understand the characteristics of

propagation of EM waves and FBG property of respective

UC. The dispersion diagram demonstrates that below the

resonance frequency, the electromagnetic band gap

structures supports TM waves, and they stay close to the

light line, similar to the metal dielectric interface at lower

frequencies. As the frequency slopes upward, the TM curve

begins to bend, which indicates that the frequency is

approaching resonance. At high frequencies, the proposed

electromagnetic band gap structures supports TE surface

waves. These TE waves start above the resonance frequency,

slope upward along the light line but travel with less

velocity, and start bending away from the light line to a small

section after the resonance frequency. At the resonance

frequency, the surface impedance of electromagnetic band

gap structures is high, and group velocities for both TE and

TM waves are very low, hence electromagnetic band gap

structures are known as slow wave structures. Because the

TM and TE bands never combine in this structure, the FBG

can be defined as the range that starts from the TM band

edge to the point of intersection of the light line with the TE

band. The TE surface waves, lie above and left to the light

line, in a short range of frequency, treated as radiative, leaky

modes, these radiate efficiently into free space only when

their phase matches with the phase of the plane wave along

the interface. Figure 6(a) showing the FBG of MEBG, whose

mode 1 is at 1.52GHz (TM mode edge) and mode 2 is at

4GHz (TE mode edge). The gap between mode 1 and mode

2 determines FBG is 2.45GHz. Figure 6(b) showing the FBG

of SEBG is 2.13GHz, which is ranging from 1.43GHz to

3.56GHz. Figure 6(c) showing the FBG of PSEBG is

1.95GHz which is ranging from 1.43GHz to 3.56GHz. The

leaky mode of MEBG is starting from 3.58GHz (figure 6(a)),

SEBG is 3.48GHz (figure 6(b)) and PSEBG is 3.06GHz

(figure 6(c)). Table III depicts the FBG of MEBG, SEBG


4769

and PSEBG, where fractional value of FBG is reducing from

MEBG to PSEBG.

TABLE III

COMPARISON OF FBG BAND GAP OF MEBG, SEBG AND PSEBG UNIT

CELLS.

Parameter

Name MEBG

SEBG

PSEBG

Mode 1 1.55GHz 1.43GHz 1.35GHz

Mode 2 4GHz 3.56GHz 3.3GHz

FBG 2.45GHz 2.13GHz 1.95GHz

Fractiona

l FBG

98% 85.2% 78%

During the FBG region, the electromagnetic band gap

structures do not allow any surface currents, even radiative

leaky TE waves to reach the edges of a radiating element that

is lying over and parallel to electromagnetic band gap

ground and operating within the FBG region. This avoids the

interference of surface waves with radiated waves of antenna

in the far field. This results, elimination of distortion or

production of a smoother radiation pattern.

IV. LOW PROFILE ANTENNA DESIGN

Electromagnetic band gap structures are employed widely

as ground plane to improve antenna performance [29-35].

Compared to a flat metal ground plane, an Electromagnetic

band gap ground plane prevents propagation of surface

waves, leads to less backward radiation of an antenna. Thus

wastage of power in unintended direction is reduced. In

literature various methods have proposed for low profile

applications. In this paper, researcher aimed to choose best

Electromagnetic band gap ground so that very low profile

antenna with enhanced radiation characteristics can produce

with minimum back radiation. During optimization process

three models of Electromagnetic band gap ground planes are

considered. Initially all three models are designed using

MEBG unit cells. After optimization of the best MEBG

ground, it is replaced by, firstly SEBG and later PSEBG

UCs ground to study its effect on the performance of patch.

The MEBG, SEBG and PSEBG UC and patch antenna are

centered at 2.5GHz. First of all, an array of MEBG UCs

surrounded the radiating aperture of rectangular patch

antenna from its three sides, second, a 3X3 array of MEBG

UCs lying underneath and covering the complete footprint of

patch aperture and third, an array of MEBG UCs lying under

the patch but placed nearer to the its radiating edges

(proposed model) are considered. All these arrangements are

designed and simulated in Ansoft HFSS to understand the

impact of MEBG ground structures on radiation

characteristics of an antenna.

A traditional linear polarized rectangular patch antenna

has a footprint of 33.3X27.6 mm2 with edge feeding, is

printed on top face of FR4 substrate of thickness 1.6mm,

while back face contains conventional conducting ground of

116X59 mm2. The simulated results showing, the resonating

bandwidth of 63MHz (fractional band width of 2.52%) at

2.5GHz and gain of 2.93dB. These results are used as a

reference for comparison of MEBG grounded results in

subsequent section.

(a) Top view

(b) Side View

Fig. 9. Rectangular patch antenna surrounded by MEBG unit cells.

The radiating patch is surrounded by a layer of MEBG

UCs [36], as shown in figure 9. The FBG and AMC band

gaps of MEBG covers the complete frequency band gap

(S11>-10dB) of patch. Hence the surface waves excited by

this patch antenna are controlled from propagation and also

its image currents will be in-phase with radiating currents.

The new antenna has dimensions of 32.4X27.2mm2, lies co-

linear with MEBG ground of 94.3X73 mm2

and achieved

good matching of 50ohm at 2.5GHz with 97.7MHz

(fractional band width of 3.9%) bandwidth and gain of

5.37dB. The complete structure has a thickness of 3.2mm.

This design enhances the gain by 2.8dB and fractional

bandwidth by 1.38% when compared with conventional

design. In this method, the aperture of antenna is scaled

down along its length by 2.7%, along its width by 1.44% and

ground is scaled down by 18.7% along its length and along

its width, the size of ground is increased by 23%. The

increase in overall size of antenna ground, makes the antenna

bulky. Table IV presents the similar kind of works available

in literature and its results for better comparison of designed

model.

TABLE IV

COMPARISON OF DESIGNED MODEL RESULTS WITH LITERATURE RESULTS

CONTAINS MICROSTRIP PATCH ANTENNA SURROUNDED BY EBG UNIT CELLS.

Reference

No. [41]

[42]

[43]

Designed

Model

EBG size 1054X1054

μm2

2.04X2.0

4

mm2

Special

Model

MEBG

Thickness 510μm 1.575mm 1.575mm 3.2mm

MEBG structure patch


4770

FBG

(GHz)

31.3-59.8 Not given 2.45- 2.55 1.55-2.45

AMC 2.85GHz Not given ~120MHz 404.25M

Hz

Gain 5dB 5.4dB 7dB 5.4dB

Back

radiation

Not given Not given Not given -13dB

Operating

band

width

15% ~8% 3.05% 3.9%

Next, the 3X3 array of MEBG UCs placed underneath

(behind) the antenna to cover the entire footprint of patch as

shown in figure 10. The new antenna contains three layers

(top layer contains patch, middle layer contains substrate,

bottom layer contains MEBG ground) with an overall

thickness of 4.8mm (186mil).The patch antenna lying above

and in parallel with resonating MEBG structures, the

combined geometry resonate at a much lower frequency. To

bring resonance frequency back to original (2.5GHz) the

antenna footprint over the 3X3 array MEBG ground is scaled

down along its length by 17%, along its width by 18.4%. The

ground is scaled down by 19.6% along its length and along

its width by 6%. The final antenna has footprint of

27.7X22.5mm2, over the 3X3 MEBG ground of 93.3X55.5

mm2 and exhibiting 102.3MHz (fractional band width of

4.08%) bandwidth at 2.5GHz and gain of 5.63dB. This

design enhances the bandwidth by 1.56% and gain by 2.7dB

compared to conventional method. Table V listed the similar

kind (backed EBG) of works available in literature for better

comparison of designed model.


Fig. 10. 3X3 array of MEBG UCs as a ground placed underneath the

rectangular patch antenna.

TABLE V

COMPARISON OF DESIGNED MODEL RESULTS WITH LITERATURE RESULTS

CONTAINS MICROSTRIP PATCH ANTENNA BACKED BY 7X7 EBG UNIT

CELLS[37], DIPOLE ANTENNA BACKED BY EBG ARRAY [38], FRACTAL

ANTENNA BACKED BY EBG ARRAY [39].

Reference

No. [37]

[38]

[39]

Designed

Model

EBG size 4.5X4.5

mm2

7.3X7.3

mm2

14.6X14.6

mm2

17.5X17.

5 mm2

Gap 2.5mm 1.3mm 0.5mm 1mm

Thickness 1.5748

mm

Not given 2mm 3.2mm

Radius of

Via

0.2mm 0.4mm 0.25mm 0.475mm

FBG

(GHz)

4.41- 6.1 4.6-6.4 Not Given 1.55-2.45

AMC

(GHz)

Not given 4.6-6.4 24.4-24.53 404.25

MHz

Gain 3.75dBi 4.8dBi 6.12 dBi 5.63dB

Back

radiation

-15dBi Not given Not given -12dB

Operating

band

width

Not given 50MHz 120MHz 102.3MH

z

Next, the proposed MEBG ground is the modified version

of 3X3 array MEBG ground, where MEBG UCs are placed

behind and nearer to the edges of radiating patch instead of

covering the complete footprint of patch. The complete

arrangement shown in figure 11. This arrangement also

restricts the surface wave propagation and provides in-phase

reflection of image currents. Now antenna has a footprint of

27.3X22.1mm2, over the proposed MEBG ground of

92.3X55.5mm2, exhibiting 130.9MHz (fractional band width

of 5.22%) bandwidth at 2.5GHz and a gain of 6.08dB. In this

method the size of radiating patch is scaled down by 18%

along its length and 19.9% along its width. The ground is

scaled down by 20.43% along its length and along its width

by 6%. In this method band width of 2.7% and gain of

3.15dB enhanced compared to conventional design.


Fig. 11. MEBG UCs placed nearer to radiating edges and underneath the

patch antenna.

TABLE VI

SUMMARY OF PROPOSED DESIGNED RESULTS.

Parameter Proposed Model results

EBG size 17.5X17.5 mm2

Gap 1mm

Thickness 3.2mm

Radius of Via 0.475mm

FBG (GHz) 1.55-2.45

AMC (GHz) 404.25

MHz

Gain 6.08dB

Back radiation -11.5dB

Operating band width

(Fractional)

5.22%

MEBG Ground

patch FR4

Substrate

MEBG Ground

patch FR4

Substrate


4771

From above results it can be concluded that the model

proposed in figure 11 is best choice for design of low profile

patch antennas. The summery of simulated results starting

from rectangular patch antenna surrounded by MEBG unit

cells to rectangular patch antenna over the proposed MEBG

ground are presented in the table VII.

TABLE VII

COMPARISON OF DESIGNED MODEL RESULTS

Parameter Convention

al Ground

Surrounde

d MEBG

Ground

Underneath

MEBG

Ground

Proposed

MEBG

Ground

EBG size 33.3X27.6

mm2

32.4X27.

2mm2

27.7X22.5

mm2

27.3X22.

1 mm2

Ground

Size

116X59

mm2

94.3X73

mm2

93.3X55.5

mm2

92.3X55.

5 mm2

Patch

length

miniaturiz

ation (%)

Reference 2.7 17 18

Patch

length

miniaturiz

ation (%)

Reference 1.44 18.4 19.9

Resonatin

g

Frequenc

y

2.5GHz 2.5GHz 2.5GHz 2.5GHz

Return

Loss (dB)

-31.55 -37.72 -36.44 -31.57

Band

width

(MHz)

63.1 97.7 101.2 130

Fractiona

l band

width (%)

2.52 3.9 4.1 5.22

Gain (dB) 1.96 5.59 5.63 6.08

Radiation

efficiency

(%)

39.6 61.62 60.62 68.25

E plane

beam

width

(Degree)

44.44 52.99 44.87 49.14

H plane

beam

width

(Degree)

37.6 54.7 61.96 57.26

VSWR 1.0543 1.0263 1.0283 1.0525

the simulated results of conventional microstrip patch

antenna (red colour), antenna surrounded by MEBG UCs

(green colour), 3X3 array of MEBG UCs ground lying

underneath the patch antenna (blue colour) and proposed

MEBG ground underneath the patch antenna (yellow colour)

are shown in figure 12(a), indicates perfect impedance

matching between connecting point to the antenna and all the

antennas are resonating at 2.5GHz. The factional bandwidth

of patch antenna over a proposed MEBG ground is more,

when compared to remaining three methods (conventional

ground, surrounded MEBG UCs, 3X3 array of MEBG

ground). Directional E pattern of above four models are

shown in figure 12(b), conventional microstrip patch antenna

(red colour) has back radiation of -12dB, front

radiation 4.6dB, antenna surrounded by MEBG UCs (blue

colour) has back radiation of -13dB, front radiation of

5.37dB, ground constructed by 3X3 array MEBG UCs lying

underneath and covering the complete foot print of the patch

antenna (green colour) has back radiation of -12dB, front

radiation of 5.6dB, proposed MEBG (figure 11) ground

underneath the patch antenna (yellow colour) has back

radiation of -11.5dB, front radiation of 6.1dB. After

comparison, it can be concluded that the proposed MEBG

structure radiating most of the its energy in forward

direction, less wastage in backward direction. TABLE VIII

SUMMARY OF SIMULATED RESULTS OF CONVENTIONAL, SURROUNDED

MEBG, 3X3 MEBG ARRAY AND PROPOSED MEBG GROUNDED MODELS.

Ground

Structure

Front

Radiation

Back

Radiation

Conventional

Ground

4.6dB -12dB

Surrounded

MEBG

5.37dB -13dB

3X3MEBG

array

5.6dB -12dB

Proposed

MEBG

6.1dB -11.6dB

(a) Return Loss

(b) 2D-Gain

Fig. 12. Simulation results of rectangular patch antenna over the

conventional, surrounded MEBG unit cells, 3X3 array of MEBG unit cells

and proposed MEBG unit cells grounded models.


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In subsequent explanations, the proposed MEBG ground

methodology shown in figure 11 is replaced first by a

ground, designed with SEBG UCs and later PSEBG UCs.

The new antenna has footprint of 24.3X19.1mm2, over the

SEBG UCs ground of 92.3X55.5mm2 and exhibiting

143.1MHz (fractional band width of 5.73%) bandwidth at

2.5GHz and gain of 6.15dB. In this method the size of

radiating patch is further miniaturized, is scaled 27% along

its length and 30.7% along its width, band width of 3.21%

and gain of 3.22dB enhanced compared to conventional

design. Next PSEBG UC ground is inserted in place of

proposed MEBG UC ground, the new antenna has footprint

of 22.35X17.15mm2, over the PSEBG UC ground of

92.3X55.5mm2 and exhibiting 167.5MHz (fractional band

width of 6.8%) bandwidth at 2.5GHz and gain of 6.13dB. In

this method the size of radiating patch is scaled 32% along

its length and 37% along its width. Bandwidth of 3.6% and

gain of 1.51dB enhanced compared to conventional design.

The aperture of radiating patch antenna is very well

minimized in proposed PSEBG ground method, but still its

size is little bit greater than the size of PSEBG UC. Further

reduction of patch antenna will make the antenna size

smaller than the UC size, results PSEBG metallization will

get excited by the feed line similar to the antenna. The

ground dimensions in SEBG and PSEBG models are same as

proposed MEBG ground. All models of antennas and its

parameters, starting from MEBG ground to PSEBG ground

embedded with patch antenna are depicted in table VIII, for

easy of comparison and better to analyze the new SEBG and

PSEBG results.

(a) Return Loss

(b) 2D-Gain

Fig. 13. Simulation results of rectangular patch antenna over the proposed

MEBG, SEBG and PSEBG grounded models.

TABLE IX

SUMMARY OF SIMULATED RESULTS OF PROPOSED MEBG, SEBG AND

PSEBG GROUNDED MODELS.

Parameter Surrounde

d MEBG

Ground

Underneath

MEBG

Ground

Proposed

MEBG

Ground

EBG size 27.3X22.

1 mm2

24.3X19.1

mm2

22.35X17.15

mm2

Ground Size 92.3X55.

5 mm2

92.3X55.5

mm2

92.3X55.5

mm2

Patch length

miniaturization (%)

18 27 32

Patch length

miniaturization (%)

19.9 30.7 37

Resonating Frequency 2.5GHz 2.5GHz 2.5GHz

Return Loss (dB) -31.57 -36.64 -46.79

Band width (MHz) 130 143.1 167.5

Fractional band width (%) 5.22 5.7 6.8

Gain (dB) 6.08 6.14 6.14

Radiation efficiency (%) 68.25 69.35 70.65

E plane beam width

(Degree)

49.14 48.72 47.86

H plane beam width

(Degree)

57.26 56.41 53.84

VSWR 1.0525 1.0299 1.009

Front Radiation 6.1dB 6.14dB 6.13dB

Back Radiation -11.5dB -9.5dB -8.5dB

Figure 13(a), showing that all the antennas are perfectly

matched to its power source. All antennas are approximately

resonating at 2.5GHz. The factional bandwidth, directivity,

radiating efficiency are increasing, the profile of antenna,

beam width are decreasing from MEBG ground patch

antenna to PSEBG grounded patch antenna. Directional E

pattern of three proposed grounded models are shown in

figure 14(b) and its results listed in table IX. From obtained

results it can be concluded that SEBG and PSEBG structures

proposed in this paper producing more improvement in

results than proposed MEBG results, so these two new

structures are well suitable in designing of low profile


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radiating antenna, also achieve miniaturization in ground

plane and improve the forward radiation .

V. CONCLUSION

In this paper the unique (FBG and AMC) properties of EBG

are utilized in enhancing the radiation characteristics of

patch antenna and produce very low profile. The MEBG

structure is considered as reference for development of two

new stacked structures named as SEBG and PSEBG. The

FBG and AMC properties of two new models are derived

using FEM based simulator, obtained results are compared

with reference MEBG model. The first objective is to

optimize the best EBG ground for low profile antenna with

minimum back radiation. During investigation three models

of MEBG grounds are considered and its effect on the

radiation characteristics of patch antenna is studied. After

optimization of MEBG UCs ground, same kind of ground

model is designed using new SEBG and PSEBG UCs,

embedded with patch antenna. The obtained results showing

that the profile of patch antenna is very low and radiation

pattern is more focused in forward direction with minimum

back radiation over the proposed new SEBG and PSEBG

grounds.

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