Indonesian J
ournal of Ele
c
trical Engin
eering and
Computer Sci
e
nce
Vol. 2, No. 3,
Jun
e
201
6, pp. 647 ~ 65
6
DOI: 10.115
9
1
/ijeecs.v2.i3.pp64
7-6
5
6
647
Re
cei
v
ed Ma
rch 1
3
, 2016;
Re
vised Ma
y 17, 2016; Accepted Ma
y 30
, 2016
Analysis and Design of High Gain NRI Superstrate
Based Antenna for RF Energy Harvesting System
KK
A D
e
v
i
*
, C
H
Ng
Facult
y
of Eng
i
ne
erin
g an
d Quatit
y
S
u
rve
y
i
n
g, IN
T
I
Internation
a
l Un
iversit
y
, Nilai 7
180
0, Mala
ysi
a
*Corres
p
o
ndi
n
g
author, e-ma
i
l
:kavurik.a
devi
@
ne
w
i
nti.e
du.
m
y
A
b
st
r
a
ct
A high
gai
n pa
tch anten
na i
n
spire
d
by 4 la
yers of
neg
ativ
e refractive i
n
d
e
x (NRI) meta
mater
i
a
l
(MT
M) superst
rate is
pro
pos
e
d
to
op
erate
at
dow
nl
ink r
a
d
i
o
frequ
ency
(RF
)
ba
nd (
9
3
5
MH
z
t
o
9
60MH
z
)
of
GSM 900). T
h
e MT
M u
n
it ce
ll co
nsists
of a
neste
d s
p
lit
r
i
ng r
e
son
a
tor (
S
RR) o
n
on
e
side
an
d stri
p l
i
n
e
la
min
a
ted on other
si
de of
F
R
4
substr
ate.
T
he effective
per
me
abi
lity a
nd
p
e
r
m
ittivity
of the u
n
it cel
l
ar
e
desi
gne
d sync
h
ron
ously t
o
a
ppro
a
ch
z
e
r
o
,
w
h
ich le
ads th
e NRI su
perstr
a
te to h
a
ve i
m
ped
anc
e
matc
h w
i
th
z
e
r
o
ne
gative r
e
fractive in
dex.
T
he NRI super
strate is
studie
d
usin
g F
abry-
Perot (F
-P) resona
nt cavity. The
gai
n of the a
n
tenn
as is i
m
pro
v
ed by
82.29
%
at the air g
ap
of 55
mm
in th
e desir
ed fre
q
u
ency b
and. T
h
e
gai
n
is
effectiv
ely enh
anc
ed
base
d
on
th
e n
egativ
e
refr
acti
ve i
ndex
MT
M. T
he
meas
ure
d
ra
diati
o
n
patt
e
rn
and s par
a
m
et
er results show
ed that it has g
ood a
g
re
e
m
ent
w
i
th the simul
a
tion res
u
lts.
Ke
y
w
ords
: Ne
gative refractiv
e
ind
e
x,
Metam
a
terial, Ne
ste
d
split rin
g
, Patch anten
na, Gain
Copy
right
©
2016 In
stitu
t
e o
f
Ad
van
ced
En
g
i
n
eerin
g and
Scien
ce. All
rig
h
t
s reser
ve
d
.
1. Introduc
tion
The environmental energ
y
harvesting has
re
cently emerged as a viable option to
supplement b
a
ttery supplies.
Ener
g
y
ha
rvesti
ng
b
y
RF
i
s
t
h
e
mo
st attr
a
c
ti
ve ap
pro
achto power
low power wireless devices especially for
the embedded wireless de
vice applications.
The mi
crostri
p
patch a
n
te
nna
s a
r
e
wid
e
ly use
d
d
u
e
to its inh
e
re
nt cha
r
a
c
teri
stics a
nd
several of its advantages
for
wireless
comm
uni
cati
ons, but have drawbacks of low gain
and
narro
w ban
d
w
idth which
limits their application.
To vercom
e these limit
ations n
u
me
rou
s
techni
que
s such
as lo
w p
e
rmittivity and thick subs
t
r
ate [1], stacki
ng of micro
s
t
r
ip ele
m
ent [2],
truncating an
d slotting the
microstri
p
pat
ch [3
] we
re propo
sed to im
prove its pe
rf
orma
nce.
Antenna i
s
th
e major vital
comp
one
nt in
RF en
ergy h
a
rvestin
g
sy
stem. In orde
r to have
a more efficie
n
t antenna, the unu
sual p
r
opertie
s
(n
eg
ative refractiv
e
index) of MTM is integrat
ed
with the
patch ante
nna fo
r the ap
plication of
RF
ene
rgy ha
rve
s
tin
g
sy
stem.Thi
s
can
be
use
d
a
s
a len
s
to
focu
s the
Ele
c
tro
m
agneti
c
(EM)
wave
radi
ated from the
free
spa
c
e t
o
wa
rd th
e n
o
r
mal
dire
ction
of th
e ante
nna. It
is a
medi
um
con
s
i
s
ts
of p
e
rme
ability a
nd p
e
rmittivity simultan
eo
usly
negative at certain fre
que
ncy ran
ge.
In [4
] explor
ed the p
r
op
e
r
tie
s
of iso
t
ro
pic me
dia w
here bo
th
th
e per
mittivity and the
permeability are
simultaneously
negati
v
e (negative
refracti
ve
index). The
propagation
vector
k, ele
c
tri
c
field
E
and magn
eti
c
field
H
o
f
th
ese
material
s for
m
a le
ft hande
d se
t o
f
vector
s w
h
ich are
opp
osite to the commonl
y kn
own ri
ght
h
ande
d mater
i
als. Th
ere
f
o
r
e,
the
s
e
ma
teri
als also ar
e
kno
w
n a
s
the l
e
ft-h
an
ded
ma
teri
als (L
HM).
sh
apes of MT
M
str
u
ctur
es w
e
re p
r
opo
se
d usin
g ZIM such as O
m
eg
a an
d
S as
an
ten
na au
bstra
t
e
to
enha
nce
gai
n [7
], fi
shn
e
t
-n
umerical
simul
a
ti
o
n
s of
Te
rah
e
rtz
doubl
e-n
e
g
a
tive MTM with
The fir
s
t
LH
M pr
ototyp
e usin
g split ring r
e
so
na
tor (SRR) a
nd
thin
wir
e
(TW)
wa
s made
suc
c
e
s
s
f
ully [5]
.
A me
ta
m
a
te
rial
(
M
T
M
)
fo
r
dir
e
ctive
emi
ssio
n
[6]
poin
t
ed th
at the gain of th
e
antenn
a can
be
en
han
ce
d thro
ugh
th
e u
s
e
of zer
o
ind
e
x metama
te
rial (Z
IM)
.
In
th
e r
e
cen
t
year
svario
us isotr
opi
c [8
], La
byrin
t
h
-
b
andwi
d
th
en
hance
m
en
t
of R
M
PA
usi
ng ENG MT
Ms
[9], Squa
re r
e
ctang
ular SRR [1
0], Triangul
ar-
tun
able MT
M d
e
sign
[11
]
all of the
m
exh
i
bi
t
the p
r
op
erti
e
s
of ZIM. Hig
h
directivi
t
y
aper
tur
e
pa
tch usi
ng MT
M [1
2]. A n
e
a
r-zero r
e
fr
a
c
tive
index
me
ta-
s
ur
face stru
ctu
r
e forimpr
o
ve
me
nt o
f
antenn
a per
formance [1
3
]. Split rin
g
and
CSR
R
use MTM
[14
]
-
[
1
5
].
So far au
tho
r
s no
t
co
me a
c
ro
ss the analysis/inve
s
tig
a
tio
n
s
o
n
the
affe
ct
of MTMs o
n
th
e an
ten
na d
e
sign
at l
o
w
fre
quen
cy ap
plica
t
ion
s
. O
u
r Obje
cti
v
e
i
s
Evaluation Warning : The document was created with Spire.PDF for Python.
ISSN: 25
02-4
752
IJEECS
Vol.
2, No. 3, Jun
e
2016 : 647
– 656
648
to e
nha
nce the g
a
in o
f
the a
n
te
nna
inte
gra
t
ing
wi
th
MTMs
for
the
ap
plica
t
ion o
f
e
nerg
y
harvesting
syste
m
. The
d
r
aw
ba
ck ob
ser
v
ed
in
the
in
ve
stig
ati
o
ns i
s
th
e hi
g
her
air
ga
p.
In this article, a defected g
r
ound plane
p
a
tch
antenna
with 4 layers
of NRI supe
rstrate is
realized and investigated.
Appropriate design has
be
en done to make the NRI unit cell
to ha
ve
negative refractive index and the imped
ance match
wi
th the air, efficiently to enhance the
g
a
in
.
The propo
se
d NRI base
d
superstrate ant
enna has been dem
onstrated by simulation and
experiments
2. Ante
nna Design and Configura
tion
The co
nfi
gur
ation
of th
e
NRI
su
per
stra
te b
a
sed
patch a
n
ten
na wi
th its
desig
n
para
m
e
t
er
sa
re sho
w
n
in
Figur
e 1. A pa
tch
s
ize
o
f
102
84
is pri
n
ted
on
FR4
sub
s
tr
ate
h
a
v
ing thi
ckn
e
ss 1.6 mm, per
mittivi
t
y 4
.
7, a
nd lo
ss
tan
gen
t 0
.
0
1
4
.
It consi
s
ts of
one rin
g
sl
o
t
S1 a
t
th
e
cen
t
er
and
bevel
s a
t
the ed
ges
of the
patch
to
enha
nce
th
e
impe
dan
ce
band
width.
The antenn
a
is direct
fed
throu
gh a 1
5
mm leng
th
of tr
an
smi
ssi
on
line and e
xci
ted b
y
a 50
Ω
m
i
c
r
os
tr
ip
f
e
ed
lin
e
of
wid
t
h
2.
93
mm
t
h
r
o
ug
h
an
SM
A
c
o
nne
c
t
o
r
situ
ated
o
n
edge of diel
ectric.
De
fe
cted gro
und stru
cture (DG
S
)
w
h
ich
is printed
a
t
b
o
tto
m
of th
e FR4 substra
t
e al
so
contribu
te
s to
increa
se
th
e impe
dan
ce
bandwi
d
th
.
The opti
m
ize
d
desig
n di
me
nsion
s
of th
e an
te
nna
ar
e show
nin T
able
1. The
width
(W
)
, le
ngth (
L)
, length
e
x
te
ns
io
n
∆
an
d
ef
fe
ct
iv
e d
i
e
l
e
c
t
r
ic c
o
n
s
ta
nt
o
f
th
e
pa
tch
an
te
nna
a
r
e
calculate
d
using
the
eq
uatio
ns (1
), (
2
), (3
)
and
(4
) o
b
tai
ned
fr
om [16].
1
2
2
1
2
o
2
1
r
r
f
o
V
r
o
r
f
W
(1)
L
o
o
re
ff
r
f
L
L
2
2
1
2
(2)
E
xtensionlen
gth
∆
L is give
n by
)
8
.
0
)(
258
.
0
(
)
26
4
.
0
)(
3
.
0
(
412
.
0
h
w
reff
h
w
ref
f
h
L
(3)
For W/h
> 1, Effective dielec
tri
c
consta
nt is given by
2
1
12
1
2
1
2
1
w
h
r
r
reff
(4)
(a)
(b)
Figure 1. Con
f
iguration of a
n
tenna (a) p
a
t
ch ant
en
na (b) patch ante
nna with
NRI
sup
e
rstrate
Evaluation Warning : The document was created with Spire.PDF for Python.
IJEECS
ISSN:
2502-4
752
Analysis a
nd
De
sign of Hi
g
h
Gain NRI Superstrate Based Anten
n
a
for RF EHS
(K.K.A.
Dev
i
)
649
Table 1. Dim
ensi
o
n
s
of the patch a
n
ten
n
a
Basic Configuration
Patch antenn
a
Feed Line
Grou
nd Plane
Variable
B1, B2
C1 C2
W L
W L
Radius RadiusW L
G
W
G
L
Dimensions (mm) 74 83
21 15
32 15
2.93 15
84 5.5
3. Designa
n
d
Simulation
of the NRI Unit Cell
The configuration of the proposed
unit cell is illust
rated in Figure 2.
It consi
s
ts of
nested
split rin
g
re
sonator
(SRR) and
stri
p line. Ne
sted
SRRs p
r
od
u
c
e
s
the n
e
g
a
tive magnet
ic
respon
se
so
it exhibits ne
gative pe
rme
ability
µ and
array of st
ri
p line
s
will
p
r
ovide
negati
v
e
permittivity
ε
belo
w
the
pl
asma
fre
que
ncy. Th
us, th
e combin
atio
n of the
s
e
two st
ru
cture
s
will
yield a negati
v
e refra
c
tive index so it is
calle
d as
NRI
material.
In Figure 2(a
)
, W
1
, L
1
,
d
,
s and
g repr
ese
n
ts the wid
t
h
,
l
eng
th,
thi
ckn
ess, dista
n
ce betwee
n
the ne
ste
d
comb
s an
d g
ap in
the
ne
sted
SRR. The
wi
dth W
sl
an
d l
e
n
g
th
L
sl.
o
f
t
h
e
s
t
r
i
p
line
ar
e
s
h
ow
n
in
Figu
r
e
2
(
b)
.
The simulated retrieval parameters
of the
unit cellare
s-paramet
ers: permeability,
per
mittivi
t
y, impe
dan
ce a
nd refra
c
tive
index are
shown in Figu
re 3. All the
simul
a
tio
n
s
are
done
usi
ng
the C
o
mpu
t
e
r
Si
mula
tio
n
Techn
o
log
y
Micr
owa
v
e
Studio
(C
ST-
M
W
S
)
so
ftw
are
.
The
resul
t
s of the s-parameter
i
n
Figu
re 3(a) illustrates
the magnitude
of S
21
is grater t
h
an
S
11
in the de
sired frequ
en
cy band. Thi
s
i
ndicates th
at
the EM waves can
easily
p
a
ss throug
h the
NRI supe
rst
r
ate within this frequen
cy ba
nd.
Effec
t
ive c
o
ns
titute parameters
μ
eff
an
d
ε
eff
of the unit cell
are
extracte
d from the
corre
s
p
ondin
g
tran
smissio
n
and reflecti
on co
efficient
s usi
ng a
sta
ndard ret
r
iev
a
l algo
rithm [17]
are in Figu
re
3(b
)
and (c).
Thr re
sult
s
indicate
s that the effective perme
ability
μ
e
ff
and permitti
vity
ε
eff
approa
ch
esto
ze
ro
whi
c
h m
a
ke the
corre
s
p
ondin
g
effective refractive i
ndex i
s
ne
gative.in
the
freque
ncy
ba
nd 9
35 M
H
z t
o
96
0 M
H
z. I
n
ad
dition,
th
e effective
pe
rmea
bility an
d pe
rmittivity has
the same val
ue at the cent
er freq
uen
cy 947M
Hz of
d
e
sired ba
nd
whi
c
h lead
s the NRI unit cell to
have both ne
gative refra
c
ti
ve index and
perfe
ct imped
ance match
with air.
The effective
refra
c
tive index n is further
calculate
d
base
d on the effective con
s
titute
para
m
eters
and it i
s
de
picted
in
Fig
u
re
3(e),
illu
strate
s th
at i
t
is n
egative
in the
de
si
red
freque
ncy ba
nd. Gain of the anten
na can be en
han
ced by u
s
ing
negative ref
r
active index
MTM
[7]. It is al
so
noted
fro
m
t
he
re
sults th
at theima
gin
a
ry p
a
rt
of th
e refra
c
tive i
ndex i
s
relati
vely
small at the
desi
r
ed fre
quen
cy ban
d
w
hi
ch me
an
s the lo
w lo
ss a
n
d resu
lt in high g
a
in
enha
ncement
.
Figure 2. Con
f
uguratio
n of unit cell (a
) SRR (b) Strip li
ne
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02-4
752
IJEECS
Vol.
2, No. 3, Jun
e
2016 : 647
– 656
650
(a)
(b)
(c)
(d)
(e)
Figure 3. Simulated re
sult
s of unit cell (a
) s pa
ramete
r (b) pe
rme
abi
lity (c) pe
rmittivity
(d) Imp
edan
ce (e)
refra
c
tive index
4. Analy
s
is o
n
the Air Ga
p of the Pro
posed
Anten
n
a
Figure 1
sh
o
w
s th
e g
eom
etry of the p
r
opo
sed
patch
antenn
a. Th
e air
gap
h i
s
betwe
e
n
two structu
r
e
s
, with refle
c
t
i
on co
efficien
t phase
s
and
re
spe
c
tively. From the point of
the ray, an electroma
gne
tic (EM) wave is exci
ted
by the Fabry-Perot
c
a
vity. In
order
to
sup
e
rim
p
o
s
e
in pha
se, the pha
se shift of the EM waves is the multip
le of 2
π
, it can be written a
s
....
2
,
1
,
0
,
2
4
N
N
h
GN
D
NRI
o
[18]
(5)
From (5), the
thickne
ss of a
i
r gap of the
NRI
supe
rst
r
ate based pat
ch ante
nna i
s
determin
ed b
y
.
...
2
,
1
,
0
,
2
4
N
N
h
o
o
GND
NR
I
(6)
Gene
rally, the anten
na p
r
ofile has
always cl
ose to
/
2
becau
se the
π
. In this
pape
r,
is the reflectio
n
p
hase of the antenn
a gro
u
n
d plan
e, wh
ich is
smalle
r than 180
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IJEECS
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752
Analysis a
nd
De
sign of Hi
g
h
Gain NRI
Superstrate Based Anten
na
for RF EHS
(K.K.A.
Dev
i
)
651
degree for a
defected g
r
ound pla
ne,
h
is the heig
h
t of the air
gap and
λ
o
is the free-sp
ace
wavele
ngth. It can be o
b
served fro
m
Fi
gure
4 the re
flection ph
ase
of the NRI
unit cell i
s
clo
s
e to 27de
gree a
nd the reflectio
n
pha
se
of the antenna is ap
proximately equal to -121
degree at 94
7 MHz. Furth
e
rmo
r
e,
the cavity height h obtained by
equatio
n (6
) is equ
al to 41.32
mm. This is
a clo
s
e with t
he simul
a
ted
resu
lt of 55 mm.The opti
m
ized g
a
in of
the antenna
can
be achieved
by using the reso
nant
hei
g
h
t of the F-P cavity.
Figure 4. Re
sults on ph
ase
s
of refle
c
tion
coefficie
n
ts for the unit cel
l
5. Metodolo
g
y
First, p
a
tch
a
n
tenna
is
de
sign
ed a
nd
simulated to
o
b
tain the
de
sired
perf
o
rma
n
ce
at
down link
RF
band of GSM
900 usi
ng
CST-MWS. To
validate the perfo
rman
ce
of the antenn
a
three frequ
en
cie
s
(935 M
H
z, 947
MHz
and 9
59 M
H
z) are
con
s
ide
r
ed i
n
the d
e
s
ire
d
fre
que
n
cy
band
of GSM
900
for
both
in
simulatio
n
and
mea
s
u
r
ement. Next, the ne
sted
(S
RR) u
n
it cell
is
desi
gne
d a
n
d
si
mulated
by usi
ng f
r
e
quen
cy d
o
m
a
in
solver in
CST
enviro
n
ment. All t
h
e
para
m
eters o
f
the
ne
sted SRR are opti
m
ized
to
a
c
hi
eve a lo
w lo
ss NRI
NSRR unit cell. After
that, the NRI supe
rst
r
ate is introd
uced
on to
the patch anten
na a
nd the air ga
p betwee
n
the
antenn
a and
NRI supe
rst
r
ate is optimi
z
ed ba
sed o
n
F-P theory. Fi
nally the prop
ose
d
anten
na
is
fabricated a
n
d
mea
s
u
r
ed t
he return l
o
ss S11 an
d ra
di
ation patte
rn
to validate th
e pe
rform
a
ce
of
simulat
i
o
n
re
sult
s.
6. Results a
nd Discu
ssi
on
The p
hotog
raph
of the
pro
p
o
s
ed
fabric
ated
a
n
tenna
is shown in
Fi
gure
5.
Measurement
s are do
ne u
s
ing a vecto
r
netwo
rk
a
nal
yser, Anapi
co
Apsin 3000
sign
al gene
ra
tor
and Gwi
n
ste
k
G
s
p
-
8
30 spectrum anal
yzer.at
th
e
o
pen sp
ace. The radi
ation
patterns
of the
patch a
n
tenn
a with and wi
thout the NRI
supe
rs
t
r
ateb
y simulation
and mea
s
u
r
e
m
ent are
sho
w
n
in Figu
re
s 7
and 8. T
he
result
s comp
a
r
iso
n
i
s
given
at 935M
Hz,
947 M
H
z an
d 959
MHz. I
t
is
noted that pl
acin
g the NRI supe
rst
r
ate
onto t
he pat
ch antenn
a re
duces th
e ha
lf powe
r
bea
m
width in E plane from 82.
3° to 76.6°. Also com
p
a
r
edthe H pla
n
e
pattern wit
h
and witho
u
t NR
I
sup
e
rstrate, it
can
be
see
n
that, in cont
ra
st to the E pl
ane p
a
ttern, t
he half p
o
wer beam
width i
n
H pla
ne i
s
al
so
narro
wed
down to 1
02.
2°. Mo
reove
r
, the mea
s
u
r
ed results
of E and
H pl
a
n
e
radiatio
n pattern sho
w
ed a
great consi
s
t
ence with the
simulation
re
sults.
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ISSN: 25
02-4
752
IJEECS
Vol.
2, No. 3, Jun
e
2016 : 647
– 656
652
(a)
(b)
Figure
5. Ph
oto
g
rap
h
of
the prop
osed
fab
r
ica
t
ed
(
a
)
p
a
tch an
ten
na (b)
pa
tch antenn
a with
4
layer
s
of N
R
I su
per
stra
te
The sim
u
lati
on re
sult
s of patch ante
n
na witout
wit
h
NRI supe
rstatein pol
ar form is
sho
w
n in Fig
u
re
s 9 and 1
0
.The gain of
the patch an
t
enna is in
cre
a
se
d from 2.71 dB to 4.94 dB
at 947MHz. Due to the high
transmi
ss
ion
prope
rtie
s of NRI supe
rst
r
ate.
(a)
(b)
(c
)
Figure 7. Rad
i
ation pattern
of patcha
n
ten
na
at
(a)
9
3
6 MHz (b) 947 MHz (c
)
959 MHz
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IJEECS
ISSN:
2502-4
752
Analysis a
nd
De
sign of Hi
g
h
Gain NRI Superstrate Based Anten
n
a
for RF EHS
(K.K.A.
Dev
i
)
653
(a)
(b)
(c
)
Figure
8.
R
a
diatio
n pa
tte
r
n
o
f
pro
pose
d
a
n
te
nna
a
t
(a) 936
MH
z (b) 947
MH
z (c)
95
9 MH
z
(a)
(b)
Figure 9. Without MTM gai
n radiatio
n pa
ttern
of patch
antenn
a (a
) E plane (b
) H
Plane
Based
on F
-
Ptheory the a
i
r gap i
s
not
vital paramet
er to affect th
e gain of the
antenn
a.
The re
sult
s on gain at
different heig
h
ts of
air g
a
p are d
epi
cted in Figu
re 11. The
gain
enha
ncement
is slightly influen
ced by th
e air gap
and
highe
st gain
was o
b
taine
d
at the air g
ap
of 55 mm.
(a)
(b)
Figure 10. Wi
th MTM gain
radiatio
n pattern of pat
ch a
n
tenna (a) E plane (b)
H Plane.
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ISSN: 25
02-4
752
IJEECS
Vol.
2, No. 3, Jun
e
2016 : 647
– 656
654
Figure 11. Co
mpari
s
o
n
on the gain of the
p
rop
o
sed ant
enna verse
s
air gap
Figure 12. Co
mpari
s
o
n
on
simulatio
n
ret
u
rn lo
ssof patch ante
nna
Comp
ari
s
o
n
on simul
a
ted
return lo
ss
for the patch
antenna wit
h
out and wit
h
NRI
sup
e
rstrate i
s
sho
w
n i
n
Fig
u
re
12. The
result in
dicate
s that the
ret
u
rn lo
ss a
n
d
the imped
an
ce
band
width a
r
e redu
ce
d by 1.89% and 6
0
%. Compa
r
i
s
on on
simul
a
ted and me
asu
r
ed return
loss
of the patch a
n
tenna
witho
u
t and with NRI sup
e
rstrat
e is sh
own in Figures 1
3
. It
is ob
serve
d
that
the retu
rn lo
ss an
d impe
da
nce
ban
dwi
d
th are
re
du
ce
d to 28.08%
and 2
5
%. Mo
reove
r
, Figu
re 14
illustrated the simulated and meas
ured
return loss of the propose
d
antenna. The results
showed
that the return loss and i
m
peda
nce b
and
width
are
redu
ced to 1.24% and 3
6
.36%. The slight
decrea
s
e in
impeda
nce b
and
width is
due to the
high quality factor cha
r
acteristic of NRI
sup
e
rstrate.
Even then it i
s
2.5 time
s
h
i
gher t
han
de
sire
d b
and
wi
dth. Ho
weve
r it seem
s to
be
good a
g
re
em
ent betwe
en the mea
s
u
r
ed
and sim
u
late
d results.
Figure 13. Co
mpari
s
o
n
of sim.and test re
turn re
su
lt
s of the propo
s
e
d
antenna
with
out NRI
s
u
pe
rs
tr
a
t
e
Evaluation Warning : The document was created with Spire.PDF for Python.
IJEECS
ISSN:
2502-4
752
Analysis a
nd
De
sign of Hi
g
h
Gain NRI Superstrate Based Anten
n
a
for RF EHS
(K.K.A.
Dev
i
)
655
Figure 14. Co
mpari
s
o
n
of sim.and test re
turnlo
ss lo
ss results for of the pro
p
o
s
ed
antenn
a with
NRI supe
rst
r
ate
7.
Con
c
lu
si
ons
This arti
cle
p
r
opo
se
d
a n
egative
refra
c
tive ind
e
x
superstrate b
a
s
ed
hig
h
-gai
n pat
c
h
antenn
afor RF
en
ergy ha
rvesting appli
c
ation. The
NRI region
of t
h
e n
e
ste
d
S
R
R-st
rip li
ne
unit
cell i
s
well b
e
yond the
de
sire
d fre
que
n
c
y ra
nge 7
7
0
MHz to 10
7
0
MHz, of wh
ich the
radi
ation
from the ante
nna an
d the free
spa
c
e i
s
conve
r
ge
d. The anten
na p
r
opo
se
d is di
rectio
nal
whi
c
h
the re
quired
feature fo
r t
he de
si
red
a
pplication
i
s
andthe gain is
in
cre
a
sed signifi
c
antly by
82.29%. Also
observe
d th
at there i
s
a
degredatio
n
i
n
impe
den
ce
band
width
du
e to hig
h
qu
a
lity
factor
ch
ara
c
teristic ofsup
e
rst
r
ate laye
r on to th
e
pa
tch ante
nna,
however it i
s
well
within t
h
e
desi
r
ed
ban
d
w
idth of GS
M 900, he
nce the propo
s
ed ante
nna i
s
suitablefo
r
the appli
c
atio
n at
this ban
d.
Ackn
o
w
l
e
dg
ement
We wo
uld like to ackn
owl
edge an
d tha
n
k the Mi
nist
ry of Higher Education Mal
a
ysia for
funding thi
s
proje
c
t un
de
r the Fun
d
a
m
ental Rese
arch G
r
ant
Schem
e (F
RGS); Gra
n
t No:
FRGS/2/20
1
3
/
ST02INTI/ 02/01.
Referen
ces
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Adrian A. Effect
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f
Microstrip Antenn
a
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h
ickness a
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d
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o
mparis
on
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heories
w
i
th
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e
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. IEEE Trans. Antennas Propag
.
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82.
[2]
Ansari JA, R
a
m RB. Broad
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-
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nn
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a
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a
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z
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ha
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