Low Profile Reflector for half wave dipole
antenna
Lokesha H R,Sahana C P,Kavya
Department of Electronics and Communication Engineering
NDRKInstitute of Technology, Hassan
Abstract- low profile reflector for half wave dipole
antenna operating in WLAN band (2.4 GHz -2.48 GHz,
5.15 GHz -5.35 GHz) is proposed. Generally, a flat
metal sheet is used with an antenna as a reflector to
increase antenna gain. Since the reflection phase of
a metal sheet is 180°, the antenna should be placed
λ/4 away from the reflector to avoid destructive
interference of the reflected wave from the metal
sheet and the radiated wave from the antenna. In this
paper, a low profile reflector is designed as a
reflector of half wave dipole reflectorantenna. The
height of reflector is 0.75λ using PEC. In addition,
improvements of both gain and front lobe to back
lobe ratio are achieved as a result of using reflector.
To demonstrate improvement of gain, directivity, s11
and input impedance, comparison between the half
wave dipole using PEC as reflector is presented.
Measured gains of reflector antenna are 5.45 dB and
7.9 dB in 2.4 GHz
design of antenna such as base station antenna where a
reflector is required [5].
A wireless LAN (WLAN) provides network
connectivity between devices, also known as stations,
by using radio as the communication medium. The basic
building block of the WLAN network is the 802.11
basic service set (BSS). A BSS defines a coverage area
where all stations within the BSS remain fully
connected.WLANs have data transfer speeds ranging
from 1 to 54Mbps. A WLAN signal can be broadcast to
cover an area ranging in size from a small office to a
large campus. So antenna designed to suit for these
conditions depending on access point.
The main aim of this paper is to design and
simulate halfwave dipole antenna with reflector to
operate at WLAN applications at 2.6 GHz with high
gain, by using HFSS simulator.Figure1: Geometric of
Half-wave Dipole Antenna is as shown below
Keywords-- Half wave-dipole Antenna; Reflector;
WLAN; Return Loss;Gain; HFSS.
I. INTRODUCTION
In recent years, there has been increasing interest in
metamaterials such as electromagnetic band-gap (EBG),
artificial magnetic conductor (AMC) [1], [2]. Among
them, AMC is considered to have many advantages
when it is used with antennas. AMC is one of
metamaterials exhibiting novel electromagnetic features
which may not occur in nature.
These characteristics of the AMC provide
followingadvantages when it is used as a low profile
reflector. Generally, a flat metal sheet is used with an
antenna as a reflector to increase the antenna gain. Such
a flat metal sheets has property of 180° reflection phase
which causes destructive interference between reflected
wave from the metal sheet and directly radiated wave
from antennas when it is closely placed to an antenna.
This problem is usually solved by placing the antenna
λ/4 away from the metal reflector. If AMC is used as a
reflector, destructive interference does not occur even
though the AMC is close to an antenna since reflection
phase of AMC is 0°. In addition, the high surface
impedance of the AMC improves the radiation
performance. Surface waves supported by a flat metal
sheet are scattered as back lobes or side lobes which
reduce the gain of antennas. By suppressing surface
waves with AMC, back lobes or side lobes can be
reduced. Due to these advantages, AMC is usable in the
Figure1: Geometric of Half-wave Dipole Antenna
Figure2: Geometric of Half-wave Dipole
Antenna with reflector is as shown below
II. DESIGN PARAMETERS OF HALF-WAVE
DIPOLE ANTENNA WITH REFLECTOR
In this section will calculate design
parameter of half-wavedipole antenna[6]. The design
proposed center frequency at 3.5GHz. Based on the
operating frequency will calculate the length of
antenna (also called the height) L by the
followingequation:
L = 143/ f
(1)
Then, the calculated length is
L=0.5*lamda =57.5mm
The wavelength:
λ = C/f
that compares the power reflected by the antenna to
the power that is fed into the antenna from
transmission line. In Figure 2 shows the return loss of
half wave dipole antenna is -2.5 dB at 3,5 GHz
which should be below -10dB.
B IMPEDANCE
Maximum power transfer requires matching the
impedance of an antenna system looking into the
transmission line to the complex conjugate of the
impedance of the receiver or transmitter. In the case
of a transmitter, the desired matching impedance
might not correspond to the dynamic output
impedance of the transmitter as analysed as a source
operation
of
the
transmitting
circuitry.
Name
X
XYPlot 1
Y
HFSSDesign1
m0.00
1 2.4141 -17.8979
hence, the calculated wavelength is
λ = 3*108 = 115mm
ANSOFT
Curve Info
dB(S(1,1))
Setup1 : Sweep
-2.00
-4.00
The gap feeding is
g = L/200
hence, the calculated gab feeding is
g = 57.5/200=0.2875mm
The Radius of dipole (thickness):
R = λ/1000
dB(S(1,1))
-6.00
-8.00
-10.00
-12.00
-14.00
-16.00
m1
Thence, the calculated Radius is
R= 115/1000= 0.115mm
The length and breadth of the reflector is taken as
0.75λ to reflect incident wave on one side.
-18.00
1.00
1.50
2.00
2.50
3.00
Freq [GHz]
3.50
4.00
4.50
5.00
Figure 2: Return loss from HFSS
Name
X
XYPlot 2
Y
HFSSDesign1
1500.00
m1 2.4949 77.5237
m2 2.4949 44.4747
re(Z(1,1))
Setup1 : Sweep
1250.00
Parameter
Frequency resonance (f)
Wave length(λ)
Length of the dipole (L)
Radius of the dipole (R)
Length of Reflector
Value
2.6GHz
115mm
57.5 mm
0.115mm
86mm
im(Z(1,1))
Setup1 : Sweep
1000.00
750.00
500.00
Y1
TABLE2: CALUCALATED PARAMETERS OF HALF WAVE
DIPOLE ANTENNA
ANSOFT
Curve Info
250.00
m1
m2
0.00
-250.00
-500.00
III. RESULT AND DISCUSSIONS
-750.00
1.00
The software used to model and simulate the
half-wave dipole antenna is HFSS. It analyzes 3D
and multilayer structures of general shapes. It has
been widely used in the design different type of
antenna. It can be used to calculate and plot the
Return Loss, VSWR as well as the radiation patterns.
A. RETURN LOSS:
The return loss is another way of expessing
mismatch. It is a logarithmic ratio measured in dB
1.50
2.00
2.50
3.00
Freq [GHz]
3.50
4.00
4.50
5.00
Figure 3: Impedance from HFSS
C. HIGH GAIN:
Another useful measure describing the
performance of antenna is the gain. Although the gain
of antenna is closely related to the directivity,
remember that directivity is measure that describes
only the directional properties of the antenna, and it
is therefore controlled only by pattern. Absolute gain
of an antenna is defined as the ratio of intensity, in a
given direction to the radiation intensity that would
be obtained if power accepted by antenna were
radiated isotropically. High gain measured at 3.5GHz
equal -1.9494dB as shown in figure 4.
D. RADIATION PATTERN:
The basic term “radiation” means that, the
distribution of power through respective fields of
antenna. An antenna radiation pattern or antenna
pattern is defined as “A mathematical function or a
graphical representation of radiation properties of the
antenna as a function of space coordinates”.
However, in most cases the radiation pattern is
determined in the far field region and is represented
as function of directional coordinates. The radiation
pattern presented worthy result as Figure 5.
Figure 6: E-field from HFSS
TABLE2:COMPARISSION OF RESULTS OF DIPOLE
ANTENNA AND DIPOLE ANTENNA WITH REFLECTOR
Figure 4: Antenna gain from HFSS
RadiationPattern1
HFSSDesign1
Dipole
antenna
Dipole with
reflector
antenna
Gain
“2.4600”dB
“7.9949”dB
Directivity
“2.9632”dB
“7.9329”dB
Return loss
“-19.7914”dB
“-17.8979”dB
Impedance
“68.8815”dB
“77.5237”dB
ANSOFT
Curve Info
0
-30
Parameter
dB(GainTotal)
Setup1 : LastAdaptive
Freq='2.6GHz' Phi='0deg'
30
0.00
dB(GainTotal)
Setup1 : LastAdaptive
Freq='2.6GHz' Phi='10deg'
-10.00
-60
60
dB(GainTotal)
Setup1 : LastAdaptive
Freq='2.6GHz' Phi='20deg'
-20.00
dB(GainTotal)
Setup1 : LastAdaptive
Freq='2.6GHz' Phi='30deg'
-30.00
-90
90
dB(GainTotal)
Setup1 : LastAdaptive
Freq='2.6GHz' Phi='40deg'
dB(GainTotal)
Setup1 : LastAdaptive
Freq='2.6GHz' Phi='50deg'
-120
120
dB(GainTotal)
Setup1 : LastAdaptive
IV. CONCLUSION
A half-wave dipole antenna with reflector
has been designed andsimulated using HFSS
software. The simulated results show that the
designed antenna offered high gain, directivity, and
low impedance, which covers the WLAN application
bands. This antenna provides maximum Gain of 7.99dB and return loss -17.89dB. The proposed half
wave dipole antenna with reflector design is suitable
for WLAN wireless communication standard.
REFERENCES
-150
150
-180
Figure 5: Radiation Pattern from HFSS
[I] Eun Young"Low Profile Dual-band Reflector Antenna
with Dual Resonant AMC" Electrical and computer
Engineering, on May 4-7, 20 08.
[2] N.I.Mohamed, T.A.Rahman, C.Y.Leow," Issues and
challengesof LTE antenna designs for USB-dongle device",
IEEE-APSTopical Conference on Antennas and
Propagation in Wireless
Communications (APWC), 2012.
[3] chen, W.-S., Yu, Y.-H "dual band printed dipole
antenna with parasitic element for WiMAX applications",
Electronics letters vol.44, 2008.
[4] Ting-Ming Hsueh, heng- Tung Hsu-Tseng chou, “Dual
band omni directional planar antenna for WiMAX
applications”. IEEE Antenna and propagation society
international symposium, 2008
[5] Qinjiang Rao and Tayeb A, Denidi, “New broad band
dual printed inverted L-shaped monopole antenna for tri
band wireless applications”, microwave and optical
technology letters, Feb 2007
[6] A.Osman,Alaa A, Yasin, B Ali, “Design and simulation
of high performance half wave dipole antenna for LTE
applications” IEEE Antenna and propagation, 2015.