Wireless Power Transfer Using Microwaves At 2.45 GHz ISM Band Muhammad loam Abbasi (muhammad
[email protected])
Center for Advanced Studies in Engineering(:CASE), Islamabad, Pakistan. Syed Atif Adnan (atif
[email protected])
Center for Advanced Studies in Engineering (CASE), Islamabad, Pakistan. Muhammad Amin (
[email protected])
Institute of Space Technology (1ST), Islamabad, Pakistan. Farrukh Kamran(
[email protected]) Center for Advanced Studies in Engineering (CASE), Islamabad, Pakistan.
Abstract
-
We have demonstrated wireless power transfer
by coupling RF power from a microwave oven magnetron RF
potential of concentrated and directed microwave beam that can provide higher efficiency for longer distances.
source using a dipole at optimum position within the cavity. A 40dBm coupled power is transmitted using a monopole corner reflector antenna having gain of 14.97dBi and a half power beam width of 22 : At the receiving end a patch antenna is
II. SIMULATION AND MEASUREMENT SETUP
foot)
We have used a microwave ovens magnetron as an RF
to 4 meters (13 feet). The measured power received varies from
power source. To couple this power we tested a dipole and a
placed at variable distances ranging from 0.307 meters 25dBm
to
3dBm
theoretically
which
calculated
is
in
value
close
agreement
using
Friis
(I
with
the
transmission
equation. The received RF power is simulated on Multisim with a rectifier circuit and it is shown that an efficiency of 5.5% to 0.2% with respect to the transmitted power can be achieved as the distance is varied from 0.307 meters to 4 meters.
loop antenna and found the dipole to be more effective for this purpose. So power coupled by the dipole antenna is transmitted using a monopole comer reflector antenna. A rectangular microstrip patch antenna (MSA) is used to receive this power. The received RF power is rectified using Multisim simulation to get the DC output.
I. INTRODUCTION
Distance
variation
from
OJ07meters t 4 meters
The idea of wireless power transfer goes back as early as work done by Nikola
Tesla[l).
Current and potential
applications of Wireless power transfer include RFID[2), charging of mobile phones and laptops[3), electrically charged vehicles[4), energy from sun to earth (huge solar panels in the outer space and then direct power to earth) and
Magnetron
Power
of
coupled
mIcrowave
u�g'JJ2
oven
dipole
Power
Power
transmis�on
reception by
DC
uSIng
patch and
output
monopole
rectification
CRA
in spying circuits devices which if contain a power source, can have greater probability of detection.
Fig. 1. Block diagram of the setup
The various methods of wireless power transfer are: •
Microwaves/ Radio waves.[5)
•
Plastic sheet.[6)
•
Inductive coupling.[7)
•
Lasers.[8)
The
advantages
III. SIMULATED AND MEASURED RESULTS A.
of
wireless
power
transfer
using
microwaves over other methods are its use for longer distances
with
relatively
higher
efficiency
and
the
technology is more mature. Highly efficient, super directive array configuration would have the
Power coupling
Two different type of antennas i.e. a dipole and a loop antenna
are
used
to
couple
microwave
power
from
magnetron to narrow beam monopole based comer reflector antenna. The optimum position of the two antennas is found where maximum energy is coupled from microwave oven
Proceedings ofinternational Bhurban Conference on Applied Sciences & Technology Islamabad, Pakistan, January 19 - 22,2009
978-969-8741-07-5/09/$25.00 © 2009 IEEE
99
RF source to the transmitting antenna. Calorimetric method
reflector antenna and the feed point length of the monopole
was used to observe the temperature change in water which
are as follows
is equivalent to the power delivered to the water mass. After number of trials by using dipole and loop antenna, we found the relationship between change in water temperature and antenna position. The dipole antenna was selected because of its better coupling. This was found out by comparing the graphs of antenna position vs. temperature change over a constant time interval (Figure 2
---
�
-
.
--
1 --�
-
--
/''
I
�
-
--
& 3).
�-
--
I
+
---
I
+-
Reflector dimensions
L=3 x 3A
Monopole length
M.=0.754A
Monopole diameter
Md=0.032
Monopole position
x=0.6, Y=0.6
AA-
• -
-, --- � -- -
I
I
- - - � /- � - - - � - - - � - - - � - - - � - - � - - � - --
-
I
-- - r-
,
- - � - --�
-
-
-
--� --1-
-
I
,
- � --
-
I
�--����--��--��--�� M w � � w ro� 00 ro ro � U
e
(degrees)
Fig. 2. Position Vs temperature change graph for loop antenna
----t- --
r I I r -------
-
-
--
-
. �II
I� : -
I T
I ---1-----
L ___ L _____ I I I I _______ L ___ L _____ I I
____
1
t
�
__
--
C.
us
T I I T
-
---------
_________
Design andfabrication of patch antenna
On the receiving side a rectangular microstrip patch antenna (MSA) was used. Since a unidirectional beam is required to
1I -------
establish a link with the transmitting antenna, the receiver antenna with a ground plane is an obvious choice that
1 _______ I
reduces additional coupling with objects which lie in the other lenis phase.
---------�------I
O�------�---L--� o � 30 00 70
e
Fig. 4. Monopole Comer reflector antenna
We are using "FR4" substrate with a dielectric constant Sr = 4.5, resonant frequency of 2.45 GHz and thickness of
substrate equals 62 mills. Width (w) and length (L) can be
(degrees)
found by the following relations.
Fig. 3. Position Vs temperature change graph for dipole antenna B.
Monopole Corner reflector antenna
This antenna is used as a transmitting antenna. We have used three reflecting planes as a comer reflector. Material used for the sheets is Aluminum of 0.75mm thickness.
In
this reflector we used monopole as a feed element. The ground plane, where the monopole is attached, has been cut diagonally in order to make our design more compact. The antenna has an input impedance of 75 n. The antenna has a gain of 14.97dBi and has maximum radiation at an angle of 40 degree. The half power beam width of this antenna is 22.68 degrees. The dimensions of the optimized comer
Where & is the extended length and Sreff is the effective dielectric constant. The dimensions of the antenna so
found
were
simulated
in
ADS
(Momentum)
and
optimized to resonate at 2.45GHz. The fmal dimensions of the antenna are shown in Figure 5. The simulated SII results are depicted in Figure 6.
Proceedings ofintemational Bhurban Conference on Applied Sciences & Technology Islamabad, Pakistan, January 19 - 22,2009
100
29mm
The rectifier circuit with schottky diodes was simulated using Multisim to obtain DC output. The schematic of the simulated rectifier circuit is shown in Figure 8. , TnTn
29mm
Vl +Dl D4 Cl �Rl '" 2. 4-SG D2 D3 drov T !
J
•
�12mm-1
31 mm
-
3
The
simulation were
results
obtained
good
agreement
in
}C
,-.] ... p,.;r.n.-
0--",
(f)(
J
I
mm
Fig. 5. Dimensions for the designed MSA
Momentum
1
�� J
ODeg
J
----:0 _
:p.
XSC1 �
from to
Fig. 8. Schematic of Rectifier circuit
the our
ADS
IV. FINAL RESULTS AND DISCUSSION
desired
frequency. The group of SII vs frequency is shown in the figure 6.
The dipole antenna is placed at an optimum position where it couples maximum power. The coupled power is measured
""W/r-S11
0
� r;1> :2;
-
1 n.
-20-
r
-.......,
3 n.
-4 0-5
n.
-6 2.34
2.36
2.38
I
2.40
2.42
2.44
2.46
2.48
J J J J I
using an RF power meter. This power was 40dBm. After measuring the power, it is fed to a monopole comer reflector antenna. The MSA used as a receiver antenna is aligned along with the direction of maximum gain while the distance is varied form 0.307 meters to 4 meters. The received power according to the Friis transmission equation is given by
2.50
Frequency
Fig. 6. Simulated reflection coefficient (SI 1) for MSA
��---'----�---'--,,--r=�==�==�
Input impedance of the above mentioned patch antenna
lS
is 50n. The patch antenna has a gain of 5.5IdRThe measured results were in good agreement to the simulated results except a frequency shift which is probably because of the low quality microwave substrate FR4 and due to the scattering effect that was not considered during simulation. o -2 --4
Ref-fee t1.on coaff/erllt -6
��
�
t;:r r---j
�
fa
=
r---j
E
......... .
'\: . ..... ;....•....•.....•....•.. ; .......•....•..........;--.-- ------...---- ... ;...--....--...--...--. ';-------,'---lj
��--·..·--· ..-- ..----· �� ·..--·.. --· ..-- ;..--·..----..--·..--·..;--·..--·..----· .. --..·i·..---- .. --..· --..--· ;..--..· --..--·..--·..,. . -- --·..----..--· .. �
-" o
.S,5f-----..------.. ------..,------·..----·,�""""'·----..----..---->----..·--..----..----· ,--..--....----..--..--., ..----....------------.,..--..--------..----� �
�
a.1D�
.................I......... ............... I .. ....................>.""'''''�''' ..... ,..........................1 ............------ ----;.------.--.----.
=
r---j
\ f \ I
11
1]
-8
Fig. 9. Theoretical and measured received power Vs
-10 -12
�
distance
H V
Where the reflection efficiency is assumed to be 90%
-1 -4
Fig. 7. Measured reflection coefficient (S 1 1) for MSA
while
the
antenna
efficiency
is
considered
100%.
A
comparison of the measured received power with that calculated theoretically using Friis transmission equation is
Proceedings ofintemational Bhurban Conference on Applied Sciences & Technology Islamabad, Pakistan, January 19 - 22,2009
lOl
VI. REFERENCES
shown in Fig 9. It can be seen that the two are in close agreement.
The
difference
between
theoretical
and
measured values can be accounted for if we consider scattering and polarization losses. The power received by the MSA is used as a source to a simulated rectifier circuit in Multisim that provides us with a DC power.
V. CONCLUSION
We have demonstrated in this paper that power can be transferred wirelessly using microwaves at 2.45 GHz ISM band. The efficiencies that can be achieved at a distance of 0.307 and 4 meter are 5.5% and 0.2% respectively with respect to the RF power transmitted. Since these efficiency values are with respect to the transmitted power, these take into account the space loss factor contrary to many papers which mention conversion efficiency with respect to the received power therefore not considering the space loss factor (SLF), which though can be improved by using more directive antennas but can not be done away completely. Since microwave oven RF source was used as transmitter, it was essential to couple the RF power to the transmitter. A calorimetric method was used to determine coupling efficiencies using loop antenna and a dipole antenna.
The change in temperature was noted
against different positions of the antennas for constant intervals of time. It was found out that a dipole antenna was more efficient. The coupled power was transmitted using monopole comer reflector antenna and received by MSA.
[ 1].Tesla, N. "Apparatus for transmitting electrical energy." U.S. patent number 1, 1 19,732, issued in Deceniber 19 14. [2]. Bemdie Strassner, Kai Chang "Integrated antenna system for wireless RFID tag ill momtoring oil drill pipe" IEEE 2003. [3].Zhu Xi Zhang, Xiaodong Wu Qingyu "Wireless Charging System Based on Switched· Beam Smart Antenna Technique" IEEE 2007. [4]. Masaharu Fujinaka, "The Practically Usable Electric Vehicle Charged by Photovoltaic Cells" IEEE 1989. [5].David C. Jenn, Robert L. Vitale "Wireless power transfer for a micro remotely piloted vehicle" IEEE 1998. [6].Makoto Takamiya, Tsuyoshi Sekitani, Yoshio Miyamoto, YOShlaki Noguchi, Hiroshi Kawaguchi , Takao Someya, Takayasu Sakurai "Design Solutions for a Multi-Object Wireless Power Transmission Sheet Based on Plastic Switches" resented at IEEE International Solid-State Circuits onference 2007.
&
[7].Jeroen de Boeij, Elena Lomonova, Jorge Duarte Member, Andre Vandenput, "Contactiess Energy Transfer to a Moving Actuator" IEEE 2006. [8].R. K. Chuyan, L. A. Kvasnikov, A. P. Smakhtin. "Wireless Power Engineering as New Development Stage of Microwave and Laser Engineering" IEEE 2003.
The received RF power was then simulated in a rectifier circuit and it was shown that the efficiency varies from 5.5% to 0.2% as the distance is varied from 0.307 m to 4 m.
Proceedings of Intemational Bhurban Conference on Applied Sciences & Technology Islamabad, Pakistan, January 19 - 22,2009
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