Wireless Power Transfer Using Microwaves At 2.45 GHz ... - IEEE Xplore

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the technology is more mature. Highly efficient, super directive array configuration would have the potential of concentrated and directed microwave beam that.
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

102