International Journal of Engineering Trends and Technology (IJETT) – Volume 16 Number 8 – Oct 2014
RF Energy Harvesting
Deep Patel1
Rohan Mehta1
Rhythm Patwa1
Sahil Thapar1
Shivani Chopra2
1
Undergraduate Electronics and Telecommunication, Dwarkadas J Sanghvi College Of Engineering
2
Graduate Electronics Shah and Anchor Kutchi Engineering College
Abstract- The aim of this paper is to investigate the levels of
power that can be harvested from the
surrounding
environment and processed to achieve levels of energy that are
sufficient to charge up low- power electronic circuits and
devices. Its implementation includes a RF generator in
Transmitter section. The RF energy transmitted by the RF
generator is picked up by a microstrip antenna in the receiver
section. This RF energy is passed through impedance matching
circuit and voltage multiplier circuit to get a resultant voltage.
II. BLOCK DIAGRAM
Keywords- RF energy, harvesting, Voltage doublers, Spectrum
analyzer, GSM, frequency response, antenna, voltage
multiplier.
I. INTRODUCTION
The major issue concerning the scientist nowadays is the
excessive use of natural gas and petroleum. It has been
predicted that these resources will be exhausted in the next
two or three decades. The overconsumption of petroleum
and natural gas has also caused adverse effect on the
environment. The scientists are trying hard to find the
alternate sources of renewable energies and reduce the
dependence on petroleum and natural gas. One such
alternative is “radio frequencies”. The radio frequencies are
electric energies that transmit through the air by ionizing the
medium on its paths. The radio frequency energy can be
easily found in surroundings as it is used widely by many
applications
like
television
broadcasting,
telecommunication, microwave etc. It is ubiquitous and free
and
highly
efficient.
The main aim of this paper is to investigate the levels of
power that can be harvested from the surrounding and to
achieve energy that is sufficient to charge low power
electronic circuit. Through a power generating circuit linked
to a receiving antenna this free flowing energy can be
captured, harvested and converted into usable DC voltage to
power up small devices.
ISSN: 2231-5381
II. WORKING
The working and testing was carried out in two parts first
wired and then wireless. Each is explained below in detail
along with the results observed:
A.Wired:
The passive receiver circuit consists of 3 stage voltage
doublers and temperature Sensor AD590 as a load. The
voltage doubler consists of SM components: Diode
SMS7630, a zero bias schottky detector diode from
skyworks and SM Capacitor which works in high frequency
range. A Marconi instruments transmitter which works in
the frequency range from 9KHz to 2.5GHz with maximum
power level 25dBm is used.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 16 Number 8 – Oct 2014
Initially to verify the efficiency of passive receiving
circuitry, we performed wired analysis. In this experiment,
the output of transmitter was directly connected at the input
of voltage. Doubler was connected at the receiving section.
The output was observed on Spectrum Analyzer working in
the range 9KHz to 2.9GHz. Two observation tables are
shown below:
Power versus Voltage and Current Table for Wired Module
at 840 MHZ. V and I measured at output of 3rd stage of
Voltage Multiplier.
TABLE I
Power Vs Output Voltage and Current
Power(dBm)
Voltage(V)
Current(mA)
24.9
24
23
22
21
20
19
1
17
16
15
14
13
12
11
10
8
6
4
2
0
-1
-2
-3
10.07
9.35
8.38
7.72
7.08
6.4
6.04
5.10
4.62
4.25
3.79
3.39
2.89
2.56
2.312
2.023
1.556
1.25
0.956
0.739
0.58
0.493
0.442
0.40
13.3
11.69
9.93
8.64
7.50
6.47
5.53
4.75
4.04
3.36
2.77
2.38
1.93
1.63
1.33
1.109
0.766
0.538
0.357
0.233
0.148
0.115
0.088
0.067
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Frequency(MHz)
750
780
800
840
850
900
950
1000
1050
1100
1150
1200
1300
Voltage(V)
1.76
2.03
1.66
3.128
3.03
2.7
2.21
2.18
1.33
1.62
2.28
1.83
1.15
Current(mA)
1.45
1.37
1.12
2.4
1.98
2.72
1.83
1.61
1.43
1.66
1.34
1.219
0.59
Table IV
Output of Temperature Sensor
Power(dBm)
TABLE II
Output Voltage and Current at each stage of Voltage
Multiplier
Voltage Vo(V)
2.64
8.48
13.14
TABLE III
Frequency Response of Wired Module
Temperature Sensor
Testing stages of Voltage Multiplier of Wired Module at
840 MHz with output power 24.9 dBm
Stage
1 st
2 nd
3 rd
Frequency versus Voltage and Current Table for wired
module at 15dBm. V and I measured at output of 3 rd stage
of Voltage Multiplier.
24.9
Supply
Voltage(V)
11.5
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10.57
9.52
8.56
7.56
6.55
5.86
4.84
4.09
3.19
2.71
2.36
2.06
1.78
1.61
Output
Voltage(V)
0.305
0.306
0.257
0.2843
0.316
0.324
0.332
0.333
0.335
0.339
0.338
0.303
0.237
0.185
0.135
Current Io(mA)
11.3
10.1
9.2
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International Journal of Engineering Trends and Technology (IJETT) – Volume 16 Number 8 – Oct 2014
B. Wireless:
From the above analysis we can conclude that this receiving
circuitry can be used wirelessly. Here at the receiving
section, a GSM antenna is used and now LED is taken as a
load. As our motive is to harvest RF Energy which is
available in bulk in our surrounding, we have used a mobile
phone working in GSM range. Whenever we receive or
make a call, text or use internet, the device works on
different uplink and downlink frequencies. This energy is
harvested using receiving circuitry.
When a call was received on cell phone and with negligible
distance between cell phone and receiving circuitry, we
observed that LED was ON for the duration of Call.
A. Environmental/Pollution
Sensor
Wireless
environmental and pollution sensor can be designed
using this system. The major advantage is that we can
have sensors which will not require an external power
supply or a battery. They can be powered by the RF
energy radiated from the cellphones. They can be
switched on when sufficient energy required to run the
sensors is stored.
B. Remote Activation - In this application we can avoid
continuous broadcast using this energy harvesting
technique. Hence only when required we can activate it
and thus save a lot of power which may otherwise be
used due to continuous broadcast.
C. Home Automation Systems - These systems would
benefit the most out of energy harvesting. This is
because it would completely cut off all the wiring that
would otherwise be required as the RF energy would
power the system. Also every system in each room
would be an independent system having their own
source.
IV. ADVANTAGES:
Figure 1- Harvesting the Mobile’s RF energy.
Figure 2- Detecting of LED which indicates energy has
been stored
III. APPLICATIONS
The RF Energy Harvesting System has the following
applications:
ISSN: 2231-5381
A. Ubiquitous- This RF energy is ubiquitous. It is
available anywhere and everywhere. Thus the
energy can be harvested from anywhere and used
to power up small devices. In contrast, systems
that rely on thermal gradients or solar power might
have special location considerations.
B. Alternative for electricity: RF energy harvested
can be used as a replacement for electricity, thus
saving this non-renewable power. Thus this type of
energy harvesting is renewable and most feasible.
C. Alternative for batteries : The use of batteries has
two disadvantages: the lifetime of the batteries is
very limited even for low-power batteries,
requiring
impractical
periodical
battery
replacement. If this harvested RF energy is used to
charge devices, then there is no need for a battery.
V. LIMITATIONS:
A. Human health: High frequency signals power is
limited by regulations due to safety and health
concerns offered by electromagnetic waves. Therefore
there will not be enough power for triggering active
elements. Passive elements will be used to minimize
the amount of power being consumed by these
elements to achieve a circuit that can be adapted to
harvest RF signals.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 16 Number 8 – Oct 2014
B. Limitation in size and shape: In order to provide the
maximum capturing power, the transmitting and the
receiving antennas should be of the same shape, size
and polarization.
C. Not enough power: Currently, energy harvesters do
not provide sufficient amount of power to produce
Mechanical movements or temperature changes
(cooks, refrigerators, etc) because there aren’t
technologies that capture energy with great efficiency.
But these technologies do provide the amount of
energy needed for low-power devices that can operate
autonomously.
D. Losses: There many types of losses involved in RF
communication system.
1) Wire loss (Skin Effect) – It is the tendency of
alternating current to become distributed within the
conductor. The skin effect causes the effective
resistance of the conductor to increase at higher
frequencies.
2) Mismatch loss– It results due to the improper
matching in impedance of two consecutive stages
which forms Standing Waves and loss of power.
3) Radio path loss–It is reduction in Power Density of
an Electromagnetic wave as it propagates through
space.
low, it can be sufficient for running low consumption
sensors and switches.
Improvements on efficiency of the RF signal harvesting is
important. This will enable more current to be re-cycled and
operate low-power circuits. The possibility of using this
harvester in energizing sensor networks appears to be the
most practical use at the moment.
Finally, we have presented a new technology that can
revolutionize the way we charge our numerous mobile
devices. It helps portability of devices without carrying
chargers around.
VII. REFERENCES
[1] Buananno, M. D'Urso and D. Pavone, “An Ultra Wide-Band System
for RF Energy Harvesting”, IEEE Journal of Antennas and Propagation
(EUCAP), Proc. 5th European Conf. , p. 388, 2011.
[2] Maryam Al-lawati, Manar Al-Busaidi, Zia Nadir, “RF Energy
Harvesting System Design For Wireless Sensors”, IEEE Journal, 9th
International Multi-Conference on Systems, 2012.
[3]http://blogs.intel.com/technology/2012/08/wireless-chargingtechnology- %E2%80%93-one-step-closer-to-reality/
[4] Daniel W. Harrist, “Wireless Battery Charging System Using Radio
Frequency Energy Harvesting”, University of Pittsburgh, 2001.
[5] Mahima Arrawaita, Maryam Shojaei Baghini, Girish kumar, “RF
Energy Harvesting Systems From Cell Towers in 900 MHz Band”, IEEE
Journal.
VI. CONCLUSION:
This report presents the design of RF Energy Harvesting
System. The potential utilization of RF signals for DC
power is experimentally investigated. Several steps are
taken to achieve this methodology. A thorough study of
various topologies of Impedance Matching, Antennas,
Voltage Multipliers have been discussed. Based on that, we
have chosen effective topology for each block.
[6]http://blogs.intel.com/technology/2012/08/wireless-chargingtechnology- %E2%80%93-one-step-closer-to-reality/
As a result of this overview, m derived Band pass filter is
designed to give a constant impedance over the selected
frequency range and Series RLC is chosen for one particular
frequency. The Microstrip Antenna having gain 7dB to 9
dB for a square patch and an omni - directional monopole
antenna suits our requirement.
Based on measurements and simulations, it can be
concluded that it is possible to use radiated, off-air RF
signals as a source for energy harvesting. Even though the
output powers of such harvester are expectedly relatively
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