International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue5- May 2013
Compatible Antenna for Software Defined
Radio and multi range RFID reader using ATU
Salman khan pattan#1, Suresh Angadi*2,
#
Final Year B.Tech, Dept. of ECE, KL University, Vaddeswaram, AP, India
Assistant Professor, Dept. of ECE, KL University, Vaddeswaram, AP, India
*
Abstract: Software defined radio is a wireless
communication platform where the hardware
components used in communication systems are
replaced with software components. The signals can be
received using different types of antennas like Smart
Antenna systems and the Automatic antenna Tuning
Unit system. RFID is the detection of the Radio
Frequencies with the use of extremely low powered tags.
Readers are present for this purpose but are only for
the limited frequency ranges. But by fixing Automatic
antenna Tuning Unit to the combination of RFID
reader and SDR, multi range frequencies can be
detected. This provides a better result in the RFID
technology.
Key words—software defined radio (SDR), Radio
Frequency Identification (RFID), smart antenna,
Automatic antenna Tuning Unit (ATU).
I.INTRODUCTION
Software defined radio is a wideband
communication system in which all the hardware
components used for signal processing are
implemented on a software platform using highly
sophisticated software tools embedded into Digital
Signal Processors and Field Programmable Gate
Arrays. Generally for the purpose of perfect
modulation and demodulation we are using
modulators, demodulators and mixers using different
hardware circuits but this method sometimes
generates erroneous results and also the components
used are expensive. To avoid these problems
replacing all these circuits with SDR is an
appropriate solution. Any new changes in the
procedures can be easily modified, dumped and can
be implemented.
Development of the concepts on the SDR were
started earlier in 1990s and now this technology has
become a sophisticated module in the wireless
communications. Moreover, SDR became the basis
for the 3G and 4G wireless communications. From
the world’s first wireless technology introduced in
the olden days to the present 2G communication
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there were several and rapid changes involving huge
amount of innovations.
As SDR introduced such a highly sophisticated
environment, it would be worth full to use other
interfaces to also be with the same pace. Thus the
major interface of signals with the circuitry i.e the
antennas used are smart antennas and ATUs. A smart
antenna consists of an array of antennas which
deploy the methods of Direction of Arrival (DoA)
estimation, spatial multiplexing and vector channel
estimation. Different architectures and models were
developed by Joint Tactical Radio System (JTRS)
Joint Program Executive Office (JPEO) and Object
Management Group (OMG). ATU consists of a
tunable antenna circuit which tunes the antenna by
detecting the signal in order to receive a particular
signal. RF MEMS are used in the ATU for the
purpose of switching and also changing the
impedance values.
RFID technology is the detection of the unique
code embedded in a small chip attached to the
antenna by the process of transmitting and receiving
the reflected signal from the RFID tags. For the
purpose of transmitting special devices are available
in the markets which are called RFID readers.
Generally the RFID readers available in the market
detect only particular range of frequencies. But by
implementing the ATU with the RFID readers and
SDR it is possible to detect any radio frequency, thus
deriving a multi range RFID reader.
II.SOFTWARE DEFINED RADIO
An SDR is a wireless communication system that
can tune up to frequencies in the range 500MHz2GHz, receive the arrived signal, process the signal
to the specific requirements using the software tool
kit and then if necessary it transmits the signal with
the specified frequency range. SDR contains different
blocks as shown in the figure 1. The receiver receives
the signals, and then the down converter changes the
frequency from a higher range to the lower level. The
purpose of down converting is that the electronic
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue5- May 2013
devices don’t support such high frequencies and
sometimes the equipment may get damaged. Now the
down converted analog signal is digitized using the
Analog to Digital converter (ADC). All the digital
signals are now processed using the software tool
kits.
The software operations can be performed in either
Digital Signal Processors (DSPs) or Field
Programmable Gate Arrays (FPGAs). But the number
of operations in the SDR are more because of more
processes are involved for the signal processing. So
the DSPs are not sufficient because the present DSPs
can only process only ten thousand MIPS (Million
Instructions per Second). Thus using the DSPs in the
SDR makes the equipment much costlier. The other
alternative cum advanced technology available for
such multiple functions is FPGA which is cheaper
and also performs the functions at the required rate.
All the software techniques designed for SDR like
modulation, mixing etc are done using FPGA. After
FPGA the application is done on the specified
module or handset. If the signal is to be transmitted
from the device then the reverse procedure is
followed. To perform different operations in the SDR
respective algorithms are developed. The main
advantage of the SDR is that if the processes are to be
changed then an algorithm for the procedure is
developed, it can be embedded into the integrated
chip and can be executed. Thus it becomes easier for
any type of modification to be done. There are
different software organizations like JTRS JPEO to
develop the algorithms.
Fig 1 Block diagram of Software Defined Radio
III. ANTENNA USED FOR SDR
For the purpose of detection of signals we have
different types of antennas, but among the available
varieties the most suitable and efficient types are
Automatic antenna Tuning Unit system and Smart
antenna systems. This paper describes the usage of
these antennas for the SDR communication systems.
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a) Automatic antenna Tuning Unit (ATU)
To have an effective and efficient communication
between different modules, the antennas should be
highly gainful so that there is no loss in signal
reception. ATU is one such antenna that provides a
wideband signal reception capability. Different
blocks present in the ATU system is shown in Fig 2.
The tunable patch antenna with a surface mounted
variable capacitor circuit is used for the purpose of
signal detection. The patch antenna is shown in the
fig 3 and the relevant variable capacitor circuit is
shown in fig 4. When the signal is reached at the
antenna then the electromagnetic wave gets induced
into the inductor in the capacitor circuit, which
generates the voltage. Depending upon the voltage
received at the capacitor side of the circuit the
capacitance gets adjusted. Suppose when the signal is
not there at the inductor side then the voltage is zero
and the diode gets switched OFF, which makes only
one capacitor C1 to work making the circuit a passive
circuit. Thus at this level the system becomes
inactive. Now when any signal is received, then the
voltage is increased, the circuit gets activated and the
capacitance gets adjusted by varying C1 and C2.
An impedance synthesizer circuit is present which
always tries to match the circuit impedance with the
received wave impedance. In this process if different
frequencies are received at different times, then
different impedances are to be provided. So for this
purpose RF MEMS (Radio Frequency Micro electro
Mechanical System) are used to switch from one
value to the another value. RF MEMS are nothing but
the electronic components of which moving sub milli
meter sized parts provide RF functionality. The
impedance synthesizer is connected to the patch
antenna using an SMA (Sub Miniature Version A)
connector whose impedance is 50 ohms. These
impedance synthesizers have combinations of
different inductors and capacitors and these are
mainly used to match the received signal with the
circuit.
In order to constantly monitor the signal to noise
ratio the incident and reflected power levels are
measured with the help of the RF power sensor
placed next to the impedance synthesizer. The SNR
should be high so that we get a proper signal instead
of noise. The directional coupler is used to allow the
reasonable and correct signals into the SDR module.
After the signal is undergone all these steps it is sent
to the towards the SDR unit where further
proceedings will take place. This type of ATU can be
used to detect the frequencies in the range of
500MHz-2GHz. The SDRs are mainly concentrated
on the newly sophisticated wireless communications,
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so for the purpose of such speedy communications
we need such type of antennas which can exist at any
type of communication environments. Moreover the
applications that are being developed now a days are
demanding the Automatic antenna Tuning Unit
systems for their efficient performance in the real
time communication systems.
Fig 2 ATU system Block diagram
Fig 3 patch antenna used for ATU
Fig 4 Equivalent circuit of variable capacitor
y=∑ w* x
Where y is the output from antenna, w is the beam
forming weights and x is the individual antenna
components.
b) SMART ANTENNAS
Smart antennas (SA) consists mainly an array of
antennas which are used to spatially detect the signals
in order to avoid the effects like multipath fading,
interference etc. A specification was defined for the
smart antenna system named SA API (Smart Antenna
Application Programming Interface) which mainly
concentrated on the software components and
algorithms related to a particular model. For the
purpose of SA systems different models were
developed since the research on SA was started in
1960s. But for the SDR like applications a Platform
Independent Model (PIM) was developed in which
the software only knows the elements of SA system,
but after implementing such a PIM the Platform
Specific Model (PSM) was developed in which all
the software required for the SA system was
embedded. Smart antenna system consists of different
subsystems which are shown in the figure 5. All these
subsystems are considered to be a SA System.
By using this SA system a perfect signal can be
received/generated. Antenna Array consists of
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multiple antennas which are spatially placed,
moreover the purpose of using multiple antennas is to
receive the signal without any loss. Most of the times
the signals are very much affected to the losses like
multipath fading and interference. To avoid such
losses, use of multiple antennas to cover each and
every part of the signal is advisable. RF/IF
subsystems consists of different blocks like low noise
amplifiers (LNA), mixers, IF section, A/D or D/A
converters etc. The Modem subsystem is for
performing the actions on the signals like modulation
and demodulation. SA subsystems consists of the
algorithms, calculation units etc. MAC layer
subsystem is used to provide multiple channels on a
single platform. Based on the signal processing
technique used the SA systems are of different types
like Beam forming systems, Diversity combining
systems, Multiple input Multiple output systems and
space time equalization systems. The main advantage
of smart antennas is that they always gives the details
of Direction of Arrival(DoA) which can be used to
align the antennas for the future reception to be
perfect.
Beam forming systems mainly concentrates on the
beam pattern in order to receive and transmit in a
specific direction. Beam forming is also known as
spatial filtering or spatial diversity combining. In this
technique all the signals of the respective antennas
are collected by using their complex weights and then
combined to generate the specified output.
The above equation gives the summed result of each
antenna’s component multiplied to its complex
weight. Adaptive beam forming is a technique in
which the antennas are steered in the particular
direction automatically in which the signal strength is
better. Various beam forming algorithms were
developed for optimizing the SNR and minimizing
the interference. Finally among different types of
Smart Antenna systems available the most
advantageous system is beam forming system
because it is covering all types of defects present in
transmission process.
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b) RFID readers
Fig 5 Smart Antenna system Methodology
IV.RFID TECHNOLOGY
Radio Frequency Identification (RFID) is a latest
technology that is mainly used for detecting a unique
code specified for a particular object. Now a days this
technology is replacing the barcode detecting devices
because of its efficient performance and also power
consumption parameters. RFID technology is being
used for collecting tolls without stopping vehicles,
counting the number of items, offices, airports etc.
The main components needed for using the RFID
technology are RFID tag, RFID reader and the
programming unit. Generally the programming unit
that could be used is the Microcontroller unit. In the
microcontroller the programming is done using either
embedded C language or Assembly language. The
details of the tags are stored in the microcontroller
and can be accessed during the presence of the tag.
The problems related to this type of procedure and
solutions are discussed in this paper along with the
range extension solution for the RFID reader.
a)RFID tags
RFID tags are a combination of a small integrated
chip and a coil which acts as an antenna. These two
components are joined together and used as a tag
(transponder) which are in the shape of a small
identity card provided in the offices. The IC consists
of an EPC (Electronically Programmable Code)
embedded into it during the time of manufacturing.
Figure 6 shows an RFID tag. There are two types of
RFID tags, Active tags and Passive tags. Active tags
have a battery embedded into them, where as the
passive tags doesn’t have any battery. The power
supply is obtained by the signal that is transmitted
form the RFID reader.
Fig 6 RFID tag
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RFID readers are the devices which detect the EPC
embedded into the IC. RFID reader generates a signal
of particular frequency of its specified range, when
the tag is brought near the RFID reader then this
signal gets induced into the coil (antenna) fixed in the
tag. This induced signal generates a very small
current in the coil and is passed along the coil
towards the IC. When the current reaches the IC, it
gets activated and reflects the current back along with
the EPC. Now these reflected signals encounter with
the antenna of the RFID reader. Then the reader
detects the code present in the RFID tag. RFID
readers are available in different ranges of
frequencies as listed in the table 1.
Frequency range
Range
13.6 MHz
1m
433 MHz
1-100 m
902-928 MHz
1-2 m
2450-5800MHz
1-2 m
3.1-10 GHz
1-200 m
c) Programming unit
The code received from the tag should be sent to the
programming device in order to know what action
has to be taken on the tag. For this purpose we can
consider the microcontroller unit or ARM processor.
But the microcontroller has some delays and
moreover in order to process the tag we need to have
memory. For example the tolls that should be
collected from huge number of vehicles, are to be
stored in a single IC which is to be implemented at
every toll plaza. But such implementation of memory
devices at many places is expensive and non
affordable. We can use another alternative as SDR
for the purpose of processing and storing the details
of the tag.
V. Multi Range RFID reader USING ATU and SDR
The readers available in the market are operated only
in a particular frequency ranges but by using
Automatic antenna Tuning Unit system we can make
the RFID reader to detect the signal of any frequency
range depending on the efficiency of the ATU
developed. The ATU discussed in this paper detects
the frequency in the range of
500 MHz-2GHz.
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue5- May 2013
The block diagram of multi range RFID reader using
ATU and SDR is shown in figure 7.
Fig 7 multi range RFID reader using ATU and SDR
The RFID readers available consists of normal
antennas depending on the frequency range used for
the reader. Now these antennas can be replaced with
the ATU system. By replacing this the frequencies in
the ATU detecting range can be accessed easily. Thus
a multi range RFID reader could be developed which
can work for any kind of RFID tags. By
implementing this module the memory required for
storing is reduced and also the accessing speed is also
increased.
An SDR is placed after the RFID reader, which is
used to process the received tag information. A
common database could be maintained on the
internet. When the tag reaches the toll plaza the code
is detected and sent to the SDR. The SDR now using
the database available on the internet checks for the
code and can cut the required amount from the
account of the user.
for performance characterization of RFID tags IEEE transactions
on instrumentation and measurement, VOL 61, No 4, APRIL 2012.
[3].Muhammad islam, M A Hannam, S A samad and A. Hussain
“Software defined radio for RFID Application”.
[4].sung hoon oh, hang song, james T.aberle, bertan Bakkaloglu
and caitali chakrabarti “Automatic antenna tuning unit for software
defined and cognitive radio”.
[5].KE-LIN
DU
&
M.N.S.SWAMY
“
WIRELESS
COMMUNICATION SYSTEMS for RF subsystems to 4G
enabling Technologies”.
[6]. Software Defined Radio Forum, 2007 [online] Available:
http://www.sdrforum.org.
[7]. Kin Seong Leong, “Synchronization of RFID Reader
Environments”, IEEE from Proceedings of 2006 Symposium on
Applications and Internet, Jan. 2006
[8]. Afshin Haghighat, “A review on essentials and technical
challenges of software defined radio”, IEEE British Crown, 2002
[9]. Aberle J, Bakkaloglu B, Charkrabarti C, et al. Automatically
tuning antenna for software-defined and cognitive radio.
Proceedings of the 2005 Software Defined Radio Technical
Conference, 2005.
[10]. Oh S-H. Automatically Tuning Antenna System for Software
Defined and Cognitive Radio. Ph.D. Dissertation, Arizona State
University, May 2006.
[11]. Aberle J, Oh S-H. Reconfigurable antenna technology for
VHF/UHF applications. Technical Report, General Dynamics
Decision System, Oct 2004.
Biography
VI. CONCLUSION
In this paper the antennas used for the SDR were
discussed. The SDR is going to be the main basic
module for the future wireless communication
technologies like 3G and 4G communications. The
process of implementation of the multi range RFID
reader using ATU and SDR is also discussed. The
software tools used in the SDR are making easier task
to embed any software and change the
communication techniques like modulation, mixing
etc. The hardware and software tools used in the SDR
are making the wireless communication system
cheaper compared to the present day technologies.
Thus SDR is going to replace many wireless
technologies in the future.
Salman khan pattan was born in
1991, Vijayawada,Andhra Pradesh.
He is studying final year B-tech in
K L University. He has done a
project on RFID technology. His
area of interest is communications.
Email: salmanece857@gmail.com
Suresh Angadi* is presently
working as a Asst.Professor in K
L University. He received his
B.Tech degree in electronics and
communication in G.V.P College
of Engineering, vizag, 2007 and
completed M.Tech in Maulana
Azad
National
Institute
of
Technology (MACT) in 2009,
Bhopal. His research interested
area is communications.
Email: Suresh.a@kluniversity.in
REFERENCES
[1].Seungheon Hyeon,
June Kim, and Seungwon Choi, Hanyang
University “ Evolution and standardization of the smart antenna
system for software defined radio”.
[2]. Luca catarinucci, Danilo De Donno, Riccardo Colella, Fabio
Ricciatio and Lucianno tarricone “A cost effective SDR platform
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