M.U of today and is of immense telecommunication

 

M.U Mustafa, M. Nabi, M. Fahim, Dr. K. Khursheed Member, IEEE
Department of Electrical Engineering
Army Public College of Management Sciences (APCOMS)
Khadim Hussain Road, Lalkurti, Rawalpindi 46000
email: [email protected], [email protected], [email protected] [email protected]

Abstract- This paper highlights the various implementation and
uses of aligning antennas. It also put emphasis on the modern day applications
and how aligning antennas can be used in a broad spectrum for achieving
different goals. It illustrates the basic ideology of two different ways
alignment can be useful. Furthermore, an in-depth analysis covers different
alignment scenarios and techniques, the results achieved by them, and how
influential the results can be on modern society.  The goal of this overview is to get a better
understanding of why do we need to align antennas and why this field should be
explored further. 

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Index Terms—
Azimuth, LabView, Line of Sight,
Microwave, Receiver, Transmitter, Ultra Wide Band

 

 

 

I.                   
INTRODUCTION1

T

his document gives a comparative analysis
of two different applications of antenna alignment and aims at providing a detailed
overview to both implementations. One of them is focused at the degree of
precision possible while manually aligning, while the other is aimed at
providing an overview to automatic antenna alignment. The importance of
alignment of antennas is an undeniable fact as of today and is of immense
telecommunication advantage. 1-2 Technology is moving towards higher data
rate and it is only a matter of time before we become greatly reliant on directional
antennas as a primary source of communication. Nonetheless, various limiting
factors are also part of this technology.

                Since wireless communication is the single most
common used method of communication, it is only evident that this medium be
used optimally. The implementation techniques used are promising horizons of
this domain and aim at increasing ever higher wireless fidelity while
maintaining a sustainable degree of practicality.

For this purpose, the first technique is aimed
at testing range measurement in different phases. A pair of miniature UWB
antennas; working as transmitter while the other as receiver has been used. In
the first phase, LOS measurements are being done while keeping both antennas in
free space. While maintaining the transmitter stationary, the tests are
repeated when the antennas are rotated on y-axis (vertical axis).

Ranging analysis is also performed on human arm.
Similarly is also carried out as to evaluate the performance when different
hindrances are put between antennas. The second technique involves Received Signal Level (RSL)
as a means of providing un-interrupted telecommunication in 2D (Azimuth and
vertical planes) while eliminating the human component required to manually realign
antennas.

II.                 
TECHNIQUE
ONE REVIEW

A.                  
Setup
Phase

The first methodology was studied under three phases. A pair of
miniature UWB antennas was used for this investigation. A miniature CPW-fed
tapered-slot UWB antenna designed for on-body communications has been used in
testing. The antenna is low-profile, very compact and lightweight. It is
designed and fabricated on Rogers RO3210 substrate with a relative permittivity
of 10.2 and thickness of 1.25 mm. It is 7.9 mm × 16.38 mm in overall physical
size including the antenna feed connector. A miniature SMP connector from
Jyebao 3 is used to feed the antenna. The impedance bandwidth of the antenna ranges from 4.9 GHz to beyond 11
GHz.

In the first phase, line of sight measurements
were done with the antennas in free space. This was done with the transmitter
antenna rotated in vertical plane. In the second phase, the ranging tests were
placed on the arms of a human test subject. The arm was then moved in the
vertical plane and its effects, such as accuracy, were studied. Lastly, ranging
analysis was performed when the line of sight was obstructed by different
hindrances. 

 

Figure
1 showing various rotating positions

This testing stage was settled to be a reference
point for subsequent testing phases. The UWB miniature antennas were setup as
such so that the right rotation was indicated as positive while the left
rotation was indicated by negative values. The rotation was carried along the
vertical plane. The receiver antenna was kept stationary during testing
process.

Figure
2 showing various tilting positions

Similarly, four other tests were carried out,
this time with the TX titled towards its front and back sides with the same
angles of 30° and 45°. Similarly, the antenna’s rotation towards the back side
was represented by negative values and the front side tilting was indicated by
positive values. The measurements were done with the distance between the two
antennas set as 50 cm and 100 cm for each orientation setup. In order to tilt
the antenna at the required positions, angled lines were sketched on a
polystyrene sheet and the antenna was then fixed on these lines to get the
appropriate tilt.

The measurements carried out on the human
subject were done with the help of two identical UWB antennas operating at 4.9
GHz. The transmitter was placed on the right wrist and the receiver was placed
on the shoulder. Cotton pad of 2mm thickness were used to provide air gap
between the skin and the antenna. The subject was to place his elbow on a flat
surface at 90° with his shoulder and start tilting it. The purpose was to
provide tilt according to the vertical plane while keeping the horizontal plane
as stationary as possible, ideally fixed. This experiment was repeated ten
times and results were recorded.

Figure
3 showing the UWB pair of antennas on the human
subject

B.                  
Computations
and Finding Phase

All the measurements were done inside the
Antenna Lab at Queen Mary University of London using an Agilent N5232A PNA-L
vector network analyzer 4. Firstly, the transfer function between the TX and
RX was found by connecting the setup to the network analyzer. Then, Inverse
Fast Fourier Transform (IFFT) is performed on the measured transfer function
data. This converts the data to the time domain from the frequency domain and
provides the Channel Impulse Response. This gives the signal Time of Arrival
(TOA), which is the time it takes for the signal to propagate from the
transmitter to the receiver. This TOA value is then used for range estimation
between the transmitter and the receiver antenna by multiplication with the
speed of light.

The absolute error values obtained in the range
estimation were subsequently commutated and where shown in the following
graphs.

C.                 
Results

 

 

Figure
4 showing results for antenna tilted sideways
(top) and antenna tilted front and back (bottom)

From the results it is clear that millimetre accuracy between the TX and
RX is achievable. The maximum error present was obtained at 0.45 cm when the antenna
was tilted 30°.

 

Figure
5 showing the Absolute Error for the Human Arm
experiment

 

The tilting of the forearm on the human subject was done with the
increment of 10°. Hence when the arm was flat on the surface, it was represented
by 90°. From the results, it can be seen that good level of accuracy can be
achieved if the TX and RX are mounted on the human body. Accuracy of 1cm or
better was achieved in most cases except when the arm was tilted at 60°. The
maximum error was of 2.45cm and it is observed when the forearm is flat on the
table. The average error was around 0.75cm. The ranging estimations were having
slightly more error then the free space ones, since it was not possible for the
human subject to stay 100% still for an extended period of time. The results
indicate that a high to fair degree of accuracy can still be achieved when the
antennas are mounted on a human subject.

 

A.       

B.       

C.       

Non Line of Sight Testing

Non line of sight testing included different
obstruction placed between the TX and RX. Tests were then carried out to
determine the absolute error in the readings. None of the hindrances were
greater than 1.8cm thick. The results were showing a distinct increase in
Absolute error while a hand was placed in between both of the TX and RX.

On the other hand, cardboard had almost no
effect when placed 50cm distant from the receiver.

 

 

Figure
6 showing non LOS absolute error

 

E.      
Conclusion

This method of line of sight projection actually
demonstrates its effect on accuracy and it’s limitation in certain scenario
when complex structures are present in the path between the TX and RX. This
actually demonstrates why it is essential to keep LOS free from physical
interruptions. This is especially true in cases like transmitting outer space
images from space stations back to earth. The path must be clear from
meteorites and other obstructions. 

The results from free space and human mounted
antenna showed a promising level of accuracy which can be achieved. This can be
particularly useful for soldiers wearing combat gear in snowy areas. This setup
can be used to track and communicate with them individually. It can also be
used to track record and send a patient’s vital monitoring signs to a hospital,
and get medical aid more swiftly in case of a cardiac arrest or asthma attack,
where each second can decide the life and death of a person.

 

                                                                                                                                               
II.        
TECHNIQUE
TWO REVIEW

A.                  
Setup Phase

This method
focuses on establishing alignment of antennas on Base Transceiver Station. This
is done so in order to eliminate the human component. As of now, the current
alignment technique relies on tower crews know as riggers. Riggers are provided
with test equipment so that calibration is achieved on both ends of the
microwave link.

 The process starts by generating the signal
in an in-door transmitting station where the power is set according to
requirements. The signal is then passed onto the physical IF channel. This IF
channel serves as an interface between the indoor transmitting facility and the
outdoor receiving station which is commonly a radio device or an antenna. The
signal is then transferred through an RF source over a free space link. On the
other end, a transceiver receives the signal which it was looking to, since it
is the same frequency as the transmitting end.

 This sets up the basic communication between
two stations. The quality of the signal received depends upon the optimal
direction of the two stations. If the stations are aligned in terms of
antennas, highest signal strength will be received through the main lobes, and
the attenuation will be at its lowest. 5-7

Figure
7 showing MW link between Near End and Far End
Antennas

B. Computation Phase

The logic implemented that setup is of a closed
loop system where all the parameters are set according to 45dbm as optimal RSL
level. If 45dbm is achieved, antennas are considered aligned, otherwise
automation process starts. The alignment will be in dual axis i.e. horizontal
and vertical. This is done by means of motors, PID controllers and other close
loop feedback systems in practice.

 The
current mechanism approach in this automation system consists of LabView and
robotics RCX trainer kit. Both modules are programmed independently and
interfaced by electrical and mechanical means. The principle behind this setup
is that the system will work as a “cause and effect” system, where
misalignment will be the cause prompting for alignment. LabView is used for
this purpose to avoid complicated setups and cost. LabView is a product of
National Instruments. It provides a user interface for the realization of most
applications from wireless to motorized systems. 8-9

 The input
device that is interfaced with LabView is tektronix real time microscope. This
is used to measure the RSL level from the receiver unit. Its virtual
counterpart used in LabView is found under the “Instrument I/O
Assistant” palette which is used to write data on LabView and it is setup
to measure peak to peak voltage. This palette is kept outside the operational
loop to give a continuous feed to the system. Apart from Instrument I/O
palette, the remaining building blocks are kept inside the While Loop.

Figure
8 showing the RSL Measurement Process

Figure
9 showing LabView Setup Simulation

 

C. Conclusion

 The
automation of antenna alignment for telecommunication systems have been
demonstrated successfully. In this setup, loop antennas have been used, however
further modification can be made so that other types of antennas are used. Many
factors are to be considered for the physical setup such as response time of
automation, different tilting and azimuth angles, etc. This can be a promising
solution for areas of limited telecommunication connectivity, such as hilly and
snowy areas. In those areas, storms are common. It is not feasible to send
riggers for recalibration of antennas, rather, this system can be used so that,
maximum service time is available for the customers.

 

III.              
CONCLUSION

Antenna alignment can yield promising results in
the future where high speed communication relies on higher bandwidths to be
used more optimally. To automate this process where possible would further help
its implementation. The uses of this technology are relatively new and research
needs to be done in order to overcome the limitations. Such system would not
only help in the advancement of science but may also open up new horizons in
the field of outer space communication, SmartCity IoT grid installation to name
a few.

 

IV.               
REFERENCES

 

1     P. S. Hall and Y. Hao, Antennas and Propagation
for Body-Centric Wireless Communications, 2nd ed. Artech House, 2012.

2     L. Taponecco, A.A. D’Amico and U. Mengali,
“Joint TOA and AOA estimation for UWB localization applications,” IEEE
Transactions on Wireless Communication, 2011, pp. 2207-2217.

3     Jyebao RF and Microwave Co., Product Catalogue,
Online. Available: http://www.jyebao.com.tw/files%20download/SMP.pdf

4     “Agilent 2-Port and 4-Port PNA-L Network
Analyzer,” 2013. Online.

Available: http://cp.literature.agilent.com/litweb/pdf/N5235-90004.pdf.

5                     Goldsmith,
Andrea: “Wireless Communications”, CambridgeUniversity Press. ISBN 0521837162.
2005.

6                     Exalt:
“Technical White Paper Microwave Fundamentals Series Antenna Alignment for
Terrestrial Microwave Systems”, April 2011.

7                     Alain
Tougas and Susan Einhor: “MicroWorlds EX Robotics,” LEGO RCX Edition, ISBN
2-89371-536-2, September 2003.

8                     NI
Team: “Introduction to LabVIEW; Three-Hour Course,” Part Number 323668B-0,
2003.

9                     Nick
Golas: “Tips Tricks and Techniques for Efficient LabVIEW Development,” IEEE
I&M Society LI Section & Long Island LabVIEW Users Group (LILUG), June
2007.

 

 

 

 

 

1 @This work was
supported in part by the University of Engineering and Technology, Taxila under
their IEEE readership access to the authors.

Assistant Professor Kiran Khursheed
is an assistant professor in the Army Public College of Management and Sciences
(APCOMS), Khadim Hussain Road, Rawalpindi 46000, Pakistan (email: [email protected]). She is
currently doing her PhD from MCS (NUST) Pakistan. Her specialization in Antenna
and RF technology has lead her being one of the few pioneers in this domain in
Pakistan. Her thesis includes implementation of 4G Technology in Pakistan.

 M. Nabi, is affiliated with APCOMS and is
pursuing his BSc Electrical Engineering degree with distinction. His works
includes numerous projects such as autonomous robots among others.

M. Fahim is currently finalizing his
BSc Electrical Engineering degree from APCOMS and has been awarded numerous
awards during his academic career which include scholarship from APCOMS. His
hobbies include prototyping and robotics.