IEEE Department of Electrical Engineering Army. Public College of Management Sciences. 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. Index Terms Azimuth LabView Line of Sight Microwave Receiver Transmitter Ultra Wide Band I. Introduction. This 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 uninterrupted 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 antennas 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. D 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 a 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.
