EE 491 PR P ROJECT LABVIEW BASED AUTOMATIC ANTENNA PATTERN MEASUREMENT AND GAIN CALCULATION
SUBMITTED BY: İsmail YILDIZ – Göksenin BOZDAĞ SUPERVISOR: Asst. Prof. Dr. A.Sevinç AYDINLIK BECHTELER Fall, 2010 – 2011 1
CONTENTS ABSTRACT…………………………………………………………………………………...............
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A)INTRODUCTION……………………………………………………………………………………
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1.LABVIEW PROGRAMMING…………………………… PROGRAMMING………………………………………………………… ……………………………………. ………. 5 2.ANTENNA PATTERN&GAIN………………………………………………………………... 5 B)MEASUREMENT SYSTEM……………………………………………………………………… 6 1.SETTING UP LABVIEW……………………………………………… LABVIEW………………………………………………………………………… ………………………… 9 2.BUILDING VIs.…………………………………………………… VIs.………………………………………………………………………………… ……………………………… …
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a)Turn Table Control SubVIs……………………………………………………………. SubVIs…………………………………………………………….
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b)Signal Generator SubVIs………………………………………………………… SubVIs……………………………………………………………. ….
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c)Spectrum Analyzer SubVIs………………………………………………… SubVIs……………………………………………………………. ………….
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3.SETTING UP HARDWARE……………………………… HARDWARE…………………………………………………………… ……………………………………. ………. 22 C)MEASURUMENTS…………………………………………………………………………………
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1.Antenna Pattern Measurement………………………… Measurement………………………………………………………… ………………………………
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a)Horn Antenna……………………………………………… Antenna………………………………………………………………………………. ……………………………….
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b)Log-Periodic Antenna…………………………………………… Antenna……………………………………………………………………. ………………………. 30 2.Antenna Gain Calculation…………………………………… Calculation…………………………………………………………………. ……………………………... 31 a)Horn Antenna……………………………………………… Antenna………………………………………………………………………………. ………………………………... 31 b)Log-Periodic Antenna ……………………………………………………… …………………………………………………………………… …………… 32 D)CONCLUSION……………………………………………………………………………………….
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E)REFERENCES…………………………………… E)REFERENCES………………………………………………………………… ……………………………………………………. ………………………. 34
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CONTENTS ABSTRACT…………………………………………………………………………………...............
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A)INTRODUCTION……………………………………………………………………………………
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1.LABVIEW PROGRAMMING…………………………… PROGRAMMING………………………………………………………… ……………………………………. ………. 5 2.ANTENNA PATTERN&GAIN………………………………………………………………... 5 B)MEASUREMENT SYSTEM……………………………………………………………………… 6 1.SETTING UP LABVIEW……………………………………………… LABVIEW………………………………………………………………………… ………………………… 9 2.BUILDING VIs.…………………………………………………… VIs.………………………………………………………………………………… ……………………………… …
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a)Turn Table Control SubVIs……………………………………………………………. SubVIs…………………………………………………………….
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b)Signal Generator SubVIs………………………………………………………… SubVIs……………………………………………………………. ….
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c)Spectrum Analyzer SubVIs………………………………………………… SubVIs……………………………………………………………. ………….
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3.SETTING UP HARDWARE……………………………… HARDWARE…………………………………………………………… ……………………………………. ………. 22 C)MEASURUMENTS…………………………………………………………………………………
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1.Antenna Pattern Measurement………………………… Measurement………………………………………………………… ………………………………
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a)Horn Antenna……………………………………………… Antenna………………………………………………………………………………. ……………………………….
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b)Log-Periodic Antenna…………………………………………… Antenna……………………………………………………………………. ………………………. 30 2.Antenna Gain Calculation…………………………………… Calculation…………………………………………………………………. ……………………………... 31 a)Horn Antenna……………………………………………… Antenna………………………………………………………………………………. ………………………………... 31 b)Log-Periodic Antenna ……………………………………………………… …………………………………………………………………… …………… 32 D)CONCLUSION……………………………………………………………………………………….
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E)REFERENCES…………………………………… E)REFERENCES………………………………………………………………… ……………………………………………………. ………………………. 34
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ABSTRACT The ambition of the project is developing an automated antenna pattern measurement and gain calculation system. Hardware components of the system are used in remote mode and they are controlled by a computer program written in LabView. All of the antenna measurements are done in a anechoic chamber. Finally, antenna patterns are got on polar diagrams and gains are calculated automatically.
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A)INTRODUCTION As a result of the growth in wireless communications, the design and testing of antennas takes on renewed importance. Two important performance characteristics of antennas are their radiation pattern and their gain. The pattern is plotted to describe how power radiation varies with direction around the antenna and the gain is simply defined as the product of the directivity by efficiency. The ambition of this thesis project is developing an “automated antenna pattern measurement and gain calculation” system. Hardware requirements of the system are a signal generator, a spectrum analyzer, a turn table with controller and a laptop. All hardware components are used in remote mode and connection of them with laptop is supplied by GPIB (General Purpose Interface Bus) cables. Remote applications and the other automation process are managed and controlled by software solution of the system, LabView.
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1.LABVIEW PROGRAMMING Laboratory Virtual Instrument Engineering Workbench, a product of National Instruments, is a powerful software system that accommodates data acquisition, instrument control, data processing and data presentation. LabVIEW that can run on PC under Windows, Sun SPAR stations as well as on Apple Macintosh computers, uses graphical programming language (G language), departing from the traditional high level languages such as the C language, Basic or Pascal. All LabVIEW graphical programs , called Virtual Instruments or simply VIs, consist of a Front Panel and a Block Diagram. Front Panel contains various controls and indicators while the Block Diagram includes a variety of functions. The functions (icons) are wired inside the Block Diagram where the wires represent the flow of data. The execution of a VI is data dependant which means that a node inside the Block Diagram will execute only if the data is available at each input terminal of that node. By contrast, the execution of a traditional program, such as the C language program, follows the order in which the instructions are written. LabVIEW incorporates data acquisition, analysis and presentation into one system. For acquiring data and controlling instruments, LabVIEW supports IEEE-488 (GPIB) and RS-232 protocols as well as other D/A and A/D and digital I/O interface boards. The Analysis Library offers the user a comprehensive array of resources for signal processing, filtering, statistical analysis, linear algebra operations and many others. LabVIEW also supports the TCP/IP protocol for exchanging data between the server and the client.
2.ANTENNA PATTERN & GAIN Antenna pattern can be called as amplitude pattern or radiation pattern. The antenna pattern is a graphical representation in three dimensions of the radiation of the antenna as a function of angular direction. Antenna radiation performance is usually measured and recorded in two orthogonal principal planes (such as E-Plane and H-plane or vertical and horizontal planes). The pattern is usually plotted either in polar or rectangular coordinates. The pattern of most base station antennas contains a main lobe and several minor lobes, termed side lobes. A side lobe occurring in space in the direction opposite to the main lobe is called back lobe. Antenna patterns are generally used in normalized type. A normalized pattern means that the power/field with respect to its maximum value yields a normalized power/field pattern with a maximum value of unity (or 0 db). The maximum gain of an antenna is simply defined as the product of the directivity by efficiency. If the efficiency is not 100 percent, the gain is less than directivity. When the reference is a loss less isoterapic antenna, the gain is expressed in dBi. When the reference is a half-wave dipole antenna the gain is expressed in dBd. (1 dBd = 2.15 dBi)
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B) MEASUREMENT SYSTEM Our measuremet system is b ased on LabView programing. It supplies u s to configure and control the neccessary devic s and process the collected data. The meas rements are done in a anechoic chamber that i s a room to design for stopping reflections of either sound or electromagnetic waves. Figur 1 is general hardware structure of the syst m.
Figure 1 (General Hardware Structure)
Signal generator generates t e signal with desired power and frequenc for transmission and this signal is sent by the transmitted antenna. The receiver antenna is placed on a turn table and it is connected to spectrum analyzer. This receiving sub sys em provides us to observe the radiated signal b tween 0 and 360 degree with desired steps or ranges. For each step, we get the data of radi ted signal from spectrum analyzer. Then, t e collected data is written in a text file. At the s ame time, this is sourced to draw pattern of antenna on plot diagram. Maximum power value is selected among the data to calculate the gain. All of this operations are managed with the LabView program set on a laptop.
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Figure 2 (LabView Front Panel – User Interface) Figure 2 is “Front Panel” of the software and it is used as a user interface. User selects the visa address of ea h device and determines speed, start-stop degrees, step size for turn table; sign l type, frequency, power for signal generator; reference level , center and span frequencies for spectrum analyzer. After determining all config urations program is run. While program is running user can bserve radiated signals for each step on the black boxes. As soon as program fini shes, antenna pattern is drawn on the white box. 7
Figure 3 (Labview Build Diagram) Figure 3 is “Block Diagram” of the software a nd it is called VI. All configuration, control, arithmetic and l ogic operations are done in the diagram. We have 5 main subVIs and they also have their own several subVIs. 3 of main subVIs are used t configure the necessary devices and two of them in the loop are used to other operations such as turning the table, getting data and measu ement. Additionally, these VIs, a for loop is used to draw normalized polar diagra m and a math node is used for gain calculation. 8
Figure 3 (Labview Build Diagram) Figure 3 is “Block Diagram” of the software a nd it is called VI. All configuration, control, arithmetic and l ogic operations are done in the diagram. We have 5 main subVIs and they also have their own several subVIs. 3 of main subVIs are used t configure the necessary devices and two of them in the loop are used to other operations such as turning the table, getting data and measu ement. Additionally, these VIs, a for loop is used to draw normalized polar diagra m and a math node is used for gain calculation. 8
1.SETTING UP LABVIE a) Install LabView 8.0 LabView 8.0 has three CDs and we use two of them for installati n. The first CD has LabView main program, the second CD has MAX (Measuremen t and Automation) program and the othe one has some drivers. Installation steps are shown below.
1.SETTING UP LABVIE a) Install LabView 8.0 LabView 8.0 has three CDs and we use two of them for installati n. The first CD has LabView main program, the second CD has MAX (Measuremen t and Automation) program and the othe one has some drivers. Installation steps are shown below.
Figure 4
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Figure 6
Figure 7
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Figure 8 Second CD is taken and Rescan Drive button is clic ed.
Figure 9
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b) Install Agilent 14.1 Although our laboratory instruments have their own GPIB ports, our computers do not have any GPIB port but our computers have many USB ports. To get communication between these different ports, we have to use a converter device (GPIB to USB). Our GPIB to USB converter is produced by Agilent. On the other hand, LabView program is developed by National Instruments. In LabView, MAX is used to control and get a communication with instruments. MAX usually detects so many devices using GPIB, USB or etc. But, if the GPIB to USB converter is not produced by National Instrument, MAX does not detect the devices. To resolve this incompatibility, we have to do some extra process.
Figure 10 Firstly, we have to install the driver of our converter (Agilent 82357A, shown in above). In this project, we use Agilent’s converter so we have to install Agilent 14.1 driver.
Figure 11 12
Figure 12
Figure 13 After installing Agilent driver, now we can connect the converter between PC and instrument. When we plug the instrument, a window appears on the Agilent program and we enter the GPIB address of instrument. Then, we see the instrument on the left side of Agilent’s program. To detect this instrument with MAX, we also fallow these steps.
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c) Measurement & A tomation (MAX) Explorer Configuration
Figure 14 As we see above, MAX is op ned and Tools/NI-Visa/Visa Options/Passp rts is selected and “NI-VISATulip.dll – NI-VISA P ssport for Tulip” is checked at the right of the window. After restarting the MAX, we get new tab “Soft Front Panel/VA-Agilent Vis a Assistant Utility” under Tools tab.
Figure 15 14
When we selected VA-Agilent Visa Assistant Utility, a window that helps us to configure the instrument appears. We select “Browse” button and ch oose this path C:\\Program Files\Agilent\IO ibraries Suite\Bin\iocfg32.exe
2.BUILDING VIs a)Turntable Sub Is Our turntable is a product
f Innco Systems, Germany. A controller c lled CO 2000 and
produced by Innco systems i s used for controlling the turntable. CO 20 00 controller has a GPIB port so we use this po rt for communication. It’s default GPIB ad dress is 7 and this number is used in the progra
.
Two main subVIs are gener ted. One of them is for configuration, th e other one is for manipulation.
Turntable Configurati n VI
Figure 16 Left side of VI includes contro ls and the right side includes indicators/con nection nodes. We choose the GPIB address of turntable for VISA session control. Start ,Sto p and Step size are entered by user in degree and user enters the turning speed of turntabl in a range from 1 to 8. When we look at the rig ht side, we see a VISA resource name out, t his indicator shows us which visa address is used in the vi. TF (True-False) case helps us determining the rotation direction of turntab le (clockwise or counter clockwise). Start, stop and step size buffers show the values of ini ially determined. 15
Figure 17 (inner part of t rntable configuration VI, it has also four di ferent subVIs)
Figure 18 (initialize VI of turntable configuration VI)
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Figure 19 (Speed Control subVI of turntable configuratio VI)
Figure 20 (This subVI makes turntable to go to desired de ree)
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Turntable control VI This VI has two differe nt version but it includes only one subVI. O e of the versions is used for counter clock wise direction and the other one is used for clockwise.
Figure 21 ( Counter Clockwise turning subVI)
Figure 22 (Clockwise turning subVI)
Note: All of the string comm nds can be found between the pages 35 an d 43 in the service manual of Innco Systems. 18
b)Signal Generator SubVI This VI is used for the configu ation of the desired transmitted signal. We can adjust signal type, frequency and power. Our signal generator is Agilent/HP 83620B an it’s necessary visa drivers are found on the libra y of National Instrument web-site.
Figure 23
Figure 24 (Developed signal generator VI including NI drivers)
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c)Spectrum Analyzer ubVI We developed two subVIs for Spectrum Analyzer. One of them is used for configuration and the other one is used for measurements. Our spectrum analyzer is Agilen /HP 8565E and it’s necessary visa drivers are fou d on the library of National Instruments web-site.
Spectrum Analyzer Configuration VI
Figure 25 (We can adjust ce ter and span frequency, amplitude scale a d reference level)
Figure 26 (Developed pectrum analyzer Configuration VI including NI drivers)
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Spectrum Analyzer M asurement VI
Figure 27
Figure 28
NOTE: All of the necessary d ivers for the used devices can be found on the web site of National Instruments at the LabVIEW developer zone. 21
3. SETTING UP HARDWARE Connection between laboratory instruments is supplied with GPIB cables. An USB GPIB is used to connect laptop to instruments. Signal generator, spectrum analyzer and turntable controller are connected to each other. Usb side of usb gpib is connected to laptop and the other side is connected to one of the instruments. Almost 5 meters coaxial cable and many connectors are used. Coaxial cables are supplied connection between instruments and antennas. Connectors are used to connection between different types of inputs. Signal generator is connected to transmitter antenna, spectrum analyzer is connected to receiver antenna, turntable controller is connected to turntable with its own cable.
Fig.29 (Coaxial cable)
Fig.30 (Connector)
Fig.31 (Connector)
Figure 32 (Coaxial cable is connected to an instrument with a connector)
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Fig.33 (GPIB cable)
Figure 34 ( Instruments are ready to measurement)
Figure 35 (Antennas are ready to measurement in the anechoic chamber)
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C) MEASUREMENT A major difficulty encountered when trying to measure antenna patterns is a phenomenon called multipath distortion, in which unwanted reflections of the transmitted signal arrive at the antenna under test and interfere with the direct signal. The multipath distortion signal distorts the measured antenna pattern. Another characteristic of multipath distortion is that all the reflected signals arrive at the test antenna with a time delayed from the direct signal. However, we can reduce multipath distortion effects by using a large, open outdoor test site for the antenna range or by taking measurements inside an anechoic chamber. An anechoic chamber has walls that absorb RF radiation, reducing the reflected signals. We chose LabVIEW software for digital data collection and display control on the antenna range. We can apply LabVIEW signal-processing techniques to the pattern measurement data to reduce the range multipath distortion effects. To mitigate the multipath distortion effects, we used time-domain processing of the received signals. For the measurement, we used far field technique where the antenna under test (AUT) is place in the far field of a range antenna.
d = where d=far field distance, D=maximum dimension of antenna, λ=wavelength λ =
f =
=
.
= 5.83GHz
We can do our measurement until 5.83GHz For 1GHz: 8
310 λ= = =0.3m 1109 Path Loss: PL =20log(
) = 20log(
. .
) = 42dB
Cable Loss(Measured): 6.7dB
For 2GHz: 8
310 λ= = =0.15m 2109 Path Loss: PL =20log(
) = 20log(
. .
Cable Loss(Measured): 9.06dB 24
) = 48dB
For 3GHz:
λ= = =0.1m Path Loss: PL =20log(
) = 20log(
= 51.5dB
Cable Loss(Measured): 15.84dB
All of the used antennas a e linearly polarized so it provides to analyze the antenna as a radiation pattern.
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AH SAS-571 Horn Ant nna:
H - Plane
E - Plane
Frequency Range: Antenna Factor: Gain (dBi): Maximum Continuous Power:
700 MHz - 18 GHz 22 to 44 dB 1.4 to 15 dBi 300 Watts
3dB Beam width (E-Field): 3dB Beam width (H-Field : Impedance:
48° 30° 50
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SAS-510-2 Lop-Perio ic Antenna: E - Plane
H - Plane
Frequency Range:
290 MHz – 2 GHz
Antenna Factor:
14 - 32 dB
Gain:
6.5 dBi
Maximum Continuous P wer:
1000 Watts
3dB Beam width (E-Field):
45°
3dB Beam width (H-Field):
100°
Impedance:
50
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HLP-3003C Compact ybrid Log Periodic Antenna:
H - Plane
E - Plane
30 MHz – 3 GHz
Frequency Range: Gain:
6 dBi
Maximum Continuous Power:
100 Watts
Impedance:
50Ω
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1.Antenna Pattern Measurement a) Horn Antenna
H-Plane Measurements:
“For a linearly polarized antenna, the plane containing the magnetic field vector and the direction of maximum radiation". For base station antenna, the H-plane usually coincides with the horizontal plane.
For 1GHz:
For 1.5GHz:
For 2GHz:
For 2.5GHz:
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For 3GHz:
For 4GHz:
E-Plane Measurements:
"For a linearly polarized antenna, the plane containing the ele ctric field vector and the direction of maximum radiation". For base station antenna, the E-plane usually coincides with the vertical plane.
For 1GHz:
For 1.5GHz:
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For 2GHz:
For 2.5GHz:
For 3GHz:
For 4GHz:
E-Plane
H-Plane 29
Original Pattern
b) Log Periodic ntenna
H-Plane Measuremen s
For 300MHz:
For 1GHz:
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2. Antenna Gain Calculation We developed two different
ays for calculation of antenna gain. The firs way is based on
determining all of the losses a nd the gains in measurement system and th e key idea of the second way is comparative (r lative) measurement of antenna gains.
The First Way: The key idea o this way is that power desiring to transmit ave to equal to sum of all losses and gains. Initially, we determined the two main losses c used from coaxial cables and path loss.
1GHz for Horn Antenna: (13+6+RX Gain)=(-23.33)+(6.7+42) 2GHz for Horn Antenna: (13+6+RX Gain)=(-28.83)+(9.06+48) 3GHz for Horn Antenna: (13+6+RX Gain)=(-37.33)+(15.84+51.5) Frequency Calculated Gain
Original Gain
1GHz
6.37
7.3
2GHz
9.23
8.6
3GHz
11.01
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RX Gain=6.37dBi RX Gain=9.23dBi RX Gain=11.01dBi
The Second Way: The key ide of this way is calculating the gain compara tively or relatively. We use two antennas, one of them is reference that its gain is known bef re, the other’s gain is desiring to find. The fo mula shown below helps us to understand t he way and calculate the gain.
a)Horn Antenna
1GHz for Horn Antenna: Gain =7.3
2GHz for Horn Antenna: Gain =7.3
3GHz for Horn Antenna: Gain =7.3
= 7.3dBi
= 9.02dBi
= 11.7dBi
Frequency Calculated Gain(dBi)
Original Gain(dBi)
1GHz
7.3
7.3
2GHz
9.02
8.6
3GHz
11.7
10 31
b)Log-periodic Antenna 300MHz for Log Periodic Antenna: Gain =7.3
1GHz for Log Periodic Antenna: Gain =7.3
. .
. .
= 3.54dBi
= 6.78dBi
Frequency Calculated Gain(dBi)
Original Gain(dBi)
300GHz
3.54
5.6
1GHz
6.78
7.2
As a result of several measurements and calculations, it is clear that the second way is more accurate because losses are ignored.
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D) CONCLUSION The importance and utilization area of antennas are getting increased and as a result of this situation, characterization problem of antenna is being critical day by day. So many systems are designed by researchers at universities and so many systems are produced commercially by companies to solve this critical problem. In this thesis project, we developed an antenna characterized system. LabView provide a highly effective and efficient solution for our system. The pattern and directivity of antenna is measured almost same as the original values. The gain is calculated by two different methods and the results of these calculations are almost same as the originals, too. As a conclusion, the initial ambitions of the our thesis project are reached. Measurements and calculations are acceptable and reliable.
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E) REFERENCES
Books 1. Bishop, Robert H. , Labview Student Edition 6i, National Instruments 2. LabVIEW Getting Started, National Instruments, April 2003 3. Jeffrey Travis, Jim Kring, LabVIEW for Everyone: Graphical Programming Made Easy and Fun, Printice-Hall Third Edition 4. David M. Pozar, Microwave Engineering,
John Willey & Sons Second Edition
Papers 1. S. Burgos., S. Pivnenkot, 0. Breinbjergt, M. Sierra-Castafier, Comparative Investigation of Four Antenna Gain Determination Techniques (pdf) 2. Leonard Skaloff, DeVry College of Technology, GPIB Instrument Control (pdf) 3. Innco Systems, Operating and Service Manual (pdf) 4. Tips on Using agilent GPIB Solutions in National Instrument’s LabVIEW Environment, Agilent Technologies 2009 USA (pdf)
Web-Sites 1. http://zone.ni.com/dzhp/app/main
(NI LabVIEW Developer Zone)
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