Labview Based Automatic Antenna Pattern Measurement and Gain Caluclation

1

EE 491 PROJECT

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

2

CONTENTS

ABSTRACT…………………………………………………………………………………............... 3

A)INTRODUCTION…………………………………………………………………………………… 4

1.LABVIEW PROGRAMMING…………………………………………………………………. 5

2.ANTENNA PATTERN&GAIN………………………………………………………………... 5

B)MEASUREMENT SYSTEM……………………………………………………………………… 6

1.SETTING UP LABVIEW………………………………………………………………………… 9

2.BUILDING VIs.…………………………………………………………………………………… 15

a)Turn Table Control SubVIs……………………………………………………………. 15

b)Signal Generator SubVIs……………………………………………………………. 19

c)Spectrum Analyzer SubVIs……………………………………………………………. 20

3.SETTING UP HARDWARE……………………………………………………………………. 22

C)MEASURUMENTS………………………………………………………………………………… 24

1.Antenna Pattern Measurement………………………………………………………… 27

a)Horn Antenna………………………………………………………………………………. 27

b)Log-Periodic Antenna……………………………………………………………………. 30

2.Antenna Gain Calculation………………………………………………………………….. 31

a)Horn Antenna……………………………………………………………………………….. 31

b)Log-Periodic Antenna …………………………………………………………………… 32

D)CONCLUSION………………………………………………………………………………………. 33

E)REFERENCES…………………………………………………………………………………………. 34

3

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.

4

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.

5

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)

B) MEASUREMENT SYSTEM

Our measuremet system is based on LabView programing. It supplies us to configure and

control the neccessary devices and process the collected data. The measurement

in a anechoic chamber that is a room to design for stopping reflections of either sound or

electromagnetic waves. Figure 1

Figure 1

Signal generator generates the sig

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 system provides us to

observe the radiated signal between 0 and 360 degree with desired steps or ranges. For each

step, we get the data of radiated signal from spectrum analyzer. Then, the collected data is

written in a text file. At the same time, this is sourced to draw pattern of antenna on p

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.

6

B) MEASUREMENT SYSTEM


control the neccessary devices and process the collected data. The measurement


electromagnetic waves. Figure 1 is general hardware structure of the system.

Figure 1 (General Hardware Structure)

Signal generator generates the signal with desired power and frequency for transmission



d signal between 0 and 360 degree with desired steps or ranges. For each


written in a text file. At the same time, this is sourced to draw pattern of antenna on p


operations are managed with the LabView program set on a laptop.


control the neccessary devices and process the collected data. The measurements are done


general hardware structure of the system.

nal with desired power and frequency for transmission



d signal between 0 and 360 degree with desired steps or ranges. For each


written in a text file. At the same time, this is sourced to draw pattern of antenna on plot


Figure 2 (LabView Front Panel

Figure 2 is “Front Panel” of the software and it is used as a user interface. User selects the visa address of each device and determines speed,

start-stop degrees, step size for turn table; signal type, frequency, power for signal generator; reference level, center and span

spectrum analyzer. After determining all configurations program is run. While program is running user can observe radiated signal

step on the black boxes. As soon as program finishes, antenna pattern is drawn on the white box.

7

Figure 2 (LabView Front Panel – User Interface)

d it is used as a user interface. User selects the visa address of each device and determines speed,

stop degrees, step size for turn table; signal type, frequency, power for signal generator; reference level, center and span

rum analyzer. After determining all configurations program is run. While program is running user can observe radiated signal

step on the black boxes. As soon as program finishes, antenna pattern is drawn on the white box.

d it is used as a user interface. User selects the visa address of each device and determines speed,

stop degrees, step size for turn table; signal type, frequency, power for signal generator; reference level, center and span frequencies for

rum analyzer. After determining all configurations program is run. While program is running user can observe radiated signals for each

Figure 3 is “Block Diagram” of the software and it is called VI. All configuration, control, arithmetic and logic operations

diagram. We have 5 main subVIs and they also have their own several subVIs. 3 of main subVIs are used

and two of them in the loop are used to other operations such as turning the table, getting data and measurement. Additional

for loop is used to draw normalized polar diagram and a math node is used for

8

Figure 3 (Labview Build Diagram)

Figure 3 is “Block Diagram” of the software and it is called VI. All configuration, control, arithmetic and logic operations

diagram. We have 5 main subVIs and they also have their own several subVIs. 3 of main subVIs are used to configure the necessary devices

and two of them in the loop are used to other operations such as turning the table, getting data and measurement. Additional

for loop is used to draw normalized polar diagram and a math node is used for gain calculation.

Figure 3 is “Block Diagram” of the software and it is called VI. All configuration, control, arithmetic and logic operations are done in the

to configure the necessary devices

and two of them in the loop are used to other operations such as turning the table, getting data and measurement. Additionally, these VIs, a

1.SETTING UP LABVIEW

a) Install LabView 8.0

LabView 8.0 has three CDs and we use two of them for installation. The first CD has

LabView main program, the second CD has MAX (Measurement and Automation)

program and the other one has some driv

9

1.SETTING UP LABVIEW

Install LabView 8.0



program and the other one has some drivers. Installation steps are shown below.

Figure 4



ers. Installation steps are shown below.

10

Figure 6

Figure 7

Second CD is taken and Rescan Drive button is clicked

11

Figure 8

Second CD is taken and Rescan Drive button is clicked

Figure 9

Second CD is taken and Rescan Drive button is clicked.

12

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

13

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.

c) Measurement & Automation (MAX) Explorer Configuration

As we see above, MAX is opened

“NI-VISATulip.dll – NI-VISA Passport for Tulip”

restarting the MAX, we get a new tab “

under Tools tab.

14

Measurement & Automation (MAX) Explorer Configuration

Figure 14

As we see above, MAX is opened and Tools/NI-Visa/Visa Options/Passports

VISA Passport for Tulip” is checked at the right of the window. After

restarting the MAX, we get a new tab “Soft Front Panel/VA-Agilent Visa Assistant Utility”

Figure 15

Measurement & Automation (MAX) Explorer Configuration

/Passports is selected and

is checked at the right of the window. After

Agilent Visa Assistant Utility”

When we selected VA-Agilent Visa Assistant Utility, a window that helps us to configure the

instrument appears. We select “Browse” button and choose this path

C:\\Program Files\Agilent\IO Libraries Suite

2.BUILDING VIs

a)Turntable SubVIs

Our turntable is a product of Innco Systems, Germany. A controller called CO 2000 and

produced by Innco systems is used for

GPIB port so we use this port for co

number is used in the program .

Two main subVIs are generated. One of them is for configuration, the other one is for

manipulation.

Turntable Configuration VI

Left side of VI includes controls and the right side includes indicators/connection nodes. We

choose the GPIB address of turntable for VISA session control. Start ,Stop and Step size are

entered by user in degree and user enters the turning speed of turntable in a ran

to 8. When we look at the right side, we see a VISA resource name out, this indicator shows

us which visa address is used in

rotation direction of turntable (clockwise or counter clockwise)

buffers show the values of initially determined.

15

Agilent Visa Assistant Utility, a window that helps us to configure the


IO Libraries Suite\Bin\iocfg32.exe

a)Turntable SubVIs


produced by Innco systems is used for controlling the turntable. CO 2000 controller has a

GPIB port so we use this port for communication. It’s default GPIB address is 7 and this

number is used in the program .


Turntable Configuration VI

Figure 16

VI includes controls and the right side includes indicators/connection nodes. We


entered by user in degree and user enters the turning speed of turntable in a ran


which visa address is used in the vi. TF (True-False) case helps us

rotation direction of turntable (clockwise or counter clockwise). Start, stop and step size

buffers show the values of initially determined.

Agilent Visa Assistant Utility, a window that helps us to configure the



controlling the turntable. CO 2000 controller has a

mmunication. It’s default GPIB address is 7 and this


VI includes controls and the right side includes indicators/connection nodes. We


entered by user in degree and user enters the turning speed of turntable in a range from 1


False) case helps us determining the

. Start, stop and step size

Figure 17 (inner part of turntable configuration VI, it has also four different subVIs)

Figure 18 (initialize VI of turntable configuration VI)

16

e 17 (inner part of turntable configuration VI, it has also four different subVIs)

Figure 18 (initialize VI of turntable configuration VI)

e 17 (inner part of turntable configuration VI, it has also four different subVIs)

Figure 19 (Speed Co

Figure 20 (This

17

Figure 19 (Speed Control subVI of turntable configuration VI)

This subVI makes turntable to go to desired degree)

ntrol subVI of turntable configuration VI)

desired degree)

Turntable control VI

This VI has two different version but it includes only one subVI. One of the versions is

used for counter clockwise direct

Figure 21 ( Counter Clockwise turning subVI)

Figure 22 (Clockwise turning subVI)

Note: All of the string commands can be found between the pages 35 and 43 in the service

manual of Innco Systems.

18


used for counter clockwise direction and the other one is used for clock

Figure 21 ( Counter Clockwise turning subVI)

Figure 22 (Clockwise turning subVI)



ion and the other one is used for clockwise.


b)Signal Generator SubVI

This VI is used for the configuration of the desired transmitted signal. We can adjust signal

type, frequency and power. Our signal generator is Agilent

drivers are found on the library of National

Figure 24 (Developed signal generator VI

19

)Signal Generator SubVI


type, frequency and power. Our signal generator is Agilent/HP 83620B and it’s necessary visa

drivers are found on the library of National Instrument web-site.

Figure 23

Figure 24 (Developed signal generator VI including NI drivers)


83620B and it’s necessary visa

NI drivers)

c)Spectrum Analyzer SubVI

We developed two subVIs for Spectrum Analyzer. One of them is used for configuration and

the other one is used for measurements.

necessary visa drivers are found on the library of National Instruments web

Spectrum Analyzer Configuration VI

Figure 25 (We can adjust center and span frequency, amplitude scale and reference lev

Figure 26 (Developed Spectrum analyzer Configuration VI including NI drivers)

20

c)Spectrum Analyzer SubVI


the other one is used for measurements. Our spectrum analyzer is Agilent/HP 8565E and it’s

necessary visa drivers are found on the library of National Instruments web

Spectrum Analyzer Configuration VI

We can adjust center and span frequency, amplitude scale and reference lev



Our spectrum analyzer is Agilent/HP 8565E and it’s

necessary visa drivers are found on the library of National Instruments web-site.

We can adjust center and span frequency, amplitude scale and reference level)


Spectrum Analyzer Measurement VI

NOTE: All of the necessary drivers for the used devices can be found on the web site of

National Instruments at the LabVIEW developer zone.

21

Spectrum Analyzer Measurement VI

Figure 27

Figure 28


ments at the LabVIEW developer zone.


22

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)

23

Fig.33 (GPIB cable) Figure 34 ( Instruments are ready to measurement)

Figure 35 (Antennas are ready to measurement in the anechoic chamber)

24

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:

λ=

=

3108

1109 =0.3m

Path Loss: PL =20log(

) = 20log(

.

.) = 42dB

Cable Loss(Measured): 6.7dB

For 2GHz:

λ=

=

3108

2109 =0.15m


) = 20log(

.

.) = 48dB

Cable Loss(Measured): 9.06dB

For 3GHz:

λ=

= 310

8

3109 =0.1m


)

Cable Loss(Measured): 15.84

All of the used antennas are linearly polarized so it provides to analyze the antenna as a

radiation pattern.

• AH SAS-571 Horn Antenna:

Frequency Range:

Antenna Factor:

Gain (dBi):

Maximum Continuous Power:

3dB Beam width (E-Field):

3dB Beam width (H-Field):

Impedance:

E - Plane

25

) = 20log(.

. = 51.5dB

.84dB

antennas are linearly polarized so it provides to analyze the antenna as a

571 Horn Antenna:

700 MHz - 18 GHz

22 to 44 dB

1.4 to 15 dBi

Maximum Continuous Power: 300 Watts

Field): 48°

Field): 30°

50

H - Plane

antennas are linearly polarized so it provides to analyze the antenna as a

• SAS-510-2 Lop-Periodic Antenna:

Frequency Range:

Antenna Factor:

Gain:


3dB Beam width (E-Field):

3dB Beam width (H-Field):

Impedance:

• HLP-3003C Compact Hybrid Log Periodic Antenna:

Frequency Range:

Gain:


Impedance:

H - Plane

H - Plane

26

Periodic Antenna:

290 MHz – 2 GHz

14 - 32 dB

6.5 dBi

uous Power: 1000 Watts

Field): 45°

Field): 100°

50

3003C Compact Hybrid Log Periodic Antenna:

30 MHz – 3 GHz

6 dBi

Maximum Continuous Power: 100 Watts

50Ω

E - Plane

Plane

E - Plane

27

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:


28

For 3GHz: For 4GHz:

E-Plane Measurements:

"For a linearly polarized antenna, the plane containing the electric field vector and the

direction of maximum radiation". For base station antenna, the E-plane usually coincides

with the vertical plane.


For 2GHz:

For 3GHz:

E-Plane

29

For 2.5GHz:

For 4GHz:

H-Plane

b) Log Periodic Antenna

H-Plane Measurements

For 300MHz:

30

Original Pattern

b) Log Periodic Antenna

Plane Measurements

For 1GHz:

2. Antenna Gain Calculation

We developed two different way

determining all of the losses and the gains in measure

second way is comparative (relative) me

The First Way: The key idea of this way is that power desiring to transmit have to equal to

sum of all losses and gains. Initially, we determined the two main losses caused from coaxial

cables and path loss.

1GHz for Horn Antenna: (13+6+RX Gain)=(



Frequency

1GHz

2GHz

3GHz

The Second Way: The key idea of this way is calculating the gain comparatively or relatively.

We use two antennas, one of them is ref

gain is desiring to find. The formula shown below

calculate the gain.

a)Horn Antenna

1GHz for Horn Antenna: Gain



Frequency Calculated Gain(dBi)

1GHz 7.3

2GHz 9.02

3GHz 11.7

31

2. Antenna Gain Calculation

two different ways for calculation of antenna gain. The first way

the losses and the gains in measurement system and the key idea of

is comparative (relative) measurement of antenna gains.

The key idea of this way is that power desiring to transmit have to equal to

Initially, we determined the two main losses caused from coaxial

(13+6+RX Gain)=(-23.33)+(6.7+42) RX Gain=6.37dBi

(13+6+RX Gain)=(-28.83)+(9.06+48) RX Gain=9.23dBi

(13+6+RX Gain)=(-37.33)+(15.84+51.5) RX Gain=11.0

Calculated Gain Original Gain

6.37 7.3

9.23 8.6

11.01 10

The key idea of this way is calculating the gain comparatively or relatively.

one of them is reference that its gain is known before,

o find. The formula shown below helps us to understand the way and

Gain =7.3 .

. = 7.3dBi

Gain =7.3 .

. = 9.02dBi

Gain =7.3 .

. = 11.7dBi

Calculated Gain(dBi) Original Gain(dBi)

7.3 7.3

9.02 8.6

11.7 10

for calculation of antenna gain. The first way is based on

ment system and the key idea of the

The key idea of this way is that power desiring to transmit have to equal to

Initially, we determined the two main losses caused from coaxial

23.33)+(6.7+42) RX Gain=6.37dBi

28.83)+(9.06+48) RX Gain=9.23dBi

37.33)+(15.84+51.5) RX Gain=11.01dBi

The key idea of this way is calculating the gain comparatively or relatively.

that its gain is known before, the other’s

helps us to understand the way and

32

b)Log-periodic Antenna

300MHz for Log Periodic Antenna: Gain =7.3 .

. = 3.54dBi

1GHz for Log Periodic Antenna: Gain =7.3 .

. = 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.

33

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.

34

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)

35

Documents

Labview Based Automatic Antenna Pattern Measurement and Gain Caluclation