Study and Design Yagi-Uda Crossed Antenna Using 4NEC2

8/10/2019 Study and Design Yagi-Uda Crossed Antenna Using 4NEC2

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Study and Design "Yagi-Uda CrossedAntenna" using 4NEC2

Hesham Mokhtar Rasim Amer Ali

College of Engineering Sciences and

Technology. Sebha University

Emails:- [email protected][email protected]


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ABSTRACT

Boils down to this project in the study of (Yagi-Uda Crossed Antenna),

and the study was in the bandwidth of (180-220MHz), using 4NEC2 "wired antennas simulator", and the simulation process shows that the

characteristics of this antenna has been improved through automatic

modification in the antenna amounts , and trough the optimization

process the obtaining gain was having a maximum value of 14.17dBic..


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INTRODUCTION

Wireless communication is one of the most important technologiesrapidly grow and spread, where the demand for data transmission

without cables and by different distances in increasing every day

,therefore become the development of wireless communication systems

is absolutely imperative, it is also known that the communications

system generally consists of, the source , which is asource of the

information or data to be sent, the power converter is usually converts

information from the source into electrical signals to be able to send it

via system transmission, the sender is based processing electrical signals

issued from the converter to be suitable for transmission through the

communication channel, the transmission channel which is the medium

that connects between the sender and the receiver, and finally the

receiver to extraction the data from the signal transmitter and delivered

to the power converter of output system which converts these signals to

the original form as it was before sending it.

The role of the antenna here in the sender and any future it an essential

part and indispensable in the communications system as that in the case

of sending it converts electrical energy from the transmission line which

connected with to the electromagnetic energy represented in waves

transmitted into the air or vice versa as in the case of reception

depending on the type and characteristics of the antenna. And generally

the Wired antenna characterized by simply installed ,Where any wire or

metal surface have the ability to be antenna and be able to pick up

electromagnetic waves but practical antennas have its forms and specific

dimensions determined by the purpose for which it was made.

And In this work was designed and study radiological characteristics to

one of the most important applications of (Yagi-Uda) antenna, a (Yagy-

Uda Crossed Antenna) at bandwidth of (180-220 MHz),its a very

practical antenna , Because the waves that radiate be circular or linear

polarized and This is appropriate in some applications such as satellite

communication systems and some radars, The designed antenna has


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been simulated by using an application software for the antennas wired

design "4NEC2" [6], This simulation allows view detailed properties of

the antenna, which provides high accuracy in the results And economize

time and effort, The software also features the ability to improve the

radiation characteristics of the antenna designed, This is happened by

doing an automatic changing process to the input dimensions of the

antenna for the optimization process and choose the best values of

results after finishing the Automatic comparison process .

1.The Software ''2NEC4'' :-

(NEC) is the abbreviation to (Numerical Electric Code) which a way for

simulate wired antennas, attributed to Gerald J. Burke and Andrew J.

Poggio originally was created by using FORTRAN language in the mid-

seventies, and to achieve this simulation the antenna must divided into a

small sections linearly with a different values of current and voltage in

each segment, the NEC is based on (Moment Methods theory),

therefore the results are very accurate and typical, It also provides a lot

of effort and time because of the difficulty and complexity of themathematical analysis using this method, and over time increased the

flaws and weaknesses in the simulation using NEC For example, the

resulting simulation errors when wires are crossed in a very short

distances or when using coated wire, In addition it was a highly

confidential for a very long time were not allowed even marketed on the

Internet, This has been overcome defects in 4NEC2,which programmed

by (Arie Voors) and so named because it combines proportion between

versions NEC2 and NEC4, In addition to it is free and also mentions in

this field the simulation program"EZNEC", which is not as potential

strong and effectiveness 4NEC2 [13].

2. Moment Methods :-

Method of moments technique known method to solve linear equations,

The conversion is used integral equations for the electric field to the

matrix equations or system of linear equations. Transactions can be

found using the current fragmentation of matrixes (LU), or using


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deletion by GaussSeidel method from linear algebraic methods. The

basic form of the equation which has been replaced by the method of

moments ]6

1[ .

)1...(..........,.........)( fuL

Where L linear variable, U undefined function, f-feeding function.

array equation written according to Ohm's law on image:-

)2(...................., mnnm VIZ

Where the impedance array be on the image:-

)3.......(..........(,, nmnm uLwZ

Where mw is a test function or weight

While the current array are:

)4.(..............................nnI

And voltage array have the following image:-

)5...(...................., fwV mm

3.Studying the antenna design:-

3.1-Specifications antenna designed:-

receiving Frequency was selected by 200Mhz and based on this

wavelength will be determined and can be calculated from following

relation:-

=

F=

3 10

200 10= 1.5m

Where : wavelength of receiving Frequency

C: is the speed of light

F: Frequency and unity hertz


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and the maximum value of the gain obtained after building antenna is

12.07 dBic were obtained value 14.17dBic after the optimization

process.

Overall Length of the antenna 3.15m

width antenna 0.675m

Number of the driven elements 1 * 2 type of folded dipole

Number of the reflectors 1 * 2

Number the director elements 9*2

The elements will be lengths depending on the typical measurements

Yagi antenna and it is as follows : -

the length of the driven element will be (0.45-0.49).

the Length of the reflector will be (0.5-0.525).

the length of the director will be (0.4-0.45).

The distance between the reflector and driven element will be

(0.15-0.25).

The distance between the directors will be (0.3-0.4).

And measurements of the lengths of the elements that have been

calculated depending on the previous typical length of the shown in the

table (1).


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Table (1) lengths of antenna elements depending on the typical lengths

Element

actor symbol of

distance in 4NEC2

software

Typical value of the

distance for wavelength ()

The value element

length by meter

(m)

Driven

Element

length FDL 0.45 0.675

width FDW 6%FDL 0.03969

The gap Gap 3%FDL 0.02

Reflector HLR*2 0.5 0.75

1stdirector HL1*2 0.4 0.6

2nddirector HL2*2 0.4 0.6

3rddirector HL3*2 0.4 0.6

4th

director HL4*2 0.4 0.6

5thdirector HL5*2 0.4 0.6

6th director HL6*2 0.4 0.6




Th

ewiresdiameters

Directors re

0.002 0.003Driven Element wr

Source wire rs

Impedance of the

transmission lineZC ___ 450()

The length of the

transmission lineLC 0.5 0.75

3.2.Installation of antenna elements: -

After knowing the typical dimensions of the antenna elements, which

will be assembled, and been installing these elements with this

dimensions and through the steps of the installing will be study the

effect of increasing the number of directors on the characteristics of the

antenna after each step and after the completion of that, the

dimensions will be optimized for the best properties as possible to the

designed antenna


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the elements have been installed starting from the horizontal feeder

element down to the ninth- vertical director which was reached a full

gain on this point its value is 12.07 dBic which is a good value before the

optimization process, and installation process have been done with the

following sequence:

Install the horizontal driven element.

Adding the horizontal reflector and the distance between the

reflector and the driven element is less than the distance between

the driven element and the nearest director[9].

Adding a horizontal director.

Installing of the vertical driven element with a minimum

separation (a quarter wavelength) and that as previously

mentioned for make phase delay rate of 90 to form the desired

circular polarization [11]

Adding the vertical reflector so that the distance from it to the

vertical driven element is equal to the distance from the

horizontal reflector to horizontal driven element

Finally, adding the vertical director so that distance to the first

vertical driven element is equal to the distance the horizontaldirector element for the horizontal driven element and then the

remaining directors are added one after the other as the

dimensions shown in the table (2).


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3.3.Simulation results using NEC: -

And the group Figuresof (1) and (2) describes sequentially a three-

dimensional Steps for installing the designed antenna and the

evolution of radiation pattern that comes from left hand circular

polarization (LHCP) at the frequency 200MHz for each step and

reaching to adding directors, each form displays the progress in two

steps together which mean installation horizontal and vertical

director together in every form, this to the large number of directors,

become clear from the forms that antenna radiation to heading for

forward direction with addition of every director and that's means

increasing the gain, the directional and the efficiency of the designed

antenna : -

Figure (1) horizontal folded dipole

Figure (2) the ninth vertical director (9TH

V)

Evidenced by a previous forms the significant impact which caused bythe increasing of each director in the radiation pattern of the antenna.


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The table(3) shows the changing in the most important characteristics

of the antenna radiation pattern when you add every the director where

we note significant positive change in most of the characteristics after

the addition of the first vertical-director, Except the significant increase

in the gain most of characteristics were not affected much with

increasing the number of directors after the first vertical director and

gain almost stabled at the ninth vertical director where the gain not

changed when you add Doubles tenth vertical and horizontal directors

and were value of 12.071dBic as well the rest of the characteristics was

approximately equal to the last result obtained from the ninth vertical

director so the design has been installed on the number of Nine Even

directors.


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Table (3) the changing in the most important characteristics of the antenna radiation

when you add every directed at 200MHz frequency

phaseZ(ohm)X(ohm)R(ohm)F/R(dBic)F/B(dBic)GAIN(dBic)Reflcoef

SWR

34.63272.14154.65223.9310.8911.397.61-2.626.68HLR1-H

35.39134.2277.74109.4111.0211.027.53-5.173.46HLR1-V

29.98135.3767.64117.2511.1513.077.89-5.543.24HLR2-H

24.56135.4356.29123.1810.2616.328.18-5.93.06HLR2-V

27.54142.3465.82126.2110.2513.338.58-5.433.31HLR3-H

30.83149.3676.54128.269.9611.59-4.973.59HLR3-V

30.79140.0671.69120.3211.4613.459.45-5.293.38HLR4-H

30.72131.9367.41113.4213.2615.759.8-5.623.20HLR4-V

28.54137.3865.63120.6913.2215.59.98-5.563.23HLR5-H

26.21143.0263.17128.3212.1215.510.15-5.483.27HLR5-V

29.16143.1369.47124.9912.4114.2110.48-5.293.38HLR6-H

32.07142.8175.82121.0211.9613.1110.81-5.113.49HLR6-V

30.02137.9969.04119.4815.5815.6411.04-5.433.30HLR7-H

28.13133.4362.89117.6713.9020.7811.23-5.753.13HLR7-V

28.18139.6365.96123.0715.8116.4911.37-5.493.26HLR8-H

28.27146.2069.33128.6813.514.311.52-5.213.41HLR8-V

30.02141.5070.07122.6015.715.711.8-5.283.38HLR9-H

31.09137.3372.05116.0215.515.912.07-5.353.35HLR9-V


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Table (4) shows the comparison between the dimensions of the antenna before and

after the optimization process

Value After Optimization(m)Value before Optimization(m)Variable Name

0.62950.675Fdl

0.03970.0397Fdw

0.3750.375Qwl

0.3590.375Hlr

0.2990.3XD

0.6520.6Hl1*2

0.6180.6Hl2*2

0.6180.6Hl3*2

0.6180.6Hl4*2

0.6100.6Hl5*2

0.6040.6Hl6*2

0.6140.6Hl7*2

0.6000.6HL8*2

0.6040.6HL9*2

0.4450.45X1

0.9140.9X2

1.3211.35X3

1.7781.8X4

2.2692.25X5

2.6682.7X6

3.0973.15X7

3.5773.6X8

4.0534.05X9

Evident from this table (4) after the optimization process of the

observed change relatively in some of lengths, such as the decrease in

the length of the driven element (FDL) and the increase in the length of

the first director (HL1) as a result of their positively effect on the specific

characteristics during the optimization process and in the process has

been the focus on (SWR-GAIN-Xin), and stability or changing of some

other values is remarkably like the driven element width (Fdw) and thedistance between the two antennas (Qwl) the lengths of the rest of the

director (hlx), and that for nonexistence of their positive effect in the

mentioned characteristics.

And the table (3.5) shows the values of the antenna characteristics after

the optimization process at the operating frequency 200MHz, where it

was a good value for (SWR) is 1.15, the value very close to 1 and reflect

the strong interdependence of the antenna elements with an

acceptable value for the impedance of the antenna by 43.603.


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Table (5) shows the values of the characteristics of the antenna after the

optimization process

phaseZ(ohm)X(ohm)R(ohm)F/R(dBic)F/B(dBic)GAIN(dBic)Reflcoef

SWR

After Optimizing in (SWR-GAIN-Xin)

-0.6243.6-0.4745.9413.6413.6414.17-23.21.15HLR9-V

Figure (3) is the final form of radiation pattern of the designed antenna

after the optimization process and noted here the improvement in the

gain and the directional of the antenna.

Figure (3) final radiation pattern of the designed antenna after the optimization process


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3.4.studying the characteristics of the antenna in the limited

bandwidth between MHz (150-250) before and after the optimization

process: -

3.4.1. The relation between the gain and the changing in the

frequency:

Figure (4) The relation between gain and the change in frequency and

noted that the gain before the optimization process began in the sharp

rise at the frequency 165MHz where the value of 2dBic and reached its

peak at the frequency 212MHz value of 13.32dBic and a sharp drop in

the gain at the frequency 220MHz, but after the optimization process of

change observed in gain the begin at the frequency 180MHz value of

5.12dBic and reaching to the highest gain at operating frequency200MHz value of 14.17dBic and sharp fall occurred after the frequency

214MHz, which fell then to 3.36dBic.

Figure (4) the relation between the gain and the change in frequency


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3.4.2. The relationship between the ratio of forward - to - back (F / B

ratio) and the change in frequency: -

evidenced by figure that the sharply change of positive values to the

ratio of forward - to - back happening in the trapped bandwidth

between MHz (178-222) beginning with value of 0.6 dBic and reaching to

value of 5.17 dBic with highly extreme value of 19.34dBic at the

frequency 196MHz and the maximum value was 28.97dBic at frequency

211MHz, In addition to this change sharp which illustrated by the

relation curve before the optimization process has dropped significantly

after this operation, This shows the relative stability that event to

change in the radiation pattern of the antenna after the optimization

process in the trapped bandwidth between (181-215)MHz.

Figure (5) the relation between forward - to - back ratio and change in frequency


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3.4.3. The relationship between the voltage standing wave ratio

(VSWR) and the change in frequency: -

Shown in Figure (6) that the best value reached by the VSWR before the

optimization process is 1.73 dBic at frequency 194MHz and after

optimization was reached the lowest value at the operating frequency

200MHz which was 1.14dBic ,a value very close to the ideal with the

observation that VSWR less than 2 per bandwidthtrapped between MHz

(195-205) and this means that the antenna works in a narrow

bandwidth, but with very high efficiency.

Figure (6) the relation between the standing wave ratio and the change in frequency


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3.4.4. The relation between the reflection coefficient and the change in

frequency: -

While the studying of the relation between the reflection coefficient

and the change in frequency was found to be before the optimization

process ranges from 0 to -1 until the frequency 177MHz where its value

reduced after this frequency up to the value of -11.59 at frequency

192MHz Similarly, after the optimization process, but begin decreasing

after frequency 184MHz and the lowest value reached was at the

operating frequency of 200MHz which is -23.28.

Figure (7) the relation between the reflection coefficient and the change in frequency


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3.4.5. The relation between the input impedance of the antenna

impedance (Zin) and the change in frequency: -

Input Impedance (Zin)Were studied, which represents tow parts the real

part which is a input resistance of the antenna (Rin) and the imaginary

part which is the reactance of the antenna (Xin), and clear of the twoforms (8) and (9), a significant decrease in the values of the resistance

and the high rising of the value of the reactor while nearing to the value

of the operating frequency 200Mhz until getting the best value for the

resistance which was 43.601 with the value of the reactance of-0.47which gave a suitable impedance to the antenna in the bandwidth (190-

210) MHz as shown in the figure (10).

Figure (8) the relation between the real part of the impedance and the change in frequency

Figure (9) the relation between the imaginary part of the impedance and the change in

frequency


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Figure (10) the relation between the real part of the impedance and the change in frequency


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CONCLUSIONS

In this work has been designed a Crossed Yagi antenna with afrequency of operating 200Mhz, and it is a one of the antennas with

Special characteristics in the applications of YAGI UDA antenna , and the

operation of the design and simulation of the antenna was done by

using the software of 4NEC2 the latest version of it (5.8.8), and the

optimization process was procedure out to reach to the fitness

characteristics at the operating frequency and with a left hand circular

polarization LHCP, And through simulation and study of these

characteristics has been reached the following conclusions: -

1. the antenna Works within bandwidth (180-220)MHz and very high

efficiency at the operating frequency as the value of input

antenna impedance wasZIN= 43.6 which is close to the ideal

value of the cable 50.

2.

The values of the antenna characteristics Improving when increaseeach director in general and the gain in particular, and all the

characteristics stabilized after adding a certain number on the

frequency and the antenna dimensions.

3. have been obtaining an SWR value of 1.15 after the optimization

process, and it is so close to the ideal value of 1.

4.

have been obtaining an gain of 12.07dBic before the optimization

process and maximum gain of 14.17dBic later at the operating

frequency.

5. Maximum relatively significant change has happened to the

dimensions of the antenna elements after the optimization

process was just only in two elements where the estimated rate of

decrease in the length of the driven element of 6.74% and an

increase in the length of the first director of 1.6%, which proves


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how great their effect in improving the characteristics of the

designed antenna.

6. ability of this antenna (Crossed Yagi) to generate linear polarized

both types of horizontal and vertical and circular polarization both

types of right and left (RHCP, LHCP), without a change in the

structure of the physical what sets it apart from a lot of other

wired antennas and qualifies it to work in more than one

application according to the desired polarization.

7. The effective of 4NEC2 in simulating wired antennas and the

ability to improve the characteristics of different dimensionsavailable within the program of the designed antenna and reach

to the accurate results, and close to the ideal values effectively,

and the possibility of studying the characteristics of the designed

antenna detailed and accurate and in addition it provides a

graphical results in two-and three-dimensional.

And accordingly, we recommend that you study this antenna in

practice and identify deficiencies by the manufacturing process.


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REFERENCES

[1] R. E. Collin, Antennas and Radiowave Propagation, International Edition,

McGrraw-Hill, Singapore, 1985.

[2] F. R. Connor, Wave Transmission, Edward Arnold Publishers Ltd, 1972.

[3] L. V. Blake, Antennas, John Wile & sons Inc, New York, 1966.

[4] C. A. Blainins,"Antenna Theory Analysis and design", 3rdEd., John Wiley & sons

Inc, New Jersey, 2005.

[5] J. D. Kraus, Antennas, 2nd

Ed., Mc Grow-Hill, Intrenational editon, New delhi,

1997.

[6] 4NEC2 , Version 5.8.8, By Air voors, Apr 2012.

[7] Dr. Mohamed Kamel and Dr. Majeed Abdul Rahman, "Electromagnetics

Engineering ", Part I, University of Jordan, Amman, 2005.

[8] translation and preparation of Mohamed Anas long, "wireless networks in the

developing countries," Research Center for International Development, Canada, 2008.

[9] d. Hassan Al Kamshushi, "antennas Engineering and wave propagation", Part II,

Dar Al Ratb university, Beirut, 1998.

[10] Dr. Nader Abdel-Hamed Ali Omar, antennas.

[11] H. R. Joseph, "Antenna Selection and Specification Made Easy", Astron

Antenna Co, available at :http://www. Scribd.com .

[12] Article published in the Union de Radioaficionados Espanoles (URE), july,

2006, available at : http://www. Scribd.com .

[13] http://en.wikipedia.org/wiki/Numerical_Electromagnetics_Code

From Wikipedia, This page was last modified on 6 April 2012 at 21:28

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Study and Design Yagi-Uda Crossed Antenna Using 4NEC2