2. Electronics - Ijecierd - Design of Dipole Arrays for the - Surendra Kumar (1)

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DESIGN OF DIPOLE ARRAYS FOR THE GENERATION OF MULTIPLE BEAMS

M SURENDRA KUMAR1

, A. GAYATRI2

& S. S. MADHAVI3

1Principal, KLR College of Engineering & Technology, Paloncha, Khammam, Telangana, India

2Assistant Professor, GITAM University, Visakhapatnam, Andhra Pradesh, India

3Associate Professor, KLR College of Engineering & Technology, Paloncha, Khammam, Telangana, India

ABSTRACT

A Dipole is a basic linear bi directional antenna available in different multiple of wave lengths like multiple of ,

/2 and /4 etc, Dipoles are very popularly used in variety of applications in wireless communications systems.

The works on the antennas for the generation of multiple beams are limited as reported in the literature. In view of this,in the present paper, desired numbers of multiple beams are generated from the arrays of dipole radiators and are compared

with the elements isotropic arrays. Taylors amplitude distribution is modified and is used for this paper. The design is

carried out for arrays of 20, 40 and 60 number of elements. The data on the patterns are generated and are useful in

wireless communication and Radar communication.

KEYWORDS:Dipole, Array Antennas, Multiple Beams, Taylors Amplitude Distribution, Radar Communication

INTRODUCTION

Wireless communication demands of spectral efficiency, antenna arrays increase the capacity of spectral

efficiency and the capacity depends mainly on the channel and the antenna characteristics. The capacity can be improved

by proper design of antenna elements and choosing appropriate array configuration and frequency bands [1].

A double-sided and center-feed of printed dipole antenna for dual-band WLAN applications was reported.

An advanced C-shaped parasitic strip with an asymmetric dipole composed for wireless communication system is reported

in the literature [2].

Propagation of electromagnetic (EM) waves above flat lossy ground for obvious applications in the area of

wireless communications reported by [3 - 4], because of the demands on the quality and capacity of the telecommunication

systems is increasing more and more, reconfigurable radiation patterns are desired. Several reconfigurable radiation pattern

antennas have been reported such as a three-layer switchable radiation pattern antenna based on the conventional Yagi

antenna, a hexagonal cylinder antenna with moderate gain, and a central circular patch with two paddle-shaped parasitic

patches. Among many types of reconfigurable antennas, planar structures [5 6] in particular have been extensively

investigated because of their attractive features such as simple structure, low profile, lightweight, and ease of fabrication

and integration. Printed monopole antennas for covering multiband have been reported and the designs occupy a relatively

larger space [7]. The length of the ground- arm of dipole antenna is larger than the signal-arm [8-9] it is beneficial to

enhance the antenna performance.

Optimization algorithms have also been widely used for different purposes in antenna array synthesis.

The uses of genetic algorithm (GA) procedures to optimize array characteristics can be found in [12-13], Direct analysis

International Journal of Electronics,

Communication & Instrumentation Engineering

Research and Development (IJECIERD)

ISSN(P): 2249-684X; ISSN(E): 2249-7951

Vol. 4, Issue 6, Dec 2014, 13-20

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2/8

14 M Surendra Kumar, A. Gayatri & S. S. Madhavi

Impact Factor (JCC): 4.9467 Index Copernicus Value (ICV): 3.0

approaches for radiating structures mounted on arbitrarily shaped platforms are typically based on either the method of

moments (MoM) [10-11], finite element methods (FEM) [14-15].

Taylors [16] reported a method of synthesis of line source for the generation of narrow beams. The same method

is extended to design amplitude distribution of line source required to produce specified number of multiple beams.

The method is further extended for the design of arrays of discrete radiators. The source positions of radiating elements in

the arrays are simply obtained from the sampled locations following the sampling theorem. Further, arrays of dipole

radiators are designed to realize the above mentioned multiple beams.

TAYLORS AMPLITUDE DISTRIBUTION AND RADIATION PATTERNS

The Taylor method is extended in the present work to produce multiple beams of desired number.

The method involves the determination of amplitude distribution for a specified multiple beams. The method of synthesis

is presented below.

(1)

Here n is an integer which divides the radiation pattern into uniform sidelobe region surrounding the main beam

and the region of decaying side lobes.

sinLu , L= array length. = angle measured from maximum radiation.

A = an adjustable real parameter having the property that cosh (A) is the side lobe ratio.

2)21n(2A

n

Using equation (1), the amplitude distribution of the array is found.

Figure 1: Line Source Geometry

RADIATION PATTERN OF A DIPLOE

Figure 2: Radiation from Dipole Antenna


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Design of Dipole Arrays for the Generation of Multiple Beams 15


The vector potential [17] at a point P due to the current element I dz is given by,

(2)

Here d is the distance from the current element to the point P. the total vector potential at P due to all current

elements is given by

(3)

=

It is of interest here to consider radiation fields, d in the denominator can be approximated to r. but in the

numerator, d is the phase term and it is given by

For a half wave dipole,

(4)

But we have

(5)

From equation (4) and (5), we have

(6)

The magnitude of E for the radiation field is


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(7)

Electric field as a function in free space for a dipole of length of 2H is given by

The amplitude of is

(8)

PATTERN MULTIPLICATION

Pattern multiplication is defined that resultant pattern is equal to the array factor multiplied with the element

pattern i.e,

E()resultant= Element Pattern Array Factor

RESULTS

Expression (1) represents the structure of the desired patterns. The number of required multiple beams of the line

source is controlled by n and the parameter A. For the specified patterns containing multiple lobes 4, the amplitude is

numerically computed for a normalized line source of length 2. The resultant radiation patterns of arrays of dipoles are

presented by using pattern multiplication. The resultant distribution for multiple lobes 4 is represented (3-8) for both small

and large arrays for number of elements N= 20, 40 and 60 are presented. A large number of results are presented toindicate the valuation of the sidelobe structure, beamwidth etc.

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

x

A(x)

Figure 3: Amplitude Distribution of Four Multiple Beam Dipole Array of 20 Elements


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-80 -60 -40 -20 0 20 40 60 80-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

theta in degrees

IE(u)Iin

dB

Array of Dipoles

Array of isotropic elements

Figure 4: Four Multiple Beam Patterns from an Array of 20 Elements

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

x

A(x)


-80 -60 -40 -20 0 20 40 60 80-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

theta in degrees

IE(u)Iin

dB

Array of Dipoles

Array of isotropic elements


-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

x

A(x)



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CONCLUSIONS

It is evident from the amplitude distributions presented that the elements at the ends of array are highly excited

and the centre elements are thinly excited. However, in the realized patterns the multiple beams of equal heights are at the

centre. Moreover, the specified numbers of multiple beams are characterized by small beam width for large arrays and high

beam width for small arrays. As discussed in the introduction, Taylors reported an excellent method for the design of line

source to produce optimal pencil beams. In the present work this method is extended for discrete arrays to produce

specified number of multiple beams for both isotropic and array of dipoles. The patterns are obtained with good agreement.

The present approach is suitable for the arrays of any type of non isotropic elements.

REFERENCES

1. Zhijun Zhang, M F. Iskander, J. C. Langer and J. Mathews, Dual-Band WLAN Dipole antenna Using an Internal

Matching Circuit, IEEE Transactions on Antennas and Propagation, Vol.53,No.5, pp. 1813-1818, 2005.

2. C. Y. D. Sim, H. Y. Chien, and C. H. Lee, Dual -/triple-band asymmetric dipole antenna for LAN operation in

laptop computer, IEEETransactionson Antennas and Propagation, vol.61, no.7, pp.38083813, 2013

3. J. R. Wait, The ancient and modern history of EM ground- wave propagation, IEEE Antennas and Propagation

Magazine vol. 40, no. 5, pp. 724, 1998.

4. C. G. Moschovitis, K. T. Karakatselos, E. G. Papkelisetal, Scattering of electromagnetic waves from a

rectangular plate using an enhanced stationary phase method approximation, IEEE Transactions on Antennas and

Propagation, vol.58, no.1, pp. 233238, 2010.

5. S.-J. Wu and T.-G. Ma, A wideband slotted bow-tie antenna with reconfigurable CPW-to-lot line transition for

pattern diversity, IEEE Transactions on Antennas and Propagation, vol. 56, no.2, pp.327334, 2008.

6. G. M. Zhang, J. S. Hong, G. Song, and B. Z. Wang, Design and analysis of a compact wideband

pattern-reconfigurable antenna with alternate reflector and radiator, IET Microwaves,Antenna and Propagation,

vol.6, no.15, pp. 16291635, 2012.

7. L. Lizzi and A. Massa, Dual-band printed fractal monopole antenna for LTE applications, IEEEAntennas and

Wireless Propagation Letters, vol. 10, pp. 760763, 2011.


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8. T.-G. Ma and S.-K. Jeng, Planar miniature tapered-slot-fed annular slot antenna as for ultra wide-band radios,

IEEETransactions on Antennas and Propagation, vol.53, no.3, pp.11941202, 2005.

9. Cabedo, J. Anguera, C. Picher, M. Rib o, and C. Puente, Multiband handset antenna combining a PIFA, slots,

and ground plane modes, IEEE Transactions on Antennas and Propagation,vol.57, no.9, pp.25262533, 2009.

10. Kumar, W, Preface, IEEE Transctions on Antennas and Propagation, Vol. AP-22, No. 1, 13,

Jan. 1974Raffaelli, S, Analysis and measurements of conformal patch array antennas on multiplayer circular

cylinder, IEEE Transctions on Antennas and Propagation, Vol. 53, No. 3, 11051113, Mar.2005.

11. Yan, K.-K. and Y. Lu, Sidelobe reduction in array-pattern synthesis using genetic algorithms, IEEE Transctions

on Antennas and Propagation, Vol. 45, 11171122, July 1997.

12. Allard, R. J, D. H. Werner, and P. L. Werner, Radiation pattern synthesis for arrays of conformal antennas

mounted on arbitrarily-shaped three-dimensional platforms using genetic algorithms, IEEE Transctions on

Antennas and Propagation, Vol. 51, No. 5, 10541062, May 2003.

13. Macon, C. A, L. C. Kempel, S. W. Schneider, and K. D. Trott, Modeling conformal antennas on metallic prolate

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Vol. 52, No. 3, 750758, Mar. 2004

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Pearson Edition, India, 2004

AUTHOR'S DETAILS

A. Gayatri received her B. Tech from JNTU University, Hyderabad and M. Tech, from JNTU University,

Kakinada. She has 10 years of teaching experience. She published 04 technical papers in National and International

conferences. Her fields of interest are Antennas and wave propagation, Microwave engineering and Radar Engineering.

Presently she is working as an Asst. prof, in GITAM UNIVERSITY Visakhapatnam. INDIA.

Dr. M. Surendra Kumar received his B. Tech from Nagarjuna University and M. Tech, Ph. D from Andhra

University. He has 17 years of teaching experience. He published 21 technical papers in National and International

conferences and journals. His fields of interest are Antennas and wave propagation, Microwave engineering and Radar

Engineering. Presently he is working as a Principal in K L R College of Engineering & Technology-Paloncha, Khammam-

Dist, INDIA.


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S. S. Madhavireceived her degree from Andhra University, M. Tech, from JNTU Kakinada. She has 11 Years of

Teaching Experience; She published 4 technical papers in National and International Conferences. Presently She is

Working as an Assoc. professor In K L R College of Engineering & Technology-Paloncha, Khammamt, INDIA.

Documents

2. Electronics - Ijecierd - Design of Dipole Arrays for the - Surendra Kumar (1)