Planar Arrays Implementation using Smart Antennas for Different Elements Configurations and Comparison

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1 Planar Arrays Implementation using Smart Antennas for Different Elements Configurations and Comparison Suraya ubeen,a.jhansi Rani 2, A..Prasad 3 Associate Professor ECE CRTC Hyderabad,Telangana,India Professor ECEVRSEC Vijayawada, Andhra Pradesh,India Professor ECE JTU Kakinada, Andhra Pradesh,India Abstract-Smart antenna systems are one of these technologies which could provide directed radiation pattern towards desired direction, better capacity and reduce interference.which affects used bandwidth antennas are not smart; it is the overall system that tell them what to do is smart. Smart antenna Systems had two main parts Beam forming, which the radiation pattern is shaped and directed through it, and Direction of Arrival (DOA) algorithm that detects the user s location and uses it to direct the pattern. The antennas in the array interact constructively in the desired direction and destructively in other directions. In this paper, various evolutionary algorithms are used to adapt the weights of the smart antenna arrays to maximize the output power of the signal in desired direction and minimize the power in the unwanted direction. Different types of arrays (i.e., Linear, Circular, and Planar) are considered here planar arrays are implemented with different elemental configurations and are compared. Simulation and results obtained Using ATLAB to indicate Preference of using smart antenna over conventional single element antenna with planar arrays and it provides a way better performance. Keywords:Planar, RadiationPattern,Plots,Array Factor. I. Introduction Planar arrays are often considered as capable array geometries for producing highly directive patterns which has very low SLL on either side of the symmetrical radiation characteristics. They are even capable of steering the beam towards any angle of interest as per requirement and application in wireless communications for smart antennas []. In this thesis we have considered a planar regular geometry with x and y dimension to form a rectangle as shown in Fig... The spacing vector is a 2D matrix in which every value is excitation coefficient of positioned element. These rectangular arrays can be further transformed in to several other 27 Surayaubeen,A.Jhansi Rani, A..Prasad geometrical shapes identical to it. In simple a square geometry can be derived from the rectangle. Fig.. 2-Dimensional Planar Array II. athematical Analysis of Uniform Linear Array It is known that the ULA typically has uniform excitation with uniform inter-element distance as well as the phase being nullified. Under such case the excitation-coefficients are given as[2] I =I 0 I 2 = I 0 e j 2I 3 = I 0 e j I = I 0 e j (.) The corresponding field distribution can be given as E θ I 0 e jkr E θ2 I 0 e j 2 4πr = E 0 (.2) e jk (r dcosθ ) 4πr = E 0 e j ( 2+kdcosθ )

2 E θ3 I 0 e j 3 e jk (r 2dcosθ ) 4πr E θ I 0 e j = E 0 e j ( 3+2kdcosθ ) e jk (r ( )dcosθ ) 4πr E 0 e j ( +( )kdcosθ ) (.3) The final reference to the field distribution is given as = E θ = E θ + E θ2 + E θ3 + + E θ = E 0 AF AF= + e j ( 2+kdcosθ ) + e j ( 3+2kdcosθ ) + +ej( +( )kdcosθ (.4) The phase representation of the ULA can mentioned as = 0 Applying (.6) in (.8) 2 = α 3 = 2 = ( ) (.5) AF= + e j (α+kdcosθ + e j2(α+kdcosθ + + ej( ) +kdcosθ (.6) = + e jψ + e j2ψ + + e j Ψ Ψ = +kdcosθ = j (n )Ψ n= e (.7) The final numerical expression is treated as the typical phasing function. This is mathematical function of several factor that control the pattern. If the array factor is multiplied by e jψ the result is AF e jψ = e jψ + e j2ψ + + e jψ (.8) Subtracting produces the following equation where AF is defined as e j ( )Ψ 2 AF e jψ = (e jψ ) AF= (e jψ ) = e j Ψ 2 e jψ sin ( Ψ 2 ) e jψ 2 e j Ψ 2 e j Ψ 2 e j Ψ 2 e j Ψ 2 = sin ( Ψ 2 ) (.9) The expression given above refers to the phase distribution with uniform amplitude excitation. The entire expression is divided in to two parts. The last typical part in the expression... refers to the phase. This is with reference to the center. If the array center is altered then the corresponding position. Under such case the AF is given as AF = sin (Ψ 2 ) sin ( Ψ 2 ) (.0) The AF values are normalized in order to have the highest value as.the normalized array factor is (AF) n = sin ( Ψ 2 ) sin ( Ψ 2 ) (.) III. Planar Array Factor Formulation ow for a Planar array elements are placed along X-axis and elements are placed along y-axis. The array factors is given by AF x = I m e j m (kd xsinθcos +β x ) m = (.2) AF y = I n e j n (kd y sinθcos +β y ) n= (.3) where sinθcosф= cosγ x. Consider x-axis as reference and the correspondingγ. is the included angle. While formulating the above it is taken in to consideration that the inter-element spacing is unaltered while the phase is nullified and refers to currentexcitation.[3]. From the geometry described above, it can be inferred that the typical representation of the array has rows and for each row there are subsequent elements forming another array.such arrays are arranged as linear arrays to form a rectangular array. Also, the scenario of uniform spacing and null phasing are incorporated. It is also important to state that the amplitude distribution and corresponding array factor values are also normalized. Then, the AF of the entire x array is AF = n= e AF = S x. S y where S y = AF y I n I m e j m (kd x sinθcos +β x ) m = j n (kd y sinθsin +β y ) S x = AF x = m = (.4) I m e j m kd x sinθcos +β x = I n e j n kd y sinθsin +β y (.5) n= 28 Surayaubeen,A.Jhansi Rani, A..Prasad

3 agnitude in db Polar Plot for Planar array on Phi plane In the array factors above we have sinθcos = x. r = cosγ x sinθsin = y. r = cosγ y As a result it can be understood that the resultant response of rectangular array is similar to array of linear arrays. As a preliminary study all the elements in the array are uniformly excited to referred as uniform planar array. Thus AF = I 0 e j m (kd xsinθcos +β x ) e j n (kd y sinθsin +β y ) m= n= The normalized array factor is obtained as below AF n θ, = sin ( Ψ x 2 ) sin ( Ψ x 2 ). WhereΨ x = kd x sinθcos + β x, sin ( Ψ y 2 ) (.6) sin ( Ψ y 2 ) (.7) (a) Polar Plot with respect to Plane Polar Plot for Planar array on theta plane Ψ y = kd y sinθsin + β y 0 III.Comparison of 5x5 Elements and 2x2 Elements Configurations A square planar array of element length 5 x 5 (i.e., 25 elements) and 2 x 2 (i.e., 44 elements) with uniform spacing of 5 and uniform element excitation of unity amplitude and phase is implemented using atlab Ver The various Radiation Pattern Characteristic parameters: 3-dB BW, ull-bw, Directivity and SLL for both array configurations are tabulated in Table and Table 2 respectively.the polar plot and magnitude plots for 5 x 5 and 2x2 planar array synthesis for smart antennas are shown in Fig.2 and Fig..3 respectively. It is depicted from the results that the radiation patterns obtained from 2 x 2 element-2d, smart antenna with planar array configuration antenna has high directivity, better SLL reduction and narrow beam width compared to 5 x 5 element-array antenna. Polar Plot for 5x5 Elements The Polar plot of the 5x5 element uniform planar array at the angles of 45 and are shown in Fig.5.2. The corresponding 3 db beam width are at angles and b) Polar plot with respect to Plane Fig.2 Polar plot representing Radiation Pattern of 5 x 5 Element /Uniform Space Planar array agnitude Plot for 5x5 Elements From the magnitude plot we can observe that there is an -3dB is marked in the graph, the Side Lobe values are observed at various angles such as (Ɵ,Ǿ) at -9.69d B and aximum value is at dB dB agnitude Plot (db) Vs Theta in degrees Fig.3 5 x 5 Elements /Uniform Space Planar Array agnitude Plot Table I. 5x5Elements/Uniform Space Planar Array 29 Surayaubeen,A.Jhansi Rani, A..Prasad

4 agnitude in db Antenna Parameters AntennaParameters 3-dB Beam Width ull-ull Beam width Directivity Side lobe level easurement Theta Phi 47 0 Theta 47 0 Phi 94 0 in ax db db db Polar Plot for 2 x2 Elements The Polar plot of the 2x2 element uniform planar array at the angles of 45 and are shown. The corresponding half power beam width are and (a) Polar plot with respect to (b) Polar plot with respect to Fig.4 Polar Plot representing Radiation Pattern of 2x2 Element /Uniform Space Planar array agnitude Plot for 2 x2 Elements Polar Plot for Planar array on Phi plane 0 Polar Plot for Planar array on theta plane From the magnitude plot we can observe that there is an -3dB is marked in the graph, the Side Lobe values are observed at various angles such as (Ɵ,Ǿ) at-9.3 d B and d B dB Theta in Degrees Fig.5 2 x2 Element /Uniform Space Planar array agnitude plot Table 2. 2x2Element/Uniform Space Planar Array Antenna Parameters Antenna Parameters 3-dB Beam Width ull-ull Beam width Directivity agnitude (db) Vs Theta in degrees easurement\ Theta Phi 7 0 Theta 4 0 Phi dB SLL inval -9.3dB axval db IV.Comparison of 5&2 Elements Configurations PAA with =25 and 44 considering inter-element distance of 5 and with broadside radiation characteristics is considered for simulation based experimentation in this Section.It is observed that with the compromise in increasing the cost and size of the antenna, the efficiency of the antenna in terms of BW and other direction characteristics are increased[4].with support to the previous statement results show the Beam width and Directivity of 2 x 2 planar arrays is greater by 0 db and 2.5 db than 5 x 5 planar array antennas. Surayaubeen,A.Jhansi Rani, A..Prasad

5 However 2x2 planar array performs provides high directivity and narrow beam width, in some context like side lobes it offers quite good number and may not suit applications where low interference from other signals (while used as receiving antenna) and high power utilization (while used as transmitting antenna) is needed. In other terms this design is costlier and massive as more array elements are needed for getting high directivity. V.Conclusion Thorough mathematical and simulation analysis of planar array antennas is provided in this Chapter. Investigations on the performance of the planar 2D antennas are carried out in terms of generated radiation patterns with different dimensions of the square array. Several parameters like first null beam width and 3dB beam width as well as the position of the main beam are measured from the obtained radiation pattern. The study revealed various characteristics like side lobe level ratio which is a very important parameter to describe the array interference characteristics. The obtained side lobe level clearly specifies the performance of the planar antenna with varying the dimensions of the geometry. Acknowledgment I thank my Guide Dr.A..Prasad Vice Principal, Professor ECE JTU Kakinada, for his constant support in my research work and also I thank my co-guide Dr.A.Jhansi Rani for her effective ideas in publishing this paper References []J.F. Deford, Phase only Synthesis of inimum Peak Side Lobe Patterns for Linear and Planar arrays,ieee Transactions on Antenna and Wave Propagation, Vol. 36,o.5, pp. 9-20,July988. [2]Pathak, arendra ath Synthesis of Thinned Planar Circular Array Antennas Using odified Particle Swarm Optimization, Progress In Electromagnetic Research Letters, Vol. 2, pp.87-97, [3]B. Preetham Kumar, Generalized Analytical Technique for the Synthesis of Unequally Spaced Arrays with Linear, Planar, Cylindrical and Spherical Geometry, IEEE Transactions on Antenna and Wave Propagation,Vol. 53,o.2,pp , February Surayaubeen,A.Jhansi Rani, A..Prasad [4] A. anikas, A. Alexiou, and H. Karimi, Comparison of the ultimate direction-finding capabilities of a number of planar array geometries, IEE Proceedings - Radar, Sonar and avigation, vol. 44, no. 6, p. 32, 997 [5] K.K. Yan and Y. Lu, Side lobe reduction in arraypattern synthesis using genetic algorithm, Antennas and Propagation, IEEE Transactions on, vol. 45, o. 7, pp. 7-22, July 997. [6]Rivas, A., J. A. Rodriguez, F. Ares, and E. oreno (200), Planar arrays with square lattices and circular boundaries: Sum patterns from distributions with uniform amplitude or very low dynamic-range ratio,ieee Antennas Propagation ag., 43(5), 93. Author(s) Profile Surayaubeen working as Associate professor in ECE department CRTC Hyderabad. I have Submitted my Ph.D in icrowave Antennas in February 207 and awaiting for report. Currently the total teaching experience is 9 years, published 0 International Journals under my research and attended 2 international Conferences and published papers in it. I have attended 4 workshops and participated in FDP s and seminars.2 B.TECH Projects completed in DLRL under my guidance,total 8 B.TECH Guided projects,3.tech Projects submitted. am reviewer of several international journals and editorial board member also.life member of IETE,ISTE. Dr. A.Jhansi Rani obtained her B.Tech Degree in Electronics and Communications Engineering from Velagapudi Ramakrishna Siddhartha Engineering College, Vijayawada in 99 and.tech Degree in icrowave Engineering from Institute of Technology, Banaras Hindu University, Varanasi in 993. Later she joined as a Faculty inece Dept., of V.R.Siddhartha Engineering College, Vijayawada. She obtained Ph.D. Degree from JTU, Hyderabad in August Presently,

6 she is working as a Professor of ECE and PG - Programme Coordinator at V. R. Siddhartha Engineering College. Dr.Jhansi has more than 22 years of teaching experience, and has about 50 technical publications in various International and ational Journals and Conferences to her credit. She is the Life ember of FIETE, ISTE, BESI, SECEI. She received grants from DST, DLRL and AICTE in the area of Shared Aperture and smart Antennas. Her fields of interest include Electromagnetics, Smart Antennas, Analysis of icrowave Components, E Waves and Transmission Lines, umerical ethods and Applications. Dr.A.allikarjuna Prasad completed his Ph.D in the field of Antennas in 2009 from JTU Kakinada. He is currently Vice Principal Administration & Professor in ECE.He has vast experience of 26 years in teaching, 2 years in research and 3 years industrial experience. He guided 6 Ph.D scholars,3submitted and 5 ongoing.he published papers in 20 conferences and 28 International Journals. 32 Surayaubeen,A.Jhansi Rani, A..Prasad