International Journal of Recent Technology and Engineering (IJRTE) ISSN: 2277-3878, Volume-8 Issue-2, July 2019 2671 Published By: Blue Eyes Intelligence Engineering & Sciences Publication Retrieval Number: B2342078219/19©BEIESP DOI: 10.35940/ijrte.B2342.078219 Null Steering In Linear Arrays for Multiple Null Positions Jyothi Budida, V. Satyanarayana Murthy, Sreerama Lakshmi Narayana Abstract In the current article, the linear array null pattern synthesis for beam forming applications is presented using the novel social group optimization algorithm(SGOA) . As a part of the simulation, the circular array of 24 element length is considered with a spacing of inter-elements of 0.5 λ is considered. These patterns are synthesized for null steering and side lobe level (SLL) optimization. Strategy of designing arrays with single and multiple nulls are presented in more robust manner in which the width of the beam and SLL are also included for objectives of design. Keywords : Beam forming, Null positioning , SGOA. I. INTRODUCTION Now a day’s challenge of the modern telecommunications is the ever-growing subscribers number. This is in conflict with the limited spectrum available with the provider. With the available resources, the capacity which is proportional to the number of users served in a sector of the cellular station is limited. With the increasing number of users, it is always an inconceivable task to detect signal coming in a particular direction. In addition to these, the environment is more polluted with several other factors like fading and co-channel interference. In order to overcome these, the solution lies in application of adaptive antenna arrays for such environment. Such radiating element consists of more than one similar type of antennas that are electrically connected with each other. These adaptive arrays are designed, so as to suppress the interference signal that leads to improved signal reception characteristics. Hence, the objectives of such array synthesis are to generate radiation patterns that are completely defined by the null steering and null positioning. The fundamental construction blocks of null placement and beam steering Null placement and beam steering are the fundamental building blocks of beam forming. Beam forming technique accepts desired signal that is arriving at an angle known as direction of arrival (DOA) of desired signal and suppresses the interference signal from other directions. Beam steering involves in directing the main beam of the required signal to the DOA while nulls are positioned in the interference signal DOA. Several synthesis techniques are proposed that effectively design the arrays for increasing the SNR in multipath environment. In this paper, one such technique known as amplitude only using SGOA is proposed. The simulation-based experiments are carried out to meet several challenges like observing narrow single and multiple nulls under constrained and unconstrained conditions. Revised Manuscript Received on July 06, 2019. Jyothi Budida, Asst. prof of physics in Aditya College of Engineering, Surampalem. Satyanarayana Murthy, Assistant Professor of physics in GIET College of Engineering, Rajahmundry. Sreerama Lakshmi Narayana, M. Sc.(Nuclear Physics with Neutron Physics as specialization) ,Andhra University, 1972 PGDIF, Andhra University, 1975 , Ph. D. in Nuclear Physics, Andhra University, 1979 The framework of the simulation experimentation is explained in the subsequent sections and divided into eight cases. SGOA is used for synthesis process. II. PROBLEM FORMULATION Array design formulation for the corresponding fitness formulation for the desired objectives are presented in this Section as follows. (A) Array factor formulation Linear array design problem involves in generating optimal set of design parameters like amplitudes or inter-element spacing or both that yields main beam of the required signal to the DOA while nulls are positioned in the interference signal DOA predefined BW. Array factor of LA is -(1) Here N relates to element n and to element n=1,2 ..... N k is the amount of the wave specified as 2Π/λ θ is the angle of observation A n relates to the nth element's excitation amplitude d n refers to the distance between the reference point and the nth component The description of this array factor is given in previous Chapters. In brief the optimization problem involves in determining the vector I of size N=12 in order to acquire the required pattern of radiation. This is given as I=[I 1 , I 2 , ……..I 24 ] -(2) The longitudinal length between two sequential elements is maintained uniformly at λ/2. III. FITNESS FORMULATION For objectives such as single or multiple narrow nulls and desired SLL, the formulation of the fitness function is given as -(3) -(4)