A Linear Antenna Array Failure Correction with Null Steering using Firefly Algorithm

The digital beamforming antenna array is one of the most important components in wireless communication systems used in defence applications to improve the system capacity and spectral efficiency. The pattern synthesis of active antenna array is required in many defence applications like radar, satellite communication, sonar, mobile communication etc., where interference signals are considered to be a main problem. It is necessary to produce nulls in specified direction to reduce the effect of interfering signals during antenna beamforming. The desired patterns of linear antenna array with suppressed sectors in the interference directions can be easily achieved with well known analytical techniques, if all array elements radiate properly. In literature, the different conventional1-3 and evolutionary techniques4-11 have been applied for producing nulls in antenna pattern. In general, the antenna array used in different applications consists of large number of radiating elements or sub-arrays. Due to ageing or excessive temperature, there is always a possibility of failure of one or more elements in the antenna array system. The failures of elements in the antenna array destroy the symmetry of the array and may cause sharp variation in field intensity across the array and distort the pattern in the form of increased side lobe level and mainbeam width. The replacement or repair of the defective element of the antenna array is not possible in systems which used for critical situation like war field, space platform etc. It is possible to re-synthesize the radiation pattern of array with minimal loss of quality and suppressed sectors in the interference directions. It can be realized by controlling the excitation of the normal antenna element of the array without replacing the defective element. Many conventional techniques have been proposed to solve only the problem of element failure of antenna array by improving the array pattern in presence of defective elements like a numerical technique based algorithm12 to re-obtain the directional pattern of linear antenna array with single element failure conditions, partial compensated the degraded pattern of planar array using combination of accumulated averaging scheme and conjugate gradient algorithm13, shore’s side lobe sector nulling method14, an orthogonal method15 and conjugate gradient based method16. Generally analytical approaches are unable to handle the antenna array failure problem, when a non uniformly spaced array is considered. This problem is also a hard problem for numerical approaches due to randomness of the geometrical layout of the remaining non defective array elements and of the desired beam shape. Population-based, stochastic search approaches can provide an effective solution for such complex problems, as they tend to explore multiple solutions simultaneously, relying only on zero order information. Many stochastic search methods have been proposed to solve the problem of antenna array failure using genetic algorithm (GA)17-18, particle swarm optimization (PSO)19, adaptive neural system20, simulated annealing (SA)21, firefly algorithm (FA)22 and hybrid methods23. Some stochastic approaches have been also proposed to solve the problem of antenna array along A Linear Antenna Array Failure Correction with Null Steering using Firefly Algorithm