Digital Beamforming Algorithms for Smart Antennas

Smart antennas have been gaining popularity in the recent times, as a means to enhance data rate. The reason behind this development is the availability of high-end processors to handle the complex computations involved. The major advantage of digital beam former is that phase shifting and array weighing can be performed on digital data rather than in hardware. Digital beam forming (DBF) is a bridge between antenna technology and digital technology. An antenna can be considered to be a device that converts spatiotemporal signals into strictly temporal signals, thereby making them available to a wide variety of signal processing techniques. In this way all of the desired information that is being carried by these signals can be extracted. The weights for the antenna elements are carefully chosen to give the desired peaks and nulls in the radiation pattern of the antenna array. Digital beam forming is the process of altering the complex weights to maximize the quality of the communications channel. A digital beam former is able to automatically optimize the array pattern by adjusting the elemental control weights until a prescribed objective function is satisfied. This project analyses the performance of three adaptive algorithms Least Mean Square (LMS), Recursive Least Square algorithm (RLS) and Conjugate gradient method (CGMETHOD) algorithm for computing the array weights. The weights obtained by the above algorithms are then used to steer the antenna array beam in the direction of interest, and forming the nulls thereby in the direction of interferer enhancing SNR. One of the major requirements for Long Term Evolution (LTE), high data rate, can hence be achieved by smart antennas.