The performance of adaptive antenna array processors is known to decline severely in the presence of array imperfections and uncertainties. Hence the robustness of an array processor against uncertainties is an important issue. Diagonal loading of the correlation matrix is a popular technique applied to the standard Frost processor to increase robustness of the array system. This paper presents a number of robust beamforming algorithms using efficient realization techniques. The techniques do not use a presteered array and allow an array designer to specify the frequency response of the processor in the look direction and steer the main beam of specified frequency response in an arbitrary direction. The proposed techniques are computationally efficient and applicable in environments with strong mutual coupling. Simulation results show the effectiveness of the proposed beamforming algorithms and compare the performance of the beamformer using the proposed techniques with that of existing methods.