A novel algorithm in a linear phased array system for side lobe and grating lobe level reduction with large element spacing

Phased array antennas are generally used for the inherent flexibility to beamforming and null-steering electronically. In the phased arrays the side lobes level (SLL) level is main problem which causes waste of energy or saturation of the receiver in the case of presence of the strong spatial blockers. In this paper, a weighting method was first used to reduce the level of SLL. However, this method increased the beam width and reduced resolution, which is not suitable for track applications. In next step hoping to increase the resolution, the distance between the antennas increased. But in this way, grating lobes appeared in the final beam. In fact, the main idea of the article is to solve this problem. Two methods of randomization at the antenna position and coefficients level were examined for a large element spacing in the order of one wavelength which cause significantly reduction in the side lobe level and grating lobe level simultaneously, while the beam resolution has increased. It is shown that for a linear 11-element phased array system with up to 180° scan angle for simultaneously beam-forming and null-steering a resolution of 10° was obtained for the amount of difference between desired beam and null points. The proposed system reduces the grating lobes to below − 13 dB, this technique leads to the realization of arrays with more number of elements, in which the weighting functions and mode excitation of the elements can be controlled by an adaptive signal processing unit in scanning phased array systems.