Abstract A practical procedure to reduce the back lobe level of linear microstrip antenna arrays is presented in this paper. The novel concept consists in the design of the radiators asymmetrically positioned with respect to the ground plane. In order to validate this technique, a four-element linearly-polarized array is designed in the HFSS software and a prototype is manufactured. Furthermore, the design of beamforming circuit to achieve broadside radiation and -20 dB side lobe level is detailed. Very good agreement between simulated and experimental results is obtained. Although the technique is presented for linearly polarized arrays, it is general and can also be applied in the circularly polarized ones.