In this paper, a new resonant slotted-waveguide antenna array based on the open-ended SIW resonator is presented. In the conventional resonant slotted-waveguide arrays an in-phase excitation is achieved by adjusting the distance between slots one half guided wavelength (λg/2) and alternating themon the opposite sides of the center line. The open-ended SIW resonator is capable of supporting infinite wavelength propagation and hence the distance between slots can be unequal with the same phases. This capability can be used for distance tapering to have low sidelobe level (SLL). A 9-element array with unequal spacing based on this kind of resonator is designed and simulated at 10 GHz. By using genetic algorithm (GA), the distances between slots is determined in order to have a low SLL. The simulation results show that the side lobe level of the designed antenna is 16 dB.

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