Cylindrical substrate integrated waveguide (CSIW) slot arrays with uniform and nonuniform spacings

Pattern synthesis of a traveling wave longitudinal slot array on the broad wall of cylindrical substrate integrated waveguide (CSIW) is presented at 25 GHz. In order to have low side lobe level (SLL) and high directivity, the Elliot´s design procedure for 1 × 25 slotted waveguide array is applied to satisfy the required slot voltage distribution found by aperture projection method for evenly distributed slot array with complex slot voltage distribution. The results are compared with the design which makes use of only the phase compensation of the resonant slots using non-uniform spacing to obtain high directivity. The advantages and disadvantages of both designs are compared in terms of the design procedure and electrical performance. CSIW array with nonuniform spacing has been fabricated and measured. Reasonable agreement between the simulation and measurement results is observed.