Design, Analysis, and Optimization of the Array of Axial Rectangular Slots on a Cylindrical Waveguide

In the current work, for the first time, the design equations for an array of rectangular slots axially placed on a cylindrical waveguide are driven and presented, making it possible to attain asymmetrical and non-broadside patterns with higher bandwidths. The method of least squares is then used for both the radiation pattern synthesis with the specified side lobe level and the array input impedance matching. For optimization, the error function comprised of the three terms of impedance matching, array pattern synthesis, and slot design equations is constructed. To minimize the error function, the genetic algorithm combined with the conjugate gradient method is utilized and the geometrical characteristic of the slots defined. This procedure increases the design speed and provides the means to synthesize any desired pattern for an array of axial rectangular slots on a cylindrical waveguide. Numerical and fabrication examples are presented as illustrations of the proposed synthesis method. The results of the proposed method are verified by using the commercial software High-Frequency Structure Simulator (HFSS) in comparison to measurement results obtained out of the proposed prototype of a fabricated antenna operating at the frequency of 9 GHz.