Design, optimization and VSWR improvement of a standing wave longitudinal slot array on a rectangular waveguide

In this paper, the least square method is used to design, optimize and improve the VSWR of a linear longitudinal slot array on the broad wall of a rectangular waveguide. This method is based on the Elliot´s design formulas and utilizes a three term error function including the two terms Elliot´s design formulas, input impedance matching and pattern synthesis at three different frequencies (namely 9.35, 9.375 and 9.4 GHz). By minimizing the error function according to the design parameters such as: slot lengths, offsets, excitation voltage of each slot and spacing between the slots, the optimum value of these parameters are derived. Knowing the optimization results, a linear slot array with appropriate VSWR and desirable pattern is designed. Advantages of this method to other design methods are the ability to find the proper parameters to improve VSWR and relatively increase the bandwidth in addition to the synthesis of a pattern with desirable properties. Results from this method of design and HFSS simulation results are in a very good agreement showing the good matching and accuracy of the proposed method.