Waveguide slot arrays with reliability and significant low loss even in micro- and millimeter-wave bands have been widely employed in communication and radar antenna systems. The design requirement for a two-dimensional (2-D) waveguide slot array as shown in Fig. 1 is to realize the aperture field distribution of uniformity or specified taper together with sufficient suppression of reflection at each waveguide input. The accurate analysis of slot active admittances including all the mutual couplings theoretically is highly required. This is achieved by developing a full-model analysis of 2-D waveguide slot arrays [1] using the method of moments (MoM) with dyadic Green's functions, where all the internal and external mutual couplings are precisely evaluated. Furthermore, the reflection from each slot still exists and no additional reflection-cancelling element is introduced for each slot. The beam-tilting technique [2] employing uniform slot spacing varied from half guided wavelength is not sufficient to suppress the reflection below -20dB. As its solution, a design procedure for slot admittance has been proposed to realize input matching in the equivalent circuit model [3].
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