Practical derivation of slot equivalent admittance in periodic waveguides

This communication describes a procedure for obtaining the equivalent-admittance representation of a slot in a waveguide. The approach is general, but it is particularly interesting for periodic waveguides, because it does not require knowing the Green's function of the wave guides or properly defining the ports in such waveguides. The procedure is demonstrated on a well-known rectangular waveguide. It is later applied to a periodic waveguide and used to design a small array. Measurements of the array performance are shown so as to validate the approach.