Analysis of finite parallel-plate waveguide arrays

An analysis has been carried out to determine the edge effects in finite parallel-plate waveguide arrays. The method used in the evaluation is to compare the element patterns and reflection coefficients versus scan for finite arrays with the corresponding results for hypothetical infinite arrays. It is found that, in arrays of empty waveguides, an element has to be about four or five elements removed from the edge in order to be regarded as being in an infinite array environment. On the other hand, when the waveguides are loaded with dielectric plugs having suitable combination of parameters, considerably more elements are needed for the simulation of an infinite array environment due to the appearance of the resonant null in the array transmission coefficient. It is found, moreover, that even though there may be substantial variation in the radiation properties from element to element in finite arrays, particularly so in the case of moderately sized arrays, this variation does not seem to severely degrade the array performance in terms of beamwidth and sidelobe levels.