Printed antenna arrays: a perturbation analysis

An analysis technique for printed arrays is presented. It is based on a perturbation approach, combined with an integral equation solved in the space domain. The initial assumption made is that the current is identical on the different array elements, except for the excitation law. This assumption is then perturbed by defining a new integral equation for each array element, yielding in the end different currents on the different radiators. The condition under which this technique will give goad results for a given array is that the variation of the current distribution between adjacent cells is smooth. Thus, it can be used to study not only periodic phased arrays, but also non-periodic arrays or bi-periodic arrays (for dual frequency for instance). It is also useful for the analysis of excitation failure in an array or to evaluate the influence of non-ideal phase shifters on a periodic phased array. This technique is related to the infinite array+spectral windowing method to which it is completely equivalent in the case of periodic structures. But as it is formulated in the space domain and does not use Floquet modes, it is not limited to the periodic case. This method is valid for arrays of any types of radiating elements but is illustrated in the present paper in the case of printed antennas. Results are shown for the active impedance and the array pattern for several examples, and compared to results obtained by a rigorous element by the element technique [Mosig, 1989].