Leakage phenomena in planar arrays

A review of some recent results concerning radiative characteristics of phased arrays of planar leaky-wave antennas is presented, with particular reference to end-of-scanning effects and to the occurrence of grating lobes. On the basis of a full-wave numerical simulation of infinite linear arrays of microstrip lines, performed via a spectral-domain moment-method approach in the unit cell, the phase and leakage constants of the involved modes have been determined as a function of the physical parameters of the structure and of the phase shift between elements. A transition region between a leaky-wave range and a guided-wave range is reported for the operating mode in correspondence to array radiation at endfire. Moreover, the excitation of a new, additional leaky mode is shown to be responsible for the presence of grating lobes in widely-spaced arrays. Numerical simulations performed on realistic array structures are presented to validate the proposed analysis.