Phase-Equalized Periodic Series-Feeding Network from Structural Asymmetry

All open 1D-periodic structures with symmetric unit cell exhibit abrupt variation in their physical parameters at the equi-phase frequency (Γ point of reciprocal space), which usually results in undesirable radiation characteristics. This is the case for leaky-wave antennas (LWAs), but also for Series Feeding Networks (SFNs), where radiation could be considered as energy propagation into the feeding ports. We show here that the response of a periodic SFN can be equalized versus frequency through the equi-phase frequency, just as that of LWAs, by the introduction a proper amount of asymmetry in its unit cell. Moreover, we illustrate this fact with the example of a millimeter-wave (77 GHz) array of antipodal Vivaldi antennas feed by such an asymmetric SFN.