The nature of the end-of-scanning region in printed-circuit arrays of leaky-wave antennas

In this work, some original behavioral features of printed-circuit arrays of leaky-wave antennas have been investigated. In particular, by means of a rigorous spectral-domain approach in the unit cell, we have studied the end-of-scanning operation of a microstrip leaky-wave antenna array as a function of the phase shift between elements. A careful analysis in terms of the involved proper and improper spatial harmonics has shown that a transition region exists for the operating mode from a spatial leaky-wave regime to a surface-wave regime. This transition corresponds to the radiated beam hitting the array plane and evolving through a previously unexplored phase gap into a surface wave propagating at an angle with respect to the microstrip line sources. Such finding allows us to achieve a more complete view of the radiation properties of this class of scanning antennas.