Unexplored Scanning Features and Relevant Interpretations for Phased Arrays of Printed Leaky-Wave Antennas

Different novel behavioural features are presented for the radiation performance of linear phased arrays based on printed-circuit leaky-wave antennas for microwave and millimetre-wave applications. By means of a rigorous spectral-domain approach in the unit cell, we have particularly investigated the relevant beamscanning properties in terms of spatial harmonics, as a function of both the phase shift and the spacing between radiating microstrip lines. We have thus found and interpreted in a consistent way various previously-unknown characteristics, such as transition regions between leaky-wave and surface-wave regimes, and the occurrence of spurious radiation in largely-spaced arrays due to the presence of additional complex improper modes. These findings seem to sensitively clarify what is to be expected from this type of structures.