Within the framework of this thesis, the analysis of the infinite slot leaky wave antenna is presented and a new geometry for the feed of a leaky lens is explored. Firstly, the analysis of the propagating leaky wave modes (TM0 and slot modes) is done leading to the findings about the location of the slot pole w.r.t. k0, as well as the contributions of the leaky waves and how they behave when the thickness of air-cavity and width of the slot change. Secondly, the spectral analysis of the near field is put forward with the goal of gaining deeper understanding of the leaky wave modes’ behaviour and their asymmetry. Finally, a new geometry: leaky wave antenna with multiple slots is explored and its potential of lowering the levels of cross pol. is shown.