Multilayer waveguide structures for radiofrequency antennas, radiofrequency antennas comprising the same

A multilayer waveguide structure for a radiofrequency antenna, the waveguide structure comprising:

• a stack of substrates separated by each other by interface layers, the substrates having a permittivity larger or equal to 1, and
• metal vias or metal trenches formed in at least some of the substrates,
• the waveguide structure being configured to guide electromagnetic waves between a first element connected to the topmost substrate and a second element connected to the lowest substrate,
• wherein each interface layer comprises a first metal layer, a second metal layer, and an adhesive layer between the first metal layer and the second metal layer,
• wherein at least one of said interface layer comprises patterned structures,
• wherein for each patterned structure, an additional metal thickness of the first metal layer is obtained by adding an additional metal layer to the first metal layer and/or an additional metal thickness of the second metal layer is obtained by adding an additional metal layer to the second metal layer and the interface layer is locally patterned so that the adhesive layer is thinner while still preventing a direct electric contact between the first and second metal layers,
• wherein the patterned structures are configured to limit the propagation of the electromagnetic waves through the adhesive layer,
• wherein each said patterned structure is located near or at the base or the top of a metal via or metal trench, and
• wherein the metal vias or trenches are configured to delimit guiding channels for the electromagnetic waves.