Gradient structure for transmitting and/or reflecting an electromagnetic signal

A method (500) for optimizing the transmittance and/or reflectance of an electromagnetic signal of a gradient structure, said gradient structure comprising a plurality of interconnected cells, wherein each cell comprises a through cavity surrounded by walls, wherein the walls of each cell have a gradually varying thickness along a longitudinal direction of the cavity of each cell, said method comprising:

• selecting at least one bandwidth range (501), within which the gradient structure should transmit and/or reflect the electromagnetic signal,
• selecting at least one incident angle (502) of a transmitter and/or a receiver arranged within the gradient structure,
• selecting a thickness of the gradient structure (503),
• dividing each cell into a plurality of layers (504) extending across a longitudinal direction of the cell,
• optimizing values of the permittivity (506) for each of the plurality of layers, in order to maximize the performance of the gradient structure,
• selecting a cell diameter (507) for the cells, wherein the cell diameter is smaller than the smallest wavelength within the at least one bandwidth range,
• selecting the wall thickness (508) for each layer of the cell such that the permittivity of each of the plurality of layers corresponds to the optimized permittivity values.