Antenna and antenna system for satellite communications

A waveguide array antenna for satellite communications, the waveguide array antenna being configured to transmit and/or receive a first polarization signal and a second polarization signal, the second polarization being orthogonal to the first polarization, and comprising an array of unit cells, plural unit cells of the array of unit cells comprising a radiating element, said waveguide array antenna further comprising:

• a grid configured to divide the radiating element into a number of radiating sub-elements having an inter-element distance that is lower than or equal to a wavelength at a highest frequency of operation of the waveguide array antenna;
• and an electromagnetic band gap layer configured to support said grid above the radiating element;
• wherein said grid comprises a number of grid unit portions, wherein said electromagnetic band gap layer comprises a number of pins protruding from walls of each of the grid unit portions wherein each unit cell of the array of unit cells further comprises a mode filter connected to the radiating element, said mode filter being located below the radiating element and being configured to pass a fundamental mode of propagation of said first polarization signal and said second polarization signal and to reject higher order modes of propagation;
• and wherein said mode filter comprises a center portion and two end portions at two sides of the center portion, wherein the center portion comprises a waveguide having a cross section with a Malta Cross shape, and wherein each of the two end portions has a form of a square waveguide comprising hollow cylindrical elements at corners of the square waveguide.