Abstract: A line-replaceable unit for a phased array antenna including a thermally conductive housing having a front face and an opposed rear face, at least one open-ended waveguide extending through the housing from the front face to the rear face, at least one first radiating element including the waveguide and adapted to emit energy in a first frequency band; and at least one second radiating element positioned on the front face of the housing and adapted to emit energy in a second frequency band distinct from the first frequency band. The waveguide is dimensioned to pass energy in the first frequency band and is exposed to the environment outside the housing at the front and rear faces to define a cooling duct passing through the housing.