Various exemplary embodiments relate to a support assembly for a planar filter. The assembly includes a u-shaped housing with angled surfaces at the inner corners of the u-shape, a first dielectric plate having a first angled surface in contact with one of the angled surfaces of the housing, a second dielectric plate having a second angled surface in contact with the other angled surface of the housing, at least one compressible ring, and a cover. The planar filter is supported between the first dielectric plate and the second dielectric plate. The cover compresses the compressible ring to apply downward force on the first and second dielectric plates. The downward force is translated to an inward force by the angled surfaces of the housing. The angled surfaces of the housing apply an inward force on the first dielectric plate and the second dielectric plate.