A non-cylindrical cable balun design having reduced space requirements and that provides for a lighter-weight RF coil is disclosed. The balun includes a balun shell having a non-cylindrical profile, a dielectric foam positioned within the balun shell so as to fill an interior volume defined by the balun shell, and one or more capacitors formed on the balun shell. A non-cylindrical coaxial cable that transmits electromagnetic signals to the balun extends through a length of the balun and is surrounded by the dielectric foam.