The ferrite-filled, antisymmetrically-biased (Ferrite-FAB) rectangular waveguide (RWG), as illustrated in Fig. 1, has been shown to provide levels of phase shift that are significantly greater than those obtained using conventional rectangular waveguides loaded with either single-slab or dual-slabs of ferrite. At millimeter-wave frequencies the device can be conveniently manufactured using multilayer ceramic technology. For example, a 2mm wide, 35 GHz ferrite-FAB nonreciprocal phase shifter has been recently demonstrated, in which the entire device, including the waveguide and its bias windings, were embedded in low temperature cofired ferrite ceramic [1]-[2].