Apertured Ferrite Slab Subsidiary Resonance Power Limiters

New geometrical structures of ferrite and dielectric, in standard rectangular waveguide, have been employed as subsidiary resonance power limiters for X-band receiver protection. The structures consist of monolithic ferrite slabs containing circular or rectangular apertures some of which are filled with low loss dielectric. The limiters combine the desirable feature of low threshold power levels, typically 30W, previously reported only for complex laminated structures, with the constructional simplicity of single slab devices. Dynamic ranges of limiting of 30dB and more have been achieved by grading the dielectric filling factors of the apertures along the lengths of the slabs. The effects of thin metallic conducting sheets for suppressing higher order modes of propagation at low input powers are also discussed.