Fine-Wire Ferrite Limiter

The subsidiary resonance observed in ferrite at high microwave magnetic field intensities is suitable for limiting purposes. The limiter threshold power is related to the units of magnetic field intensity produced in the ferrite per unit of power input. The circumferential field about a wire is directly proportional to the current and inversely proportional to the wire diameter. Thus a fine wire embedded in ferrite will produce intense microwave fields at low microwave power levels provided that the wire is properly matched to the microwave structure. The response of a ferrite limiter to a microwave pulse characteristically exhibits a leakage spike and a plateau whose power level is proportional to ΔHK2. Thus, low threshold power levels normally can be achieved with narrow-linewidth materials. This paper analyzes the fine-wire technique for limiter applications and shows that threshold power levels less than a watt can be achieved in ferritewith wide linewidths. Particular structures were designed, built, and evaluated. It was found that a threshold power level less than one watt was achieved, and that the spike duration decreases rapidly with increasing power.