Low-Level Garnet Limiters

S- and L-band low-level passive limiters preselectors using polished single crystals of narrow line-width yttrium-irongarnet have been developed. The S-band limiter employed unsubstituted YIG and has an insertion loss of 0.6 db, a limiting threshold of -26 dbm, and a dynamic range greater than 30 db. The L-band limiter used specially grown gallium-substituted YIG crystals, which, when ground into spheres and polished to a high finish, exhibited extremely narrow line widths. The L-band limiter had an insertion loss of 1.1 db, a limiting threshold of -21 dbm, and a dynamic range greater than 25 db. A tuning range from 1120 to 1305 Mc was obtained. Data on frequency sensitivity and SWR are given and indicate that such limiters have a high off-band rejection and a fair power-handling capability. A leading-edge spike of 0.1μ-sec duration was observed. The decline of the various components of the magnetic susceptibility tensor can be used to construct other novel types of limiters. The operation of three such devices-electronically-tunable preselectors, and cavity-type and comb-type limiters-will be described and experimental data given.