S‐Band Lithium Ferrite Phase Shifters by Arc Plasma Spraying

Abstract

The arc plasma fabrication of ferrite phase shifters has been extended from C‐band to S‐band. Two S‐band lithium ferrite compositions, Ampex 3–601 and Ampex 3–750, were sprayed around a dielectric for phase shifter applications in the 3 to 4 GHz range. The larger dielectric and greater ferrite wall thickness of the S‐band phase shifter necessitated a moderation of the arc plasma parameters from those established for C‐band. The remanence of arc plasma fabricated phase shifters was 250 gauss and 380 gauss for the 3–601 and 3–750 compositions respectively, which were significantly less than the stress free Br's for these compositions. These remanence values produced differential phase shifts of 55°/in. and 81°/in. which were in relative agreement with the 77°/in. differential phase shift produced by a commercial YIG phase shifter with a remanence of 355 gauss. Most significantly, the insertion loss of the arc plasma fabricated lithium ferrite phase shifters was the same as for the commercial YIG phase shifter, i.e. 0.4 dB for a 2.3 inch length. Also, the temperature dependence of Br for the arc plasma phase shifters vas more stable than the commercial YIG.