A Standing-Wave Method for the Microwave Evaluation of Dielectric and Magnetic Materials

摘要

The report presents results of an investigation into the standing-wave method for evaluation of microwave loss and effective dielectric constant of low-loss ceramic materials. The objective of the study was primarily to devise a sensitive method for determination of the dependence of loss on the magnetic state of ferrites and ferrimagnetic garnets in various conditions of remanence. Design of a special coaxial slotted line and specimen holder is described. Preparation of specimens, including metallization of surfaces, is discussed. Data taken at S-band (approx. 3 GHz) on a dielectric and garnet material are presented. They show that the sensitivity of the method in its present form is marginal for the purpose, although within an order of magnitude of that of conventional resonant-cavity methods. A means for accurately determining a correction for distributed loss in the slotted line is presented. The report includes graphs of the theoretical voltage ratio (1/VSWR) versus electrical length of the specimen, for low-loss material having dielectric constants in the range 8 -- 16, together with the computer program used to calculate these graphs. (Author)