Automatic Matching of Microwave Energy Transfer and Simultaneous Measurements of Permittivity

The microwave energy transferred into a material varies with dielectric parameters. Thefunctionofimpedance adaptation is to send back to the material the wave part reflected by it. If the material undergoes significant changes, mainly due to its temperature, automatic impedance adaptation is required. Our purpose was to achieve simultaneously automatic adaptation and measurement of dielectric parameters derivedfrom instantaneous measurements of reflection coefficients of the changing material.The device that was used consists of a standard hybrid tee with two sliding short circuits. After determining the tee scattering matrix, we established the relation between the two sliding short circuits positions and the material complex reflection coefficient was established. Thus complex permittivity (ε’-jε”) could be obtained. Implementation was carried out in X band (9.5GHz) and then in S band (2.45 GHz).