General Purpose High Temperature Microwave Measurement of Electromagnetic Properties

Abstract

ABSTRACTAn efficient general purpose method has been developed for implementing a variety of broad band microwave measurement techniques at high temperature. Central to these techniques has been the development of a “dual-waveguide” test fixture. These techniques have been selected, out of necessity, to cover a variety of material types and geometries such as slabs, posts and sheets. These include measurement of complex permittivity and permeability using a modified Nicolson-Ross technique for slabs and Marcuwitz' algorithm for posts. In the implementation of the dual-waveguide, two adjacent and symmetric X-band waveguides are machined from a single block of Inconel alloy 601*, one serving as a test waveguide, the other as a reference waveguide. The dual-waveguide is surrounded by a programmable clam-shell furnace. The reference waveguide provides data which is used to compensate for electrical and dimensional thermal changes in the test section. Combined with commonly used HP 8510 Network Analyzer methods, automated test procedures have been developed to accommodate the various measurement types and sample shapes. Prototypical data will be presented illustrating the effectiveness of some of these techniques. The methods discussed are most useful for rapid data generation over temperatures ranging from room temperature to 2000 degrees F (1093 degrees C) and at frequencies defined by the waveguide dimensions. This paper highlights developments in the dual waveguide system since its construction over one year ago.