New technique for microwave characterization of material under compressive stress

To investigate the high frequency properties of ferrite materials under stress, a new reflection/transmission cell is designed. A uniaxial compressive stress is applied along a hollow cylinder type sample inserted in a modified coaxial cell. This setup allows measurement of permittivity and permeability under stress (values up to 30 MPa) from 150 MHz up to 10 GHz. Specific calculations are used to take into account the modifications in the line geometry. Accuracy of the measurement method is then evaluated.