Ferrite Material Characterization in a Static Bias Field for the Design of a Tunable Cavity
During the development of ferrite-loaded accelerating cavities, the electromagnetic properties of the dispersive ferrite material need to be known. We describe a coaxial short-circuit measurement technique to measure the complex permeability of toroidal-shaped samples (127mm outer and 70mm inner diameter) that are exposed to an external magnetic bias field. The external magnetic bias field is applied perpendicular to the RF magnetic field. With this method it is possible to characterize the frequency dependence of the permeability for a frequency range of 1100MHz. The dependence of the permeability on the external magnetic bias is presented for the ferrite G-510 from Trans-Tech Inc. and the material characterization is shown in the same frequency range. The measurement results are verified by simulations of the measurement set-up.
Accurate Measurement of Ferrite Garnets to be used for Fast-Tuned loaded cavities in the range of 20-40 MHZ
For the implementation of ferrite-tuned cavities with orthogonally biased ferrites in the frequency range of 2040 MHz, different types of ferrite garnets were evaluated in terms of their electromagnetic properties. This paper describes a precision measurement method applicable to small-sized ferrite samples of 1-square-inch surface and 1.8 mm thickness in the given frequency range by means of a one-port reflection method. The material samples are exposed to a magnetic bias field range with different orientations. We present a detailed description of this technique as well as material results obtained.
A Broad-Band, Automated, Stripline Technique for the Simultaneous Measurement of Complex Permittivity and Permeability
A broad-band automated technique for making frequency-swept measurements of complex permittivity and permeability simultaneously is described. Epsilon/sub r/ and µ/sub r/ are computed from S-parameter measurements made on a strip transmission-line device loaded with the material under test. The derivation of epsilon/sub r/ and µ/sub r/ as functions of S/sub 11/ and S/sub 21/ is included, as well as a practical design for a stripline sample holder. Measured epsilon/sub r/ and µ/sub r/ data for several dielectrics and ceramic ferrites is also presented. The technique has been found to have an overall accuracy of better than +-5 percent.