Higher-Frequency Permeability Measurement by Harmonic Resonance Cavity Perturbation Method

A new combination of electric field antenna and coupling hole plates is introduced to extend the measurable frequency range of rectangular waveguide-type harmonic resonator to evaluate complex relative permeability of magnetic composites by perturbation method from 18 to 38 GHz (
$K$
-Ka-band). The noise suppression performance parameter
$\omega \mu ^{\prime \prime }=2\pi f\mu _{0}\mu _{r}^{\prime \prime }$
(
$\text{k}\Omega $
/m) is useful to estimate the performance of magnetic powder composite sheets, especially beyond the 10 GHz range where relative permeability is as small as 0–2. The
$\omega \mu ^{\prime \prime }$
exhibited a maximum of 166
$\text{k}\Omega $
/m at 27 GHz for a carbonyl iron powder (CIP) composite sheet, and as high as 510 at 38 GHz for a Sendust sheet. These values meet
$\omega \mu ^{\prime \prime } \ge100 \text{k}\Omega $
/m criteria that some commercially available noise suppression sheets exhibit in their recommended frequency range. These performances match Sub-6 and 28 GHz bands used for 5G telecommunication equipment.