RF Characterization of 3-D-Printed Tunable Resonators on a Composite Substrate Infused With Magnetic Nanoparticles

Three-dimensional additive manufacturing methods are being continuously improved with great interest in low cost and small size radio frequency (RF) circuits. Recent developments in magnetically tunable microwave/RF components are attractive for externally controlled circuits without influencing RF characteristics. This letter focuses on additive manufacturing of ferroic nanomaterials along with their implementation in frequency-tuned RF circuits using an applied magnetic field. Extraction of the additively manufactured magneto-dielectric composite was performed at
$S$
-band frequencies using least squares curve fitting of measured and simulated
$S$
-parameters for annular ring resonator modes. Polylactide (PLA) material used for additive manufacturing was extracted to have
$\varepsilon = 1.80 - j0.031$
. Meanwhile, magnetic CoFe2O4 with 45-nm average nanoparticles size was extracted to have
$\varepsilon $
=
$3.10 - j0.084$
and
$\mu $
=
$1.70 - j0.145$
; while Protopasta’s magnetic filament had
$\varepsilon $
=
$1.80 - j0.031$
and
$\mu $
=
$2.19 - j0.569$
. The 3-D printed magnetic composite is used to design tunable annular ring resonators at 2.4 GHz with up to 38-MHz frequency tuning for an applied 1-kG magnetic field.