Abstract-We demonstrate, for the first time to our knowledge, a passive, electrically tunable integrated radio frequency (RF) inductor based on a planar solenoid with a thin-film ferromagnetic(FM) (NiFe) core. Variation of inductance is achieved by leading an additional dc current through the same device, thereby changing the effective permeability of the FM core. Tuning ranges (relative variations in inductance) of 85%, 35%, and 20% are achieved at 0.1, 1, and 2 GHz, respectively, for inductances in the range of 1 to 150 nH.Index Terms-Inductor, on-chip, radio frequency (RF), tunable circuits and devices.
We propose and theoretically investigate a superlattice consisting of alternating normal-metal and ferromagnetic layers as a low-loss conductor for realization of planar-integrated radio-frequency devices. At sufficiently high frequencies, the negative permeability of the ferromagnetic films effectively compensates the positive permeability of the nonmagnetic metal layers, leading to an overall suppression of the skin effect. Simulations based on realistic material parameters demonstrate the effectiveness of this approach regardless of intrinsic relaxation losses in the magnetic films.
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AbstractIntegrated solenoidal radio-frequency (RF) inductors and transformers with a ferromagnetic core are demonstrated by using a fully IC-compatible fabrication process. For a 500-nmthick NisUFQo film, a cut-off frequency of over 7.5 GHz for a 2.5-nH inductor is realized. Optimum inductor design based on tailored inductance, quality factor, and cut-off frequency is discussed. RF transformers realized have a coupling factor of -70% up to 200 MHz.
Abstract-We present a self-consistent calculation of the effective anisotropy of patterned, integrated ferromagnetic films. For comparison, experimental data were obtained from electroplated thin (0.5 m) Ni-Fe films with different patterns. The effective anisotropy of patterned samples was increased by shape demagnetizing effects from just 10 Oe up to 100 Oe. The samples with suitable characteristics were subsequently used as cores for on-chip inductors and microstrips.
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