Search

We report a simple wireless power charging (WPC) antenna system (50 mm \times40 mm \times0.1 mm) for use in simulating power transfer efficiency ( \eta ) with and without ferrite and a metallic object (battery case), thereby identifying suitable magnetic parameters and ferrite sheet thickness. The simulation results suggest that magnetic loss tangent (tan ) and permeability ( \mu ' ) need to be less than 0.05 and higher than 125 at 13.56 MHz, respectively, to achieve at least 75% of the transfer efficiency ( \eta \mathrm {max} ) of the WPC antenna without ferrite and the metallic object. Accordingly, we have fabricated NixZn0.85–xCu0.15Fe2O4 (x = 0.32 – 0.38) spinel ferrites using a one-step sintering process and obtained relatively high \mu ' of 169 and low tan \delta \mu of 0.1 with a nickel (Ni) concentration of 0.38. This magnetic loss is still too high to achieve 75% of the \eta \mathrm {max} value. In order to further reduce the magnetic loss, a two-step sintering process was used. The two-step sintered Ni0.38Zn0.47Cu0.15Fe2O4 shows $\mu '$ of 132 and a tan \delta \mu of 0.03 at 13.56 MHz, respectively. Therefore, this ferrite meets criteria identified by the transfer efficiency simulation and is a good candidate for 13.56-MHz wireless power transfer charging antenna system. In addition, our designed WPC system is capable of evaluating other magnetic materials that are suitable for WPC antenna applications. [ABSTRACT FROM AUTHOR]

ABSTRACT We have developed a miniaturized implantable ferrite antenna, operating in the industrial, scientific, and medical band (2.4-2.5 GHz). The dip-coated NiCo ferrite films effectively reduces the antenna resonance by 110 MHz, with a 4.2 dB reflection coefficient improvement as compared with an antenna without ferrite. The ferrite antenna also reveals a 6 dBi and 35 MHz improvement in realized gain and −10 dB bandwidth, respectively, at resonance. The effects of ferrite film loading on antenna performance are further investigated with parametric simulations and experimental comparisons.© 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2745-2749, 2016 [ABSTRACT FROM AUTHOR]

Miniature low-profile multiband ferrite antennas were designed with various BaCo1.4Zn0.6Fe16O27 hexaferrite loading configurations and fabricated for telematics applications. Experimental permeability ( \mu ^\prime ) of 2.0, permittivity ( \varepsilon ^\prime ) of 7.3, magnetic loss tangent (tan \delta \mu ) of 0.035, and dielectric loss tangent (tan \delta \varepsilon ) of 0.005 at 1 GHz were used for antenna performance simulations. It is observed that a hollow rectangular ferrite substrate loading shows simulated maximum ripple levels ( \Delta = E\theta \\max -E\theta \\min ) of 2.2, 3.0, and 1.9 dB at the first ( f1 ), second ( f2 ), and third ( f3 ) resonant frequencies, respectively, implying wider coverage than other loading configurations. Miniaturization factor is greater than that of air-core antenna, and the impedance matching and bandwidth are improved with the ferrite loading. Higher gain of the ferrite-loaded antenna than the air-core antenna was observed at f2 and f3 , while the gain at f1 remains almost the same. Moreover, the vertical component E\theta is greater than the horizontal component E\phi , showing the vertically polarized operation of the antenna. Based on the measured and simulated results, it is concluded that the BaCo1.4Zn0.6Fe16O27 substrate loading allows antenna miniaturization with enhanced antenna performance. [ABSTRACT FROM PUBLISHER]

Bluetooth ferrite antenna was fabricated on CoZ (BaCoFeO) hexaferrite-glass composite substrate and characterized. The fabricated antenna has a total volume of 36 mm (3 × 8 × 1.5 mm) and showed wide bandwidth (390 MHz at VSWR < 2). The maximum 3D peak-gain and radiation efficiency were measured to be 3.32 dBi at 2.35 GHz and 77.7% at 2.3 GHz, respectively. The 3D peak gain of 2.45 dBi and 3D average gain of −1.89 dBi were obtained at the Bluetooth central frequency of 2.45 GHz. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1222-1225, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25982 [ABSTRACT FROM AUTHOR]

We have studied soft M-type BaFe9.6Co1.2Ti1.2O19 hexaferrite for T-DMB (terrestrial digital media broadcasting) antenna applications. The effect of magneto-dynamic properties on antenna size, bandwidth, and radiation efficiency was investigated. The soft M-type BaFe9.6Co1.2Ti1.2O19 hexaferrite (Co/Ti-substituted BaM) was synthesized by a combination of ball-milling and two-step sintering processes. Permeability and loss tan δµ of the Co/Ti-substituted BaM were measured to be 4.5 and 0.039 at 200 MHz, respectively. The Wheeler cap method and network analyzer were used to evaluate antenna radiation efficiency and measure return losses, respectively. Our experimental results show that the low-loss Co/Ti-substituted BaM is an excellent soft magnetic material for VHF (very high frequency: 30-300 MHz) miniature antenna applications. [ABSTRACT FROM AUTHOR]

Low magnetic and dielectric loss Co2Z (Ba3Co2Fe24O41)-glass composite in the frequency range of 1-3 GHz is reported. Co2Z-glass composite was prepared by firing a mixture of 40 h shake-milled Co2Z hexaferrite powder and borosilicate glass at 950 °C for 1 h. The real part of permeability decreased slightly from 2.29 to 1.96 at 2.4 GHz as the glass content increased from 0 to 4 wt. %, but magnetic loss decreased less than 0.02. On the other hand, the real part of permittivity was 7.29 at 0 wt. % and 7.28 at 4 wt. % glass and dielectric loss was less than 0.01 at 2.4 GHz. The 3D peak gain of Co2Z-glass composite chip antenna was measured to be 3.32 dBi at 2.35 GHz. These results imply that the Co2Z-glass composite is an underpinning magnetodielectric material for gigahertz antenna applications. [ABSTRACT FROM AUTHOR]

We report a low magnetic loss Ba 3 Co 2 Fe 24 O 41 (Co 2 Z) hexaferrite for use in gigahertz (GHz) antennas. Acid-etching was very effective in removal of unwanted Y-type hexaferrite (Ba 2 Co 2 Fe 12 O 22 ) from calcined Co 2 Z powder. It is found that the calcined and acid etched (AE) Co 2 Z hexaferrite shows a low magnetic loss tangent (tan δ μ ) of 0.012 and 0.037 at 1 and 2 GHz, respectively. These low tan δ μ are attributed to removal of Y-type hexaferrite, which possesses a lower anisotropy field ( H k ) than W-type hexaferrite (BaCo 2 Fe 16 O 27 ). The figure of merit (FOM) of the AE Co 2 Z hexaferrite is 141.7 and 48.7 at 1 and 2 GHz, respectively. These FOM are much higher than the FOM of previously reported low-loss magnetic materials. Therefore, the AE Co 2 Z hexaferrite can be a good candidate for GHz antenna application in the ultra-high frequency (UHF) band. [ABSTRACT FROM AUTHOR]