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 $\delta _{\mu }$ ) 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 Ni x Zn 0.85–x Cu 0.15 Fe 2 O 4 (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 Ni 0.38 Zn 0.47 Cu 0.15 Fe 2 O 4 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.

Miniature low-profile multiband ferrite antennas were designed with various BaCo 1.4 Zn 0.6 Fe 16 O 27 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 ( $f_{1}$ ), second ( $f_{2}$ ), and third ( $f_{3}$ ) 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 $f_{2}$ and $f_{3}$ , while the gain at $f_{1}$ 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 BaCo 1.4 Zn 0.6 Fe 16 O 27 substrate loading allows antenna miniaturization with enhanced antenna performance.

An omnidirectional low-profile multiband antenna is designed and fabricated for vehicular telecommunication applications. The fabricated antenna with a radiator patch size of 0.26 lambda(L) x 0.3 lambda(L) has a low-profile of 0.022 lambda(L) and shows multiple resonant frequencies at 1.14, 1.91, and 2.45 GHz. Omnidirectional radiation patterns in the azimuth plane and vertical polarization at all operating frequency bands were obtained. Antenna gains greater than 1.7 dBi were obtained at the three operating frequencies, and the antenna height is 6 mm. Therefore, the proposed antenna is applicable to the vehicular telecommunication system.

A method to design an adjustable wideband impedance matching structure based on the impedance transformer concept is proposed in order to enhance wideband impedance matching. The designed coupled line feed structure (CLFS) provides a wide impedance characteristic via an operating principle similar to that of an impedance transformer. The CLFS enables tuning capability for the impedance characteristic of an inverted-F antenna (IFA) through adjustments in the line width and gap between the two CLFS spirals. By adding the proposed CLFS to the antenna feed, the bandwidth of the original IFA can provide about 22% wider coverage when compared with an IFA alone, especially over the LTE band, without changing the original antenna design. For frequencies below 1100 MHz, the impedance bandwidth of an IFA is about 40% at a center frequency of 862 MHz. This covers the LTE 17 (704746 MHz)/13 (746787 MHz), GSM 850 (824894 MHz)/900 (890960 MHz)/1800 (17101880 MHz)/1900 (18501990 MHz), and WCDMA (17102170 MHz) bands. (C) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:522526, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27356

We demonstrate that even small relative permeability (μ r <; 2) is effective enough in the improvement of gigahertz (GHz) antenna performance. Based on antenna performance simulation results, a 1.57 GHz small permeability (μ r = 1.97) hexaferrite antenna (8 mm × 5 mm × 1.5 mm) was fabricated and characterized for antenna miniaturization factor, fractional bandwidth (FBW), and radiation efficiency (RE). Return loss and FBW were 13 dB at the resonance frequency fr of 1.57 GHz and 7% at voltage standing wave ratio of 2.5:1, respectively. On the other hand, antenna simulation results show that an alumina ( ε r = 9.4) antenna with tan δ ε of 0.01 and 0.05 resonates at fr of 1.65 GHz and has FBW of 4.1% and 6.0%. The hexaferrite antenna volume was 30% of the alumina dielectric antenna volume. The experimental RE of the hexaferrite antenna was 66% at 1.57 GHz, which is much higher than the simulated RE of 55.4% for the lossy dielectric antenna (ε r = 11; tan δ μ = 0; tan δ ε = 0.05), even though ferrite has tan δ μ = 0.05 and tan δ ε = 0.008. The antenna performance simulation results confirmed that the RE of the ferrite antenna can be increased to 80% at tan δ μ of 0.01. Both simulation and experimental results demonstrate that even small permeability of GHz hexaferrite greatly contributes to miniaturization, FBW, impedance matching, and RE.

We demonstrate that magnetic loss tangent of M-type hexaferrite can be controlled by a small dc magnetic field, thereby improving radio frequency (RF) antenna radiation efficiency and realizing antenna miniaturization. Magnetic loss tangent (tan δμ) of the M-type BaFe9.6Co1.2Ti1.2O19 hexaferrite at 200 MHz decreased significantly from 11.8% to less than 1% as the applied dc magnetic field increased from 0 to 400 Oe. This is because the contribution of domain wall motion to permeability dispersion is decreased, and the ferromagnetic resonance frequency increases with the magnetic field. Antenna simulation results showed that radiation efficiency of the designed ferrite helical antenna increased from −22.9 to −9.2 dB with dc magnetic field of 400 Oe. Therefore, the small dc magnetic field played a key role in reduction of tan δμ of hexaferrite and improvement of antenna performance in the RF range.

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.

Magnetic properties and ferromagnetic resonance (FMR) frequency of Ni0.7Mn0.3−xCoxFe2O4 ferrites (NiMnCo: x = 0.00, 0.04, 0.06, and 0.10) were controllable with the concentration of cobalt (Co). The measured saturation magnetization remains almost constant at 57 emu/g in the studied range of the Co content. However, the coercivity increased to 72 Oe (x = 0.10) from 12 Oe (x = 0.00). Ferromagnetic resonance frequency increased from 129 MHz to the GHz frequency with increasing the Co content from x = 0.00 to x = 0.10, but the real part of permeability decreased to 1.6 from 16.7. This is because FMR frequency increases with the magnetocrystalline anisotropy (Hk) of the Co according to fr = (γ/2π)Hk. The permeability decreased with the Co content by µ = 1 + (4πMs/Hk). Temperature coefficient, in the range of 20–100 °C, was 0.002 for Ni0.7Mn0.3Fe2O4 (x = 0.00) and 0.008 for Ni0.7Mn0.2Co0.1Fe2O4 (x = 0.10). The results suggest that Ni0.7Mn0.3−xCoxFe2O4 ferrites have excellent temperature stability, and also are applicable to very high frequency: 30–300 MHz) and ultra high frequency: 300 MHz–3 GHz) devices.

This article describes the design, fabrication, and measurement of an internal FM radio ferrite sheet flexible antenna using an arrow‐shaped patch to enhance passive gain performance for mobile handsets.To obtain sufficient passive gain performance ≥–20 dBi, an arrow‐shaped patch is inserted in the antenna radiator and monopole type wire is used. The measured result of the fabricated antenna provides passive gain performance (15.6–13.5 dBi) from 86 to 108 MHz with the frequency modulation (FM) bandwidth from 83.20 to 123.72 MHz (≤voltage standing wave ratio (VSWR) 6:1). Also, a good radiation pattern is achieved within the FM bandwidth (86–108 MHz) range. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26180

We demonstrate that Sn/Zn-substituted strontium M-type hexaferrite (SrSn2.5Zn2.5Fe7O19 = Sn/Zn-SrM) can provide high performance and a uniform radiation pattern over a wide frequency band for gigahertz chip-antenna applications. Saturation magnetization and coercivity were 68.5 emu/g and 46 Oe. Real parts of permeability and permittivity were 1.37 (loss tan δμ = 0.13) and 22.2 (loss tan δε = 0.09) at 2.44 GHz, respectively. A Bluetooth Sn/Zn-SrM chip antenna has a bandwidth of 780 MHz (2.15-2.93 GHz) at S11 <; -10 dB, maximum three-dimensional (3-D) peak gain of 1.25 dBi, and radiation efficiency of 60% at 2.4 GHz. Our antenna performance simulation suggests that radiation efficiency can be increased up to 98% with a low magnetic loss tan δμ of 0.01. 3-D radiation patterns were omnidirectional in the Bluetooth frequency range. Therefore, Sn/Zn-substituted strontium M-type hexaferrite is a promising magnetic material for future gigahertz antenna applications.

Bluetooth ferrite antenna was fabricated on Co(2)Z (Ba3Co2Fe24O41) hexaferrite-glass composite substrate and characterized. The fabricated antenna has a total volume of 36 mm(3) (3 x 8 x 1.5 mm(3)) 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. (C) 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1222-1225, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25982

In these days, RFID adoption in supply chain management system needs technically part of the performance improvement of RFID Anti-Collision technology. We contrived new scanning algorithm that improve RFID Anti Collision performance, also can be applied to existing RFID readers. In this paper, the proposed algorithm were applied to the actual logistics scene recognition performance much better than the existing practices are presented. For improve of RFID Anti Collision performance, our algorithm implemented in the middleware associated with RFID PDA readers, and actually mount the RFID inventory data from the experiment were accumulated. Through this experiment, the proposed algorithm was confirmed that helps to minimize unaware area of the existing RFID inventory system and significantly improves performance of RFID field solution.

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.

An internal MIMO antenna for mobile applications is proposed. Helical-type antenna elements are used to construct the MIMO system. The resonance frequencies of the MIMO antenna are controlled by the number of turns per helix. A multi suspended line with lumped elements is used to reduce the coupling between the antenna elements. The antenna elements are located at the top edges of the ground plane, and a decoupling network is inserted between the ova antenna elements. The performance of the prototype antenna is analyzed through the scattering parameters, actual diversity gain, envelope correlation coefficient, and channel capacity measurements. The isolation characteristic and MIMO performance can be improved by using the decoupling network at the LTE service band. (C) 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2314-2317, 2011; View this article online at wileyonlinelibrary.com. DOT 10.1002/mop.26293

Dual band fen ire chip antenna having 105 mm(3) of volume was fabricated with Ba3Co2Fe24O41 (Co(2)Z) glass composite and antenna performance was evaluated The permeability and permitivity of the composite woe in the range of 1 92-2 12 and 733-745 respectively flout 1 575 to 2 45 GHz Magnetic and dielectric loss tan delta of CO(2)Z glass composite Itas <3 5% in the 1 5-30 GHz range The 3D average gain and bandwidth of the 4011 shake milled and sintered Co(2)Z glass composite antenna were 1 27 dB and 355 MHz at 1 575 GHz -4 08 dB and 270 MHz at 2 45 GHz respectively Simulated S parameter spectrum units in good am cement with experimental results (C) 2010 Wiley Periodicals Inc Microwave Opt Technol Lett 53 14-17 2011 View this article online at wileyonlinelibrary com DOI 10 1002/mop 25672

A method to extend the bandwidth of epsilon negative (ENG) zeroth‐order resonator (ZOR) antennas using a Co2Y hexagonal ferrite (Ba2Co1Zn0.7Cu0.3Fe12O22) is presented.It is accomplished by using the ferrite helical loading for shunt inductance of ENG ZOR unit cell. The Co2Y hexagonal ferrite has been developed for performance improvement of mobile handset antennas. The permittivity of the developed Co2Y hexagonal ferrite is about 9.3, and the permeability is about 4. An ENG ZOR antenna based on simplified planar mushroom structure unit cell was fabricated, and bandwidth enhancement and good radiation performance were achieved. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:87–90, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25650

A long-term evolution (LTE) MIMO ferrite antenna was fabricated on Ni0.5Mn0.2Co0.07Fe2.23O4 ferrite substrate (14 × 7 × 3 mm3) and characterized for antenna performance. Measured return loss and isolation were -26 and -16.4 dB at 720 MHz, respectively. Correlation coefficient calculated from experimental S-parameters (S11, S22, S12, and S21) was less than 0.02 in the LTE band. Three-dimensional peak gain at 746 MHz was measured to be -8.83 dBi for antenna 1 and -8.32 dBi for antenna 2. These low antenna gains are attributed to high magnetic loss of ferrite substrate. Performance simulation suggests that antenna gain can be further improved up to -3.14 dBi with the use of low-loss ferrite.

An internal broadband IFA antenna for mobile is proposed. The designed internal antenna consists of L-shaped zeroth order resonator and folded first order Inverted-F element and has a comparatively small volume of 45 mm × 10 mm × 1 mm. The proposed antenna can achieve the wide bandwidth for GSM band.

In this paper, a low-loss Ni-Mn-Co ferrite (Ni0.76Mn0.24-xCoxFe2O4 with x = 0-0.04) has been developed for miniaturization and performance improvement of mobile handset antennas. The developed ferrite material has almost equal permittivity and permeability of 7-9, as well as sufficiently low dielectric and magnetic loss tangent less than 0.001 and 0.01 below 200 MHz, respectively. Miniaturization factor of about 8 and normalized impedance of about 1 were obtained at 200 MHz. A helical antenna operating at terrestrial digital multimedia broadcasting (T-DMB, 174-216 MHz) band was fabricated on the ferrite substrate, which has compact size, low loss, wide bandwidth, and good radiation performance.