• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.904-912
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• 2007

In this paper, a broadband 4-way power divider which can be used from 20 MHz to 500 MHz in the V/UHF band is designed using transmission-line transformer and ferrite toroid. A 4:1 impedance transformer is realized and this 4:1 transformer is connected with bridge-type 2-way dividers to form a 4-way rower divider, Insertion loss of about 6.8dB, isolation of less than -20dB, and return loss of less than -15dB in most band of interest are measured.

• Journal of the Korean Ceramic Society
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• v.30 no.5
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• pp.357-364
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• 1993

Chemical reaction occurred in the interface of Mn-Zn ferrite and glass after bonding. Effects of the formation of reaction layer on the magnetic properties were investigated. The composition of glass was 23PbO-61SiO2-6ZnO-8Na2O-2K2O and the ferrite was chosen to have a high permeability. Toroid samples of ferrites bonded with glasses, were heat-treated at $700^{\circ}C$, 80$0^{\circ}C$ and 90$0^{\circ}C$ for 1h. The reaction was observed to increase with bonding temperature, resulting in the development of reaction layer. Subsequently the initial permeability was found to be decreased. The permeabilities decreased by 25% with increasing bonding temperature from $700^{\circ}C$ to 80$0^{\circ}C$. At the bonding temperature of 90$0^{\circ}C$, the permeability was decreased by 45%, compared to that of 80$0^{\circ}C$.

• Journal of electromagnetic engineering and science
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• v.16 no.3
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• pp.150-158
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• 2016

This paper reports on a study of LiNiZn-ferrite composite as a radiation absorbent material (RAM). The electromagnetic (EM) wave absorbers are composed of an EM wave absorbing material and a polymeric binder. The surface morphology, chemical composition, weight percent of the ferrite composite of the toroid sample, magnetic properties, and return loss are investigated using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and network analyzer. For preparing the absorbing sheet, chlorinated polyethylene (CPE) is used as a polymeric binder. The EM wave absorption properties of the prepared samples were studied at 4 - 8 GHz. We can confirm the effects of the thickness of the samples for absorption properties. An absorption bandwidth of more than a 10-dB return loss shifts toward a lower frequency range along with an increase in the thickness of the absorber.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.730-734
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• 1995

The variation of magnetic permeability and dielectric constant and their relationship with microwave absorbing properties are investigated in sintered Ni-Zn ferrite. Toroid specimens of ${(Ni_{0.5}Zn_{0.5}O)}_{1-y}{(Fe_{2}O_{3})}_{1+y}$ ferrites are prepared by conventional ceramic processing technique. The large change in magnetic permeability is observed by the variation of excess $Fe_{2}O_{3}$ in the Ni-Zn ferrites. The more the iron-excess from y=0.04 to y=0.12, the lower value of both $\mu_{r}'$ and $\mu_{r}"$ is observed. However dielectric permittivity increases with the increase of the increase of the excess $Fe_{2}O_{3}$. The control of permittivity is realized by nitrogen sintering atmosphere and excess $Fe_{2}O_{3}$ respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.1
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• pp.43-52
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• 1996

Nonreciprocal twin-toroid ferrite phase shifter is designed, fabricated, and tested. ABCD matrix method is used to design the phase shifter and to compute its optimum dimen- sions. Quarter-wave two-section impedance matching transformers are utilized in order to match the impedance of the empty guide to that of the ferrite-loaded guide. Driving circuit controls the current needed to drive the phase shifter. Measured insertion loss and VSWR characteristics within the operaring band(9.1GHz ~ 9.5GHz) are less than 1.2dB and 1.15, respectively. After temperature compensation technique is appied to the phase shifter, the measured phase error of the phase shifter is less than $\pm4$ between $-10^{\circ}C\;and\;+60^{\circ}C$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.416-422
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• 2007

In this paper, a broadband 2-way power divider which can be used from 20 MHz to 500 MHz in the V/UHF band is designed using transmission-line transformer and ferrite toroid. A 2:1 impedance transformer instead of the conventional 4:1 impedance transformer is realized and this 2:1 transformer is connected with the conventional bridge-type 2-way divider to form a 2-way power divider. Insertion loss of about 3.5 dB, isolation of less than -10 dB, and return loss of less than -10 dB in most band of interest are measured.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.331-334
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• 2001

In this study, the magnetic properties for Ni-Zn ferrite were investigated as the function of $Co_3$ $O_4$ additive contents which was predicted to improve the resonance frequency. Toroid specimens with the composition of N $i_{0.8-x}$Z $n_{0.2+x}$F $e_2$ $O_4$(x = 0, 0.05, 0.1, 0.15) ferrites were preparation by conventional ceramic processing technique. The maximum resonance frequency of 19.905 MHz and the permeability of 90.88 in 10 MHz were attained to the N $i_{0.8}$Z $n_{0.2}$F $e_2$ $O_4$with $Co_3$ $O_4$0.3 wt%. Both of the permeability in 10 MHz and the resonance increased to 107.11 and 19.005 MHz respectively for the N $i_{0.8}$Z $n_{0.2}$F $e_2$ $O_4$with $Co_3$ $O_4$wt% than the N $i_{0.8}$Z $n_{0.2}$F $e_2$ $O_4$/ with the free $Co_3$ $O_4$composition.composition.

• Journal of the Korean Magnetics Society
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• v.7 no.1
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• pp.13-18
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• 1997

The effects of the various raw material composition and sintered temperature on the physical properties of Ni-Zn ferrite have been investigated. They turned out to be spinel structure by X-ray diffraction and the size of grain from microscope was from 6 ${\mu}{\textrm}{m}$ to 16 ${\mu}{\textrm}{m}$. As the sintering temperature was increased from 1030 $^{\circ}C$ to 1070 $^{\circ}C$, the initial permeability and magnetic induction has increased and the both of Q factor and coercive force has decreased. The coercive force and curie temperature were almost the same at each specimen. Their values were about 0.20 Oe and 220 $^{\circ}C$. The frequency of specimen will used in the range from 400 kHz to 20 MHz. The basic composition of $Ni_{0.14}Zn_{0.64}Cu_{0.22}Fe_2O_4$ (specimen B) sintered at 1050 $^{\circ}C$ shows the best results at magnetic induction($B_r & B_m$).

• Journal of the Korean Magnetics Society
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• v.16 no.5
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• pp.255-260
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• 2006

The basic composition of Ni-Zn ferrite was $(Ni_{0.35}Cu_{0.2}Zn_{0.45})_{1.02}(Fe_2O_3)_{0.98}$ (group A) and $(Ni_{0.4}Cu_{0.2}Zn_{0.4})_{1.02}(Fe_2O_3)_{0.98}$(group B) with additional 0.1 mol% $CaCO_3$ and 0.03 mol% $V_2O_5$. For high permeability and acceleration of grain growth, $CaCO_3$ and $V_2O_5$ was added. The mixture of the law materials was calcinated at $600^{\circ}C$ for 2 hours and then milled. The compacts of toroidal type were sintered at different temperature ($1,050^{\circ}C,\;1,070^{\circ}C,\;1,100^{\circ}C$) for 2 hours in air followed by an air cooling. Then, effects of various composition and sintering temperatures on the microstructure and physical properties such as density, resistivity, magnetic induction, coercive force, initial permeability, quality factor, and curie temperature of the Ni-Zn ferrite were investigated. The density of the Ni-Zn ferrite was $4.90{\sim}5.10g/cm^3$, resistivity revealed $10^8{\sim}10^{12}{\Omega}-cm$. The average grain size increased with the increase of sintering temperatures. The magnetic properties obtained from the aforementioned Ni-Zn ferrite specimens were 4,000 gauss for the maximum induction, 0.25 oersted for the coercive force, 2,997 for the initial permeability, 208 for the quality factor, and $202^{\circ}C$ for the curie temperature. The physical properties indicated that the specimens could be utilized as the core of microwave communication and high permeability deflection yoke of high permeability.

• Journal of the Korean Magnetics Society
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• v.5 no.4
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• pp.269-274
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• 1995

The basic composition of Mn-Zn ferrite was $Mn_{0.631}Zn_{0.316}Fe_{2.053}O_{4}$(specimen A), $Mn_{0.584}Zn_{0.312}Fe_{2.104}O_{4}$(specimen B) and $Mn_{0.538}Zn_{0.308}Fe_{2.154}O_{4}$(specimen C) with additional 0.1 mol % $CaCo_{3}$ and 0.04 mol % $V_{2}O_{5}$. For high per¬meability and acceleration of grain growth, $CaCo_{3}$ and $V_{2}O_{5}$. was added. The mixture of the law materials was calcinated at $950^{\circ}C$ for 3 hours and then milled. The compacts of toroidal type were sintered at different temperature($1250^{\circ}C$, $1300^{\circ}C$, $1350^{\circ}C$) for 2 hours in $N_2$ atmosphere. The effects of the various raw material composition and sintered temperature on the physical properties of Mn-Zn ferrite have been investigated. They turned out to be spinel structure by X-ray diffraction and the size of grain from SEM was from $18\;\mu\textrm{m}\;to\;23\;\mu\textrm{m}$. As the sintering temperature was increased from $1250^{\circ}C$ to $1350^{\circ}C$, the initial permeability and magnetic induction has increased and the both of Q factor and coercive force has decreased. The coercive force and curie temperature were almost the same at each specimen Their values were about 0.45 Oe and $200^{\circ}C$. The frequency of specimen will used in the range from 200 kHz to 2 MHz. The basic composition of $Mn_{0.584}Zn_{0.312}Fe_{2.104}O_{4}$(specimen B) sintered at $1300^{\circ}C$ shows the best results at magnetic induction (Br & Bm).