• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.4
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• pp.715-720
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• 2012

This study presents a hybrid balanced voltage controlled oscillator (VCO) circuit which is suitable for low phase noise operation at sub-1V supply voltages. Half circuits of the proposed VCO use the varactor-integrated feedback capacitors in their respective circuit. The varactor-integrated feedback capacitors further increase the negative resistance of the equivalent tank thereby ensuring stable start-up of oscillation even at the sub-1V supply voltage. In addition, this work theoretically analyses the phenomenon of the increase of the negative resistance. Simulation results using a $0.18{\mu}m$ RF CMOS technology exhibit the phase noises of -122.4 to -125.5.8 dBc/Hz at 1 MHz offset from oscillation frequency of 4.87 GHz over the supply voltages of 0.6 through 0.9 V.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.556-560
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• 1995

The absorption properties of Cu-Zn ferrite/rubber composite microwave absorbers with PZT(Lead Zirconate Titanate) additive were evaluated. The composite specimens have prepared by molding and curing the mixture of matrix rubber and Cu-Zn ferrite powders which are synthesized by the coprecipitation method using Fe Cl/sub 3/ .center dot. 6H/sub 2/O, CuCl/sub 2/ .center dot. 2H/sub 2/O and Zn Cl/sub 2/ as a starting raw materials. PZT is used as another filler particles to adjust the material constants of Cu-Zn ferrite/rubber composite specimens. We have found that the material constants of specimens could be controlled by various PZT mixing ratio. On the Cu-Zn ferrite/rubber composite specimens with PZT 10[wt%] additive, the reflection losses were larger than 30[dB] in the frequency range from 2.72 to 4.4[GHz]' by adjusing the thickness.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.333-339
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• 2003

Ba (Co$_{1}$ 3/Nb$_{2}$ 3/)O$_3$(BCN) has a 1:2 ordered hexagonal structure. Q-value of BCN increased with increasing sintering temperature however, it significantly decreased when the sintering temperature exceeded 140$0^{\circ}C$ Ba (Co$_{1}$ 3/Nb$_{2}$ 3/)O$_3$(BZN) has the 1:2 ordered hexagonal structure and the degree of the 1 : 2 ordering decreased with the increase of the sintering temperature. The Q value of the BZN increased with increasing the sintering temperature and BZN sintered at 140$0^{\circ}C$ for 6h has a maximum Q-value. For (1-x) Ba (Co$_{1}$ 3/Nb$_{2}$ 3/)O$_3$-zBa(Zn$_{1}$ 3/Nb$_{2}$ 3/)O$_3$[(1-x)BCN-xBZN] ceramics the 1:2 ordered hexagonal structure was observed in the specimens with x$\leq$0.3 and the BaNb$_{6}$ O$^{16}$ second phase was found in the specimens with x$\geq$0.6. Grain Growth, which is rotated to the BaNb$_{6}$ O$^{16}$ second phase occurred in the specimens with x$\geq$ 0.5. In this work, the excellent microwave dielectric properties of $\tau$r=0.0 ppm/$^{\circ}C$$\varepsilon$r=34.5 and Q,$\times$f=97000GHz sere obtained for the 0.7BCV-0.3BZN ceramics sintered at 1400$0^{\circ}C$ for 20h.

• Journal of the Korean Ceramic Society
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• v.55 no.4
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• pp.364-367
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• 2018

The phase evolution, microstructure, and microwave dielectric properties of Sr-substituted $Ba(Mg_{0.5}W_{0.5})O_3$ ceramics, i.e., $(Ba_{1-x}Sr_x)(Mg_{0.5}W_{0.5})O_3$ ($0{\leq}x{\leq}0.30$), sintered at $1700^{\circ}C$ for 1 h were investigated. All compositions showed a 1 : 1 ordered perovskite structure. In all the compositions, $BaWO_4$ was detected as the secondary phase. With increasing x in ($Ba_{1-x}Sr_x$) $(Mg_{0.5}W_{0.5})O_3$, the lattice parameter increased linearly, indicating that a substitutional solid solution occurred. All compositions exhibited a dense microstructure. The value of ${\varepsilon}_r$ increased slightly with increasing x. The value of $Q{\times}f_0$ increased with the increase in x up to x = 0.10 and reached a saturated value of about 100,000 GHz. The composition for x = 0.20, i.e., $(Ba_{0.80}Sr_{0.20})(Mg_{0.5}W_{0.5})O_3$, sintered at $1700^{\circ}C$ for 1 h exhibited superior microwave dielectric properties of ${\varepsilon}_r=19.6$, $Q{\times}f_0=99,358GHz$, and ${\tau}_f=0.0ppm/^{\circ}C$, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.919-930
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• 2001

This paper presents a wideband technique of impedance and axial-ratio bandwidth which uses the stacked planar array structure through optimum design of sub-polarization generating sections and parasitic patch. So, the effect of the dual-resonance characteristic can contribute to the bandwidth expansion of single fed planar array antenna using circular polarization which doesn\`t hire previous bandwidth expansion technique. The antenna can be used as a dual-band antenna by adjusting the resonance frequencies as well, and then the antenna is designed and fabricated in the frequency band of domestic satellite-TV service. This antenna has the performance of 9.7 % impedance bandwidth and 24 dBi of antenna gain. And it has also 2.8 % and 1.4 % of 3 dB Axial-ratio bandwidth at 11.4 GHz and 11.8 GHz respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.6
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• pp.574-581
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• 2002

Microstrip $8{ imes}2$ sub-array antennas for a extension to active phased array antennas are designed, fabricated and measured for TX/RX dual operation in satellite communication and a reception of satellite broadcasting. For the frequency range from 11.7 to 12.75 GHz for RX and from 14 to 14.5 GHz for TX, two orthogonal linear polarizations of ${pm}45^{\circ}$ are used to transmit and receive simultaneously with one radiator. They adopt dual resonance between two patches for wideband characteristics in RX band and show isolation characteristics over 20 dB. An electrical beam tilt of $30^{\circ}$ is achieved and a tapered power distribution, narrow element spacing are used for the purpose of low side-lobe characteristics.

• Electronics and Telecommunications Trends
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• v.32 no.5
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• pp.85-96
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• 2017

The research, design, and development of wireless access technologies using the new 6 to 100GHz band mmWave are actively underway in order to address the frequency shortage problem in the sub-6GHz band and accommodate the 5G technical requirements, such as the increased transmission capacity. Technical elements to efficiently overcome the problems caused by mmWave signal characteristics, support an effective interworking with a conventional communication service, and ensure smooth mobility between mmWave base stations and existing base stations are also being investigated. This paper discusses the technical solutions for an mmWave-based 5G RAN configuration and their considerations under various operational scenarios.

• Journal of information and communication convergence engineering
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• v.8 no.6
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• pp.635-639
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• 2010

A multi-resonance antenna for wireless communications is reported. By using double inverted-L strips, the antenna demonstrated compact size (15 mm ${\times}$ 14 mm) including the ground, multi-band operation for IEEE 802.11 a/b/g/p applications, and wide bandwidth of 1.7 GHz at 5 GHz band. Good radiation features of omni-directional patterns and 1.98 and 2.29 dBi peak antenna gains for the lower and upper bands, respectively, have been achieved.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.105
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• pp.134-138
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• 2006

The isolation performance of the S-band single-pole single-throw(SPST) monolithic microwave integrated circuit (MMIC) switch with two different RF-interconnection approaches, microstrip and grounded coplanar waveguide(GCPW) lines, are investigated. On-to-off isolation is improved by 5.8 dB with the GCPW design compared with the microstrip design and additional improvement of 6.9 dB is obtained with the coplanar wire-bond interconnection(CWBI) at a 3.4 GHz. The measured insertion loss and third-order inter-modulation distortion(IMD3) are less than 1.94 dB over $3.2{\sim}3.6\;GHz$ and greater than 64 dBc.

• Transactions on Electrical and Electronic Materials
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• v.17 no.5
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• pp.257-260
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• 2016

In this paper, two configurations (T-type and Y-type) of dual band Wilkinson Power Divider based upon Hilbert curves are presented. Formerly, the concept of Hilbert Curves was implemented in only designing microstrip antennas. In power dividers, this is the very first attempt of incorporating them for size reduction. In addition to this, an effect of inculcation of high-dielectric constant layer (Hafnium-oxide, HfO₂, ε_r= 25) between a substrate and top metallization in both configurations was investigated. The proposed configurations are designed on a high resistive silicon substrate (HRS) for L and S bands with resonating frequencies of 1.575 and 3.4 GHz. Both configurations have return loss that is better than 20 dB and an insertion loss of around 6 dB; isolation better than 30 dB was achieved for both models.