• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.11
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• pp.56-60
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• 2009

In this paper, a novel voltage controlled oscillator (VCO) has been presented by using the microstrip square multiple spiral resonator for reducing the phase noise of VCO. The microstrip multiple square resonator has the large coupling coefficient value, which makes a high Q value, and has reduced phase noise of VCO. The VCO with 1.8 V power supply has phase noise of -115.0~-117.34 dBc/Hz @100 kHz in the tuning range, 8.935~9.4 GHz. When it has been compared with microstrip square multiple spiral resonator and coventional spiral resonator, the reduced Q value has been -32.7 dB and -57.6 dB respectively. This low phase noise VCO could ve available to a VCO in X-band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.2 s.117
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• pp.213-218
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• 2007

In this paper, we propose the design and fabrication on high frequency CMOS VCO for DS-UWB(Direct-Sequence Ultra-WideBand) applications using 0.18 ${\mu}m$ process. The complementary cross-coupled LC oscillator architecture which is composed of PMOS, NMOS symmetrically, is designed for improving the phase noise characteristic. The resistor is used instead of current source that reduce the 1/f noise of current source. The high-speed buffer is needed for measuring the output characteristic of VCO using spectrum analyzer, therefore the high-speed inverter buffer is designed with VCO. A fabricated core VCO size is $340{\mu}m{\times}535{\mu}m$. The VCO is tunable between 7.09 and 7.52 GHz and has a phase noise lower than -107 dBc/Hz at 1-MHz offset over entire tuning range. The measured harmonic suppression is 32 dB. The VCO core circuit draws 2.0 mA from a 1.8 V supply.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.1963-1970
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• 1998

In this paper, a two-dimensional slotline coupling structure is proposed for the planar active phased array antenna system with scanning the beam by coupled oscillators without phase shifters. The operating characteristics are analyzed and experimentally demonstrated. The proposed two-dimensional slotline coupling structure consists of $|{=}|$-type slotline in the ground plane for the coupling of E-plane and H-plane. From the simulation results of coupling strength with the variation of width, length and the number of slotlines, the optimal coupling structure is proposed and applied to $2{\times}5$ elements of planear phased array antenna. The experimental results show that the beamwidth of E-plane and H-pland are $42^{\circ}$ and $15^{\circ}$, respectivly, and the scanning range is from $-20^{\circ}$ to $15^{\circ}$ from the broadside. Therefore, it is shown the two-dimensional slotline coupling structure for oscillator-type active phased array antenna can be applied to the planar phased array antenna system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.486-495
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• 2007

In this paper, we present the design procedure of BPF(Band Pass Filter) for the suppression of LO(Local Oscillator) harmonics. The required suppression at given harmonics is the key issues in such a filter design, while the bandwidth and the suppression of the unwanted signals are more important in the conventional RF filter design. In LO filter design the bandwidth is used for the minimization of the insertion loss for the desired signal. In addition, we propose the novel tuning procedure based on Momentum to consider the unknown parasitic effects, which usually are not included in the circuit design step and results in undesirable and frustrating tuning after fabrication.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.1
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• pp.50-55
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• 2008

In this paper, New LC VCO with $8{\sim}10.9$ GHz Band has been designed using commercial $0.35-{\mu}m$ CMOS technology. This proposed circuit is consisted of the parallel construction of the typical NMOS and PMOS cross-coupled pair which is based on the LC tank, MOS cross-coupled pair which has same tail current of complementary NMOS and PMOS, and output buffer. The designed LC VCO, which is according to proposed structure in this paper, takes a 29% improvement of the wide tuning range as 8 GHz to 10.9 GHz, and a 6.48mW of low power dissipation. Its core size is $270{\mu}m{\times}340{\mu}m$ and its phase noise is as -117dBc Hz and -137dBc Hz at 1-MHz and 10-MHz offset, respectively. FOM of the new proposed LC VCO gets -189dBc/Hz at a 1-MHz offset from a 10GHz center frequency. This design is very useful for the 10Gb/s clock generator and data recovery integrated circuit(IC) and SONET communication applications.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.3 no.2
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• pp.25-30
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• 2010

In this paper, a novel notch resonator is proposed based on Rectanglar Split Ring Resonator (R-RSS) element. We represented the electrical characteristics for R-SRR elements coupled with microstrip line, and measured result is compared with electromagnetic simulation (HFSS) result. We also solved equivalent circuit for R-SRR element, and also discussed influences of change structural parameters of R-SRR. the size of R-SRR is the most important parameters for frequency tuning. Also we can make tunable resonator form the basic structure. This novel resonator can apply to design of tunable bandpass filter and voltage control oscillator.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1399-1400
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• 2008

본 논문에서는 TSMC 0.18um 공정을 이용하여 2.45GHz 대역에서 동작하는 RFID 리더에 적용 할 수 있는 전압제어 발진기를 설계하였다. 위상 잡음 특성 향상을 위해 PMOS, NMOS 소자를 대칭으로 구성한 complementary cross-coupled LC 발진기 구조로 설계 하였고 MOS 배렉터를 이용하여 주파수를 가변 하였다. 또한 공정에서 사용되는 인덕터에 차폐 도체면(PGS:Patterned Ground Shield) 구조를 삽입했을 때 인덕터의 품질계수가 약 5.82% 향상되었고. 이에 따른 위상 잡음은 1MHz offset 주파수에서 PGS를 삽입하지 않는 구조에서는 -102.666dBc/Hz 이며, PGS 구조를 삽입한 구조는 -104.328dBc/Hz로 약1.662dBc 정도의 성능이 향상 되었다. 전압제어 발진기 Core 사이즈는 900um ${\times}$ 590um이고 주파수 가변 범위는 배렉터 전압 1.2${\sim}$2.1V에서 249MHz로 11.4% 특성을 보였다. 1.8V공급전압에서 5.76mW의 전력소모를 보였다.

• Wind and Structures
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• v.29 no.6
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• pp.441-455
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• 2019

In this study, vortex induced vibrations of a cylinder mounted on a flexible rod are analyzed. This simple configuration represents the key element of new conception bladeless wind turbine (Whitlock 2015). In this study the structure oscillations equation coupled to the wake oscillation equation for this configuration are solved using analytical perturbation method, for the first time. An analytical expression that predicts the lock-in phenomena range of wind speed is derived. The discretized equations of motion are also solved using RKF45 numerical method. The equations of motion are discretized by Galerkin method. Free vibration mode shape of the structure taking into account the discontinuity of the cross section are used as comparison function. Numerical results are compared to the analytical results, and they show a satisfying agreement. The effect of system parameters on the oscillations of structure and wake as well as on the lock-in domain are presented. Moreover, it is shown that the values of wind speed triggering the start and the stop of the lock-in phenomenon, for increasing wind speed are different from those values obtained during the reverse process, i.e., when the wind speed decreases.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.297.2-297.2
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• 2014

Strong exciton-photon coupling in microcavities have generated an intense research effort since quasiparticles called exciton polaritons are produced and shows interesting phenomena. Most of studies have been done with GaAs based microcavities at cryogenic temperature. Recently, GaN material which has large exciton binding energy and oscillator strength has much attention because strong coupling between photon and exciton could be realized at room temperature. However, fabrication of high quality microcavity using GaN is challengeable due to the large mismatch between the lattice and the thermal expansion coefficient in GaN based distributed Bragg mirror. Here, we observed strong coupling regime of exciton-photon in GaN micro-rods which were grown by metalorganic vapour phase epitaxy (MOCVD) on Si substrate. Owing to the hexagonal cross-section of micro-rod, whispering gallery modes of photon are naturally formed and could be coupled with exciton in GaN. Using angle-resolved micro-photoluminescence measurement, exciton polariton dispersion curves were directly observed from GaN micro-rod. We expect room temperature exciton polariton condensation could be realized in high quality GaN micro-rod.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.8
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• pp.3880-3899
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• 2019

Distributive desynchronization algorithms based on pulse-coupled oscillator (PCO) models have been proposed for achieving collision-free wireless transmissions. These algorithms do not depend on a global clock or infrastructure overheads. Moreover, they gradually converge to fair time-division multiple access (TDMA) scheduling by broadcasting a periodic pulse signal (called a 'firing') and adjusting the next firing time based on firings from other nodes. The time required to achieve constant spacing between phase neighbors is estimated in a closed form or via stochastic modeling. However, because these algorithms cannot guarantee the completion of desynchronization in a short and bounded timeframe, they are not practical. Motivated by the limitations of these methods, we propose a practical solution called PD-DESYNC that provides a short and deterministic convergence time using a flag firing to indicate the beginning of a cycle. We demonstrate that the proposed method guarantees the completion of desynchronization within three cycles, regardless of the number of nodes. Through extensive simulations and experiments, we confirm that PD-DESYNC not only outperforms other algorithms in terms of convergence time but also is a practical solution.