• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.1
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• pp.69-74
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• 2021

This paper introduces a low-power voltage-controlled oscillator(VCO) with filters that consist of resistors and capacitors. The proposed VCO contains a 5-stage current mode buffer, and each buffer cell has a resistor-capacitor filter that connects input and output terminals. The filter adds a zero to the buffer cell. Because the zero moves the oscillation condition to high frequencies, the proposed VCO can generate a high frequency clock with low power consumption. The proposed circuit has been designed with 0.18 ㎛ CMOS process. The power consumption is 9.83 mW at 2.7 GHz. The proposed VCO shows 3.64 pJ/Hz in our simulation study, whereas the conventional circuit shows 4.79 pJ/Hz, indicating that our VCO achieves 24% reduction in power consumption.

• Journal of Energy Engineering
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• v.13 no.2
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• pp.144-151
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• 2004

Stabilization and reduction of combustion noise and NOx emission from dry low NOx combustor of GE MS7001F gas turbine were achieved. Dry low NOx gas turbines that adopt the lean premixed combustion technology frequently generate the flame instability and high NOx emissions if not adequately tuned. Dynamic pressure oscillation during the combustion mode transfer increased as ambient temperature decreased with frequency of 80㎐ and magnitude of 4-9 psi. Effects of both combustor tuning for uniform fuel flow with burner nozzles and fuel pre-filling into transfer fuel valves on stabilisation of the dry low NOx combustor were very significant. Dynamic pressure oscillation during the combustion mode change was decreased up to 2.5 psi. Also, NOx emission from GE7F DLN-1 combustor can be maintained as low as 35-43ppm (15% O$_2$) in base load operation of 150 MW.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1143-1150
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• 2001

In this paper, we designed a downconverter for K-band satellite multipoint distribution service(SMDS). The designed downconverter consists of a low noise amplifiers, bandpass filter, stable local oscillator, drain mixer and If Amplifiers. Low noise amplifiers show 28㏈ gain and 1.5㏈ noise figure in the frequency range of 19.2㎓~20.2㎓, and a band pass filter has a -l㏈ insertion loss, and 18.25㎓ Stable local oscillator which is dielectric resonant oscillation, We obtained that the output power of the 18.25㎓ oscillation frequency is 0.5㏈m and the phase noise is the -84.67㏈c at 10KHz offset frequency. With the input RF signal the 19.2㎓~20.2㎓, conversion gain of the drain mixer shows 5㏈ at the Intermediate frequency range of 950MHz~1950MHz. We have proved that the designed downconverter satisfied the specification of a K-band satellite multipoint distribution service and it can be applied to the satellite internet receiver.

• The Journal of the Convergence on Culture Technology
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• v.6 no.3
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• pp.419-425
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• 2020

In this paper, when a refractive index grating and a gain grating are simultaneously present in a DFB (Distributed Feedback) laser for a 1.55 um wavelength with two mirror surfaces without an anti-reflective coating, an analysis program was developed to determine the beam distribution of the oscillation mode in the longitudinal direction. As the phases of the index and gain gratings on the mirror faces are varied, the lasing gain and the beam profiles |R(z)| and |S(z)| of the lasing mode with the emitted power ratio P_l/P_r are analyzed and examined in case of δL<0. In order to reduce the threshold current of a oscillation mode and enhance the frequency stability, κL should be greater than 8, regardless of the grating phase values at the mirror surface.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.6
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• pp.8-15
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• 2003

In this paper, the issue of the differential ring oscillator in designing low phase noise is linearity improvement of delay cell's load resistor. A novel differential delay cell that improves on the Maneatis load is proposed. The linearity improvement of load resistor results in lower phase noise in ring oscillator. For comparison of the phase noise characteristics, Ali Hajimiri's phase noise model is used. In order to have a low ISF(impulse sensitivity function), it is important to have a symmetry between rise time and fall time of oscillation waveform. The ISF value of ing oscillator based on the proposed delay cell is lower than that of the existing ring oscillators. Due to this result, the phase noise is improved by 2~3dBc/Hz for the same power dissipation and oscillation frequency.

• Journal of Korea Multimedia Society
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• v.14 no.5
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• pp.614-621
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• 2011

This paper presents design of a wide tuning range digitally controlled oscillator(DCO) for Mobile-DTV applications. DCO is the key element of the ADPLL block that generates oscillation frequencies. We proposed a binary delay chain(BDC) structure, for wide tuning range DCO, modifying conventional fixed delay chain. The proposed structure generates oscillation frequencies by delay cell combination which has a variable delay time of $2^i$ in the range of $0{\leq}i{\leq}n-1$. The BOC structure can reduce the number of delay cells because it make possible to select delay cell and resolution. We simulated the proposed DCO by Cadence's Spectre RF tool in 1.8V chartered $0.18{\mu}m$ CMOS process. The simulation results showed 77MHz~2.07GHz frequency range and 3ps resolution. The phase noise yields -101dBc/Hz@1MHz at Mobile-DTV maximum frequency 1675MHz and the power consumption is 5.87mW. The proposed DCO satisfies Mobile-DTV standards such as ATSC-M/H, DVB-H, ISDB-T, T-DMB.

• Journal of electromagnetic engineering and science
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• v.12 no.4
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• pp.234-239
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• 2012

This paper presents a compact K-band Doppler radar sensor for human vital signal detection that uses a radar configuration with only single coupler. The proposed radar front-end configuration can reduce the chip size and the additional RF power loss. The radar front-end IC is composed of a Lange coupler, VCO, and single balanced mixer. The oscillation frequency of the VCO is from 27.3 to 27.8 GHz. The phase noise of the VCO is -91.2 dBc/Hz at a 1 MHz offset frequency, and the output power is -4.8 dBm. The conversion gain of the mixer is about 11 dB. The chip size is $0.89{\times}1.47mm^2$. The compact Ka-band Doppler radar system was developed in order to demonstrate remote human vital signal detection. The radar system consists of a Ka-band Doppler radar module with a $2{\times}2$ patch array antenna, baseband signal conditioning block, DAQ system, and signal processing program. The front-end module size is $2.5{\times}2.5cm^2$. The proposed radar sensor can properly capture a human heartbeat and respiration rate at the distance of 50 cm.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1409-1420
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• 2015

In this paper, an algorithm using two bi-quad filters to suppress the wide-band resonance for PMSM servo systems is proposed. This algorithm is based on the double bi-quad filters structure, so it is named, "double bi-quad filter." The conventional single bi-quad filter method cannot suppress unexpected mechanical terms, which may lead to oscillations on the load side. A double bi-quad filter structure, which can cancel the effects of compliant coupling and suppress wide-band resonance, is realized by inserting a virtual filter after the motor speed output. In practical implementation, the proposed control structure is composed of two bi-quad filters on both the forward and feedback paths of the speed control loop. Both of them collectively complete the wide-band resonance suppression, and the filter on the feedback path can solve the oscillation on the load side. Meanwhile, with this approach, in certain cases, the servo system can be more robust than with the single bi-quad filter method. A step by step design procedure is provided for the proposed algorithm. Finally, its advantages are verified by theoretical analysis and experimental results.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.65-67
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• 2006

This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system. Under the combination operation of single & three phase load, voltage unbalance will be generated and current unbalance will be more severe by the dropped voltage quality. All power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. Motors may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration.

• Journal of electromagnetic engineering and science
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• v.5 no.1
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• pp.8-13
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• 2005

The InGaP/GaAs hetero-junction bipolar transistor(HBT) monolithic voltage-controlled dielectric resonator oscillator(VCDRO) is first demonstrated for a Ku-band low noise block down-converter(LNB) system. The on-chip voltage control oscillator core employing base-collector(B-C) junction diodes is proposed for simpler frequency tuning and easy fabrication instead of the general off-chip varactor diodes. The fabricated VCDRO achieves a high output power of 6.45 to 5.31 dBm and a wide frequency tuning range of ]65 MHz( 1.53 $\%$) with a low phase noise of below -95dBc/Hz at 100 kHz offset and -115 dBc/Hz at ] MHz offset. A]so, the InGaP/GaAs HBT monolithic DRO with the same topology as the proposed VCDRO is fabricated to verify that the intrinsic low l/f noise of the HBT and the high Q of the DR contribute to the low phase noise performance. The fabricated DRO exhibits an output power of 1.33 dBm, and an extremely low phase noise of -109 dBc/Hz at 100 kHz and -131 dBc/Hz at ] MHz offset from the 10.75 GHz oscillation frequency.