• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.261-261
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• 2006

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.127-128
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• 2006

The proposed differential LC cross-coupled VCO is implemented in InGap/GaAs HBT process for an adaptive Global Positioning system(GPS) application. Two filtering capacitors are used at the base of output buffer amplifiers at the both sides of the core m order to improve phase noise characteristics. The VCO produced a phase noise of -133 dBc/Hz at 3MHz offset frequency from the carrier frequency of 1.489GHz and the second harmonic suppression is significantly suppresed up to -49dBc/Hz in simulation result. The three pairs of BC diodes are integrated m the tank circuit to increase the VCO Tunning range.

• ETRI Journal
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• v.28 no.4
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• pp.486-494
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• 2006

Two current-mode and/or voltage-mode quadrature oscillator circuits each using one fully-differential second-generation current conveyor (FDCCII), two grounded capacitors, and two (or three) grounded resistors are presented. In the proposed circuits, the current-mode quadrature signals have the advantage of high-output impedance. The oscillation conditions and oscillation frequencies are orthogonally (or independently) controllable. The current-mode and voltage-mode quadrature signals can be simultaneously obtained from the second proposed circuit. The use of only grounded capacitors and resistors makes the proposed circuits ideal for integrated circuit implementation. Simulation results are also included.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.106-109
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• 1998

Wireless communication systems, in particular, must operate in a crowded electro-magnetic environmnet where in-band undesired signals are treated as noise by the receiver. These interfering signals are often random but not Gaussian Due to nongaussian noise, the distribution of the observables cannot be specified by a finite set of parameters; instead r-dimensioal sample space (pure noise samples) is equiprobably partitioned into a finite number of disjointed regions using quantiles and a vector quantizer based on training samples. If we assume that the detected symbols are correct, then we can observe the pure noise samples during the training and transmitting mode. The algorithm proposed is based on a piecewise approximation to a regression function based on quantities and conditional partition moments which are estimated by a RMSA (Robbins-Monro Stochastic Approximation) algorithm. In this paper, we develop a diversity combiner with modified detector, called Non-Linear Detector, and the receiver has a differential phase detector in each diversity branch and at the combiner each detector output is proportional to the second power of the envelope of branches. Monte-Carlo simulations were used as means of generating the system performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.7 no.1
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• pp.37-45
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• 1982

We have analyzed the effect of multipath cochannel interference and Gaussian noise on binary DPSK systems used in land mobile radio communications. Considering multipath channel as non-selective Rayleigh channel, we have found a gnenral equation for bit error rates (BER) deriving the probability density function (p.d.f) of output of phase detector. The numerical results are shown in graphs and discussed as functions of carrier to noise power ratio (CNR), carrier to interferer power ratio (CIR) and correlation of signal component over the pulse length.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2656-2658
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• 1999

This paper presents a control scheme for a three-phase PWM converter system without any voltage sensors. Two input currents and one load current are measured. In a general PWM converter system, the required AC input and DC output voltage values in order to control the converter are estimated using the differential equations of the converter from the measured input currents and load current values in the switch modes of the converter circuit. The PI controller is used as DC voltage controller and sinusoidal tracking controller which tracks directly AC input current is used as input current controller. The Proposed method is verified by simulations. This paper describes the estimation method and configuration of the controller, and discusses steady state and transient performances of the converter

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.8
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• pp.1580-1584
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• 2009

We have theoretically analyzed the monolithic integration of vertical cavity lasers with depleted optical thyristor (VCL-DOT) structure and experimentally demonstrated optical logic gates such as AND-gate, OR-gate, and INVERTER implemented by VCL-DOT for an optical programmable gate array. The optical AND and OR gates have been realized by changing a input bias of the single VCL-DOTs and all kinds of optical logic functions are also implemented by adjusting an intensity of the reference input beams into the differential VCL-DOTs. To achieve the high sensitivity, high slope efficiency and low threshold current, a small active region of lasing part and a wide detecting area are simultaneously designed by using a selective oxidation process. The fabricated devices clearly show nonlinear s-shaped current-voltage characteristics and lasing characteristics of a low threshold current with 0.65 mA and output spectrum at 854 nm.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.547-552
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• 1989

Single mode optical fiber interferometeric sensors using phase tracking homodyne detection are typically susceptible to environmentally induced temperature fluctuations and other types of disturbances. In this paper compensator is described, which is a simple and effective phase tracking feedback electronic circuit must be output signal stabilized to achieve maximln sensitivity and linearity of Mach-Zehnder fiber-optic interferomter in the presence of differential phase drift. The phase tracking range of the piezoelectric cylinder in the reference arm is .+-.3.7.pi.rad, and the probe mass about 1 gram in the sensing ann was used for measurements of the gravity acceleration.

• Proceedings of the IEEK Conference
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• 2002.06b
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• pp.133-136
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• 2002

This paper discusses the design of a sample-and -hold amplifier(SHA) that has a 12-bit resolution with a 100 MS/s speed. The sample-and-hold amplifier uses the open-loop architecture with hold-mode feedthrough cancellation for high accuracy and high sampling speed. The designed SHA is composed of input buffer, sampling switch, and output buffer with additional amplifier for offset cancellation Hard Ware. The input buffer is implemented with folded-cascode type operational transconductance Amplifier(OTA), and sampling switch is implemented with switched source follower(SSF). A spurious free dynamic range (SFDR) of this circuit is 72.6 dB al 100 MS/s. Input signal dynamic range is 1 Vpp differential. Power consumption is 65 ㎽.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.1117-1120
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• 2003

In this paper, a 1.5V CMOS high frequency operational amplifier for high frequency signal processing systems is presented. For obtaining the high gain and the high unity gain frequency with the 1.5V supply voltage, the op-amp is designed with simple two stages which are consisting of the rail-to-rail differential input stage and the class-AB output stage. The designed op-amp operates with the 1.5V supply voltage, and shows well the push-pull class-AB operation. The simulation results show the DC open loop gain of 77dB and the unity gain frequency of 100MHz for the 1㏁ ┃ 10pF load. When the resistive load R$_1$. is varied from 1㏁ to 1 ㏀, the DC open loop gain decreases by only 4dB.