• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.4
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• pp.25-35
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• 2002

This work describes an 8b 200MHz time-interleaved subranging analog-to-digital converter (ADC) based on a single-poly digital CMOS process. Two fine ADCs for lower digital bits of the proposed ADC employ a time-sharing double-channel architecture to increase system speed and a new reference voltage switching scheme to reduce settling time of the reference voltages and chip area. The proposed intermeshed resistor string, which generates reference voltages for fine ADCs, improves linearity and settling time of the reference voltages simultaneously. The proposed sample- and-hold amplifier(SHA) is based on a highly linear common-drain amplifier and passive differential circuits to minimize power consumption and chip area with 8b accuracy and employs input dynamic common mode feedback circuits for high dynamic performance at a 200MHz sampling rate. A new encoding circuit in a coarse ADC simplifies the signal processing between the coarse ADC and two successive fine ADCs.

• Korean Journal of Optics and Photonics
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• v.11 no.1
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• pp.37-42
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• 2000

We have numerically solved rate-equations of semiconductor optical amplifier (SOA) to understand the characteristics of SOA. The rate-equations we have used can describe injection carrier density, amplified spontaneous emission and signal photon density in spatial and time domain by dividing the cavity into multi-section. We have investigated injection carrier density, amplified spontaneous emission and signal photon density as a function of position and time in the case of single channel input in the form of square pulse. Also we have analyzed the non-linear phenomena of SOA in the case of injecting multi-channel wavelengths as in WDM. Intermodulation distortion (IMD) caused by beat among channels has significant effects on the signal distortion as the channel spacing becomes narrower, and channel crosstalk becomes larger as the power of signals increases. In the case of the injection of another CW laser whose wavelength is far enough from the signal wavelengths, the crosstalk and the output signal distortion can be significantly reduced. duced.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.769-772
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• 2005

This paper describes a low-voltage and low-power channel selection analog front end with continuous-time low pass filters and highly linear programmable-gain amplifier(PGA). The filters were realized as balanced Gm-C biquadratic filters to achieve a low current consumption. High linearity and a constant wide bandwidth are achieved by using a new transconductance(Gm) cell. The PGA has a voltage gain varying from 0 to 65dB, while maintaining a constant bandwidth. A filter tuning circuit that requires an accurate time base but no external components is presented. With a 1-Vrms differential input and output, the filter achieves -85dB THD and a 78dB signal-to-noise ratio. Both the filter and PGA were implemented in a 0.18um 1P6M n-well CMOS process. They consume 3.2mW from a 1.8V power supply and occupy an area of $0.19mm^2$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.4
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• pp.599-609
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• 2000

In this paper, sub-harmonically pumped single balanced resistive mixers are presented . Frequency bandwidth is selected for a Ku-band, which is 11.75-12.25GHz for RF, 5.375∼5.625 GHz for LO, and 1 GHz for IF signals. A rat-race hybrid is designed for the accomplishment of single balanced type. A low pass filter (LPF) with photonic band gap(PBG) structure is used for good conversion loss and unwanted harmonics suppression. Two types of mixers are suggested, which are one with no gate bias for no DC power consumption and the other with the IF amplifier for conversion gain. When a LO signal with the power of 6 dBm at 5.5 GHz is injected, a conversion loss of 12.17dB and a conversion gain of 7.83 dB are obtained for each mixer. For the both mixers , LO to RF isolation of 20 dB and LO to IF isolation of 60dB are obtained. With the RF power of -30dBm to -3dBm, the mixer shows linear characteristics region of IF. this mixer can be applied for Ku-band and other microwave communication systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.308-315
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• 2018

In this paper, we present the basic design results for high-resolution radar development at S-band frequency that can precisely measure the miss distance between two targets. The basic system requirement is proposed for the design of a 3.5 GHz linear frequency-modulated (LFM) radar with maximum detection distance and distance resolution of 2 km and 1 m, respectively, and the specifications of each module are determined using the radar equation. Our calculations revealed a signal-to-noise ratio ${\geq}30dB$ with a bandwidth of 150 MHz, transmission power of 43 dBm for the power amplifier, gain of 26 dBi for the antenna, noise figure of 8 dB, and radar cross-section of $1m^2$ at a target distance of 2 km from the radar. Based on the calculation results and the theory and method of LFM radar design, the hardware was designed using software defined radar technology. The results of the subsequent field test are presented that prove that the designed radar system satisfies the requirements.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.5
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• pp.456-463
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• 2015

Nowadays, small quantity batch production, which is so-called a flexible manufacturing system, is a major trend in the modern factory automation industry. The demands for new transportation system are increased gradually, with which multiple passive carriers carrying materials and semi-products are precisely and individually controlled along a single closed rail. Thus, a new type of permanent magnet linear synchronous motor (PMLSM), which consists of state coils on a single rail and PM movers as many as carriers, is proposed in this paper. The rail can be segmented as modules with pairs of coils and a current amplifier, which makes the transportation system simple; therefore, the rail can be easily extended and repaired. A design method of the new PMLSM with a single carrier is proposed, which can be thought as a new version of PMLSM, a coil-segmented coreless PMLSM (CS-CLPMLSM). Experimental setup for it is made, and propulsion results show that with the help of a new effective coil selection and switching algorithms, the conventional current-based vector control is sufficient to fulfill the position and velocity control of the new PMLSM. The proposed PMLSM is expected to fulfill seamless servo-control of multiple carriers also in process line, such as a new generation of flat panel display manufacturing line.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.1044-1052
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• 1999

A 2-stage 1 watt MMIC(Monolithic Microwave Integrated Circuits) HPA(High Power Amplifiers) at 20 GHz band has been designed and fabricated. The $0.15\mu\textrm{m}$ with the width of $400\mu\textrm{m}$for single device pHEMT technology was used for the fabrication of this MMIC HPA. Due to the series feedback technique from source to ground, bias circuits and stabilization circuits on the main microstrip line, the stability factors(Ks) are more than one at full frequency. The independent operation for each stage and excellent S11, S22 less than -20 dB have been obtained by using lange couplers. For beginning the easy design, linear S-parameters have been extracted from the nonlinear equivalent circuit in foundry library, and equivalent circuits of devices at in/output ports were calculated from this S-parameters. The measured performances, which are in well agreement with the predicted ones, showed the MMIC HPA in this paper has the minimum 15 dB of linear gain, -20 dB of reflection coefficients and 31 dBm of output power over 17~25 GHz.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5A
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• pp.290-297
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• 2012

In this paper, we proposed new modulation schemes, Offset Phase Rotation Shift Keying (OPRSK) and Phase Shift Rotation Shift Keying (PSRSK), for medical in-body wireless body area network (WBAN) systems. In IEEE, the WBAN system is assigned as 802.15. Task Group (TG) 6, and the related standardization is being progressed. Recently, in this Group, Phase Silence Shift Keying (PSSK), Phase Silence Position Keying (PSPK) and Phase Rotation Shift Keying (PRSK), which can obtain higher power efficiency, are proposed as new modulation schemes for low-power operation of WBAN system. However, they have a disadvantage for non-linear amplifier distortion. Therefore, in this paper, we proposed OPRSK and PSRSK, which are robust to non-linear amplification, by employing a phase offset in constellation and a power distribution in symbol duration, and verified that the proposed methods have good perfomance and stable operation through performance evaluation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.10
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• pp.2165-2170
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• 1997

In this paepr, the distortion effects of impairments in CDMA transmitter system were analyzed. We considered not only linear distortion effects, for example, I/Q imbalance, quadrature offset and carrier leakage, but also nonlinear distortion effects such as AM-AM and AM-PM noise in power amplifier. To investigate how the impariments impact on the performance of CDMA transmitter, all effects represented as a function of CDMA modulation quality which is an important measure of the transmitted signal. These results show the limitation value of each impairment which is required to satisfy the IS-95 standard.

• Journal of the Korean Vacuum Society
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• v.8 no.4B
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• pp.536-540
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• 1999

We have developed a refractory WNx self-aligned gate GaAs metal-semiconductor field-effect transistor(MESFET) using $SiO_2$ side-wall process. The MESFET hasa fully ion-implanted, planar, symmetric self-alignment structure, and it is quite suitable for integration. The uniform trans-conductance of 354nS/mm up to Vgs=+0.6V and the saturation current of 171mA/mm were obtained. As high as 43GHz of cut-off frequency hs been realized without any de-embedding of parasitic effects. The refractory WNx self-aligned gate GaAs MESFET technology is one of the most promising candidates for realizing linear power amplifier ICs and multifunction monolithic ICs for use in the digital mobile communication systems such as hand-held phone(HHP), personal communication system (PCS) and wireless local loop(WLL).