Hyun-Sik Choi

An adaptive predistortion RF power amplifier with a spectrum monitor for multicarrier WCDMA applications

This paper presents an adaptive predistortion RF power amplifier for repeater systems with a spectrum monitor. For adaptive control of cancellation, we implement a spectrum monitor that improves the adjacent channel leakage ratio (ACLR) characteristics of the power amplifier by analyzing the output spectrums of RF power amplifiers directly and simultaneously. For experimental validation, we also implement a class-AB RF power amplifier that adopts a predistortion linearizer with the spectrum monitor and measure the characteristics for the wide-band code division multiple access (WCDMA) band. With an optimum gate bias voltage of the power amplifier, ACLRs of 22 and 20.5 dB are improved for the cases of one- and four-carrier WCDMA applications, respectively. The predistortion power amplifier with the spectrum monitor delivers a Pout of 37.5 dBm with an ACLR of -45 dBc for four-carrier WCDMA applications. Furthermore, excellent ACLR characteristics are consistently maintained with the minimization algorithm by adaptively controlling the vector modulator in the predistorter under various environments that include varying input power levels, temperatures, and operating frequencies

Characterization and Modeling of 1/

In this paper, the volume trap densities Nt are extracted from gate-all-around silicone-nanowire FETs with different gate oxides, using a cylindrical-coordinate-based flicker noise model developed. For extracting Nt, the drain-current power spectral densities were measured from a large number of identical devices and averaged over, thereby mimicking the spatial distribution of trap sites inducing 1/f curve. Also, effective mobility and threshold voltage were simultaneously extracted with the series resistance to characterize the 1/f noise in terms of intrinsic values of these two channel parameters. The volume trap densities thus extracted from different oxides (in situ steam-generated oxide/rapid thermal oxide/nitride-gated oxide) are compared and further examined using hot-carrier stress data. Finally, radius dependence of the cylindrical 1/f model developed is discussed.

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An individually controllable 3/sup rd/-order intermodulation (IM3) and 5/sup th/-order intermodulation (IM5) predistortion linearizer for RF power amplifiers of band-type global system of mobile (GSM) repeaters is proposed. In order to effectively improve the linearity of RF power amplifiers, the IM3 and the IM5 powers are canceled by the predistortion circuit, which independently controls amplitude and phase of the IM3 and the IM5. The fabricated predistorter linearizes the power amplifier at 940 MHz. The IMD3 and the IMD5 suppressions of 30 dB and 26 dB, respectively, are achieved with an average power of 33 dBm for the GSM repeaters.

Noise in Si-nanowire FETs: Effects of Cylindrical Geometry and Different Processing of Oxides

When we attempted to introduce an extractive approach to a company, we were faced with a challenging project situation where legacy applications did not have many commonalities among their implementations as they were developed independently by different teams without sharing a common code base. Although there were not many structural similarities, we expected to find similarities if we view them from the domain model perspective as they were in the same domain and were developed with the object-oriented paradigm. Therefore, we decided to place the domain model at the center of extraction and reengineering, thus developing a domain model-based extractive method. The method has been successfully applied to introduce software product line to a set-top box manufacturing company.

Independently controllable 3/sup rd/- and 5/sup th/-order analog predistortion linearizer for RF power amplifier in GSM

In this letter, a new physical 1/f noise model is developed for double-stack high-k dielectric MOSFETs. This new model modifies the trapping-time-constant term in multistack unified noise model. Conventional 1/f noise model is built on the simple square potential approximation which did not account the electric field dependence on trapping time constant. The new model takes into account of a resultant tunneling process from the actual sloped potential in order to eliminate the discrepancies of dielectric trap density on the dielectric thickness and the gate bias. Our model successfully predicts 1/f noise data obtained from SiO2/HfO2 double-stack high- k devices with various gate-dielectric thicknesses using a single set of modeling parameter.

Experience Report on Using a Domain Model-Based Extractive Approach to Software Product Line Asset Development

In this paper, we introduce the cylindrical coordinate based flicker noise model for Silicon NanoWire Field Effect Transistor (Si-NWFET) with Gate-All-Around (GAA) structure. For the accurate extraction of the volume trap density, Nt, with 1/f noise modeling, the parameters which represent the intrinsic channel properties are determined by rejecting the series resistance Rsd effect. Due to the random distribution of traps in Si-NWFETs, the 1/f noise data are obtained by averaging the drain current power spectral density, Sid, for several devices. By using the proposed 1/f model, the extracted volume trap density is compared for three different oxide processes (ISSG/RTO/GNOx) and verified by hot carrier stress test.

A New Physical

Machines have greatly contributed to the human civilization, enabling tasks beyond our capacities for improved quality of life. Recently, the progress in nanotechnology has triggered to build a miniaturized machine of nanoscale. In this context, synthetic nanomotors have gained considerable interest because of their great promise for diverse applications. Currently, the movement control of these nanomotors has been widely investigated using various stimuli. Here, we demonstrate near-infrared (NIR) light controlled on/off motion of stomatocyte nanomotors powered by the conversion of hydrogen peroxide. The nanomotors encapsulating naphthalocyanine (NC) are aggregated or separated (collective motion) with or without near-IR light illumination, resulting in the well-controlled movement. Remarkably, the nanomotors can move directionally toward hydrogen peroxide released from cancer cells and photothermally ablate the cancer cells. Taken together, our stomatocyte nanomotor systems can be effectively harnessed for autonomous photothermal cancer therapy.

\hbox{1}/f

In this paper, a novel method for effective mobility extraction of the advanced MOSFET devices using RF modeling scheme is proposed. The proposed method is robust to high gate leakage current and parasitic source/drain resistance. Also, this method can substantially reduce error from drain bias mismatch between channel conductance and gate-to-channel capacitance measurement, uses only single device, and is applicable to small-area devices. nMOSFET with HfSiON gate dielectric and TiN gate electrode is demonstrated with the proposed method.

Noise Model for Double-Stack High-

We investigate RF performances and hot carrier effects of nMOSFETs at cryogenic temperature. RF performances of HfO<inf>2</inf> dielectric nMOSFET at 77 K are improved more than those of SiO<inf>2</inf> dielectric nMOSFET although DC performances are improved similarly. The nMOSFET with HfO<inf>2</inf> dielectric has 127.4 GHz f<inf>T</inf> and 75.4 GHz f<inf>max</inf> at 77 K. In hot carrier injection measurement, g<inf>m</inf> of HfO<inf>2</inf> nMOSFET at 77 K is degraded more than 300 K although V<inf>th</inf> shift is less. The cause of g<inf>m</inf> reduction is discussed related to the trapping.

k

RF performances of 100-nm metal gate/high-k dielectric nMOSFET and parameters degradation by hot carrier injection to apply to RF integrated circuits are investigated. The attained nMOSFETs RF performances are 132-GHz f<inf>T</inf> and 44-GHz f<inf>max</inf>. In addition to RF figures of merit (FOM, f<inf>T</inf> and f<inf>max</inf>), variation of capacitance and resistance is monitored to study hot carrier effects.