Sungyong Jung

Hidden Markov Model-Based Weighted Likelihood Discriminant for 2-D Shape Classification

The goal of this paper is to present a weighted likelihood discriminant for minimum error shape classification. Different from traditional maximum likelihood (ML) methods, in which classification is based on probabilities from independent individual class models as is the case for general hidden Markov model (HMM) methods, proposed method utilizes information from all classes to minimize classification error. The proposed approach uses a HMM for shape curvature as its 2-D shape descriptor. We introduce a weighted likelihood discriminant function and present a minimum classification error strategy based on generalized probabilistic descent method. We show comparative results obtained with our approach and classic ML classification with various HMM topologies alongside Fourier descriptor and Zernike moments-based support vector machine classification for a variety of shapes.

Ultra wideband CMOS low noise amplifier with active input matching

A new low noise amplifier (LNA) with broadband input matching and excellent gain flatness operating at the frequency range of 3.1-4.8 GHz is designed using a 0.18 /spl mu/m CMOS process. Wideband input matching using common-gate at the input stage is proposed. From a supply voltage of 1.8 V, the two-stage LNA exhibits a noise figure (NF) of 3.95-4.3 dB within the required bandwidth. The LNA has S11 less than -15 dB over the entire 3.1-4.8 GHz band. A reversed isolation (S12) less than -43 dB was achieved. A power gain (S21) of 16.5 dB with only 0.6 dB variations was obtained within the 3.1-4.8 GHz band. Input IP3 and 1 dB compression points are not of much concern in the case of the UWB LNA, since transmit power is restricted to be less than -42 dBm/Hz.

A Tunable CMOS UWB Pulse Generator

A tunable ultra-wideband (UWB) pulse generator is designed and simulated with standard 0.18 mum CMOS technology. By using a voltage controlled delay line (VCDL) technique, the proposed UWB pulse generator can adjust the pulse width, adding flexibility for use with different UWB applications. Moreover, each peak of the proposed UWB pulse is separately controlled so that it complies with the FCC regulation. The proposed UWB pulse generator achieves the fifth-order derivative of the Gaussian pulse and can tune the pulse width from 0.38-ns to 4-ns. In particular, the maximum and minimum pulse widths comply with 3-10 GHz and sub-GHz FCC regulations, respectively

Microsystem optoelectronic integration for mixed multisignal systems

The integration and packaging of optoelectronic devices with electronic circuits and systems has growing application in many fields, ranging from long to micro haul links. An exploration of the opportunities, integration technologies, and some recent results using thin-film device heterogeneous integration with Si CMOS VLSI and GaAs MESFET circuit technologies are presented. Applications explored include alignment tolerant optoelectronic links for network interconnections, smart pixel focal plane array processing through the integration of imaging arrays with sigma delta analog to digital converters underneath each pixel, and three-dimensional computational systems using vertical through-Si optical interconnections.

An accurate current source with on-chip self-calibration circuits for low-voltage current-mode differential drivers

An accurate CMOS current source for current-mode low-voltage differential transmitter drivers has been designed and fabricated. It is composed of binary weighted current mirrors with built-in self-calibration circuits. The proposed self-measurement and calibration circuits can calibrate upon the collective effects of different error contributors due to process, power supply, and temperature variations. The design has been fabricated in standard 0.35-/spl mu/m CMOS technology. Measurement results show that the differential output voltage can be self-calibrated to /spl plusmn/1% accuracy with 16% reference current variation, 60% power supply variation, or 13% load resistance variation, respectively.

An Electronic Circuit System for Time-Reversal of Ultra-Wideband Short Impulses Based on Frequency-Domain Approach

In this paper, a compact and low-cost electronic circuit system is designed for time-reversal of ultra-wideband short impulses (with nanosecond and sub-nanosecond temporal durations). A frequency-domain approach is adopted to avoid high sampling rate in time. Specifically, the proposed system obtains the discrete spectra of input impulses first; then realizes time-reversal in frequency domain; and finally synthesizes the time-reversed impulses using discrete continuous wave elements. This system is composed of common and commercially available circuits, and hence, can embody a system-on-chip implementation. Its performance is verified by circuit-electromagnetic co-simulations using impulses with 3-10-GHz frequency band coverage. Advanced Design System and two full-wave Maxwells equations solvers are used for circuit and electromagnetic simulations, respectively, and their results are coupled and integrated. In the circuit part, most of nonidealities of realistic circuits are taken into account. It is shown by the simulation results that, although realistic circuits unavoidably introduce errors to time-reversal, such errors do not affect the ¿focusing¿ phenomena in the context of electromagnetic wave propagation. As a conclusion, the proposed system can be deployed in practical time-reversal communication and radar applications.

A CMOS Transmitter Leakage Canceller for WCDMA Applications

A transmitter (TX) leakage canceller is proposed for improving the dynamic range of the receiver (RX) for wideband code division multiple access applications. A TX leakage canceller circuit in this paper is simple in implementation and has low noise figure (NF) contribution. It is a feed-forward canceller that samples a reference signal from the TX output and injects the amplitude-adjusted and phase-rotated signal to the RX chain. The canceller circuit is integrated with a low-noise amplifier and implemented in a 0.18-μm CMOS technology. A cancellation of 23 dB is achieved with only 10-mA current consumption increase and low NF increase.

Digitally controllable bi-phase CMOS UWB pulse generator

Digitally controllable bi-phase ultra wideband (UWB) pulse generator is designed with standard 0.18-/spl mu/m CMOS technology. Since the phase and amplitude of UWB pulse are digitally controlled, it is able to use bi-phase modulation and control the emission power with several pulse amplitudes. Assuming that FCC emission power limit is maximally used, the proposed pulse generator can be operated with pulse repetition frequency (PRF) of 77-MHz. The power consumption is maximally 1.88-mW and proportionally decreased as PRF is smaller. The proposed UWB pulse generator is a good candidate for a low-cost low-power impulse radio (IR).

Real-time Planar Surface Segmentation in Disparity Space

An iterative Segmentation-Estimation framework for segmentation of planar surfaces in the disparity space is implemented on a Digital Signal Processor (DSP). Disparity of a scene is modeled by approximating various surfaces in the scene to be planar. The surface labels are estimated during the segmentation phase of the framework with help of the underlying plane parameters. After segmentation, planar surfaces are separated into spatially continuous regions. The largest of these regions is used to compute the estimates for the plane parameters. The iterative process is continued till convergence. The algorithm was optimized and implemented on TMS320DM642 based embedded system that operates at 3 to 5 frames per second on images of size 320 x 240.

A two-stage cascode CMOS LNA for UWB wireless systems

Ultra-wideband (UWB) is a promising new technology with great potential for short-range ultra-high-speed wireless communication systems. In this paper, a low noise amplifier (LNA) with broadband matching using a resonant circuit that has excellent gain flatness in the frequency range of 3 GHz to 6 GHz is designed for UWB applications. The TSMC 0.18 mum RF CMOS technology was used for simulation. Thus the final design does not require any off-chip components, being fully integrated. The LNA presented utilizes feedback and is composed of two cascode stages for the purpose of controlling both gain and noise. This paper describes the design approaches as well as the simulation results of the broadband LNA