• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.832-842
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• 2020

The coordination control of multiple Underactuated Underwater Vehicles (UUVs) moving in three dimensional space is investigated in this paper. The coordinated path following control task is decomposed into two sub tasks, that is, path following control and coordination control. In the spatial curve path following control task, path following error dynamics is build in the Serret-Frenet coordinate frame. The virtual reference object can be chosen freely on the desired spatial path. Considering the speed of the UUV, the line-of-sight navigation is introduced to help the path following errors quickly converge to zero. In the coordination control sub task, the communication topology of multiple UUVs is described by the graph theory. The speed of each UUV is adjusted to achieve the coordination. The path following system and the coordination control system are viewed as the feedback connection system. Input-to-state stable of the coordinated path following system can be proved by small gain theorem. The simulation experiments can further demonstrate the good performance of the control method.

• ETRI Journal
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• v.44 no.5
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• pp.715-732
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• 2022

Despite the successful launch of Advanced Television Systems Committee (ATSC) 3.0 broadcasting worldwide, broadcasters are facing obstacles in constructing void-less large-scale single-frequency networks (SFNs). The bottleneck is the absence of decent on-channel repeater (OCR) solutions necessary for SFNs. In the real world, OCRs suffer from the maleficent feedback interference (FI) problem, which overwhelms the desired input signal. Moreover, the undesired multipaths between studio-linked transmitters and the OCR deteriorate the forward signals' quality as well. These problems crucially restrict the feasibility of conventional OCR systems, arousing the strong need for cost-worthy advanced OCR solutions. This paper presents an ATSC 3.0-specific solution of advanced OCR that solves the FI problem and refines the input signal. To this end, the FI canceler and channel equalizer functionalities are carefully implemented into the OCR system. The presented OCR system is designed to be fully compliant with the ATSC 3.0 specifications and performs a fast and efficient signal processing by exploiting the specific frame structure. The real product of ATSC 3.0 OCR is fabricated as well, and its feasibility is verified via field and laboratory experiments. The implemented solution is installed at a commercial on-air site and shown to provide substantial coverage gain in practice.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.32-36
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• 2015

This study explores the issue of program management consortia involving multinational participants. The aim of this research was to leverage advantages in program management (PM) skills and PM model improvement in product line construction in mega scale construction programs, typically funded by public funds. Such ventures involve multinational parties using dedicated partnering based on a program management consortium (PMC) to reduce confrontation between parties in complex circumstances, allowing an open and non-adversarial approach to project management. This research also seeks to implement an ongoing feedback program of best practices and lessons learned to minimize the repetition of mistakes and to reduce costs in sequenced construction. Recently, the Korean government has planned to undertake three large new projects: the Korean Peninsula major river maintenance, the reclamation of Se-Mangum, and the Science/Business City. This paper starts by providing a framework for the cost-reduction strategy for the United States Forces Korea (USFK) Relocation Program, which will be funded with public funds and a private fund investment (PFI) that combines programs executed by two governments as owners and multinational stakeholders, joined in the PMC. The establishment of project-oriented consortia is an innovative and non-adversarial approach to massive international construction projects. Such projects have used various tools effectively and skillfully. This experience may offer an opportunity to practice new and advanced program management delivery methods, and it is expected that Korea will gain a competitive advantage in the international construction market.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.40-48
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• 2013

This paper presents multi-channel transimpedance amplifier(TIA) arrays in short-range LADAR systems for unmanned vehicles, by using a 0.18um CMOS technology. Two $4{\times}4$ channel TIA arrays including a voltage-mode INV-TIA and a current-mode CG-TIA are introduced. First, the INV-TIA consists of a inverter stage with a feedback resistor and a CML output buffer with virtual ground so as to achieve low noise, low power, easy current control for gain and impedance. Second, the CG-TIA utilizes a bias from on-chip bandgap reference and exploits a source-follower for high-frequency peaking, yielding 1.26 times smaller chip area per channel than INV-TIA. Post-layout simulations demonstrate that the INV-TIA achieves 57.5-dB${\Omega}$ transimpedance gain, 340-MHz bandwidth, 3.7-pA/sqrt(Hz) average noise current spectral density, and 2.84mW power dissipation, whereas the CG-TIA obtains 54.5-dB${\Omega}$ transimpedance gain, 360-MHz bandwidth, 9.17-pA/sqrt(Hz) average noise current spectral density, and 4.24mW power dissipation. Yet, the pulse simulations reveal that the CG-TIA array shows better output pulses in the range of 200-500-Mb/s operations.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.80-87
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• 2013

A novel instrumentation amplifier(IA) using positive polarity current-conveyor(CCII+) for electronic measurement systems with low cost, wideband, and gain control with wide range is designed. The IA consists of two CCII+, three resistor, and an operational amplifier(op-amp). The principal of the operating is that the difference of two input voltages applied into two CCII+ used voltage and current follower converts into same currents, and then these current drive resistor of (+) terminal and feedback resistor of op-amp to obtain output voltage. To verify operating principal of the IA, we designed the CCII+ and used commercial op-amp LF356. Simulation results show that voltage follower used CCII+ has offset voltage of 0.21mV at linear range of ${\pm}$4V. The IA had wide gain range from -20dB to 60dB by variation of only one resistor and -3dB frequency for the gain of 60dB was 400kHz. The IA also has merits without matching of external resistor and controllable offset voltage using the other resistor. The power dissipation of the IA is 130mW at supply voltage of ${\pm}$5V.

• Journal of Software Assessment and Valuation
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• v.16 no.1
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• pp.55-63
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• 2020

Lasers for optical broadband communication systems should have excellent frequency selectivity and modal stability. DFB lasers have low lasing frequency shift during high speed current modulation. In this paper, when a refractive index grating and a gain grating are simultaneously present in a DFB laser having a wavelength of 1.55 ㎛, the dielectric film is coated so that reflection does not occur on the right mirror surface, so that ρ_r=0. For the first mode, which requires a minimum gain at the threshold, the beam distribution of the oscillation mode in the longitudinal direction and the radiated power ratio P_l/P_r were analyzed and compared for the cases of the phase of ρ_l=π and π/2. If the phase of ρ_l=π, in order to obtain a low threshold current and high frequency stability, κL should be greater than 8. In the case of the phase of ρ_l=π/2, for low threshold current, κL is necessary to be 1.0, where the oscillation frequency coincides with the lattice frequency. DFB lasers with an anti-reflection coated mirror have excellent mode selectivity than 1.55um DFB lasers with two mirror facets

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.4
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• pp.280-287
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• 2008

For the reduction of common-mode noise level in Indirect-contact ECG (IDC-ECG) measurement a driven-right-leg grounding method was a lied to the IDC-ECG. Because the IDC-ECG does not require any direct contact between the electrodes and the human skin. it is adequate for un-constraining long-term ECG measurement at home and its various applications are now under development. However, larger 60 Hz noise induced by power line a ears in IDC-BCG than in conventional ECG, that is a restriction of IDC-ECG a application. In this study, the driven-right-leg ground which has been used in conventional direct-contact ECG, was adapted to the IDC-ECG measurement by feedback of the inversion of amplified common-mode noise to the body through the conductive fertile laid on the chair seat By this study, indirect-contact driven-right-leg ground was developed and it was shown to work stably. It was shown that the level of 60Hz power line noise was reduced to about -40 dB when the driven-right-leg gain was 1000. This study shows that we can extend the upper limit of the frequency band of IDC-ECG to 100Hz from 30Hz which is conventional upper limit in IDC-ECG, and we can raise the ground impedance between the body and conductive textile. So it is expected that the application area of the IDC-ECG will be extended by the results of this study.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.2
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• pp.121-128
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• 2010

This paper presents a design of a 100 W high-efficiency power amplifier, whose operational frequency band expands from 30 to 512 MHz, using negative feedback network, push-pull structure, broadband RF choke, and transmission line transformer for balun configuration. The push-pull amplifier has been tuned for higher output power using a shunt capacitor as a matching component at its load especially for high-frequency region. The implemented power amplifier exhibited a very flat power gain of $18.34{\pm}0.9\;dB$ throughout the operating frequency band and very high power-added efficiency(PAE) of greater than 40% at an output power of 100 W. It also showed second- and third-harmonic distortion levels of below -34 dBc and -12 dBc, respectively, through the entire operating frequency band.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.6
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• pp.39-47
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• 1998

A fourth-order $\Sigma$-$\Delta$ modulator is designed and implemented in 0.6 $\mu\textrm{m}$ CMOS technology. The modulator is verified by introducing nonlinear factors such as DC gain and slew rate in system model that determines the transfer function in S-domain and in time-domain. Dynamic range is more than 110 dB and the peak SM is 102.6 dB at a clock rate of 2.8224 MHz for voiceband signal. The structure of a ∑-$\Delta$ modulator is a modified fourth-order ∑-$\Delta$ modulator using direct feedback loop method, which improves performance and consumes less power. The transmission zero for noise is located in the first-second integrator loop, which reduces entire size of capacitors, reduces the active area of the chip, improves the performance, and reduces power dissipation. The system is stable because the output variation with respect to unit time is small compared with that of the third integrator. It is easy to implement because the size of the capacitor in the first integrator, and the size of the third integrator is small because we use the noise reduction technique. This paper represents a new design method by modeling that conceptually decides transfer function in S-domain and in Z-domain, determines the cutoff frequency of signal, maximizes signal power in each integrator, and decides optimal transmission-zero frequency for noise. The active area of the prototype chip is 5.25$\textrm{mm}^2$, and it dissipates 10 mW of power from a 5V supply.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.8
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• pp.22-26
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• 2012

This paper introduces a 2.5-Gb/s optical receiver implemented in a standard 1P4M 0.18um CMOS technology for the applications of active optical HDMI cables. The optical receiver consists of a differential transimpedance amplifier(TIA), a five-stage differential limiting amplifier(LA), and an output buffer. The TIA exploits the inverter input configuration with a resistive feedback for low noise and power consumption. It is cascaded by an additional differential amplifier and a DC-balanced buffer to facilitate the following LA design. The LA consists of five gain cells, an output buffer, and an offset cancellation circuit. The proposed optical receiver demonstrates $91dB{\Omega}$ transimpedance gain, 1.55 GHz bandwidth even with the large photodiode capacitance of 320 fF, 16 pA/sqrt(Hz) average noise current spectral density within the bandwidth (corresponding to the optical sensitivity of -21.6 dBm for $10^{-12}$ BER), and 40 mW power dissipation from a single 1.8-V supply. Test chips occupy the area of $1.35{\times}2.46mm^2$ including pads. The optically measured eye-diagrams confirms wide and clear eye-openings for 2.5-Gb/s operations.