• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.81-90
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• 2015

This paper investigates the droop control-based real and reactive power load sharing with a virtual inductor when the line impedance between inverter and Point of Common Coupling (PCC) is partly and unequally resistive in high-capacity systems. In this paper, the virtual inductor method is applied to parallel inverter systems with resistive and inductive line impedance. Reactive power sharing error has been improved by applying droop control after considering each line impedance voltage drop. However, in high capacity parallel systems with large output current, the reference output voltage, which is the output of droop controller, becomes lower than the rated value because of the high voltage drop from virtual inductance. Hence, line impedance voltage drop has been added to the droop equation so that parallel inverters operate within the range of rated output voltage. Additionally, the virtual inductor value has been selected via small signal modeling to analyze stability in transient conditions. Finally, the proposed droop method has been verified by MATLAB and PSIM simulation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.11 s.102
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• pp.1099-1105
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• 2005

TRL error correction method is widely used for measuring high frequency device mounted on PCB. In order to correct error more precisely, the characteristic impedance of standard transmission line should be known mounted for error correction. The capacitance per the unit length of transmission line is calculated by using standard transmission line which terminate resistor additionally at previous method and the characteristic impedance of standard transmission line is calculated with fitting method according to frequency, but the characteristic impedance extracted by a manufacturing inaccuracy is influenced. In this study, a novel method can reduce the manufacturing inaccuracy using measured s-parameters and can extract more accurate characteristic impedance than the previous method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.1007-1015
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• 2000

This paper proposes an adaptive trajectory generation strategy of using on-line ZMP information and an impedance control method for biped robots. Since robots experience various disturbances during their locomotion, their walking mechanism should have the robustness against those disturbances, which requires an on-line adaptation capability. In this context, an on-line trajectory planner is proposed to compensate the required moment for recovering stability. The ZMP equation and sensed ZMP information are used in this trajectory generation strategy. In order to control a biped robot to be able to walk stably, its controller should guarantee stable footing at the moment of feet contacts with the ground as well as maintaining good trajectory tracking performance. Otherwise, the stability of robot will be significantly compromised. To reduce the magnitude of an impact and guarantee a stable footing when a foot contacts with the ground, this paper. proposes to increase the damping of the leg drastically and to modify the reference trajectory of the leg. In the proposed control scheme, the constrained leg is controlled by impedance control using the impedance model with respect to the base link. Computer simulations performed with a 3-dof environment model that consists of combination of a nonlinear and linear compliant contact model show that the proposed controller performs well and that it has robustness against unknown uneven surface. Moreover, the biped robot with the proposed trajectory generator can walk even when it is pushed with a certain amount of external force.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2009-2010
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• 2006

This paper presents an adaptive line coupler to match input impedance of the Power line Communication(PLC) modem between access impedance of the power line. This line coupler provides maximum signal power transmiting capability, high reliability. The structure of this coupler is simple and designed to make a easy and low cost. The proposed line coupler is suitable for Amplitude Shift Keying(ASK) or Phase Shift Keying(PSK) modem. To figure out our models, the analysis of the transmitting features of power line channel is performed in the time domain at the carrier frequency. As a result of this study, we present the values of capacitors in the capacitor bank and adaptive line coupler circuit.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.10
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• pp.1409-1415
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• 2021

The Gysel divider has the advantage of easily setting the resistor in the circuit. If the line impedance in the Gysel divider is set differently, the input signal can be distributed to the two output ports at various distribution ratios. This paper proposes the Gysel divider that can change the power distribution to 1:3 or 3:1 by changing the line impedance. The impedance change of the line can be implemented by placing a floating copper plate on the bottom of the microstrip-line. When the floating copper plate and the ground plane are connected, the line operates as the microstrip-line, and when the floating copper plate and the ground plane are disconnected, the line operates as the coplanar-line. The proposed Gysel divider was fabricated at the center frequency of 1.5GHz. The fabricated 3:1 Gysel divider has a stable value S₁₁ of below -17dB, S₂₁/S₃₁ of 4.8±0.2dB, S₂₁(to high output port) of -1.39±0.12dB and S₃₁(to low output port) of -6.15±0.08dB over 1.3~1.7GHz.

• ETRI Journal
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• v.34 no.3
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• pp.454-457
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• 2012

A miniaturized planar digital video broadcasting terrestrial (DVB-T) antenna, which is composed of a patterned helical line, an open stub, and an impedance matching circuit on an FR4 (${\varepsilon}_r$=4.4) substrate for portable media player applications, is presented in this letter. The antenna has monopole-like, omni-directional radiation characteristics and a wide impedance bandwidth (VSWR<3) in the DVB-T band from 174 MHz to 230 MHz at the VHF band.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.9 no.4
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• pp.164-167
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• 2010

In this paper, an artificial transmission line of triangular-patch type with slots is proposed. This artificial transmission line is useful for miniaturizing the electrical lengths of conventional transmission lines. Also, this structure is easy to regulate the characteristic impedance and electrical lengths. The electrical lengths and the characteristic impedances of the proposed artificial transmission line with some parameters are researched and summarized The proposed artificial transmission line could be useful for compact designs for most of the passive microwave components. The optional-artificial transmission line is fabricated and measured at 2.45GHz.

• Progress in Superconductivity and Cryogenics
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• v.4 no.2
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• pp.11-15
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• 2002

High speed probe for measurement of sin91e flux quantum circuits is comprised of coaxial cables and microstrip lines in order to carry high speed signals without loss. For the impedance matching between coaxial cable and microstrip line, we have determined the dimension of the microstrip line with 50${\Omega}$ impedance by simulation and then have investigated the effect of line width and cross-sectional shape of signal line, dielectric material, thickness of soldering lead at the coaxial-to-microstrip transition Point, and the an91c between dielectric material and end part of the signal line on the characteristics of signal transmission of the microstrip line. From the simulation, we have found that these all parameter's had influenced on the characteristic of signal transmission on the microstrip line and should be reflected in fabricating high speed probe, We have also determined the dimension of coplanar waveguide to fabricate testing sample for performance test of high speed probe.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2541-2548
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• 2010

This paper describes the calculation for characteristic impedance of transmission line with periodic structures such as defected ground structure (DGS) and photonic bandgap (PBG). The previous method which uses the ${\lambda}$/4 transmission line model is reviewed and its disadvantage that the calculated characteristic impedance is strongly dependent on the frequency is discussed. The characteristic impedance of transmission lines with periodic structures are calculated using the ${\lambda}$/4 transmission line model and analytic method. The calculated characteristic impedance by the latter method is an almost constant value while that from the first method depends on the frequency strongly. In addition, the characteristic impedance of the transmission line with PBG is calculated and proposed, while it has been rarely studied ever. S-parameters are obtained from the measurement using the fabricated sample as well as simulation, and used for calculating the characteristic impedances and comparison. The characteristic impedances calculated from the measured S-parameters agree well with the simulated results. It is well described that the analytic method to calculate the characteristic impedance of transmission lines on uniform dielectric structures can be applied successfully to the transmission lines with periodic structures such as DGS and PBG.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.202-207
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• 2016

An auxiliary real-time train communications system among drivers, train-traffic controllers and field workers is necessary to share hazard information (i.e. rockfall detection, track maintenance) in low visibility zones (long tunnels and steep curved track). To develop the appropriate communication system, this paper proposes a new way of power line communication using the rail track (Rail - PLC), which has little noise and distortion of attenuation. Therefore, it is important to measure the impedance of the rail and to apply an impedance matching technique to increase the transmission characteristic of the Rail - PLC. This study would evaluate the reflection and the transmission characteristics of the rail using a network analyzer and an impedance matching transformer. The suitable impedance matching ratio was 1:3.28 from the result of back-to-back testing. The results confirmed that the transformer can improve the performance of the transmission signal in Rail - PLC using an impedance matching technique.