• Journal of electromagnetic engineering and science
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• v.3 no.1
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• pp.1-6
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• 2003

In this paper, a sub-harmonic dual-gate FET mixer is suggested to improve the isolation characteristic between LO and RF ports of an unbalanced mixer. The mixer was designed by using single-gate FET cascode structure and driven by the second harmonic component of LO signal. A dual-gate FET mixer has good isolation characteristic since RF and LO signals are injected into gatel and gate2, respectively. In addition, the isolation characteristic of a sub-harmonic mixer is better than that of a fundamental mixer due to the large frequency separation between the LO and RF frequencies. As RF power was -30 ㏈m and LO power was 0 ㏈m, the designed mixer yielded the -47.17 ㏈m LO-to-RF leakage power level, 10 ㏈ conversion gain, -2.5 ㏈m OIP3, -12.5 ㏈m IIP3 and -1 ㏈m 1 ㏈ gain compression point. Since the LO-to-RF leakage power level of the designed mixer is as good as that of a double-balanced mixer, the sub-harmonic dual-gate FET mixer can be utilized instead.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.8
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• pp.788-793
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• 2004

This paper proposes new configuration for the dual power amplifier that operates at 5.8 GHz for the wireless LAN and 1.8 GHz for the PCS. It dose not select the input signal but amplify the dual band signals simultaneously. Broadband diplexer is used at the input to separate the dual band signals. Output power of each amplifier is 1 W. The PBG is employed to improve the performance of power amplifier. Generally, the PBG is employed at the end of output matching network. But in this paper, the PBG is employed in the load pull output matching circuit of amplifer to maximize the output power.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.579-584
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• 2001

The reinforced concrete(RC) beam is developed cracks because the compression strength of concrete is strong but the tensile strength is weak. The structural strength and stiffness is decreased by reduction of tension resistance capacity of concrete due to the developed cracks. Using the fiber reinforced concrete that is increased the flexural strength and tensile strength at tensile part can enhance the strength and stiffness of concrete structure and decrease the tensile flexural cracks and deflection. Therefore, The reinforced concrete used the fiber reinforced concrete at tensile part ensure the safety and serviceability of the concrete structures. In this study, analytical model of a dual concrete beam that is composed of the normal strength concrete at compression part and the high tensile strength concrete at tensile part is developed by using the equilibrium condition of forces and compatibility condition of strains and is parted into elastic analytical model and ultimate analytical model. Three group of test beam that is formed of one reinforced concrete beam and two dual concrete beams for each steel reinforcement ratio is tested to examine the flexural behavior of dual concrete beams. The comparative study of total nine test beams is shown that the ultimate load of a dual concrete beams relative to the reinforced concrete beams have an increase in approximately 30%. In addition, the initial flexural rigidity, as used here, refer to the slope of load-deflection curves in elastic state is increased and the deflection is decreased.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.109-113
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• 2015

This paper presents the study results on a dual band feed horn for the focused reflector. A coaxial waveguide structure is attractive to avoid blockage from the feeder. The inner conductor as a hollow waveguide is designed to excite TE11 of a circular waveguide for high frequency. For low frequency, the design of the outer coaxial waveguide that propagates coaxial TE11 and prevents fundamental TEM is presented. The horn size for generation of these modes results in the degradation of performance. The return loss is improved by a capacitive iris and an inductive iris The enhanced pattern symmetry by dual mode is presented. The horn design in this paper are verified through the test.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.1
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• pp.119-123
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• 2005

In this paper. It is proposed and fabricated that the new antenna of dual T type structure is shifted easily center frequency. This antenna consists of dual dipoles resemblance to dual T type, which are fed by a coplanar waveguide (CPW) on signal plane. The analyzed and measured characteristic of new antenna is controled between distance of two dipoles for shifting center frequency. The proposed antenna is 450MHz bandwidth for using IMT2000 band. The characteristic parameters of the proposed antenna are analyzed by using a FDTD methods.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.4
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• pp.643-650
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• 2017

This pap4er analyzes resonance characteristics of a slave motor that is not controlled by load and parameter differences between Dual motors during parallel operation in middle-low speed. Dual SPMSMs(Surface mounted Permanent Magnet Synchronous Motor) connected in parallel to a single inverter controlled by the master and slave control in this paper. Based on the stability analysis of the SPMSM for a variation of torque angle, the 6th nonlinear state equation of the torque angle variation in the SIMM(Single Inverter Multi Motor) structure is derived according to a mathematical model for the dual motors. In general, an analysis of the 6th order nonlinear state equation is complex. Therefore, a resonance frequency generated from the slave motor is found from the characteristic equation of the 2nd order system obtained by linearization and model reduction near steady state operation point. Through simulations and experiments, it is confirmed that the stability analysis of the SPMSMs and state equation models are useful for the variation of the torque angle analyzed in this paper.

• Journal of Ocean Engineering and Technology
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• v.15 no.2
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• pp.22-32
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• 2001

The numerical investigation of obliquely incident wave interactions with fully submerged dual buoy/porous-membrane floating breakwaters placed in parallel with spacing is studied based on linear potential theory and Darcy's law. The numerical solutions are obtained by using a discrete-membrane dynamic model and second-kind modified Bessel function distribution over the entire boundaries of fluid regions. First, numerical solutions for an idealized dual submerged system without buoys are obtained. Second, a more practical dual submerged system with membrane tension provided by buoys at its tops is investigated by the multi-domain boundary element method particularly devised for dual buoy/porous-membrane problems with gaps. The velocity potentials of wave motion are coupled with porous-membrane deformation, and solved simultaneously since the boundary condition on porous-membrane is not known in advance. The effects of varying permeability on membranes and wave characteristics are discussed for the optimum design parameters of systems previously studied. The inclusion of permeability on membrane eliminates the resonances that aggravate the breakwater performance. The system is highly efficient when waves generated by the buoys and membranes were mutually canceled and its energy at resonance frequency dissipates through fine pores on membranes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.5
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• pp.401-406
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• 2005

Two dimensional MEDICI simulator is used to study the electrical characteristics of Dual Gate Emitter Switched Thyristor. The simulation is done in terms of the current-voltage characteristics with the variations of p-base impurity concentrations and current flow. Compared with the other power devices such as MOS Controlled Cascade Thyristor(MCCT), Conventional Emitter Switched Thyristor(C-EST) and Dual Channel Emitter Switched Thyristor(DC-EST), Dual Gate Emitter Switched Thyristor(DG-EST) shows to have tile better electrical characteristics, which is the high latch-up current density and low forward voltage-drop. The proposed DG-EST which has a non-planer u-base structure under the floating N+ emitter indicates to have the better characteristics of latch-up current and breakover voltage in spite of the same turn-off characteristics.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.3
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• pp.22-30
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• 2011

There is a many way of LPRE throttling methods, high-pressure-drop systems, dual-manifold injector, gas injection, multiple chambers, pulse modulation and movable injector components. Especially dual-manifold injector is essentially combines two fixed-area injectors into a common structure, with independent feed systems controlling flow to each injector manifold. In this paper, using indirect photography and liquid film thickness measurement with various injection pressure and tangential entry diameter to decide stability of spray over a wide thrust range in dual manifold injector.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.2
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• pp.126-133
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• 2022

This study proposes a suppression of zero sequence current (ZSC), which is caused by zero sequence voltage (ZSV) for a dual two-level inverter with single DC bus. Large output voltages enable the dual inverter with single DC bus to improve a system efficiency compared with single inverter. However, the structure of dual inverter with single DC bus inevitably generates ZSC, which reduces the system efficiency and causes a current ripple. ZSV is also produced by dead time, and its magnitude is determined by the DC bus and current direction. This study presents a novel space vector modulation method that allows the instantaneous suppression of ZSC. Based on a condition where a switching period is twice a sampling (control) period, the proposed control method is implemented by injecting the offset voltage at the primary inverter. This offset voltage is injected in half of the switching period to suppress the ZSC. Simulation and experiments are used to compare the proposed and conventional methods to determine the ZSC suppression performance.