Jongsik Lim

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This paper presents a novel approach to the design of tunable dual-band bandpass filter with broadband harmonic suppression characteristics. The proposed filter structure offers the possibility of two tunable passbands, as well as a fixed first passband and controllable second passband. The tunable passband frequency usually causes a shift of the harmonics,(More)
This paper presents a novel approach to the design of tunable dual-band bandpass filter (BPF) with independently tunable passband center frequencies and bandwidths. The newly proposed dual-band filter principally comprises two dual-mode single band filters using common input/output lines. Each single BPF is realized using a varactor-loaded transmission-line(More)
This paper presents a novel approach to the design and implementation of a distributed transmission line negative group delay filter (NGDF) with a predefined negative group delay (NGD) time. The newly proposed filter is based on a simple frequency transformation from a low-pass filter to a bandstop filter. The NGD time can be purely controlled by the(More)
A class-F high efficiency GaN power amplifier (PA) for dual band operation at 2.14 GHz and 2.35 GHz is proposed. A novel dual band harmonic-rejection load network, which controls the terminating impedances of the second and third harmonics, and contributes greatly to efficiency improvement of PA, is described. In addition, a matching network which(More)
An unequal Wilkinson power divider with adjustable power dividing ratio is proposed. The proposed power divider consists of rectangular defected ground structure (DGS), isolated island in DGS, and varactor diodes. The impedance of the microstrip line greatly increases due to the DGS, and varies because of the varying capacitance of diodes. The measured(More)
The proposed EBG Structure consists of stepped impedance Microstrip line with slots etched on the ground plane. The T-shaped DMS (Defected microstrip structure) causes large attenuation in the stop-band. A comparison is made between the non-DMS Structure and a DMS Structure. The overall size is 35*20 mm2. The structure is able to achieve a wide Stop band(More)
A virtual laboratory uses computer-based simulation to emulate hardware. In this paper, we proposed a virtual laboratory on microcontroller 8051. The microcontroller virtual laboratory is a Web-based laboratory for students’ operation at any place and in any time. It is accomplished using Java applet and Flash animation for complete comprehension of(More)
This paper presents web-based virtual laboratory system for electronic and digital circuit experiments. Through our virtual laboratory, the learners will be capable of learning the concepts and theories related to circuit experiments and how to operate the virtual experimental equipments such as multimeters, function generators, digital oscilloscopes, DC(More)