Chul-Soo Kim

A novel 1-D periodic defected ground structure for planar circuits

A new one-dimensional (1-D) defected ground unit lattice is proposed in order to improve the effective inductance. Increasing the effective inductance makes it easy to control the cutoff frequency characteristics. The proposed periodic defected ground structure (DGS) provides the excellent cutoff and stopband characteristics. In order to show the improved the effective inductance, three DGS circuits were fabricated with identical periodic and different dimensions. Measurements on the fabricated DGS circuits show that the cutoff and stopband center frequency characteristics depend on the physical dimension of the proposed DGS unit lattice,.

Design of low-pass filters using defected ground structure

A method to design low-pass filters (LPF) having a defected ground structure (DGS) and broadened transmission-line elements is proposed. The previously presented technique for obtaining a three-stage LPF using DGS by Lim et al. is generalized to propose a method that can be applied in design N-pole LPFs for N/spl les/5. As an example, a five-pole LPF having a DGS is designed and measured. Accurate curve-fitting results and the successive design process to determine the required size of the DGS corresponding to the LPF prototype elements are described. The proposed LPF having a DGS, called a DGS-LPF, includes transmission-line elements with very low impedance instead of open stubs in realizing the required shunt capacitance. Therefore, open stubs, teeor cross-junction elements, and high-impedance line sections are not required for the proposed LPF, while they all have been essential in conventional LPFs. Due to the widely broadened transmission-line elements, the size of the DGS-LPF is compact.

A 4.1 unequal Wilkinson power divider

This letter presents the design and measured performances of a microstrip 4:1 unequal Wilkinson power divider. The divider is designed using the conventional Wilkinson topology with the defected ground structure (DGS). The DGS on the ground plane provides an additional effective inductive component to the microstrip line. This enables the microstrip line to be realized with very high impedance of over 150 /spl Omega/. By employing the DGS to the unequal Wilkinson topology, 4:1 power dividing ratio can be obtained easily without any problem in realization, while it has been impractical to fabricate a 4:1 divider using the conventional microstrip line because of very thin conductor width and extremely low aspect ratio (W/H). As an example, a 4:1 divider has been designed and measured at 1.5 GHz in order to show the validity of the proposed DGS and unequal divider. The measured performances of the 4:1 unequal power divider well agree with the exactly same dividing ratio as that expected.

A spiral-shaped defected ground structure for coplanar waveguide

The authors present a spiral-shaped defected ground structure for coplanar waveguides (DGSCPW), which can be used as a kind of periodic structure for a planar transmission line. The proposed spiral-DGSCPW adopts spiral-shaped defects on both ground planes of CPW. Due to the spiral-shaped defects, the equivalent shunt inductance and slow-wave effects increase more rapidly than the standard CPW or CPW lines combined with the conventional PBG. The modeling and analysis to extract the equivalent circuit, increased slow-wave factor, and simulated and measured performances are presented.

A compact-size microstrip spiral resonator and its application to microwave oscillator

This letter presents a compact size microstrip spiral resonator and its application to a low phase noise oscillator. This resonator has stopband characteristics to be used in the series feedback oscillator topology. The whole circuit area of the proposed resonator is within 1/10 wavelength, which results in the reduction of the circuit area and cost. A 10-GHz oscillator incorporated with this resonator was designed, fabricated and measured. It shows low phase noise performance of -95.4-dBc/Hz at 100 kHz offset.

Modeling of a photonic bandgap and its application for the low-pass filter design

A new photonic bandgap unit structure for microstrip line is proposed. The equivalent circuit for the proposed photonic bandgap unit structure is derived by means of three dimensional field analysis methods. The equivalent circuit parameters are extracted by using the circuit analysis method. By employing the extracted parameters, the wide-band harmonic rejection low-pass filter is designed. The experimental results show the excellent agreements with theoretical results.

Pd- and Pt-SiC Schottky diodes for detection of H2 and CH4 at high temperature

Abstract Hydrogen- and methane-sensing characteristics of Pt- and Pd-SiC Schottky diodes, fabricated on the same SiC substrate, have been compared and analyzed as a function of hydrogen partial pressure and temperature by I – V and Δ I – t methods under steady-state and transient conditions at high temperature. The effects of the gas adsorption on the parameters such as barrier height, initial rate of gas adsorption, and gas reaction kinetics are investigated. Analysis of steady-state reaction kinetics using I – V method confirmed that the atomistic hydrogen adsorption process is responsible for the barrier height change in the diodes.

A study on a platinum–silicon carbide Schottky diode as a hydrogen gas sensor

Abstract The mechanism of hydrogen sensing by platinum–silicon carbide Schottky diode was investigated over the temperature range of 100–500°C. The effects of hydrogen adsorption on the parameters such as barrier height, initial rate of hydrogen adsorption, and hydrogen reaction kinetics were investigated.

A vertically periodic defected ground structure and its application in reducing the size of microwave circuits

The microstrip and coplanar waveguide transmission lines combined by a vertically periodic defected ground structure (VPDGS) are proposed. The slow-wave effect, equivalent circuit, and the performances are shown. As an application example, VPDGS is adopted in the matching networks of an amplifier for size-reduction. Two series microstrip lines in input and output matching networks of the amplifier are reduced to 38.5% and 44.4% of the original lengths, respectively, due to the increased slow-wave effects, while the amplifier performances are preserved.

A 10dB Branch Line Coupler Using Defected Ground Structure

This paper presents a novel 90° branch-line coupler with DGS(Defected Ground Structure), which is etched on the backside metallic plane. The DGS section can implement high impedance transmission line easily with microstrip configuration. DGS sections under a conventional microstrip line are analyzed to find the characteristic impedance and electrical length by means of three dimensional field analysis. In order to show the validity of the proposed DGS section, a branch-line coupler with the loose coupling of lOdB is fabricated and measured. Measured performances of lOdB branch line coupler with DGS show excellent agreement with predicted results.