• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.834-838
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• 2007

A coupled-defected ground structure(C-DGS) having closely-located DGS cells is proposed for high performance bandstop filter applications. The negative coupling of ground currents between adjacent DGS cells greatly improves the stopband characteristics. We have measured the attenuation slope of 110.8 dB/GHz and -20 dB rejection band from 3.8 GHz to 15.5 GHz. Compared to the double-plane BSF, the proposed BSF improved the sharp cutoff response 7.6 times. We expect the C-DGS be helpful to improve the performance of DGS application circuits and also to extend the possible DGS applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.2
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• pp.115-123
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• 2009

In this paper, we extract the parasitic elements of the transmission line with the defected ground structure(DGS) and the short-circuited comb line section using the Short-Open Calibration(SOC). The scattering matrixes of short, open and the distributed elements in microstrip line are measured by full electro-magnetic(EM) simulator and Vector Network Analyser(VNA). The electro-magnetic effects of the proposed structures are considered by the II and T equivalent circuits with frequency independent elements, and the relations between the measured scattering parameters and the elements in the circuits are shown by performing 2 port network analysis. Moreover, to design the 2.4 GHz bandpass filter with second order butterworth prototype, the proposed methods are applied. As results, the measured $S_{11}$ and $S_{21}$ indicate -20 dB and -1.3 dB at center frequency, and these are shown within 5 % error compare to the predicted results at $0.5{\sim}5\;GHz$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2443-2448
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• 2013

In this paper, a design of size-reduced microwave oscillator using common defected ground structure (common DGS) is described. At first, an oscillator is designed using the normal stub resonator, and the conventional DGS patterns are inserted for the first trial of size-reduction. Finally, the DGS resonator section is folded by half size in order to adopt the common DGS, and this produces the proposed size-reduced oscillator. Common DGS pattern is inserted for a better size-reduction than when conventional DGSs are used. The folded transmission line is connected using the 3-dimensional signal via-holes. For an example of design, a 2.1GHz oscillator is designed and fabricated using a small signal transistor and common DGS, which shows the size-reduction of 11 mm. The measurement shows 6.7dBm of output power and -133dBc/Hz@1MHz of phase noise. The measured performances are so similar to those of the oscillators before size-reduction and prove the proposed size-reduction method of oscillators using common DGS.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.5
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• pp.1193-1200
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• 2008

This paper describes a developed 5Watt power amplifier module fer mobile communication system using Gallium Nitride (GaN) devices. Three amplification stages such as pre-amplifier, driver amplifier, and power amplifier have been fabricated and measured separately in advance for incorporating the total power amplifier module and estimating the performances. In addition, a defected ground structure is combined with the output stage of the power amplifier module for improving harmonic rejection and adjacent channel power (ACP) characteristics. The measured performances of the GaN power amplifier module include 58dB,min of gain, 37dBm,min of output power, 50dBc,min of harmonic rejection, 35dBc,min of IMD3 for 2-tone input, and 35dBc,min of ACP at 2.1GHz frequency band.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.4
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• pp.765-770
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• 2009

This paper presents a new open stub structure of Kuroda low-pass filter using DGS(Defected Ground Structure). The open stub having 130ohm is made with equivalent new structure using DGS. This method enable to the fabrication of Kuroda low-pass filter by extending width of the line. In case of FR4(er=4.8, h=0.7874mm), the width of open stub(130ohm) is under 0.1mm. But, the width of open stub using DGS can extend to the width of 0.5mm. 5th order Kuroda low-pass filter design using open stub with DGS shows excellent agreement between theoretical simulation and experimental results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.12 s.103
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• pp.1186-1193
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• 2005

In this paper, a new 3 dB branch line hybrid using asymmetric spiral-shaped defected ground structure(DGS) microstrip is proposed. The proposed branch line hybrid suppresses the 2nd and the 3rd harmonic component effectively. Also a DGS $\lambda$/4 bias line that can suppress high frequency harmonics as well as low frequency intermodulation component is proposed. With the harmonic termination tuner using the proposed hybrid and the harmonic blocking bias line, the 2nd and the 3rd harmonic components of the fabricated amplifier that operated in IMT-2000 basestation transmitting band were suppressed up 25 dB and 27 dB, respectively. The proposed harmonic load-pull setup of amplifier is more easily accomplished with proposed circuits than the previous.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.852-857
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• 2011

In this paper, the application of a variable characteristic impedance transmission line that can be used to design a dual-band bandpass filter(BPF) is presented. The proposed filter offers a fixed first frequency passband and a controllable second passband. The tuning of the second passband is achieved by varying the characteristic impedance of and open shunt stub line in a stub loaded resonator(SLR) with the help of a defected ground structure(DGS) transmission line and varactor diodes. In order to validate the proposed structure, a two stage dual-band BPF with three transmission zeros was implemeted and experimentally verified based on its theoretical predictions and simulations.

• Journal of the Institute of Convergence Signal Processing
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• v.4 no.1
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• pp.41-48
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• 2003

In this paper, a new equivalent circuit for a defected ground structure(DGS) is proposed and adapted to design of a power amplifier for performance improvement. The DGS equivalent circuit presented in this paper consists of parallel LC resonator and parallel capacitance to describe the fringing fields due to the etched defects on the metallic ground plane, and also is used to optimize the matching circuit of a power amplifier. A previous research has also used a DGS for harmonic rejection and efficiency improvement of a power amplifier(1), however, there was no exact equivalent circuit analysis. In this paper, we suggest a novel design method and show the performance improvement of a class AB power amplifier by using the equivalent circuit of a DGS applied to output matching circuit. The design method presented in this paper can provide very accurate design results to satisfy the optimum load condition and the desirable harmonic rejection, simultaneously. As a design example, we have designed a 20W power amplifier with and without circuit simulation of DGS, and compared the measurement results.

• Corrosion Science and Technology
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• v.19 no.4
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• pp.211-223
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• 2020

The external corrosion of buried piping can be controlled using both coating and cathodic protection. Several factors are involved in the damage and deterioration of the coating on pipes. There are many detection methods for coating defects on pipes and the direct current voltage gradient (DCVG) method is one of the most powerful methods. However, the detection reliability of DCVG can be affected by interferences such as stray current, metal objects connected to rectifiers, and copper grids. Therefore, this study focused on the interference effects of rectifiers and a copper grid on the reliability of coating flaw detection. As the length of the interference pipe connected to the rectifier increased, the reliability decreased. In contrast, as the distance between the pipe and the copper grid increased, the reliability of the coating flaw detection increased. The detection results produced by the DCVG method were discussed using current and potential simulations for a pipe with a rectifier and copper grid interference in the soil.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.9
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• pp.1039-1046
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• 2007

In this paper, a coupled-defected ground structure(C-DGS) using negative inductive coupling is proposed and a bandstop filter(BSF) using C-DGS is designed and fabricated. The proposed C-DGS is the closely-located DGS cells for the negative coupling, the negative coupling of ground currents between adjacent DGS cells greatly improves the stopband characteristics. The proposed BSF utilizing the sharp cutoff response of the C-DGS has a -10 dB rejection band from 4 GHz to 11.3 GHz. A maximum attenuation rate is -64.3 dB/GHz in 3 cell structure, -108 dB/GHz in 5 cell structure. The C-DGS BSF shows the improved attenuation rate 3.8 times in 3 cell structure, 2.4 times in 5 cell structure, Also, the C-DGS BSF is reduced to 35.2 % and 40 % of the DGS BSF, respectively, due to the closely-located DGS cells. We fabricated the single gate mixer using C-DGS BSF. The single gate mixer has 6.6 dB conversion gain.