• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.414-422
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• 2013

This paper describes a 10-bit 10-MS/s asynchronous successive approximation register (SAR) analog-to-digital converter (ADC) using a split-capacitor-based differential digital-to-analog converter (DAC). SAR logic and comparator are asynchronously operated to increase the sampling frequency. The time-domain comparator with an offset calibration technique is used to achieve a high resolution. The proposed 10-bit 10-MS/s asynchronous SAR ADC with the area of $140{\times}420{\mu}m^2$ is fabricated using a 0.18-${\mu}m$ CMOS process. Its power consumption is 1.19 mW at 1.8 V supply. The measured SNDR is 49.95 dB for the analog input frequency of 101 kHz. The DNL and INL are +0.57/-0.67 and +1.73/-1.58, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.5
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• pp.528-537
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• 2011

In this paper, a broadband antenna of the CPW structure with a band-notched characteristic is presented. To obtain this characteristic, the complementary split ring resonator(CSRR) is inserted in the ground plane. In addition, the IEEE 802.11a WLAN band(5.15～5.825 GHz) appears in the band-notched characteristic. The proposed antenna dimension is $36{\times}60{\times}1.6\;mm^3$, and it is designed on the FR-4 substrate having a relative dielectric constant of 4.4. The designed antenna shows that the resonant frequency is 2.03～10.78 GHz below the return loss of -10 dB and a VSWR less than 2 was satisfied. As a result, the proposed CSRR has a band-notched characteristic in the range of 4.917～6.017 GHz which the center frequency is about 5.4 GHz band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.123-130
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• 2016

In this paper, a novel flexible microfluidic metamaterial absorber is proposed for remote chemical sensor applications. The proposed metamaterial absorber consists of a periodic of split-ring-cross resonators(SRCRs) and a microfluidic channel. The SRCR patterns are inkjet-printed using silver nanoparticle inks on paper. The microfluidic channels are laser-etched on polydimethylsiloxane(PDMS) material. The proposed absorber can detect change of the effective permittivity at different liquids. Therefore, the absorber can be used for a remote chemical sensor by detecting change of the resonant frequencies. The performance of the proposed absorber is demonstrated with full-wave simulation and measurement results. The experimental results shows that the resonant frequency is 10.49 GHz at the empty channel. When ethanol and DI-water are injected into the channel, the resonant frequencies are 10.04 GHz and 8.9 GHz, respectively.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1945-1954
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• 2017

In recent years, several LCL filter design methods for different converter topologies have been published, many of which use analytical expressions to calculate the ideal converter AC voltage harmonic spectrum. This paper presents the LCL filter design methodology but the focus is on presentation and validation of the non-iterative filter design method for a grid-connected three-phase two-level PWM-VSC. The developed method can be adapted for different converter topologies and PWM algorithms. Furthermore, as a starting point for the design procedure, only the range of PWM carrier frequencies is required instead of an exact value. System nonlinearities, usually omitted from analysis have a significant influence on VSC AC voltage harmonic spectrum. In order to achieve better accuracy of the proposed procedure, the system nonlinear model is incorporated into the method. Optimal filter parameters are determined using the novel cost function based on higher frequency losses of the filter. An example of LCL filter design for a 40 kVA grid-connected PWM-VSC has been presented. Obtained results have been used to construct the corresponding laboratory setup and measurements have been performed to verify the proposed method.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.4
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• pp.22-31
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• 2010

In this paper, a new split ring resonator using left-handed meta-material adapted in a bandpass filter with 2-stages is suggested. In this proposed bandpass filter, the size of the novel resonator can be easily controlled. Also, the bandwidth can be adjusted with the position of the tapped-line. The proposed resonator and filter has the center frequency of 10 GHz for I-band in military-satellite communication system with the Qe value of 184. The experimental results of the filter show that the insertion and return losses are 1.43 dB and 16.8 dB with bandwidth of 10 %, respectively.

• Current Optics and Photonics
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• v.4 no.4
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• pp.373-379
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• 2020

In this study, we investigate terahertz (THz) generation by a photoconductive antenna with electrodes in the shape of split-ring resonators. According to our theoretical investigation based on a lumped-circuit model, the inductance of this electrode structure leads to resonant behavior of the photo-induced current. Hence, near the resonance frequency the spectral components generated by a resonant photoconductive antenna can be greater than those produced by a non-resonant one. For experimental verification, a resonant photoconductive antenna, which possesses a resonance mode at 0.6 THz, and a non-resonant photoconductive antenna with stripe-shaped electrodes were fabricated on a semi-insulating GaAs substrate. The THz generation by both of the photoconductive antennas demonstrated a good agreement with the theoretically expected results. The observed relationship between the resonant electrodes of the photoconductive antenna and the generated THz spectrum can be further employed to design a narrow-band THz source with an on-demand frequency.

• Journal of The Korean Society of Grassland and Forage Science
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• v.22 no.1
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• pp.9-14
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• 2002

Evegradies 71' kenaf (Hibiscus cannabinus L.) was grown at 160,000 plants per ha in a volcanic ash soil in Jeju island to determine the optimum frequency of split N application fer forage production. Nitrogen fertilizer was applied with 240 kg/ha, and frequencies of the split N applications were 1, 2, 3, 4 and 5 times. Plant height averaged across two harvests increased from 187 to 201cm as N was split-applied from one to three applications and then decreased to 201cm in five applications. This pattern held for the number of branches and leaves per plant stem diameter and weight of plant per plant. Fresh forage yield increased from 91.8 to 114.2 MT/ha. dry matter yield from 12.70 to 16.6 MT/ha, crude protein yield from 1.75 to 2.48MT/ha, and total digestible nutrients (TDN) yield from 5.39 to 7.63 MT/ha as N was split-applied from one to four applications, and then decreased to 106.6, 15.0, 2.32, and 7.22 MT/ha in five applications, respectively As N was split-applied from one to five applications, crude protein content increased from 13.8 to 15.4%. ether extract content from 4.1 to 5.9%, and TDN content from 42.4 to 48.1%. but crude fiber decreased from 38.2 to 37.1% and crude ash content from 11.5 to 8.6%. Nitrogen free extract content was about 19.0% regardless of cutting height.

• Journal of electromagnetic engineering and science
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• v.12 no.4
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• pp.240-246
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• 2012

This paper presents a novel modeling technique for traces that cross a defected ground structure. A simple and accurate equivalent circuit model provides clear insight into the coupling mechanism between a microstrip line and a slot or split. The circuit models consist of a transformer as the coupling mechanism and LC resonators as the ground with a slot or split structure. Resistors, capacitors, and inductors are added to the model to increase accuracy and equivalence at high frequency. Simulated and measured S-parameters are presented for defected ground structures. The accuracy and validity of the proposed equivalent circuit model is verified by evaluation of the S-parameter characteristics of the defected ground structures and comparison with measured results.

• Smart Structures and Systems
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• v.5 no.3
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• pp.279-290
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• 2009

Two degrees of freedom resonant systems are employed to improve the resonant property of resonant sensor, as compared to a single degree of freedom resonant system. This paper presents design, development and testing of two degrees of freedom resonant sensor. To measure absolute mass, cantilever shaped two different masses (smaller/absorber mass and bigger/drive mass) with identical resonant frequency are mechanically linked to form 2 - Degree-of-Freedom (DOF) resonator which exhibits higher amplitude of displacement at the smaller mass. The same concept is extended for measuring differential quantity, by having two bigger mass and one smaller mass. The main features of this work are the 3 - DOF resonator for differential detection and the microcontroller based closed loop electronics for resonant sensor with piezoelectric sensing and excitation. The advantage of using microcontroller is that the method can be easily extended for any range of measurand.

• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.134-136
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• 2013

This paper examines various aspects of the electromagnetic responses of the ring resonator located in the transverse electromagnetic cell. In addition, an equivalent circuit for the ring resonator is proposed and analyzed based on the electromagnetic phenomenon of the resonator. The equivalent circuit was simply modeled based on the concept of magnetization. A method for achieving a wider operating bandwidth of the negative permeability is provided. The ring resonator with its resonant frequency of 13.56 MHz was designed and its characteristics were examined in terms of S-parameters, effective permeability, loss rate, bandwidth, etc. The circuit and electromagnetic simulation results show an excellent agreement as well as that of theory.