• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.9
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• pp.2362-2372
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• 1996

This paper deals with the design and development of an Injection-Locking Coupled Oscillators(ILCO), which functions like phase-shifter in the Active Intergrated Phased Array Antenna(AIPAA). This linear array 2-element ILCO consists of two Injection Locking Hair-pin Resonator Oscillators(ILHRO) and an unilateral amplifier. The first and second elements of the ILCO have same frequency tuning range but locking bandwidths of 11.5MHz and 14MHz respectively. A phase shift of .DELTA..PHI.=158.4.deg.(-78.0.deg. to 80.4.deg.) could be obtained inthe second element of ILCO when the first elementof the ILCO was in the reference locking mode(.DELTA..PHI.=0.deg.). When the ILCO is applied to the AIPAA, the predicted beam scanning angle value will be 38.4.deg.. Each ILCO gives good frequency stability and lower AM, FM, and PM noise charactheristics in the mutual coupling lockingmode. The ILCO can not only play a part as the phase shifter for the AIPAA but it can also be usedas the power combining device in the mm-wave frequency range and as a part of a T/R MMIC module.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.796-808
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• 2007

In this paper, two novel compact microstrip bandstop filters using complimentary split ring resonators(CSRRs) and spiral resonators is proposed. The first one is the bandstop filter using an array of CSRRs etched on the center line of a microstrip. The bandstop is due to the presence of negative effective permittivity and positive permeability near resonant frequency which prevent the wave propagation. The second on is the bandstop filter using an array of spiral resonators etched on the center line of a microstrip. The bandstop is due to the self-resonance of spiral circuit. We have achieved controllable resonance frequency and bandwidth, super compact dimension, low insertion losses in the passband and high level of rejection in the stopband with sharp cutoff. The electrical sizes of two proposed filter are very small. Additionally, they can be easily fabricated and compatible with MMIC or PCB technology.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.10
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• pp.1727-1730
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• 2016

Magnetic resonance imaging has a potential to produce clear anatomical as well as functional images of human body. However, the ability to diagnose is limited by signal to noise ratio (SNR) and the resolution of current medical systems. To remove the challenges prevalent due to the use of high field scanners, dedicated radio frequency coils are used. Transverse electromagnetic coils have an advantage of providing homogeneous magnetic field throughout the region but with low signal to noise ratio while surface coils have an advantage of providing higher signal to noise ratio but with low homogeneity. This research combines both the advantage into one by utilizing transmit only transverse electromagnetic radio frequency coils (8 channel) along with receive only surface coils (by varying the number) for better imaging of brain. A 7 Tesla 32-channel close fitting helmet shaped phased-array surface coils along with the combination of 8 channel transmit only transverse electromagnetic coils provided good homogeneity as well as significant SNR improvements throughout the human brain.

• Journal of IKEEE
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• v.24 no.2
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• pp.446-452
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• 2020

In this paper, we propose a energy-saving LED module using K-band microwave motion detecting sensor. To oscillate K-band microwave signal, An oscillator using a hairpin-type microstrip resonator was designed to increase stability and make fabrication easier. To radiate the microwave signal, a two-channel(TX/RX) patch antenna arrays was developed. Wilkinson power divider and ring hybrid mixer were developed and applied to obtain Doppler shift from the received signal. Shield cans were installed to protect the stability of the signals and unwanted external noise. The proposed motion detection sensor was mounted on a demonstration LED module and the energy saving performance through pre-test was verified.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.10
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• pp.739-744
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• 2018

In this paper, a double split-ring resonator(DSRR) is proposed to improve the isolation between Vivaldi antenna elements. The DSRR was designed using a unit cell simulation and applied to a $1{\times}2$ Vivaldi antenna array to confirm the improvement in the isolation. The unit cell size of the proposed DSRR is $5mm{\times}5mm{\times}1.52mm$ and six unit cells are used. To verify the performance of the proposed DSRR, $1{\times}2$ Vivaldi antenna arrays with and without the DSRR were fabricated and measured. The results show an isolation improvement of 20 dB in the Vivaldi antennas with the DSRR when compared to the Vivaldi antennas without the DSRR.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.7
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• pp.840-843
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• 2012

In this paper, the authors present a new design for a dual-band metamaterial(MTM) absorber that utilizes resonant-magnetic inclusion of a split-ring resonator(SRR). The proposed MTM unit cell is constructed by two open complementary split-ring resonators(OCSRRs) and an SRR arrangement. To avoid the need for metallic back plate a planar array of SRRs for resonant-magnetic inclusion is placed facing toward the incident wave propagation direction. Each unit cell is printed on the two sides of a FR-4 substrate. A prototype absorber was fabricated with a planar array of $39{\times}39$ unit cells, and measured. The proposed backplane-less absorber can be used for microwave applications.

• Journal of electromagnetic engineering and science
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• v.14 no.1
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• pp.43-45
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• 2014

We propose a printed circuit board (PCB)-embedded antenna for millimeter-wave chip-to-chip communication. The antenna is 0.18 mm in height which is 1/20 wavelength at 80 GHz. In order to realize such a low profile, a zeroth-order resonator antenna with a periodic array of four unit cells is employed, and its geometry is optimized to cover an 8-GHz bandwidth from 76 to 84 GHz. With this;the antenna is capable of radiating in a direction parallel to the board length despite the short distance between the ground and the radiator. Simulation and measurement results show that the optimized design has low reflection coefficients and consistent radiation patterns throughout the target bandwidth.

• Journal of electromagnetic engineering and science
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• v.12 no.4
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• pp.247-253
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• 2012

This study presents a new, simple method for improving the front-to-back (F/B) ratio of a microstrip patch antenna. The back radiation of the microstrip patch antenna is reduced by removing some metallic parts around the ground plane and placing a new soft-surface configuration, consisting of an array of stand-up split-ring resonators on a bare dielectric substrate near the two ground plane edges. Compared to the F/B ratio of a conventional microstrip patch antenna with a full ground plane of the same size, our proposed microstrip patch antenna experimentally achieves an improved F/B ratio of 9.6 dB.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.7
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• pp.679-684
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• 2009

Low frequency exhaust noise of marine diesel engine is one of the most important noise sources in vessels. However, conventional absorptive silencers are ineffective to control exhaust noise because of low absorption in the low frequency range. In the paper, exhaust noise control of marine diesel engine was studied by using the hybrid silencer, which was composed of virtually divided array of concentric hole-cavity resonators and conventional absorptive silencer. A series of tests including field tests were performed to investigate the acoustic performance of the hybrid silencer. Consequently, its high performance of 5${\sim}$10 dB noise reduction in the low frequency range was confirmed and it is expected to be very helpful in reducing the exhaust noise of marine diesel engine.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.220-223
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• 2007

Acoustic test of the payload fairing of Korea satellite launch vehicle was conducted to verify the performance of acoustic protection system installed inside the payload fairing. This paper briefly introduces the acoustic test procedures and its results. Overall 148 dB acoustic loads were exerted on the payload fairing structures which mated with the upper stage structure of the launch vehicle. In order to verify the increase of insertion loss by the acoustic protection system, two kinds of test were performed. One is conducted with acoustic protection system and the other without acoustic protection system. Internal acoustic loads as well as external ones were measured and the measured insertion losses were compared with the requirement. The results showed that the acoustic protection system increases the insertion loss by more than 6 dB above 125 Hz. They also indicated that some design modification of Helmholtz resonator array is required to increase the insertion loss at a cavity resonant frequency.