• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.6
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• pp.583-590
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• 2010

In this paper, a novel CRLH-TL unit cell with controllable transmission zeros was proposed. Proposed composite right/left handed transmission line(CRLH-TL) unit cell is implemented in the form of the metal-insulator-metal(MIM) capacitors, the microstrip stub inductors, and the co-planar waveguide(CPW) inductor. And this proposed CRLH-TL generates two transmission zeros in lower/upper passband by the effort of electromagnetic couplings between each MIM capacitors and microstrip stub inductors. Using this proposed CRLH-TL, broad bandpass filter for UWB system was designed and fabricated. The measured results reveal that the two transmission zeros are observed in lower/upper passband and the overall size of the filter, excluding the feed line is about 8 mm$\times$8 mm, less then $\lambda_g$/4 on electric size.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1143-1150
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• 2001

In this paper, we designed a downconverter for K-band satellite multipoint distribution service(SMDS). The designed downconverter consists of a low noise amplifiers, bandpass filter, stable local oscillator, drain mixer and If Amplifiers. Low noise amplifiers show 28㏈ gain and 1.5㏈ noise figure in the frequency range of 19.2㎓~20.2㎓, and a band pass filter has a -l㏈ insertion loss, and 18.25㎓ Stable local oscillator which is dielectric resonant oscillation, We obtained that the output power of the 18.25㎓ oscillation frequency is 0.5㏈m and the phase noise is the -84.67㏈c at 10KHz offset frequency. With the input RF signal the 19.2㎓~20.2㎓, conversion gain of the drain mixer shows 5㏈ at the Intermediate frequency range of 950MHz~1950MHz. We have proved that the designed downconverter satisfied the specification of a K-band satellite multipoint distribution service and it can be applied to the satellite internet receiver.

• Journal of Advanced Navigation Technology
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• v.16 no.3
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• pp.433-439
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• 2012

In this paper, we proposed the triplexer using unit-cell of CRLH transmission line which has a bandpass characteristic to reduce adjacent channel interference. The input impedance of triplexer with each channel filter is operated open-circuit at the resonance frequencies of other channels. Such property is due to the combination a series and parallel resonance circuits of CRLH-TL unit-cell. The measured triplexer results are showed a measured insertion loss of each channel, less than 1.5 dB, matching at each port, less than 15dB and isolation between channel, better than 25 dB. Also, to validate the triplexer, a small signal amplifier with triple-band is designed and tested. the measured amplifier results show good agreements with prediction.

• Korean Journal of Optics and Photonics
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• v.14 no.5
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• pp.555-564
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• 2003

WDM thin film filters for fiber optical communication were designed using Fabry-Prot type multiple cavity filters and an equivalent thin film technique. As the number of cavities in multiple cavity filters increases, it becomes difficult to design the filters due to a great number of variables (the number of cavities, period of reflectors, order of spacers). To solve the problem of design, we treated the fewest variables, regarding symmetrical thin films as equivalent layers, and we applied structural and numerical formulas based on an analysis method of multiple cavity filters. The equivalent thin film technique was able to provide systematic and quantitative design of the WDM thin film filters.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.85.1-85.1
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• 2017

We develop a coronagraph to measure the coronal electron density, temperature, and speed by observing the linearly polarized brightness of solar corona with 4 different wavelengths. Through the total solar eclipse on 21 August 2017, we test an operating software of a prototype coronagraph working with two sub-systems of two motorized filter wheels and a CCD camera that are controlled by a portable embedded computer. A Core Flight System (CFS) is a reusable software framework and set of reusable software applications which take advantage of a rich heritage of successful space mission of NASA. We use the CFS software framework to develop the operating software that can control the two sub-systems asynchronously in an observation scenario and communicate with a remote computer about commands, housekeeping data through Ethernet. The software works successfully and obtains about 160 images of 12 filter sets (4 bandpass filters and 3 polarization angles) during the total phase of the total solar eclipse. For the future, we can improve the software reliability by testing the software with a sufficient number of test cases using a testing framework COSMOS. The software will be integrated into the coronagraph for balloon-borne experiments in 2019.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.2
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• pp.134-139
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• 2004

A clock recovery circuit for a 40 Gb/s optical receiver has been designed and implemented. The clock recovery circuit consists of pre-amplifiers, a nonlinear circuit with diodes, a bandpass filter and a clock amplifier. Before implementing the 40 Gb/s clock recovery circuit, a 10 Gb/s clock recovery circuit has been successfully implemented and tested. With the 40 Gb/s clock recovery circuit, when a 40 Gb/s signal of -10 dBm was applied to the input of the circuit, the 40 GHz clock was recovered with the -20 dBm output power after passing through the nonlinear circuit. The output signal from the nonlinear circuit passes through a narrow-band filter, and then amplified. The implemented clock recovery circuit is planned to be used for the input of a phase locked loop to further stabilize the recovered clock signal and to reduce the clock jitter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.6
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• pp.590-598
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• 2004

An active capacitance circuit which employs series feedback network for the implement of negative resistance and low noise operation is analyzed in depth and its application to low noise active RF BPF's is discussed. Whereas many authors reported a lot of circuits that embody negative resistance circuit most of them have concerns for the equivalent resistance and reactance value at the center frequency. In this case, it could be possible to face a problem that the negative resistance circuit becomes unstable, or have poor flatness in passband because of insufficient forecast for the negative resistance values as the frequency goes higher or lower. In this paper, we extracted the exact equivalent values of this circuit and analyzed the RF characteristics with the varying the values of active devices and feedback circuits and presented the method that the flatness of passband can be improved. We have designed a 4-pole active BPF, which has the bandwidth of 60 ㎒, 0.67 ㏈ insertion loss, 0.3 ㏈ ripple, and noise figure of 3.0 ㏈ at 1.99 ㎓ band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.4
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• pp.323-331
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• 1997

In this paper, the high efficiency balanced amplifier is presented as high efficiency power amplifier. This amplifier is basically composed of two FETs, an input power divider, output power combiner, input matching circuits, output matching circuits, second harmonic interconnection circuit and lowpass filter. The second harmonic interconnection circuit is composed of second harmonic frequency bandpass filter and transmission line. This circuit is inserted between the output terminals of the two FEF's output matching circuit, there is a second harmonic standing wave generated between two FET outputs. The electric wall termination is equivalent to the short circuit termination. As a result, the FET output termination condition needed to attain high efficiency is realized. Experimental high efficiency balanced amplifier is constructed to determine its practically attainable efficiency. The input VSWR is 1.27, and the output VSWR is 1.18. Power added efficiency of 75% is attained at 1.75 GHz band about 3W to balanced amplifier.

• Geophysics and Geophysical Exploration
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• v.19 no.2
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• pp.84-90
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• 2016

The validation of performance test for newly developed or old-used sensor is very important in the earthquake monitoring and seismology using earthquake data. Especially the frequency response of the sensor is mainly used to correct the earthquake data. The technique of the calculation of phase and amplitude with Hilbert transformation for earthquake data that is filtered with band limited frequency in time domain is applied to calculate the frequency response of the sensor. This technique was tested for the acceleration sensors, CMG-5T of 1g and 2g installed on the vibration table at the laboratory and we could obtain satisfactory result. Tohoku large earthquake in 2011 observed at the station SNU that has accelerometer, ES-T and seismometer, STS-2 operated by KIGAM was also used to test the field data applicability. We could successfully get the low frequency response of broad band sensor, STS-2. The technique by using band limited frequency filter and Hilbert transformation showed the superior frequency response to the frequency spectrum ratio method for noisy part in data.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.3
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• pp.307-314
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• 2010

In this paper, a novel ultra-wideband microstrip-to-suspended stripline(SSL) transition is proposed, and SSL filters with low-loss and high selectivity have been realized using this transition. Since the proposed transition has low-loss and wide bandwidth characteristic, the design procedure of SSL filters become simplified. Additionally, the designed filters do not require extra time-consuming tuning. As design examples, SSL low-pass and high-pass filters have been implemented, and a implemented bandpass filter with connection of the low and high-pass filters performs 2.3~10.5 GHz bandwidth with less than 1.2 dB insertion loss and high selectivity.