• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.2014-2016
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• 2004

In order to obtain a low-loss ferroelectric phase shifter, the reflection-type phase shifter with ferroelectric defected ground structure (DGS) resonators has been designed in this paper. The proposed phase shifter is consist of a 3-dB $90^{\circ}$ branch-line hybrid coupler and terminated reflective circuit with tunable ferroelectric DGS resonator. The ferroelectric DGS unit structure can provide high Q resonator characteristic at high frequencies. The design parameters of equivalent circuit for the tunable DGS resonator are derived by using simple circuit analysis method and three-dimensional full wave finite element method. The fabricated phase shifter has an insertion loss of better than 3.4dB at 13.5GHz.

• Journal of electromagnetic engineering and science
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• v.12 no.4
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• pp.234-239
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• 2012

This paper presents a compact K-band Doppler radar sensor for human vital signal detection that uses a radar configuration with only single coupler. The proposed radar front-end configuration can reduce the chip size and the additional RF power loss. The radar front-end IC is composed of a Lange coupler, VCO, and single balanced mixer. The oscillation frequency of the VCO is from 27.3 to 27.8 GHz. The phase noise of the VCO is -91.2 dBc/Hz at a 1 MHz offset frequency, and the output power is -4.8 dBm. The conversion gain of the mixer is about 11 dB. The chip size is $0.89{\times}1.47mm^2$. The compact Ka-band Doppler radar system was developed in order to demonstrate remote human vital signal detection. The radar system consists of a Ka-band Doppler radar module with a $2{\times}2$ patch array antenna, baseband signal conditioning block, DAQ system, and signal processing program. The front-end module size is $2.5{\times}2.5cm^2$. The proposed radar sensor can properly capture a human heartbeat and respiration rate at the distance of 50 cm.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.1
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• pp.1-8
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• 2011

In this paper, dual-feed circularly polarized microstrip patch antenna for GPS L1, GPS L2, GLONASS L1 signal was fabricated by using stacked patch. It was fed by dual coaxial probe on the patch at 50ohm impedance, and was simulated to resonate at GPS L1, GPS L2, GLONASS L1. To realize characteristics of right hand circular polarization using dual-feed stacked patch antenna and hybrid coupler for $90^{\circ}$ phase difference. Output of hybrid coupler was contacted input of Low Noise Amplifier(LNA). The LNA using dual band pass filter was designed and fabricated. The measured results of the implemented antenna is VSWR < 1.5 : 1 and the gain of 32dB(Zenith) over at GPS L1, L2, GLONASS L1.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1321-1328
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• 2003

In this paper, we demonstrate that the directivity of the CPW(Coplanar Waveguide) directional coupler with finite-extent backed conductor is enhanced by eliminating center region of backed conductor appropriately. If the backed conductor is removed at center region of couplers, the couplers have two backed conductors. If effective odd mode dielectric constant is decreased at center region, the electrical length for odd mode is changed and phase velocity is same at the directional couplers. Hence, directivity is improved. The eliminated length is solved by an odd and even mode analysis. The designed moderate CPW directional coupler with the proposed compensation structure has excellent directivity and matching characteristic at center frequency in simulation and measurement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.7
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• pp.643-649
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• 2013

In this paper, human heartbeat detection using signal reflected from the antenna which is varied reflection coefficient by near field variation of the antenna. For detection reflected signal from antenna, 20 dB directional coupler is used because of not affecting transmitting signal. Variance of reflection coefficient of dipole antenna is about 0.07 dB which is too small the distinction between heartbeat and noise. Sensitivity increasing method is applied and heartbeat is clearly detected. Due to phase and magnitude errors come from discrete value components, antenna is located some points in experiments ro find optimum sensitivity position. And providing verification of using communication signal, heartbeat detection when frequency modulated signal which have 4 MHz bandwidth is applied.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2A
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• pp.139-146
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• 2009

This paper presents an average internal loop-back antenna calibration method for array antenna in TDD(Time Division Duplex) systems. The proposed method calibrates the amplitude and the phase of RF systems using into mal coupler and switches without aids of external calibration systems. The average calibration scheme of the proposed method also increases reliability of calibration performance. Computer simulation demonstrates that the proposed method corrects beamforming angles of DOA estimation algorithm and BER performance in transmit power allocation scheme.

• Korean Journal of Optics and Photonics
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• v.2 no.3
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• pp.139-148
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• 1991

A fiber-optic magnetic sensor system for the detection of small ac magnetic field(200Hz-2 kHz) was constructed. Magnetic field sensing part was fabricated by bonding a section of optical fiber to amorphous metallic glass(2605SC) having large magnetostriction effect. And with the directional coupler, all fiber type Mach-Zehnder interferometer was constructed to measure the variation of the external magnetic field by translating it into the optical phase shift in the interferometer. The signal fading problem of the interferometer, which is due to random phase drifts originated from the environment, i.e., temperature fluctuation, vibrations, etc., was elliminated by feedback phase compensation. This allows the sensitivity to be maintained at the maximum by keeping the interferometer in quadrature phase condition. The frequency response of metallic glass was found to be nearly flat in the range of 90 Hz-2 kHz and dc bias field for the maximum ac response was 3.5 Oe. The interferometer output showed good linearity over the range $\pm$0.5 Oe. For 1 kHz ac magnetic field the scale factor S and the minimum detectable magnetic field were measured to be 8.0 rad/Oe and $3X10^{-6} Oe/\sqrt{Hz}$at 1 Hz detection bandwidth respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.862-865
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• 2007

Rx and Tx signal use same band in RFID. Then RFID system is not used duplexer and used coupler. RFID system have problem about Rx part to Tx leakage signal because that Rx signal port is Tx signal port's Isolation port. We proposal using phase shifter Tx leakage signal decrease than other RFID system. It is same signal Tx signal port's coupling port and isolation port signal except amplitude and phase. So if make coupling signal and isolation signal is in all same signal. We cancel Tx leakage signal used coupling port. And verification about ADS2006.

• ETRI Journal
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• v.34 no.6
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• pp.946-949
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• 2012

We present the optimization of a birefringence-enhanced-waveguide (BWG)-based polarization beam splitter (PBS) in a Mach-Zehnder interferometer (MZI) configuration and analyze the structure-dependent or polarization-dependent phase difference, using a delay-line MZI (DL-MZI). We fabricate the DL-MZI using silica-based planar lightwave circuit technology and, using the DL-MZI, demonstrate the ability to optimize a PBS by measuring the birefringence of the BWG and structure-dependent phase offset.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.3
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• pp.158-164
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• 2002

2-6 GHz digital phase shifter module has been designed and fabricated. For the broadband operation and performance, MMIC phase shifter chip for phase shifter module was designed and fabricated by using the reflection-type circuits with Lange coupler. The fabricated phase shifter module shows 6.1$^{\circ}$RMS phase error, 13.5 dB maximum insertion loss, and 8 dB and 10 dB input and output return losses, respectively. Computer controlled measurement systems are realized in order to get the measured data of 32 phase states. The RMS insertion phase error and the average insertion loss deviation among 8${\times}$8 modules for the phased-array system are less than ${\pm}$0.5$^{\circ}$and ${\pm}$0.5 dB, respectively. The size of fabricated phase shifter module is 45 ${\times}$ 22.5 ${\times}$60㎣.