• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.379-388
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• 2007

This paper presents a real-time respiration and heartbeat detector comprised of a 1.6 GHz single-channel Doppler sensor and analog/digital signal processing block for remote vital sign detection. The RF front end of the Doppler sensor consists of an oscillator, mixer, low noise amplifier, branch-line hybrid and patch antenna. We apply artificial transmission lines(ATLs) to the branch-line hybrid, which leads to a size reduction of 40 % in the hybrid, while its performance is very comparable to that of a conventional hybrid. The analog signal conditioning block is implemented using second order Sallen-Key active filters and the digital signal processing block is realized with a LabVIEW program on a computer. The respiration and heartbeat detection is demonstrated at a distance of 50 cm using the developed system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.224-227
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• 2016

This paper proposes a design of W-band mm-wave wideband monopulse comparator using waveguide structure for applications. The main idea of proposed design is to combine a self-compensating phase shifter on $90^{\circ}$ hybrid for wideband $180^{\circ}$ hybrid. Using multiple conventional phase shifters, because of their narrow-band characteristics, tends to restrict working bandwidth of system including antennas. Proposed comparator could relieve the problem since it applies the self-compensating phase shifter. The comparator has waveguide structure so it shows excellent characteristic in loss. It also show wideband characteristic in amplitude and phase response between ports.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11C
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• pp.889-895
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• 2010

MIMO system generally requires more than one antenna at the communication device. However, many wireless devices are limited by size, cost or hardware complexity to one antenna. To overcome such restrictions, we used a new technique, called cooperative communication. We propose a new cooperative transmission strategy system using cross-layer coding method base on H-ARQ for optimal communication. Proposed cooperative H-ARQ system that can improve the above problems and can get the better performance. In proposed cooperative system with H-ARQ method, if the received signal from source node is satisfied by the destination preferentially, the destination transmit ACK message to both relay node and source node, and then recovers the received signal. In addition, if ARQ message indicates NACK message, relay node operates selective retransmission. Based on the simulation results in aspect to BER performance and throughput, the proposed method which combined cooperative system with H-ARQ based on cross-layer coding can improve spectral efficiency reliability of system compared with that of general one by one system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.502-507
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• 2013

In this paper, a circular dual mode horn with modified aperture is proposed to improve a E/H-plane radiation pattern symmetry of a conventional oversized circular dual mode horn. The proposed antenna consists of a feeding section, a mode generation section and a phase matching section which has aperture shape transition from circle to ellipse or rectangle to improve a E/H-plane radiation pattern symmetry. To compare the performances between the proposed antenna and the convenional circular dual mode horn, the conventional circular dual mode horn and the proposed circular dual mode horn with rectangular aperture are fabricated and researched at 15 GHz. The measured results show that the conventional circular dual mode horn has 3.394 dB difference while the proposed antenna has only 0.539 dB difference between E and H-plane radiation patterns within the -11 dB beamwidth($53^{\circ}$) which is required beamwidth of the feed horn for the maximum aperture efficiency where f/d ratio of reflector antenna is 1.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.461-475
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• 2006

In this paper, it is described about the tri-band mobile antenna system design to provide broadband multimedia and direct broadcasting services using goo-stationary Koreasat 3, simultaneously operated in Ka/K/Ku band. The radiating part of the antenna system with a fan beam characteristic in the elevation plane is composed of the quasi-offset dual shaped reflector and the tri-band feeder. The tri-band feeder is also composed of the Ka/K dual band feeder with the protruding dielectric rod, the circular polarizer, the ortho-mode transducer and the circular-polarized Ku band feed array. Especially, the Ka/K dual band circular polarizer was realized firstly using the comb-type structure. For fast satellite-tracking on the movement, the Ku band feed array has the structure of the $2{\times}2$ active phased array which can make electrical beams. And, the circular-polarized characteristic in the feed array was improved by $90^{\circ}$ rotating arrangement of four radiating elements polarized circularly by a $90^{\circ}$ hybrid coupler, respectively. Four beam forming channels to make electrical beams at Ku band are divided into the main beam channel and the tracking beam channel in the output, and noise temperature characteristics of each channel were analyzed on the basis of the contributions of internal sub_units. From the fabricated antenna system, the output power at $P_{1dBc}$ of Ka_Tx channel was measured more than 34.1 dBm and the measured noise figures of K/Ku_Rx channels were less than 2.4 dB and 1.5 dB, respectively, over the operating band. The radiation patterns with co- and cross-polarization in the tri-band were measured using a near-field measurement in the anechoic chamber. Especially, Ku radiation patterns were measured after correcting each initial phase of active channels with partial radiation patterns obtained from the independent excitation of each channel. The antenna gains measured in Ka/K/Ku band of the antenna system were more than 39.6 dBi, 37.5 dBi, 29.6 dBi, respectively. And, the antenna system showed good system performances such as Ka_Tx EIRP more than 43.7 dBW and K/Ku_Rx G/T more than 13.2 dB/K and 7.12 dB/K, respectively.

• 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.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.5
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• pp.21-29
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• 2008

This paper proposes a carrier frequency of set estimation algorithm for IEEE802.11n system. As IEEE802.11n is a multiple input multiple output(MIMO) system, so there are several combining techniques which are used in multiple receive antenna system. In this paper, we propose hybrid carrier frequency offset estimation algorithms using combining techniques in multiple receive antenna systems, and show that the proposed selection combining carrier frequency offset (CFO) estimation algorithm can estimate carrier frequency offset within 1/10 MSE error at SNR 10 dB in channel B and within 1/2 MSE error at SNR 10 dB in channel D rather than the conventional MIMO CFO one.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.6
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• pp.694-701
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• 2016

According to revolutionary developments in automobile technologies, eco-friendly advanced vehicles (hybrid vehicle, hydrogen fuel-cell vehicle, electric vehicle, etc.) are rapidly increasing. The electromagnetic compatibility is getting more important for development of a vehicle because those advanced vehicles are driven by electric energy and equipped with more electric systems. In general, electromagnetic compatibility tests consist of an electromagnetic interference(EMI) test and an electromagnetic susceptibility(EMS) test. EMI test of the electric vehicles are needed not only in driving mode but also in charging mode because they must be recharged by much electric energy for driving. Depending on vehicle manufacturers, the charging device type and the location of charging device inlet in electric vehicles are various. In this paper, in order to investigate EMI of electric vehicles in charging mode in consideration of the direction of measuring antenna and the location of charging device inlet, a series of electromagnetic emission tests are conducted using three electric vehicles (neighborhood electric vehicle, electric vehicle and electric vehicle-bus). The test results show that electromagnetic emission measurements in charging mode are dependent on the direction of measuring antenna and the location of charging device inlet.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.3
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• pp.308-315
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• 2002

In this paper, the 5-bit digital phase shiftier with 10 InGaAs HEMTs is designed and fabricated for U.S. mobile DBS receiving active phased array antenna system in 12 GHz band. 11.25 $^{\circ}$, 22.5$^{\circ}$ and 45$^{\circ}$ phase bits are designed in leaded-line type. 90$^{\circ}$ and 180$^{\circ}$ phase bits are designed in reflection type combined with ring hybrid. The return loss more than 17.5 ㏈, insertion louts less than 7.8 ㏈, and maximum phase error of $\pm$6$^{\circ}$for 32 phase responses are measured in 12.2 GHz~ 12.7 GHz band.

• Journal of the Korean Institute of Telematics and Electronics
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• v.17 no.5
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• pp.48-55
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• 1980

For the purpose of composing an anti-ghost antenna system, 2 antennas, which have the identical radiation pattern, are fixed parallel to each other with a constant separation. In view of the fact that the phase differnce between the added power and the subtracted power of the two undesired signal which is recieved from all direction except from the real front one becomes radian, now It is Possible to make the amplitude of each Power become equal and the phase of the subtracted power become out of phase with that of the added power, by adjusting the amplitude of the subtracted power and shifting its phase by + or radian. Therefore the sum of the added power and the above modified subtracted power will be able to become zero. According to the above study, a hybrid circuit is designed and through operation of this circuit , the undesired wave can be seen to be reduced by 20 dB.