• Journal of Astronomy and Space Sciences
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• v.24 no.4
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• pp.397-408
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• 2007

Diplexer is one of core devices needed to communicate with satellite using single ground antenna by separating uplink and downlink signal. This paper presents the design of the S-band diplexer for LEO TT&C application, especially for KOMPSAT (KOrea Multi-Purpose SATellite). To cope with requirements such as high handling power, low insertion loss, air-cavity resonator with high quality factor was considered as one of design drivers. Design was started with predicting unloaded Q and equivalent circuit from the structure of air-cavity resonator. For the convenience of adjustment, the coupling factor placed between resonators was estimated from COTSEM (Electro-Magnetic) simulator, EESOF $ADS^{TM}$, and expressed with 2-order polynomial regression. To improve the isolation between transmitting part (Tx) and receiving part (Rx), the inductive and capacitive attenuation poles were inserted between $4^{th}\;and\;6^{th}$ resonator respectively. The fabricated diplexer consists of two bandpass filters and each filter has eight resonants. From the measurement, it was shown that major requirements such as 0.5dB of insertion loss, 20dB of return loss and 100dB of isolation were fully satisfied within passband.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.6
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• pp.83-88
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• 2017

In this paper, a 3-port waveguide circulator of Ka-band millimeter-wave for isolation between transmit channel and receive channel at high power transmit mode is designed and fabricated for the seeker of the guided missile and circulator performance is verified through the S-parameter, high power and operation temperature test. At the configuration design, interface design between a seeker antenna and the circulator is considered and half-height of standard waveguide is applied for minimum and light weight body. The shape of permanent magnet and ferrite is optimized by simulation and tuning dielectrics at each port are placed for the best performance. In Fc(center frequency)${\pm}1000MHz$, designed waveguide circulator has below -20 dB return loss, below 0.5 dB insertion loss and below -23 dB isolation. It is found that circulator characteristics is similar to design results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.426-435
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• 2013

In this paper, we propose the MIMO circular polarization feed network to enhance the communication performances from the previous $2{\times}2$ MIMO channel to $4{\times}4$ channel for Land Mobile Satellite communication system. The only possibility to extend the communication channel is to use the additional satellite because of the limitation of satellite spaces to install additional antennas. For overcoming this problems, we propose the MIMO circular polarization feed network to secure the isolation characteristics without the distant antenna space. The port isolation characteristics and each port impedance matching conditions are numerically verified and we suggest the $4{\times}4$ MIMO channel model of the proposed system and the performances are verified. The fabricated circular polarization patch antennas with the proposed feed network are measured in the reverberation chamber and 7~10 dB of diversity gain and 80 % increasement of channel capacity are obtained.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.295-302
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• 2011

In this paper we consider technological requirements to broadcast digital television signals using single frequency networks(SFN) in the Advanced Television Systems Committee(ATSC) transmission systems and propose Interference Cancellation Digital On Channel Regenerative Repeater(IC-DOCR) thar overcomes the limitation of EDOCR(Equalization Digital On Channel Repeater) proposed by ETRI. The proposed IC-DOCR maintains the benefits of EDOCR that have good output signal quality removing multi-path, additive white Gaussian noise(AWGN). In additional, since the Interference Cancellation algorithm using the 8-VSB symbol demodulation of received signal removes the Interference of feedback signal, IC-DOCR improve the weakness of EDOCR that have low isolation between receive and transmit antenna so that can overcome the limitation of output signal power. we did analysis and verification of the proposed system performance using computational simulation.

• Journal of Broadcast Engineering
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• v.9 no.4 s.25
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• pp.371-383
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• 2004

In this paper we consider technological requirements to broadcast digital television signals using single frequency networks (SFN) in the Advanced Television Systems Committee (ATSC) transmission systems and propose equalization digital on-channel repeater (EDOCR) that overcomes the limitations of conventional digital on-channel repeaters (DOCRs). Since there are no forward error correction (FEC) decoder and encoder, the EDOCR does not have an ambiguity problem. In addition, since an adaptive equalizer in the EDOCR removes multi-path signals, additive white Gaussian noise (A WGN), and feedback signal due to low antenna isolation, the EDOCR may have good output signal quality with high power.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.12
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• pp.949-954
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• 2012

The K-PCS and W-CDMA dual band dielectric duplexer and bandpass filters have been designed and fabricated. The dual band duplexer consists of the separate monoblock K-PCS and W-CDMA duplexers using common antenna port. The coupling capacitance and I/O impedance matching have been designed to minimize the cross interference between the bands. Isolations of crosspoint between Tx and Rx in K-PCS and W-CDMA dualband were about 47 dB and 100 dB, respectively. On the other hand, isolations of Tx and Rx in K-PCS and W-CDMA were about 66 dB and 65 dB, respectively. The difference between 47 dB and 100 dB originated from the different center frequencies in Tx and Rx of K-PCS and W-CDMA bands. The coupling capacitance of the bandwidth, I/O capacitance of I/O matching and impedance matching, and various capacitances were important role to fabricate the dielectric duplexer and bandpass filters.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.6
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• pp.574-581
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• 2002

Microstrip $8{ imes}2$ sub-array antennas for a extension to active phased array antennas are designed, fabricated and measured for TX/RX dual operation in satellite communication and a reception of satellite broadcasting. For the frequency range from 11.7 to 12.75 GHz for RX and from 14 to 14.5 GHz for TX, two orthogonal linear polarizations of ${pm}45^{\circ}$ are used to transmit and receive simultaneously with one radiator. They adopt dual resonance between two patches for wideband characteristics in RX band and show isolation characteristics over 20 dB. An electrical beam tilt of $30^{\circ}$ is achieved and a tapered power distribution, narrow element spacing are used for the purpose of low side-lobe characteristics.

• Journal of Korea Water Resources Association
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• v.48 no.8
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• pp.613-623
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• 2015

To overcome the difficulties of discharge measurements during flood season, MWSCM(micowave water surface current meter) which measures river surface velocities without contacting water has been applied in field work since its development. The existing version of MWSCM is for floods so that its applicability is low due to the short periods of floods. Therefore the renovative redesign of MWSCM to increase the applicability was conducted so that it can be applied to the discharge measurements during normal flows as well as flood ones by extending the measurable range of velocity. A newly developed high-performance MWSCM for general use can measure the velocity range of 0.03-20.0 m/s from flood flows to normal flows, whereas MWSCM for floods can measure the velocity range of 0.5-10.0 m/s. The improvement of antenna isolation between transmitter and receiver to block the inflow of transmitted singals to receiver and the improvement of phase noise of oscillator are necessary for detecting low velocity with MWSCM technology. Separate type antenna of transmitting and receiving signals is developed for isolation enhancement and phase locked loop synthesizer as an oscillator is applied to high-performance MWSCM for general use. Microwave frequency of 24 GHz is applied to the new MWSCM rather than 10 GHz to make the new MWSCM small and light for convenient use of it at fields. Improvement requests on MWSCM for floods-stable velocity measurement, self test, low power consumtion, and waterproof and dampproof-from the users of it has been reflected on the development of the new version of MWSCM.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.7
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• pp.711-719
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• 2011

A study of miniaturization of an L-band orthomode transducer(OMT) for field experiments of radar backscatter is presented in this paper. The proposed OMT is not required the additional waveguide taper structures to connect with a standard adaptor by the newly designed junction structure which bases on a waveguide taper. Total length of the OMT for L-band is about 1.2 ${\lambda}_o$(310 mm) and it's a size of 60 % of the existing OMTs. And, to increase the matching and isolation performances of each polarization, two conducting posts are inserted. The bandwidth of 420 MHz and the isolation level of about 40 dB are measured in the operating frequency. The L-band scatterometer consisting of the manufactured OMT, a horn-antenna and network analyzer(Agilent 8753E) was used STCT and 2DTST to analysis the measurement accuracy of radar backscatter. The full-polarimetric RCSs of test-target, 55 cm trihedral corner reflector, measured by the calibrated scatterometer have errors of -0.2 dB and 0.25 dB for vv-/hh-polarization, respectively. The effective isolation level is about 35.8 dB in the operating frequency. Then, the horn-antenna used to measure has the length of 300 mm, the aperture size of $450{\times}450\;mm^2$, and HPBWs of $29.5^{\circ}$ and $36.5^{\circ}$ on the principle E-/H-planes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1181-1189
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• 2013

In this paper, a retrodirective anatenna array system is proposed and the possibility of actively cancelling electromagnetic waves based on this system is investigated. When a rectrodirective array system receives an electromagnetic wave, it can send waves in the direction of the incoming signal without prior knowledge of the direction. In applications to cancellation of radar signals, the system can generate and send signals to the radar so that it cancels the radar signals that are reflected back to the radar. In such a system, isolation between the input and output ports is a key factor that determines the effectiveness of cancellation. In this work, a dual-conversion mixer system is proposed to maximize the isolation. Since this minimizes the difference between the direction of reflection of radar signals and the transmission of cancellation signals, the effectiveness of cancellation is maximized. Experimental results for a metallic plate and metallic cylinder shows as much as 29-dB reduction in reflection for a $2{\times}2$ retrodirective array based on proposed dual-conversion mixer system, which verifies the proposed method of active cancellation.