• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.85-91
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• 2015

We investigated the structure of inductive coupler and its magnetic coupling to increase the transmission coefficient for power line communication. A Rogowski coil, which is an air-cored inductive coupler, and a magnetic cored coupler were fabricated to analyze the transmission coefficient for different coupler parameters. This paper proposes the impedance matching method using lumped elements and an impedance transformer to increase the transmission coefficient. In the experiment, the transmission coefficient of the proposed system was increased in both narrowband and broadband cases, and a trade-off between the transmission coefficient and the bandwidth was shown. This method will be useful for the further study of impedance matching with the load variation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.129-132
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• 2008

The generally six-port phase correlator is comprised of a wilkinson power divider and three $90^{\circ}$ hybrid coupler, got bandwidth performance of less than 10%. in this paper, the six-port phase correlator using two section power divider has 33% bandwidth and external matching hybrid coupler has 15% bandwidth was designed with the center frequency of 2.5GHz. Analysis of the simulation result indicates that RF port and LO port got frequency bandwidth of 13%. Insert loss performance of fabricated six-port phase correlator is incremented, but bandwidth resembles simulation result. And phase tolerance within bandwidth is less than $90^{\circ}$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.1
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• pp.23-28
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• 2009

The general six-port phase correlator is comprised of a Wilkinson power divider and three $90^{\circ}$ hybrid coupler, which has less than 10 % bandwidth. In this paper, the six-port phase correlator using two section power divider has 33 % bandwidth and external matching $90^{\circ}$ hybrid coupler with 15 % bandwidth was designed at the center frequency of 2.5 GHz. The simulation result by ADS2003A indicates that RF port and LO port of proposed six-port phase correlator got wide frequency bandwidth of 14 % for VSWR of 1.5. The fabricated six-port phase correlator has a bandwidth of 12 % similar to the simulation result. The maximum phase discrepancy and insertion loss are $6^{\circ}$ and 2.5 dB over a bandwidth, respectively.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.6
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• pp.34-40
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• 2011

From the present paper researched about the Design of Image Rejection SSB Modulator for X-Band Monopulse RADAR using Waveguide Hybrid Coupler. Generally, SSB modulator mixes IF(RF) and LO signals, and then it converts to RF(IF) frequency band. In this case, in order to transmit one sideband from RF band, SSB modulator is demanded the removal of image and LO signal. The balanced mixer was designed using waveguide hybrid coupler and crystal mixer diode to mix LO and IF signal. And also the IF Amplifier was designed for IF(+) and IF(-) signal generation which have $90^{\circ}$ phase differences which are suitable in two crystal mixer diode inputs. In order to maintain a high electric reliability from high frequency band the waveguide and IF amplifier's case were manufactured with aluminum using deep brazing techniques. The test result of SSB modulator, LO and sideband signal rejection ratio were 14.2dB and 18.5dB respectively.

• Journal of Advanced Navigation Technology
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• v.17 no.6
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• pp.658-663
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• 2013

In this paper, a microstrip line implementation using via transition and its application of multilayer compact ring hybrid coupler are presented. This transition is the sandwich structure with via hole to connect two microstrip lines in different layer. For designing a compact RF/Microwave passive circuit, the microstrip line using via-hole transition is proposed to reduce a size of microwave circuit with long transmission line. For the validation of the microstrip line with via-hole transition, the multilayer ring hybrid coupler is implemented at center frequency of 2 GHz. The measured performances are in good agreement with simulation results and about 50% size reduction compare to conventional ring hybrid coupler.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.5 no.2 s.10
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• pp.55-60
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• 2006

In this paper, a broadband double balanced mixer is presented using a wideband Marchand balun implementation by vertical coupler. Frequency is selected as $1.0{\sim}3.7GHz$ for RF, $1.14{\sim}3.84GHz$ for LO, and 140 MHz for IF signals. When LO signal with 7 dBm at 2.64 GHz is injected, a conversion loss of 7.5 dB and RF to LO isolation of -45 dB are obtained. Also, an average conversion loss of 9 dB and RF to LO isolation of -25 dB are obtained for frequency band of $1.0{\sim}3.7GHz$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.8
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• pp.632-639
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• 2018

This paper presents a single antenna radar sensor with a Ku-band radar transceiver IC realized by 130 nm CMOS processes. In this radar receiver, sensitivity time control using a DC offset cancellation feedback loop is employed to achieve a constant SNR, irrespective of distance. In addition, the receiver RF block has gain control to adjust high dynamic range. The RF output power is 9 dBm and the full chain gain of the Rx is 82 dB. To reduce the direct-coupled Tx signal to the Rx in a single antenna radar, a stub-tuned hybrid coupler is adopted instead of a bulky circulator. The maximum measured distance between the horn antenna and a metal plate target is 6 m.

• 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.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2642-2648
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• 2010

The design of coupling and rectifying circuits for the maritime VHF digital modem is investigated in this paper. To monitor the transmitting power of the modem, a directional coupler which is used to extract a small fraction of the transmitter signal power, and a rectifying circuit which make DC voltage proportional to the coupled rf power are designed and fabricated. The parallel-coupled line coupler with directivity of above 25 dB at 160 MHz bands is designed and it is shown that the output voltage of the rectifying circuit is linearly changing from 0.85 V to 1.6 V when the transmitting power of the modem is varying from 1 W to 25 W. The proposed coupler and rectifying circuits are expected to be suitable for maritime VHF digital modem.

• Journal of electromagnetic engineering and science
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• v.16 no.4
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• pp.199-205
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• 2016

We present a novel schematic using a 3-dB coupler to transmit radiofrequency (RF) power to two receivers selectively. Whereas previous multiple receiver supporting schemes used hardware-switched methods, our scheme uses a soft power-allocating method, which has the advantage of variable power allocation in real time to each receiver. Using our scheme, we can split the charging area and focus the RF power on the targeted areas. We present our soft power-allocating method in three main points. First, we propose a new power distribution hardware structure using a FPGA (field-programmable gate array) and a 3-dB coupler. It can reconfigure the transmitting power to two receivers selectively using accurate FPGA-controlled signals with the aid of software. Second, we propose a power control method in our platform. We can variably control the total power of transmitter using the DC bias of the drain input of the amplifier. Third, we provide the possibility of expansion in multiple systems by extending these two wireless power transfer systems. We believe that this method is a new approach to controlling power amplifier output softly to support multiple receivers.