• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.12
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• pp.1243-1251
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• 2009

This paper presents design and test results of X-Band Transmit/Receive(T/R) module for active phased-array radar. Active phased array radars typically require solid state T/R modules with high output power, low noise figure, high Third Order Intercept(TOI), and sufficient gain in both transmit and receive. The output power of the module is 9 watts over a wide bandwidth. The noise figure is as low as 2.8 dB. Phase and amplitude are controlled by the 6-bit phase shifter and 5-bit attenuator, respectively. Highly integrated T/R module is achieved by using LTCC(Low Temperature Co-fired Ceramic) multiple layer substrate. The module incorporates a compact digital interface, requires only three supply voltages.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.2
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• pp.75-82
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• 2000

In this Paper, a new type of feedforward linearizer using a delay line which controls the phase characteristics of the correction amplifier block is proposed. The extra delay line provides the control-ability of IM signals so that the IM rejection is accomplished without the conventional pilot tone. The error signal loop consists of several key components such as phase shifter and attenuator, subtractor. These key components are replaced by new designs in order to obtain better linearization characteristics without the pilot tone generator which is indispensable in the conventional linearizer designs. The proposed linearizer was designed at Korean PCS band and combined with 35W HPA manufactured by KMW inc., and tested with two-tone signals separated 0.6MHz apart at the center frequency of 1855MHz. The experimental results show C/l improvement by 16.9 ~ 24.6 dB over 15 dB dynamic range(30 ~45 dBm) which gave IMD of 58.5~63.2 dBc for the designed LPA.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.5
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• pp.521-524
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• 2015

This letter presents a selective wireless power transfer architecture using a reconfigurable multi-port amplifier. The proposed wireless power transfer architecture is composed of a phase shifter part controlled by FPGA, two class-E power amplifiers, a four-port power combiner and two coil loads. Depending on the phase control of FPGA, the power ratio of outputs at the two coil loads becomes 1:1, 2:0 and 0:2. The manufactured system has delivered 1W DC power to loads at 125 kHz. The total DC-to-DC conversion efficiency shows more than 40 % including PA efficiency of 79 %.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.8 s.111
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• pp.767-772
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• 2006

The receiver of this paper is Dual-band monopulse type for prototype of tracking radar. Localization of radar technology is an issue of SamsungThales and go into development. Dual-band radar in comparison with Single-band radar requires higher cost and power consumption but there are many advantages of dealing with jamming, detection range, image signal rejection, cloud-rain influence, clutter, resolution. The receiver is comprised of X-band RF head module, Ka-band RF head module and common IF module. Each signal of X-band and Ka-band is selected by the switch in If module. Phase shifter in IF module of local stage controls the phase of sum, azimuth, elevation channel. In the test result, gain is $40{\pm}3 dB$, isolation of transmitter/receiver is 39 dBc, dynamic range is 110 dB and noise figure of each channel is 4.5dB and 6.9dB.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.6
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• pp.43-55
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• 2013

In this paper, we propose a cylindrical active phased array antenna of Beam Steering Characteristics in the horizontal plane(H-plane) and vertical plane(E-Plane) on the cylinder form array structure. We design the bent dipole antenna of the cylindrical array structure adapted excellent mutual-coupling characteristics, designed and manufactured the cylindrical array antennas and power combiner/divider unit for power dividing and combining on the antenna. The radiating elements array spacing of Cylindrical array antenna were determined to avoid grating lobes at half power beam steering. Beam steering of the antenna was implemented with 6-bit phase shifter in the transceiver and have been designed based on the characteristics the antenna beam steering at -24 degrees to 24 degrees horizontal, vertical 0 degrees to 36 degrees beam steering. A cylindrical active phased array antenna that produced for verification the performance of the antenna are measured radiation characteristics in accordance with beam steering at L-Band.

• Korean Journal of Optics and Photonics
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• v.15 no.6
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• pp.591-596
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• 2004

In this paper, a photonic RF true-time delay based on a partially side-polished fiber Bragg grating with heating electrode has been proposed and fabricated. It features continuous voltage-controlled operation, requiring no mechanical perturbation and no moving parts. For an RF signal carried over an optical signal, the time delay has been obtained by controlling the voltage applied to the electrode and thus adjusting its reflection positions from the fiber grating via the thermooptic effect. The achieved time delay is about 100 ps with the electrical power consumption of 280 mW.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.301-306
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• 2014

We proposed a new PCB-type 'common-mode current($I_c$) and differential-mode current($I_d$) detector' working for fast detection of $I_c$ and $I_d$ from the differential-mode signaling, with miniaturization effect and possibility of cheaper fabrication. In order to realize this device, we suggest a branch-line-coupler balun having a composite right- and left-handed(CRLH) one-layer microstrip phase-shifting line as compact as roughly ${\lambda}_g/14$. The presented balun obviously is different from the conventional bent-&-folded delay lines or slits on the ground for coupling the lines on the top and bottom dielectrics. As we connect the suggested balun output ports of the differential-mode signal lines via the through-port named U and coupled-port named L, $I_c$ and $I_d$ will appear at port ${\Delta}$ and port ${\Sigma}$ of the present device, in order. The validity of the design scheme is verified by the circuit-and numerical electromagnetic analyses, and the dispersion curve proving the metamaterial characteristics of the geometry. Besides, the examples of the $I_c$ and $I_d$ indicator are observed as the even and odd modes in differential-mode signal feeding. Also, the proposed device is shown to be very compact, compared with the conventional structure.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.4
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• pp.489-499
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• 2011

RFID technologies, which allow collecting, storing, processing, and tracking information by wirelessly recognizing the inherent ID of object through an attached electronic tag, have a variety of application areas. This paper presents a novel carrier leakage suppression RF(CLS-RF) front-end for ultra-high-frequency RF identification reader. The proposed reader CLS-RF front-end structure generates the carrier leakage replica through the nonlinear path that contains limiter. The limiting function only preserves the frequency and phase information of the leakage signal and rejects the amplitude modulated tag signal in the envelope. The carrier leakage replica is then injected into the linear path that contains phase shifter. Therefore, the carrier leakage signal is effectively cancelled out, while not affecting the gain of the desired tag backscattering signal. We experimentally confirm that the prototype shows a significant improvement in the leakage to signal ratio by up to 36 dB in 910 MHz, which is consistent with our simulation results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.1
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• pp.25-30
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• 2017

Millimeter wave (mmWave) bands are expected to improve date rate of 5G systems due to the wide available bandwidth. While severe path loss in those bands has impeded the utilization, short wavelength enables a large number of antennas packed in a compact form, which can mitigate the path loss. However, estimating the channel with a conventional scheme requires a huge training overhead, hence an efficient estimation scheme operating with a small overhead needs to be developed. The sparsity of mmWave channels caused by the limited scatterers can be exploited to reduce the overhead by utilizing compressed sensing. In this paper, we introduce compressed sensing techniques for mmWave channel estimation. First, we formulate wideband channel estimation into a sparse recovery problem. We also analyze the characteristics of random measurement matrix constructed using quantized phase shifters in terms of mutual incoherence.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.9
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• pp.818-823
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• 2016

Millimeter wave (mm-wave) communication systems provide high data rates owing to the large bandwidths available at mm-wave frequencies. Recently, analogue and digital combined beamforming, namely "hybrid beamforming" has drawn attentions owing to its ability to realize the required link margins in mm-wave systems. Taking into account the radio frequency (RF) hardware limitations, such as the analogue phase shifter gain constraint and the low resolution of the phase controller, we introduce an uplink hybrid beamforming system that includes discrete Fourier transform (DFT) based "fixed" analogue beamforming. We adopt a zero-forcing (ZF) multiple-input multiple-output (MIMO) equalizer to eliminate the uplink inter-user interferences. Moreover, to improve the sum-rate performances, we propose a transmit beam selection algorithm which makes the uplink effective channels, i.e., the beamformed channels, become near orthogonal. The effectiveness of the proposed beam selection algorithm was verified through numerical simulations.