• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.290-298
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• 2018

Herein, an S-band internally-matched power amplifier that shows a power capability of 300 W in a Long Term Evolution(LTE) band 7 is designed and fabricated using a CGHV40320D GaN HEMT from Wolfspeed. Based on the nonlinear model, the optimum source and load impedance are extracted from the source-pull and load-pull simulations at the fundamental and harmonic frequencies, and the harmonic impedance tuning circuits are implemented inside a ceramic package. The internally matched power amplifier, which is fabricated using a thin-film substrate with a high relative permittivity of 40 and an RF35TC PCB substrate, is measured at the pulsed condition with a pulse period of 1 ms and a duty cycle of 10%. The measured results show a maximum output power of 257~323 W, a drain efficiency of 64~71%, and a power gain of 11.5~14.0 dB at 2.62~2.69 GHz. The LTE-based measurement shows a drain efficiency of 42~49% and an ACLR of less than -30 dBc(excluding 2.62 GHz) at an average power of 79 W.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.77-82
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• 2019

In this paper, a 0.6~6GHz quad-ridge horn antenna which can be used for the antenna measurement of 5.8GHz WiFi system from lowest frequency band of mobile LTE (Long Term Evolution) is designed and implemented. The quad-ridge horn antenna has quadruple ridges of exponential function, a back-short and a cavity. Based on this structure, we design the cavity size, ridge gap and feed gap to have broadband characteristics. For implementation, the plates material of aluminum and copper are used for the horn and four ridges, respectively. And the insulator supports are used to maintain the gap between ridges. By measurement, antenna has the gain of 6.2~13.35dBi with the return loss of less than -6dB (under VSWR 3 : 1) in the entire design band. The results of this study can be widely used to the antenna studies on the mobile communication including low frequency band of LTE, the EMI measurement and the standard calibration measurement.

• Journal of electromagnetic engineering and science
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• v.14 no.2
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• pp.61-67
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• 2014

This paper presents a zero-IF CMOS RF receiver, which supports three channel bandwidths of 5/10/40MHz for LTE-Advanced systems. The receiver operates at IMT-band of 2,500 to 2,690MHz. The simulated noise figure of the overall receiver is 1.6 dB at 7MHz (7.5 dB at 7.5 kHz). The receiver is composed of two parts: an RF front-end and a baseband circuit. In the RF front-end, a RF input signal is amplified by a low noise amplifier and $G_m$ with configurable gain steps (41/35/29/23 dB) with optimized noise and linearity performances for a wide dynamic range. The proposed baseband circuit provides a -1 dB cutoff frequency of up to 40MHz using a proposed wideband OP-amp, which has a phase margin of $77^{\circ}$ and an unit-gain bandwidth of 2.04 GHz. The proposed zero-IF CMOS RF receiver has been implemented in $0.13-{\mu}m$ CMOS technology and consumes 116 (for high gain mode)/106 (for low gain mode) mA from a 1.2 V supply voltage. The measurement of a fabricated chip for a 10-MHz 3G LTE input signal with 16-QAM shows more than 8.3 dB of minimum signal-to-noise ratio, while receiving the input channel power from -88 to -12 dBm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.9
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• pp.783-789
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• 2015

This paper presents a Doherty power amplifier(DPA) operating in the 2.6 GHz band for long term evolution(LTE) systems. In order to achieve high efficiency, second and third harmonic impedances are controlled using a compact output matching network. The DPA was implemented using a gallium nitride high electron mobility transistor(GaN-HEMT) that has many advantages, such as high power density and high efficiency. The implemented DPA was measured using an LTE downlink signal with a 10 MHz bandwidth and 6.5 dB PAPR. The implemented DPA exhibited a gain of 13.1 dB, a power-added efficiency(PAE) of 57.6 %, and an ACLR of -25.7 dBc at an average output power of 33.4 dBm.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.10
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• pp.929-934
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• 2016

In this paper, we studied the design and fabrication of array antenna at around 1.8 GHz band. To improve of frequency properties of antenna, single feed microstrip patch antenna was simulated by HFSS(High Frequency Structure Simulator). A $1{\times}2$ array antenna of 1.8 GHz for LTE band was designed and fabricated by photolithography on an FR4 substrate (dielectric constant of 4.4 and thickness of 0.8 mm). The fabricated antenna was analyzed by network analyzer. The measured results agree well with the simulations, which confirmed the validity of this study. The fabricated $1{\times}2$ array antenna showed a center frequency, the minimum return loss and impedance were 1.82GHz, -30.5dB, and $49.6{\Omega}$ respectively.

• Journal of Integrative Natural Science
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• v.14 no.2
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• pp.50-56
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• 2021

Due to the recent increase in the mobile streaming market, mobile traffic is increasing exponentially. IMT-2020, named as the next generation mobile communication standard by ITU, is called the 5th generation mobile communication (5G), and is a technology that satisfies the data traffic capacity, low latency, high energy efficiency, and economic efficiency compared to the existing LTE (Long Term Evolution) system. 5G implements this technology by utilizing a high frequency band, but there is a problem of path loss due to the use of a high frequency band, which is greatly affected by system performance. In this paper, small cell technology was presented as a solution to the high frequency utilization of 5G mobile communication system, and furthermore, the system performance was improved by applying machine learning technology to macro communication and small cell communication method decision. It was found that the system performance was improved due to the technical application and the application of machine learning techniques.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.2
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• pp.127-134
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• 2015

In this paper, we propose 2.6 GHz single band dual polarization MIMO omni antenna for in-building applications. The proposed antenna operates at 2.6 GHz single LTE band, Up-link 2.52~2.54 GHz and Down-link 2.64~2.66 GHz. Horizontal and vertical polarizations of the antenna has been, respectively, constructed by the synthesis of four folded loop antennas and the folded monopole antenna. The height of the MIMO omni-directional antenna is minimized to be less than ${\lambda}/13.5$ from the ground. The measurement results show excellent MIMO omni antenna performance of 2.85 dBi vertical polarization gain, 2.29 dBi horizontal polarization gain, and 19.25 dB port isolation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.270-276
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• 2018

Fifth-generation communications are approaching, and they will require broadband antennas that include the existing LTE frequency band (1.7 GHz to 2.7 GHz) and the newly allocated frequency band (3.4 GHz to 3.7 GHz). Many kinds of antennas satisfy the required broadband characteristics, including the dual-element folded dipole antenna proposed in this paper. A zigzag line was used to make the antenna more compact. This was accomplished by reducing the physical length while maintaining the electrical length. To validate the proposed antenna, a prototype was fabricated using PCB (${\epsilon}_r$:4.4, Height: 1.6 mm) and its performance was evaluated. Results obtained by simulation and experiment showed good agreement.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.6
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• pp.825-831
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• 2016

In this paper, a transimpedance amplifier based on a new DC offset cancellation (DCOC) method is proposed for WCDMA/LTE applications. The proposed method applies a sample and hold mechanism to the conventional DCOC method with a DC feedback loop. It prevents the removal of information around the DC, so it avoids signal-to-noise ratio degradation. It also reduces area and power consumption. It was designed in a $0.13{\mu}m$ deep n-well CMOS technology and drew a maximum current of 1.58 mA from a 1.2 V supply voltage. It showed a transimpedance gain of $80dB{\Omega}$, an input-referred noise current lower than 0.9 pA/${\surd}$Hz, an out-of-band input-referred 3rd-order intercept point more than 9.5 dBm, and an output DC offset lower than 10 mV. Its area is $0.46mm{\times}0.48mm$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.11
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• pp.2015-2021
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• 2017

Recently, a lot of attention is fallen to IoT(Internet of Things) for hyper-connected society and the number of unlicensed wireless device has been increasing. Thus, this paper analyzed the impact of unlicensed wireless device on the basis of 802.11ah on licensed LTE user equipment in 900 MHz frequency band for efficient frequency use. As the interference analysis method, Minimum Coupling Loss (MCL) method and Monte Carlo (MC) method were used. In case of one interferer, minimum separation distance between interferer and victim was calculated as about 22 m through the MCL method under the assumption of the worst case. The maximum number of interferer to meet the interference probability of 5% below within a cell radius of the victim was computed as about 3000 by using MC method based on statistical technique. The analysis method and results in this paper are expected to be used for the coexistence between unlicensed wireless device and licensed wireless device.