• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.1
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• pp.7-12
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• 2015

In this paper, we studied the design and fabrication of dual T type antenna to be used in LTE communication systems operating at around 1.8 GHz band. In order to improve of frequency properties of antenna, single feed microstrip patch antenna and CPWG antenna was simulated by HFSS(High Frequency Structure Simulator). The fabricated dual T type antennat showed that the measured center frequency, the minimum return loss and -10dB bandwidth were 1.79 GHz, -23.26 dB and 23 MHz, respectively.

• 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.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.7 no.4
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• pp.188-194
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• 2014

In this paper, an antenna which has quad band in LTE (0.746 ~ 0.798 GHz), GSM(0.824 ~ 0.960 GHz), DCS(1.71 ~ 1.88 GHz), WCDMA(1.91 ~ 2.17 GHz) is proposed. An antenna size is $122mm{\times}50mm{\times}0.8mm$ on FR4(${\epsilon}_r=4.4$) ground substrate. In the proposed antenna, branch line is applied to the conventional PIFA architecture to achieve multi-bandwidth. Coupling power supply is applied for a wide bandwidth. Result of the measurement is as follows. When the low frequency, the antenna presents gain of 0.93 ~ 1.92dBi, and radiation efficiency of 49.60 ~ 76.35 %, and When the high frequency, gain is 2.19 ~ 4.66dBi, and radiation efficiency is 60.40 ~ 80.01 %, and with a VSWR < 2 (${\leq}-10dB$)measurement results for standard satisfies all band. Judging from the result, proposed multiband antenna is expected to be applied. B4G mobile terminals since the antenna shows an outstanding performance.

• 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.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.8
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• pp.98-103
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• 2015

Power plant is that very high reliability when industrial and economic impact on the overall electric power system is required, it is essential to improve the reliability, especially the fault prediction diagnosis. Since an accident caused by the partial discharge in the power plant is above state has a faster response characteristic than the other indications in the case of any, the partial discharge generated in the power plant immediately detect the deterioration of insulation due to the accident of the power plant and the non-drawn It should prevent or reduce. Partial Discharge Measuring Systems for UHV SF6 Gas Insulated Switchgear and power transformer on site installed has some probability of abnormal recognition in case of non-flexible deal with on site noise. Many methode to eliminate these kinds of noises, UHF Detection System is chosen as purchase description in Korea, but this system having a bandwidth between 500MHz 1.5GHz wide band. Initial install periods(about 20 years ago), this band had no strong signal source, but in these days this wide band have strong signals, such as LTE. So, module described in this paper is designed as simultaneously use with wide and narrow band for solve this noise problem, and introduce this system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.833-839
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• 2011

This paper has suggested a technique for measuring VSWR at 1.8 GHz band for various modulated signals. By using directional coupler the power of incident and reflected wave is measured, and in order to minimize the size and cost of the measuring circuit, a SPDT(Single Pole Double Throw) switch is adopted to realize the circuit with just one detector and one A/D(Analog to Digital) converter. MCU(Micro Control Unit) is used to calculate the voltage reflection coefficient and VSWR, and the measured VSWR error has improved by approximately 0.2 with applying a simple bubble sorting algorithm to reduce the measurement error, the MCU process time and load.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.9
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• pp.895-902
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• 2014

This paper presents a 2-stage CMOS power amplifier for the 1.75 GHz band using a $0.18-{\mu}m$ CMOS process. Using ADS simulation, a power gain of 28 dB and an efficiency of 45 % at an 1dB compression point of 27 dBm were achieved. The implemented CMOS power amplifier delivered an output power of up to 24.8 dBm with a power-added efficiency of 41.3 % and a power gain of 22.9 dB. For a 16-QAM uplink LTE signal, the PA exhibited a power gain of 22.6 dB and an average output power of 23.1 dBm with a PAE of 35.1 % while meeting an ACLR(Adjacent Channel Leakage Ratio) level of -30 dBc.

• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.76-79
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• 2010

본 논문에서는 고 효율 및 고 출력 특성을 가지는 질화갈륨(GaN) 소자를 이용하여 WiMAX 및 LTE System에 사용될 수 있는 DPD용 Pallet Amplifier를 제작하였다. 제작된 Pallet Amplifier는 Pre-drive로써 저 전류의 MMIC를 채택하고, Drive 단과 Main 단에 15W 급과 30W 급의 질화갈륨 소자를 사용 하였으며, 추가적인 효율 개선을 위해 PCB상에 Doherty Structure를 적용함으로써 보다 높은 효율을 구현하였다. 제작된 Pallet Amplifier는 음 전원 Bias 제어 회로, 온도에 따른 Gain 보상회로, Sequence 회로 및 Main 전원 Drop에 따른 보호 회로를 구현하였다. WiMAX Signal을 이용한 Modulation Power 10Watt Test에서 약 36.8~38.3%의 Pallet 효율과 DPD Solution인 TI GC5325SEK DPD Board 사용 시 ACLR은 약 46dBc 이상을 가지는 것으로 측정되었다. 본 논문에서 제작된 Pallet Amplifier는 Upper Band와 Lower Band로 나누어 제작되었던 기존 Pallet Amplifier와 달리 하나의 Pallet Amplifier로 2496~2690MHz에서 모두 사용하면서 종전에 사용되고 있는 Pallet Amplifier에 비해 Size가 최소 10% 이상 축소되어 효율 및 크기 면에서 종전 Pallet Amplifier보다 큰 이점을 갖는다.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.8
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• pp.3-10
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• 2014

Millimeter wave (mmWave) has attracted great interest recently and the necessity of Millimeter Mobile Broadband (MMB) system has appeared based on the 4 Generation Long Term Evolution-Advanced (LTE-A) Specification. Currently, there are many studies about the mmWave communication channel. And it is subject of interest to analyze the performance in MMB channel environments. In this paper, we design the MMB system for 5th Generation mobile communication and propose channel models through the analysis of the mmWave propagation characteristics. Also, we have analyzed the performance of the MMB system of 28 GHz band in MMB channel environments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.8
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• pp.740-747
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• 2015

Recently, mobile communication systems using the millimeter-wave frequency band have been proposed, and the importance of efficient compensation of the nonlinearity caused by 60 GHz high-power amplifiers(HPAs) is increasing. In this paper, we propose a predistorter structure based on multiple coefficient sets which are separately used to different ranges of input power values. These ranges correspond to varying levels of nonlinearity characteristics. The structure is applied to the 60 GHz HPA FMM5715X and the performance of correcting the nonlinearity of LTE signals is evaluated. Evaluation results using a hardware testbed demonstrate that the proposed predistorter structure achieves the maximum of 6 dB gain over the conventional method in terms of the adjacent channel leakage ratio(ACLR).