• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.761-766
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• 2004

Rayleigh fading due to multi-path degrades the mobile service quality, especially high data rate mobile services such as 1xEVDO and W-CDMA. The field test showed that down load date rate of 1xEVDO is seriously affected by Rayleigh fading. To reduce the effect of Rayleigh fading, transmit diversity was implemented in RF repeater. In field test, transmit diversity function increased the data rate about twice comparing with no transmit diversity repeater. Recently high data rate service is getting more important, so transmit diverstiy function will be an important function in repeater.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.777-783
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• 2009

In this paper, we implemented a wireless power transmission system at 2.45 GHz. The transmission power is limited within 20 dBm according to the ISM frequency regulations. We used two zero-bias Schottky diode and optimized the RF-DC converter for working a clock at 80 cm distance using a receiver with a single antenna and an Rf-DC converter to reduce parts and cost compared to previously reported literatures.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.124-127
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• 2005

국내에서는 언제 어디서나 휴대용 단말을 이용하여 저렴한 요금으로 고속의 무선인터넷을 사용할 수 있는 휴대인터넷 서비스를 2006년부터 서비스 할 계획이다. 앞으로 서비스 될 WiBro 휴대인터넷 서비스 방식은 기존 이동통신 방식과 달리 RF 송신 주파수와 수신 주파수가 동일한 TDD (time division duplexing) 방식을 사용한다. WiBro 무선통신 기지국 장비에 있어서도 기존 CDMA 이동통신 기지국 장비에서와 마찬가지로 RF Power Amplifier (PA)가 매우 고가의 핵심 부품이라 할 수 있다. 물론, 기존 FDD (frequency division duplexing) 방식의 CDMA 기지국 PA와 달리 WiBro용 기지국 PA는 TDD 신호를 처리할 수 있는 새로운 기술을 필요로 한다. TDD 방식인 WiBro 기지국용으로 사용할 수 있는 새로운 2.3 GHz 42 W PA를 설계, 제작한 결과를 본 논문에서는 발표하고자 한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.8
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• pp.805-808
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• 2011

This paper presents a design of high-efficiency and high-power class E power transmitter. The transmitter is composed of 300 Watt class E power amplifier and AC-DC converter. The AC-DC converter converts 220 V and 60 Hz AC to a 290 V DC. The generated DC voltage is directly applied to a bias of the class E power amplifier. Because the converter does not have DC-DC converter unit, it has very high conversion efficiency of about 98.03 %. To minimize the loss at the output of the power amplifier, high-Q inductor was implemented and deployed to the output resonant circuit. As a result, the 13.56 MHz class E power amplifier has a high power-added efficiency of 84.2 % at the peak output power of 323.6 W. The overall efficiency of class E power transmitter, including the AC-DC converter, is as high as 82.87 %.

• Journal of Advanced Navigation Technology
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• v.24 no.1
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• pp.53-60
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• 2020

In this paper, We have studied the structure of a Telemetry Transmitter capable of transmitting variable data rates. This paper proposed a structure combining variable pre-modulation filter with cutoff characteristic with variable input sample rate converter. Variable pre-modulation filter has the same characteristics as pre-modulation filter and is converted to a constant sampling rate without structural changes according to the variable input data rate. We propose a software program that actively controls variable pre-modulation filter and variable input sample rate converter to respond to real-time changing data.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1205-1214
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• 2013

Recently spaceborne SAR systems are increasing image resolution and frequency. As a high quality image resolution, the wider bandwidth is required and a wideband signal generator with RF component is very complicated and RF impairments of device is increased. Therefore, it is very important to improve performance by reducing these errors. In this study, the transmission signal of the wideband signal generator is applied to the phase noise, IQ imbalance, ripple gain, nonlinear model of high power amplifier. And we define possible structures of wideband signal generator and measure the PSLR and ISLR for the performance assesment. Also, we extract error of the amplitude and phase from the waveform and use a quadratic polynomial curve fitting and examine the performance change due to nonlinear device. Finally, we apply a high power amplifier predistortion method for non-linear error compensation. And we confirm that distortion in the output of the amplifier by intermodulation component is decreased by 15 dB.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.2
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• pp.143-152
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• 2019

In this paper, we described the design of Ka-band planar active phased array antenna which is applicable for small RADAR for airborne and seeker of guided missile. The antenna consists of about 1000 array radiating elements and is designed to be within 200mm diameter. We optimized the spacing of radiating elements to allow beem steering above ${\pm}55$ degrees of Field of view, and analyzed the performance of antenna. We confirmed that the Effective Isotropic Radiated Power (EIRP) of the antenna can be 94.22 dBm and receive G/T can be 1.68 dB/k through the designs of RF components and the verification of RF budget. The TX output of TR Module is designed to be over 1.3W for EIRP, and Receive noise figure of TR Module is designed to be less than 5dB for G/T.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.11
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• pp.34-41
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• 2003

In this paper, 60GHz band transmitter and receiver for wireless LAN are designed and implemented using the broband amplifier and mixer fabricated by standard 0.1${\mu}{\textrm}{m}$ MIMIC process of MINT. Output power and gain of the RF transmitter are 0 ㏈m and 1.7㏈, respectively. Noise figure and gain of the receiver are 4.2㏈ and l5.7dB, respectively. Considering the sensitivity and LOS test, this system can communicate with BER of below than 10$^{-6}$ at a distance more than 35m. DSSS, which is strong for concealment and disturbance, is adopted.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3C
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• pp.248-255
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• 2002

An RF module in compliance with the IEEE 802.11a standard has been designed and its performance has been measured. Conventional heterodyne architecture with 580MHz intermediate frequency has been realized. Measurement results show that the receiver has a low Noise Figure of 5dB, the maximum gain of 70dB, and dynamic range as wide as 61dB. Also, the SAW filter used for channel selection in the IF section allowed minimum inter-channel interference. in addition to satisfying the RF output power requirement, the transmitter features its output P1dB as high as 34dBm so that the high peak-to-average ratio of the Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme can be handled with minimum nonlinear distortion. The output P1dB of 34dBm of the transmitter corresponds to back-off powers of 18dB and 11dB with respect to the output power for the low and the middle frequency bands, respectively.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.4
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• pp.159-167
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• 2018

In this paper, we propose an algorithm to optimize energy efficiency in a multi-user decoupled RF energy harvesting network and experiment on the trend of energy efficiency change assuming users' various geographical distribution scenarios. In the RF energy harvesting network where both wireless data transmission and RF energy harvesting are simultaneously performed, the energy efficiency is a key indicator of network performance, and it is necessary to investigate how various factors can affect the energy efficiency. In order to increase energy efficiency effectively, we can confirm that users' distributions are important factors in the RF energy harvesting network from the simulation results.