• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.2
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• pp.213-219
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• 2012

Recently, we are simultaneously exposed by various electromagnetic sources due to an increase of mobile communication services. However, EMF(Electric, Magnetic and Electromagnetic Field) study has been performed mainly about only single frequency. The objective of this paper is to develop an multiple-frequency exposure system for in vitro experiment. The exposure unit for in vitro experiments was designed by radial transmission line type to get broadband characteristics to generate signals of CDMA at 836.5 MHz and WCDMA at 1950 MHz frequency simultaneously. The modulated signals were delivered to the conical antenna through amplifier, digital attenuator and RF combiner. SAR values were obtained by the averaged values of 3 measured values at 9 points in petri dish using the fiber optic temperature probe. The measured return loss was under -15 dB. For 1 W input power, the mean value and standard deviation of SAR were $0.105{\pm}0.019$ for the CDMA frequency and $0.262{\pm}0.055$ for the WCDMA frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.1
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• pp.49-60
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• 2017

In this paper, we presented the result of the study on high-power handling capability of the X-band circular waveguide cavity filter configured at the output of high power amplifier(120 W) for geostationary satellites. The dual mode circular waveguide cavity filter with 6th order is selected and the physical model of the filter is designed after determination of the size of resonator from mode chart. Multipactor margin analysis is performed by the SEM method and the VMF method. The result shows that the VMF method predicts lower multipactor breakdown thresholds than the SEM method. Evaluating the multipactor margin obtained by the VMF method to ECSS criteria, we could decide to perform multipactor test. The multipactor test conducted in ESA facility shows that multipactor did not occur even until the RF power increased up to 540 W. In consequence, by both analysis and test, we could verify that the X-band circular waveguide cavity filter has the sufficient high-power handling capability to operate on orbit.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4C
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• pp.230-238
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• 2005

An orthogonal frequency division multiplexing (OFDM) system consists of a number of independently modulated subcarriers and, thus, a high peak-to-average power ratio (PAR) can occur when the subcarriers are added coherently. The high PAR brings such disadvantages as an increased complexity of the analog-to-digital (ADC) and digital-to-analog (DAC) converters and a reduced efficiency of the radio frequency (RF) power amplifier. In this paper, we propose a novel PAR reduction scheme called selective mapping of partial tones (SMOPT). The SMOPT scheme has a reduced complexity, lower sensitivity to peak reduction tones (PRT) positions, and a shorter processing time as compared with the conventional tone reservation (TR) scheme. The performance of the SMOPT scheme is analyzed based on the IEEE 802.1la wireless local area network(WLAM) physical layer model. Numerical results show that the SMOPT scheme outperforms the TR scheme under various scenarios.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.339-342
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• 2004

본 논문은 밀리미터파 대역 무선통신 시스템 송신부의 응용을 위해 CPW 구조를 이용하여 V-band용 상향 주파수 혼합기와 2단 구동증폭기를 설계$\cdot$제작하였다. 능동소자는 본 연구실에서 제작한 $0.1{\mu}m$ 게이트 GaAs Pseudomorphic HEMTs(PHEMTs)를 사용하였으며 입$\cdot$출력단은 CPW를 사용해 정합 회로를 설계하였다. 제작된 상향 주파수 혼합기는 LO power 5.4 dBm, 2.4 GHz IF 신호를 -10.25 dBm으로 입력하였을 때 Conversion Loss 1.25 dB, LO-to-RF Isolation은 58 GHz에서 13.2 dB의 특성을 나타내었다 2단 구동 증폭기는 측정결과 60 GHz에서 S21 이득 13 dB, $58\;GHz\;\~\;64\;GHz$ 대역에서 S21 이득 12 dB 이상을 유지하는 광대역 특성을 얻었고 증폭기의 Pl dB는 3.8 dBm, 최대 출력전력은 6.5 dBm의 특성을 얻었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.7 s.110
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• pp.659-664
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• 2006

This paper reports a high power 60 GHz push-push oscillator fabricated using $0.12{\mu}m$ metamorphic high electron-mobility transistors(mHEMTs). The devices with a $0.12{\mu}m$ gate-length exhibited good DC and RF characteristics such as a maximum drain current of 700 mA/mm, a peak gm of 660 mS/mm, an $f_T$ of 170 GHz, and an $f_{MAX}$ of more than 300 GHz. By combining two sub-oscillators having $6{\times}50{\mu}m$ periphery mHEMT, the push-push oscillator achieved a 6.3 dBm of output power at 59.5 GHz with more than - 35 dBc fundamental suppression. The phase noise of - 81.5 dBc/Hz at 1 MHz offset was measured. This is one of the highest output power obtained using mHEMT technology without buffer amplifier, and demonstrates the potential of mHEMT technology for cost effective millimeter-wave commercial applications.

• Journal of electromagnetic engineering and science
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• v.18 no.3
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• pp.188-198
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• 2018

In this study, we propose an approach for the design and satisfy the requirements of the fabrication of a small, lightweight, reliable, and stable ultra-wideband receiver for millimeter-wave bands and the contents of the approach. In this paper, we designed and fabricated a stable receiver with having low noise figure, flat gain characteristics, and low noise characteristics, suitable for millimeter-wave bands. The method uses the chip-and-wire process for the assembly and operation of a bare MMIC device. In order to compensate for the mismatch between the components used in the receiver, an amplifier, mixer, multiplier, and filter suitable for wideband frequency characteristics were designed and applied to the receiver. To improve the low frequency and narrow bandwidth of existing products, mathematical modeling of the wideband receiver was performed and based on this spurious signals generated from complex local oscillation signals were designed so as not to affect the RF path. In the ultra-wideband receiver, the gain was between 22.2 dB and 28.5 dB at Band A (input frequency, 18-26 GHz) with a flatness of approximately 6.3 dB, while the gain was between 21.9 dB and 26.0 dB at Band B (input frequency, 26-40 GHz) with a flatness of approximately 4.1 dB. The measured value of the noise figure at Band A was 7.92 dB and the maximum value of noise figure, measured at Band B was 8.58 dB. The leakage signal of the local oscillator (LO) was -97.3 dBm and -90 dBm at the 33 GHz and 44 GHz path, respectively. Measurement was made at the 15 GHz IF output of band A (LO, 33 GHz) and the suppression characteristic obtained through the measurement was approximately 30 dBc.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.771-774
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• 2003

Passivation Ledge's device is taken possession on one-side to the Emitter in this Paper. contact used in this paper Pt as Passivation Ledge of device to use Schottky Diode which has leitmotif, It is accomplished Current Modulation that we wish to do purpose using this device. Space Charge acts as single device which is becoming Passivation to know this phenomenon. This device becomes floating as well as Punched-through. V$_{L}$ (Voltage for Ledge) = - 0.5V ~ 0.5V variable values , PD(Partially Depleted ; Λ＞0), as seeing FD(Fully Depleted ; A = 0) maximum electric current gains and Gummel Plot of I-V characteristics (V$_{L}$ = 0.1/ V$_{L}$ = -0.1 ). Becomming Degradation under more than V$_{L}$ = 0.1 , less than V$_{L}$ =-0.05 and Maximum Gain(=98.617076 A/A) value in the condition V$_{L}$ = 0.1. A Change of Modulation is electric current gains by using Schottky Diode and Extrinsic Base PN Diode of Passivation Ledge to Emitter Depletion Layer in HBT of Gummel-Poon I-V characteristics and the RF wide-band electric current gains change the Modulation of CE(Common-Emitter) amplifier description, and it had accomplished Current Gain Modulation by Ledge Bias that change in high frequency and wide bands. wide bands.s.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1304-1310
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• 2010

This study is to design FMCW radar transceiver of K-band which is used to detect and track approaching high speed targets with low altitude. The transmitter needs high output power due to small RCS targets and wide beamwidth of transmit antenna. Multi-channel receivers are required to detect and track targets by interferometer method. Transmitter consists of high power amplifier, waveguide switch, and frequency up-converter. Receiver is composed of five channel receivers, up and down converters, X-band local oscillator and waveform generator. Before manufacturing it, the proposed architecture of transceiver is proved by modeling and simulation using several parameters. Then, it is manufactured by using industrial RF components. The performance parameters are measured through experiment. In the experiment, transmitting power and receiver gain were measured with 39.64 dBm and 29.1 dB, respectively. All other parameters in the specification were satisfied as well.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.78-84
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• 2012

In this paper, we introduced the design technique about a Ka band receive module for millimeter wave seekers. The receiver module consists of a waveguide, circulator and transition for antenna connection, and a limiter and gain control amplifier for receiver protection. This module is comprised of a sum, azimuth and elevation channel for receiving monopules signal, and a SLB channel for the acquisition of jamming signal. In this paper, receiver gain and range of gain control dependent on ADC nonlinear characteristic was analyzed and designed for wide dynamic range receive. In the test result of the fabricated Ka-band receive, the frequency band is 1 GHz, the noise figure is as low as 8.2 dB, the gain is $56{\pm}2dB$, the dynamic range is 135 dB, the gain congtrol is more than 86 dB, the channel isolation is more than 35 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.1
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• pp.61-70
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• 2008

This paper presents the flexible MEMS transmitter based on flexible printed circuit board or FPCB, which can be transformed to arbitrary shape. The FPCB is suitable to fabricate light weight and small size modules with the help of its thin thickness. Moreover a module based on FPCB can be attached on the arbitrary curved surface due to its flexible enough to be lolled up like paper. In this paper, the flexible MEMS transmitter integrated on FPCB for a short-distance sensor network which is based on orthogonal frequency division multiplexing(OFDM) communication system is proposed. The active device of the proposed flexible MEMS transmitter is fabricated on InGaP/GaAs HBT process which has been used for power amplifier design to take advantages of high linear and high efficient characteristics. Moreover, the passive devices such as the filter and signal lines are integrated and fabricated on the FPCB board. The performance of the fabricated flexible MEMS transmitter is analyzed with EVM characteristics of the output signal.