• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.2
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• pp.65-70
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• 2004

This paper presents a novel linearization scheme for a nonlinear RF amplifier It is based on the amplitude modulation with envelope signal. The 3rd order distortion generator is composed of two FETs and it adopts a balanced structure for the purpose of main carrier cancellation. The amplitude and phase of the IM3 component can be controlled at RF band. This predistorter is implemented and tested at the KOREA PCS Tx. band (1840∼1870MHz). Experimental results of two-tone test show that the IM3 cancellation is achieved about 30-40 ㏈ for the wide dynamic range. The adjacent channel power ratio is improved by over 10 ㏈ at the broad-band CDMA signal with a peak to average power ratio of l0㏈, and this improvement is maintained through a wide range of output power levels.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.10
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• pp.34-41
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• 1998

In this paper, we evaluate synchronization techniques suitable for high-speed ATM satellite communications with a transmission rate of 155Mbit/s, and propose optimal algorithms that improve the tracking performance, where QPSK is selected for a modulation scheme, and the receiver is operated in burst mode. Based on these asumptions, we proposed modified algorithms and architectures for automatic frequency control(AFC), carrier recovery(CR), and symbol timing recovery(STR) for burst acquisition. Analysis is performed under AWGN environments with respect to the number of required symbol, steady-state stability, and hardware implementation for the proposed algorithms.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.503-504
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• 2006

This paper presents the design and fabrication of a LC voltage-controlled oscillator (VCO) using 1-poly 6-metal mixed signal CMOS process. To obtain the high-quality factor inductor in LC resonator, patterned-ground shields (PGS) is placed under the symmetric inductor to reduce the effect from image current of resistive Si substrate. Moreover, due to the incapability of using thick top metal layer of which the thickness is over $2{\mu}m$, as used in many RF CMOS process, the structure of dual-metal layer in which we make electrically short circuit between the top metal and the next metal below it by a great number of via materials along the metal traces is adopted. The circuit operated from 2.63 GHz to 3.09 GHz tuned by accumulation-mode MOS varactor. The corresponding tuning range was 460 MHz. The measured phase noise was -115 dBc/Hz @ 1MHz offset at 2.63 GHz carrier frequency and the current consumption and the corresponding power consumption were about 2.6 mA and 4.68 mW respectively.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.4
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• pp.295-301
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• 2011

A triple-band transceiver module for 2.3/2.5/3.5 GHz mobile WiMAX, IEEE 802.16e, applications is introduced. The suggested transceiver module consists of RFIC, reconfigurable/multi-resonance MIMO antenna, embedded PCB, mobile WiMAX base band, memory and channel selection front-end module. The RFIC is fabricated in $0.13{\mu}m$ RF CMOS process and has 3.5 dB noise figure(NF) of receiver and 1 dBm maximum power of transmitter with 68-pin QFN package, $8{\times}8\;mm^2$ area. The area reduction of transceiver module is achieved by using embedded PCB which decreases area by 9% of the area of transceiver module with normal PCB. The developed triple-band mobile WiMAX transceiver module is tested by performing radio conformance test(RCT) and measuring carrier to interference plus noise ratio (CINR) and received signal strength indication (RSSI) in each 2.3/2.5/3.5 GHz frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.715-722
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• 2000

In this paper, the PLDRO is designed and implemented for X-band. It is comprised of tunable high Q resonator with a varactor diode for frequency tuning, loop filter and a 1/8 prescaler which up to 10GHz. Also, it is implemented a TCXO and a VCO signal into the phase detector and achieved a highly stable signal source. From the measurement, the designed PLDRO has the output power of 2.5dBm at 8GHz and phase noise of -64.33dBc at 10KHz offset from carrier. Its characteristic is 26 dBc. This PLDRO has much better temperature stability.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.7
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• pp.679-686
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• 2002

Based on the alternating series expansion of error probability function due to phase noise in PSK systems, the performance evaluations for Tikhonov and Gaussian probability density functions were performed in this paper. The range of the signal-to-noise ratio of recovered carrier signal which provides the same dependency between the error performances by Tikhonov function and Gaussian function was analyzed via loss evaluation due to phase noise. The phase noise with 1/f$^2$ characteristic was generated based on the relationship of the phase noise spectral density and the modulation index for frequency modulation signal. Using the generated phase noise as the input signal for digital satellite communication receiver, the performance losses due to the phase noise were measured and evaluated with the analyzed performance characteristics.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.5
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• pp.582-589
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• 2016

Multi-mode monopulse system is widely used for satellite terminal like UAV because of high tracking accuracy and low size/weight profile. In order to calculate tracking error, Multi-mode monopulse system utilizes high-order mode signal, and it should have enough C/N(carrier to noise) level therefore tracking system needs narrow band filtering of received satellite beacon signal as much as possible. However, UAV suffers for beacon frequency drift derived from Doppler effect due to satellite figure 8 movement and UAV maneuvering. Therefore wideband signal processing needs to be considered in advance for exact doppler compensation and consequent time delay. In this paper, we propose the multi-stage Digital Signal processing system for beacon signal, which could minimize the signal delay under high Doppler and low C/N condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1A
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• pp.1-12
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• 2002

Ultra Wideband (UWB) system uses wide band signal, which power spectral density likes as a noise floor, so UWB system can be used high speed communication without interfering with other communication system. As this system doesn't use radio frequency carrier. Its structure would be very simple and consume very low power. For the first time, we adopted Rayleigh monopulse multiple access system. And under the AWGN, we analysis and compare error probability, the number of user and data rate of the two methods that pulse position modulation and antipodal. In the result, We concluded that the antipodal method had much better probability of error, the number of user and data rate than PPM.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.67-70
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• 1998

In this work, the freestanding GaN single crystalline substrates without cracks were grown by hydride vapor phase epitaxy (HVPE). The GaN substrates, having a current maximum size of 350 $\mu\textrm{m}$-thickness and 10${\times}$10 $\textrm{mm}^2$ area, were obtained by HVPE growth GaN on sapphire substrate and subsequent mechanical removal of the sapphire substrate. A lattice constant of c$\_$0/=5.18486 ${\AA}$ and a FWHM of DCXRD was 650 arcsec for the single crystalline freestanding GaN substrate. The low temperature PL spectrum consist of excitonic emission and deep donor to acceptor pair recombination at 1.8 eV. The Raman E$_2$ (high) mode frequency was 567 cm$\^$-1/ which was the same as that of strain free bulk single crystals. The Hall mobility and carrier concentration was 283 $\textrm{cm}^2$/V$.$sec and 1.1${\times}$10$\^$18/ cm$\^$-3/, respectively. The freestanding and crack-free GaN single crystalline substrate suitable for the homoepitaxial growth of GaN, and the HVPE method are promising approaches for the preparation of large area, crack-free GaN substrates.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.5
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• pp.8-15
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• 2011

LTE-Advanced aims at peak data rates of 1Gbits/s for the downlink and 500 Mbits/s for the uplink, which can be accomplished only by using wide spectrum allocation of 100MHz as well as advanced multiple input multiple output antenna techniques to the uplink. This paper analyzes the uplink precoding techniques which include LTE codebook of downlink, singular value decomposition codebook, and equal gain transmission codebook over LTE defined single carrier frequency division multiplexing systems. Finally considering nonlinear transmit power amplifier model, it is shown that link-level performance of EGT is superior to those of any other precoding schemes.