• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.10A
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• pp.958-964
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• 2005

In this thesis, the matching network at the local oscillator port of the sub-harmonic mixer is optimized for reducing the conversion loss. A downconverter for point to point system applications is designed and fabricated using the such sub-harmonic mixer. The sub-harmonic mixer achieved the conversion loss of 11.8 dB at the 12 dBm input power of the local oscillator and the isolation of less than -40 dB. The downconverter achieved the IF output power flatness of 2 dB and the total noise figure of 5.9 dB.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.2 s.332
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• pp.9-14
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• 2005

This paper reports the hot carrier induced RF performance degradation of bulk dynamic threshold voltage MOSFET (B-DTMOS) compared with bulk MOSFET (B-MOS). In the normal and moderate mode operations, the degradations of cut-off frequency $(f_{T})$ and minimum noise figure $(F_{min})$ of B-DTMOS are less significant than those of B-MOS devices. Our experimental results show that the RF performance degradation is more significant than the U performance degradation after hot carrier stressing. Also, the degradation characteristics of RF power Performance of B-DTMOS due to hot carrier effects are measured for the first time.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.139-143
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• 2005

In this paper, we propose the design on LNA and Down-mixer for MB-OFDM UWB using $0.18\;{\mu}m$ CMOS. LNA, Down-mixer design result shows that it covers the frequency range ken 3 GHz to 5 GHz. The LNA gain is larger than 12.8 dB, and noise figure about 2.6 dB. Double balanced differential down-mixer is designed less than 2 dB gainflatness, and it has over 30 dB LO leakage, feedthrough characteristics.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.3
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• pp.264-269
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• 2013

Since MFC(macro-fiber composite) transducer has been developed, many researchers have tried to apply this transducer on SHM(structural health monitoring), because it is so flexible and durable that it can be easily embedded to various kinds of structures. The objective of this paper is to figure out the benefits and feasibility of applying MFC transducers to guided wave technique. For this, we have experimentally tested the performance of MFC patches as transmitter and sensors for excitation and reception of guided waves on the thin aluminum alloy plate. In order to enhance the signal accuracy, we applied the FIR filter for noise reduction as well as used STFT(short-time Fourier transform) algorithm to image the guided wave characteristics clearly. From the results, the guided wave generated based on MFC showed good agreement with its theoretical dispersion curves. Moreover, the ultrasonic Lamb wave techniques based on MFC patches in pitch-catch manner was tested for detection of surface notch defects of which depths are 10%, 20%, 30% and 40% of the aluminum plate thickness. Results showed that the notch was detectable well when the notch depth was 10% of the thickness or greater.

• Structural Engineering and Mechanics
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• v.58 no.1
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• pp.163-179
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• 2016

The Cuckoo search (CS) algorithm is a simple and efficient global optimization algorithm and it has been applied to figure out large range of real-world optimization problem. In this paper, a new formula is introduced to the discovering probability process to improve the convergence rate and the Tournament Selection Strategy is adopted to enhance global search ability of the certain algorithm. Then an approach for structural damage identification based on modified Cuckoo search (MCS) is presented. Meanwhile, we take frequency residual error and the modal assurance criterion (MAC) as indexes of damage detection in view of the crack damage, and the MCS algorithm is utilized to identifying the structural damage. A simply supported beam and a 31-bar truss are studied as numerical example to illustrate the correctness and efficiency of the propose method. Besides, a laboratory work is also conducted to further verification. Studies show that, the proposed method can judge the damage location and degree of structures more accurately than its counterpart even under measurement noise, which demonstrates the MCS algorithm has a higher damage diagnosis precision.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.5
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• pp.1-10
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• 1999

A low power concumption 2.4 GHz one-chip transceiver MMIC was designed and fabricated using $1.0\mu\textrm{m}$ ion-implantation MESFET process and packaged on a 24 lead SSOP. In the transmitter mode, it revealed conversion gain of 7.5 dB, output IP3 of -3.5 dBm, and noise figure of 3.9 dB at 2.44 GHz with 3.9 mA current consumption. In the receiver mode, it revealed voltage sensitivity of 6.5 mV/$\mu\$W with 2 .0 mA current consumption. Comparing the fabricated MMIC with the results of MMICs reported elsewhere, it was shown that the fabricated MMIC had good performance. The low power consumption 2.4 GHz transceiver MMIC is expected to be used for various applications such as wireless local area networks, wireless local loops and RFID tags in ISM-band.

• Journal of the Korea Society of Computer and Information
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• v.16 no.10
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• pp.131-136
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• 2011

In this paper, we fabricate multi channel receiver for radar system. This receiver at X-band can be received 8 signal of an identical characteristic, dynamic range has more than 80[dB]. To process direct received signals, this system has the built-in two digital de-modulators which offer the minimum loss on the receiving signal path and has high stability by adding Built-In Test. The gain, noise figure, difference of amplitude and phase on the signal path is respectively 20${\pm}$2[dB], 19[dB], ${\pm}$2[dB], $10^{\circ}$ and below.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.4
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• pp.295-301
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• 2008

Recently, the demand on mm-wave (millimeter-wave) applications has increased dramatically. While circuits operating in the mm-wave frequency band have been traditionally implemented in III-V or SiGe technologies, recent advances in Si MOSFET operation speed enabled mm-wave circuits realized in a Si CMOS technology. In this work, a 58 GHz CMOS LC cross-coupled VCO (Voltage Controlled Oscillator) was fabricated in a $0.13-{\mu}m$ Si RF CMOS technology. In the course of the circuit design, active device models were modified for improved accuracy in the mm-wave range and EM (electromagnetic) simulation was heavily employed for passive device performance predicttion and interconnection parasitic extraction. The measured operating frequency ranged from 56.5 to 58.5 GHz with a tuning voltage swept from 0 to 2.3 V. The minimum phase noise of -96 dBc/Hz at 5 MHz offset was achieved. The output power varied around -20 dBm over the measured tuning range. The circuit drew current (including buffer current) of 10 mA from 1.5 V supply voltage. The FOM (Figure-Of-Merit) was estimated to be -165.5 dBc/Hz.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.2
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• pp.321-326
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• 2018

This study describes the design and implementation of TRM(Transmit and Receiver Module) for detection for targets of small RCS(Radar Cross Section). Through the pre-simulation analysis of radar system about RF, the main specifications of TRM are verified. After the fabrication of TRM, the main characteristics such as the maximum output, noise figure, spurious were confirmed. In the future, the radar system test will be carried out by assembling TRMs, antenna radiator, and the transceiver that generates and receivers the radar waveform reflected.

• Journal of Advanced Navigation Technology
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• v.21 no.3
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• pp.243-250
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• 2017

GPS(Global Positioning System) signal structure uses spread spectrum and the received power is relatively lower than the receiver noise figure. Therefore, it is vulnerable to the RF interferences and it could restrict on the safety navigation. The objective of this paper is to research on the spectral domain GPS interference rejection algorithm using proposed K-median filtering threshold setting method. In the performance test, the proposed algorithm has a relatively higher ISR(interference to signal ratio) compared with the conventional temporal domain technique in case of time variant interference signals.