• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.12 s.354
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• pp.33-39
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• 2006

An empirical nonlinear model with intrinsic nonlinear elements has been newly developed to predict the RF nonlinear characteristics of nano-scale bulk MOSFET accurately over the wide bias range. Using an extraction method suitable for nano-scale MOSFET, the bias-dependent data of intrinsic model parameters have been accurately obtained from measured S-parameters. The intrinsic nonlinear capacitance and drain current equations have been empirically obtained through 3-dimensional curve-fitting to their bias-dependent curves. The modeled S-parameters of 60nm MOSFET have good agreements with measured ones up to 20GHz in the wide bias range, verifying the accuracy of the nano-scale MOSFET model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.3
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• pp.243-253
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• 1997

In land mobile communications, incident waves to mobile antenna com mostly from directions having low elevation angles about $60^{\circ}$ down from the vertical plane. In order to receive this waves effectively, planar type antenna was fabricated and its characteristics were analyzed. This type of antenna is achieved using superstrate effect criteria which are derived for a nonzero radiation field extending down to the substrate layer surface plan. A small planar type microstrip antenna which can receive incident waves having low elevation angle was fabricated. Experimental results show that the band width of the fabricated antenna is 70 MHz at 1.2 GHz and have nonzero field down to the layer surface.

• Journal of the Korea Convergence Society
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• v.11 no.10
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• pp.63-69
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• 2020

In this paper, a small microwave sensor that can be applied to a wearable device is proposed because it can detect the heartbeat signal of a human body moving irregularly at low speed. It consist of balanced microstrip radiation patches in the 2.4 GHz ISM band, self-oscillation detection circuit, and feedback circuit. Based on the theoretical development and simulation, the validity of the proposed structure was confirmed and the manufactured prototype was tested. The board size of the circuit is as small as 65mm × 85㎟, and has a low power consumption of 60mW thanks to the simple RF circuit structure. Finally heartbeat signal has been obtained from a human body moving at low speed (0.5Hz) within a linear distance of 2 to 30mm close to the sensor and a lateral distance of ±20mm.

• Journal of Navigation and Port Research
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• v.34 no.7
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• pp.539-542
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• 2010

In this paper, we designed and fabricated the Electro-Magnetic (EM) wave absorber for wireless LAN by using Amorphous and CPE. The material constants and the absorption properties were measured for the samples containing 50 %, 60 %, and 70 % weight fraction of Amorphous. Moreover, the EM wave absorption abilities were simulated for the EM absorbers in different thicknesses by adopting the measured permittivity and permeability, and then the EM wave absorber was fabricated based on the simulated design values. As a result, the EM wave absorber with the composition ratio in Amorphous : CPE = 60 : 40 wt.% with the thickness of 4 mm has the absorption ability more than 35 dB at 2.4 GHz. Thus, it is expected the wireless LAN environment can be improved by using the developed absorber.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.3
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• pp.26-31
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• 2009

In this paper, we propose the receiver algorithms suitable for the ECMA standard proposed for multi-gigabit packet transmission in 60 GHz band. In the ECMA standard, various modulation schemes are used for system flexibility. Hence, it is crucial to develop receiver algorithms supporting various modulation schemes with an uniform hardware structure. In this paper, we propose the receiver algorithms supporting DBPSK, DQPSK and OOK modulation schemes simultaneously. The proposed algorithms are not only hardware efficient but also support various modulation schemes with an uniform hardware structure.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.9
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• pp.903-911
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• 2014

This paper proposes a high speed frequency synthesizer with dual phase-locked loop(PLL) structure to improve phase noise level and shape in a wideband receiver. To reduce phase noise and fractional spur, a output frequency of $1^{st}$ PLL used as reference frequency of $2^{nd}$ PLL is changed. The frequency synthesizer has been designed with 1 Hz frequency resolution using digital NCO in 6.5~8.5 GHz wide spectrum. The measured results of the fabricated frequency synthesizer show that the output power is about -3 dBm, the maximum lock-in time and phase noise are within 60 us and -95 dBc/Hz at 10 kHz offset, respectively.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.3
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• pp.79-84
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• 2011

In this paper, we analyzed performance of vehicle detection for ITS (Intelligent Transport System) applications. We simulated the vehicle detection at Hi-Pass System is based on DSRC (Dedicated Short Range Communication). DSRC is a wireless network using ITS, including GPS (Global Positioning System) satellites in conjunction with the national transportation system. The system performance is evaluated in terms of bit error probability. In the simulation, the vehicle speed is set at 60 km/h and carrier frequency is 5.8 GHz. Wireless channel is modeled as the Rician fading channel. In the transmitter, the ASK (amplitude shift keying) modulation scheme is applied. From simulation results, we confirmed that performance of applied Alamouti scheme is better than other systems.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.5
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• pp.71-78
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• 2011

In this paper, we describe the design and implementation of a high efficiency and broad-band Class-J mode power amplifier using gallium nitride(GaN) high-electron mobility transistor(HEMT). The matching circuit of proposed class-J mode power amplifier for 2nd harmonic impedance designed to provide pure reactance alone. The measurement results show that output power of $40{\pm}1$ dBm, power-added efficiency of 50%, and drain efficiency of 60% for a continuous wave signal at 1.4 to 2.6 GHz.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3A
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• pp.245-253
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• 2010

In this paper, we derive the performance analysis of the coded cooperation over a Rician fading channel. A new scheme called coded cooperation was suggested by using user cooperation and channel codes simultaneously. In previous works, it was verified that the coded cooperation schemes have better performance than other relay schemes in a Rayleigh fading channel. However, the high speed short range indoor wireless communication system has recently attracted research attention and its channel with very high carrier frequency(60GHz) can be typically modeled as a Rician fading channel. We derive analytical outage probabilities and bit error probabilities of the coded cooperation over the Rician fading channel and prove it to have full diversity order.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.60.2-60.2
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• 2011

We introduce the preliminary results of flux monitoring of BL Lac object 0716+714 with the KVN Ulsan 21m radio telescope. This radio source is well known as the intraday variable (IDV) source which is characterized by the rapid flux variation on the time scale of a day or less. In general, the IDV phenomenon is interpreted as the effect of refractive scintillation in the interstellar medium or the evidence of intrinsic flux variation. In previous observations that took a few days, however, it had not been detected the flux variation of short time scale but the monotonic increase and decrease. Therefore, to investigate the longer time scale of 0716+714, we had the flux variation monitoring at 22GHz and 43GHz simultaneously for 9 months from October 2010 to June 2011. We present here the structure functions and the cross correlation functions between different frequencies as well as the light curves.