• Journal of Advanced Navigation Technology
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• v.8 no.1
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• pp.73-80
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• 2004

In the case of Non-Line-of-Sight (NLOS), common telecommunication systems typically have Rayleigh distributed amplitude characteristics. However measurement result of Ultra Wideband (UWB) Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) system which is proposed as one of candidate standard in IEEE 802. 15. 3a for Wireless Personal Area Network (WPAN) shows that it has independent log normal fading in each cluster as well as in each ray within the cluster. Based on this clustering phenomenon observed, MB-OFDM channel model derived from Saleh-Valenzuela model with a couple of slight modifications. In this paper, channel remodeling for RF frequency hopping in MB-OFDM system is achieved, and performances of MB-OFDM system for each channel mode and data rate are verified using modified channel model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.11
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• pp.2238-2248
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• 1994

In this paper, we analyze a Microwave Amplifier Ultra-Wideband charateristic to apply Multi-Giga b/s optical receiver preamplifier in high speed optical communication system. To obtain frequency expanding effect. we analyze the frequency gain degradation effects of capacitances in the GaAs MESFET small-signal equivalent circuit and design Feedback amplifier Module(FAM) which has inductor peaking elements to compensate its effects and to expand frequency band. We derive optimum inductor peaking values in order to get flat gain in frequency band. The input and the output impedances of FAM are matched by Real Frequency Method and we design one and two stage ultra wideband microwave amplifier. With simulation results, it show $6.36\sim6.86dB$ and $9.1\sim10.3dB$ gains and execllent gain flatness in $0.5\sim12GHz$ respectively.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.3
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• pp.395-400
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• 2021

In this paper, the wideband patch antenna is simulated and manufactured for the wireless LAN of 5GHz band that is defined in IEEE 802.11a. In the 802.11a, 200 channels of 675MHz are defined. Therefore, the bandwidth is needed more than 12.3%. For the wideband characteristics, low dielectric constant is realized with the multi-layer of 2 teflon substrates and the air dielectric layer and the feeding method of the coupled-line is used. Optimized wideband patch antenna is simulated with the return loss of 38.99dB at the center frequency of 5.43GHz and the bandwidth of 12.9%. The gain of manufactured patch antenna is 4.38, 4.52, and 5.12dBi at the channel number of 46, 56, and 153, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.4
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• pp.305-313
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• 2013

As an FMT (Filtered Multi-Tone) transmission method of Wideband VHF communication system specified by the ETS (European Telecommunications Standards) EN 300 392-2, this paper introduces three existing realization methods, i.e., the direct filtering method using different band SRRC (Square-Root Raised Cosine) filters for each subcarrier, the PPN-DFT method using the IDFT-PPN (Poly-Phase Network) and PPN-DFT at the transmitter and receiver, respectively, and the Extended DFT method. Then, it proposes the extended IDFT-SDFT (Sliding Discrete Fourier Transform) that computes the DFT values only for interested subcarriers every sample time, and shows that it has an advantage of blind symbol timing (using no training symbol) individually for each user signal (independently of other users' signals) in the multi-user environment where the subcarriers are assigned in contiguous or interleaved blocks to each user and each user signal possibly experiences different channels.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.4
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• pp.449-456
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• 2012

Herein, we design a wideband $8{\times}8$ waveguide Butler matrix in order to use in a multi-port amplifiers(MPAs) at Ka-band. To achieve the broadband characteristic, we design a binomial 6-slot 3 dB directional coupler which is used to configure the $8{\times}8$ Butler matrix. The measured results of the fabricated $8{\times}8$ Butler matrix have low insertion loss of less than 0.3 dB, good return loss of over 26 dB and high isolation of over 35 dB within the design bandwidth of 3 GHz.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.1
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• pp.13-19
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• 2004

This paper demonstrates the detailed study of a microstrip Yagi-Uda antenna with and without PBG structure at wireless LAN(5725∼5825 MHz) frequency band. The impedance bandwidth of the antenna with the PBG holes is greater than (about 30 MHz) that of its counter part without PBG holes. The measured gains of the antenna at the frequency band are 7 dB and 6 dB respectively for antenna with and without PBG. The improvement of gain of about 1 dB is likely due to the suppression of surface wave.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.853-861
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• 2009

In this paper, we propose the architecture of a multi-band receiver which can receive X-band, Ku-band, K-band and Ka-band signals. For implementing this architecture, we designed a wideband and high power VCO with a buffer stage. In order that a buffer does not affect the characteristic of a oscillation in steady state condition, output impedance of a oscillation part and input impedance of a buffer are orthogonally crossed. The fabricated VCO meets the performance parameter of the multi-band receiver which has a $14.00{\sim}15.20\;GHz$ bandwidth with respect to the tuning voltage, $0.0{\sim}8.0\;V$, and output power of $12{\sim}13\;dBm$.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.4
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• pp.71-75
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• 2008

A folded monopole antenna is proposed for mobile communication applications. The proposed antenna covers CDMA and GSM at low frequency band, and it has a wide bandwidth (6.85 GHz) at high frequency band to cover GPS, DCS, USPCS, UHfS, WLAN (2.4, 5.2, 5.8 GHz), and the future application of IEEE 802.16e mobile WiMAX.

• The Journal of the Acoustical Society of Korea
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• v.39 no.2
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• pp.87-97
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• 2020

In this paper, the design of piezoelectric Micro-machined Ultrasonic Transducer (pMUT) for wideband ultrasonic radiation in air was investigated. One of the methods to achieve wide frequency bandwidth in single device is modeling the transducer to multi-resonance system. The new pMUT was designed as a multi-resonance system with the addition of a suitable acoustic structure to the front and back of a thin film structure. A new pMUT consisting of thin film parts, radiation parts, and packaging parts is designed with a Lumped Parameter Model (L.P.M). Finally, it was validated as a Finite Element Method (FEM) simulation. The final designed pMUT achieved a frequency band of 102 kHz ~ 132 kHz (-3 dB).

• Journal of Advanced Navigation Technology
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• v.9 no.1
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• pp.1-8
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• 2005

In this paper, an impulse generator for UWB(Ultra Wide-band) technique with great possibility to be adopted as a next generation indoor WLAN(Wireless Local Area Network) has been designed by using SRD(Step Recovery Diode). Design goal is to design an impulse generator with simple structure, low cost, small size, and high performance. The impulse generator satisfied by FCC's regulation ( frequency range: 3.1~10.6 GHz, limit of power level: -41.25 dBm ) has been simulated by using ADS(Advanced Design System) which is the trade name of the Agilent Technologies. The output power of the impulse generator has been explained separately for single and multi band purposes, respectively.