• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.699-705
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• 2001

It is considered DPSK modulation and the channel is modeled as multipath Nakagami fading type which has been recently taken as a general model in the communication environments in this paper. Most paper assumed that Nakagami fading index(m) of each branch of Rake receiver was fixed the same value in recent years. However, Nakagami fading index(m) of each branch of Rake receiver takes several value through communication environments. In this case, the branch ,which takes a small Nakagami fading index(m), exclude. So we can improve performance. We are considered phase error and analyzed wideband DS/CDMA cellular system. When nakagami fading index(m) takes voluntary value, we analyze BER of wideband DS/CDMA cellular system. Finally, When the branch, which takes a small Nakagami fading index(m), exclude, we analyze BER of wideband DS/CDMA cellular system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.86-89
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• 2009

In this paper, a broadband power line communication modem and network technology to develop tests with actual characteristics of the underground power line communication channel to be interpreted. Length and structure of the underground distribution line due to underground distribution line to the broadband powerline communication channels to measure the amount of attenuation on the signal generator, spectrum analyzer, such as contactless coupler was used to configure the channel measurement system. Demonstration tests in the test line as a single line by selecting the longest high-voltage lines where the two-channel measurement and signal attenuation on the noise level was measured. Measuring results degrade communication performance can be quite sure that was the presence of impulse noise, long lines, the line length was confirmed by the high-frequency attenuation appears.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1A
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• pp.28-34
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• 2011

In this paper, we proposed the architecture of the Hybrid Quadrature Polar transmitter which has the wideband characteristics available for the SRD(Short Range Device). First, we developed the simulation environment and carried out performance degradation analysis. Second, we considered the slewrate of the VVA(Voltage Variable Attenuator), time delay between magnitude signal and phase signal and the number of bits for DAC(Digital-to-Analog Converter) as the main performance factors. Then we obtained the minimum required values to meet the transmitting performance requirements of 3GPP standards through simulation results. Based on these results, we implemented the Wideband Hybrid Quadrature Polar transmitter platform and varified the performance requirements through practical measurement.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.12
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• pp.1529-1538
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• 1999

광대역 액세스 망은 B-ISDN 환경에서 다양한 유형의 가입자들을 서비스 노드로 집선하는 기능을 수행한다. ITU-T의 SG13에서는 광대역 액세스 망과 서비스 노드 사이에서 ATM 자원의 동적인 할당 및 해제를 위하여 연결 제어 프로토콜의 표준화를 수행하고 있다. ATM 연결의 설정을 위한 연결 제어 프로토콜과 신호 프로토콜의 연동 기능은 서비스 노드에서 수행되며, ITU-T에서는 순차적 연동 모델을 채택하고 있다. 순차적 연동 모델은 SN에서 각 프로토콜의 절차가 순차적 방식으로 연동되므로 연결 지연이 크다. 본 논문에서는 광대역 액세스 망의 도입으로 인한 연결 설정 지연을 최소화하기 위하여 병렬형으로 수행되는 연동 모델을 제시하였다. 그리고 본 논문에서 제안한 병렬형 연동 모델의 성능 분석을 통하여 순차적 연동 모델과의 연결 설정 지연 및 완료비에 대한 비교, 분석을 수행하였다. 성능 분석에서 사용된 워크로드 파라미터는 RACE MAGIC 프로젝트의 결과를 적용하였다. Abstract In B-ISDN environment, various subscribers are concentrated into a service node via a broadband access network. The SG13 of ITU-T is standardizing a connection control protocol which provides dynamic allocation of ATM resources between an access network and a service node. To establish an ATM connection, interworking functions between the connection control protocol and the signaling protocol are performed at the service node. ITU-T adopts the sequential interworking model. In this paper, we propose the parallel interworking model which minimizes the overall connection setup delay by introducing the access network. Using the performance analysis, we compare our proposed parallel model with the existing sequential model in terms of connection setup delay and completion ratio. The workload parameters of RACE MAGIC project are applied to the analysis and simulation.

• The Journal of the Korea Contents Association
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• v.6 no.4
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• pp.1-10
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• 2006

In this paper, a broadband RF module is designed and tested for 2.4GHz band applications. The RF module is composed of a low noise amplifier (LNA) with a three stage amplifier, a single ended gate mixer, matching circuits, a hairpin line band pass filter and a Chebyshev low pass filter to convert the radio frequency (RF) into the intermediate frequency (IF). The LNA has a high gain and stability, and the single ended gate mixer has a high conversion gain and wide dynamic range. In the analysis of the broadband RF module, the composite harmonic balance technique is used to analyze the operating characteristics of an RF module circuit. The RF module has a 55.2dB conversion gain with a 1.54dB low noise figure, $-120{\sim}-60dBm$ wide RF power dynamic range, -60dBm low harmonic spectrum and a good isolation factor among the RF, IF, and local oscillator (LO) ports.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.497-502
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• 2007

Broadband monolithic SiGe HBT variable gain amplifier with a feedforward configuration have been newly developed to improve bandwidth and dB-linearly controlled gain characteristics. The VGA has been implemented in a $0.35-{\mu}m$ BiCMOS process. The VGA achieves a dynamic gain-control range of 19.6 dB and a 3-dB bandwidth of 4 GHz ($4{\sim}8\;GHz$) with the control-voltage range from 0.6 to 2.6 V. The VGA produces a maximum gain of 9.3 dB at 6 GHz and a output power of -3 dBm at 8 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.384-393
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• 2013

In this paper, a design of planar microwave bias-tee using lumped elements was presented. The bias-tee is composed of 2 blocks; DC block and RF choke. For this design of the bias-tee, a wideband capacitor was used for DC block. For a RF choke, a series connection of inductors which have different SRFs is used for a RF choke. In the RF choke, a series connection of resistor and capacitor was added in shunt to eliminate a loss from a series resonance. The designed bias-tee was implemented by using 1608 SMT chip components. The fabricated bias-tee was measured using Anritsu 3680K fixture which enables to remove an effect of a connector. The fabricated bias-tee presented -15 dB of return loss and -1.5 dB insertion loss at 10 MHz~18 GHz.

• Journal of the Korean Society for Nondestructive Testing
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• v.37 no.1
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• pp.37-43
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• 2017

Ultrasonic transducers with high resolution and resonant frequency are required to detect small defects (less than hundreds of ${\mu}m$) by ultrasonic testing. The resonance frequency and resolution of an ultrasonic transducer are closely related to the thickness of piezo-electric materials, backing materials, and the electric impedance matching technique. Among these factors, electrical impedance matching plays an important role because it can reduce the loss and reflection of ultrasonic energy differences in electrical impedance between an ultrasonic transducer and an ultrasonic defects detecting system. An LC matching circuit is the most frequently used electric matching method. It is necessary for the electrical impedance of an ultrasonic transducer to correspond to approximately $50{\Omega}$ to compensate the difference in electrical impedance between both connections. In this study, a 15 MHz immersion ultrasonic transducer was fabricated and an LC electrical impedance circuit was applied to that for having broad-band frequency characteristic.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.4
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• pp.407-415
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• 2011

The stability condition and wideband characteristics of 3D ID-FDTD algorithm which has low dispersion error with isotropic dispersion are presented in this paper. 3D ID-FDTD method was proposed to improve the defect of the Yee FDTD such as the anisotropy and large dispersion error. The published paper calculated the stability condition of 3D ID-FDTD algorithm by using numerical method, however, it is thought that the examples were not sufficient to verify the stability condition. Thus, in this paper, various simulations are included in order to hold reliability under the conditions that the plane wave propagation is assumed with a single frequency and a wideband frequency. Also, the 3D ID-FDTD algorithm is compared to those that have the similar FDTD algorithm with ID-FDTD such as Forgy's method and non-standard FDTD method in a wideband. Finally, the radar cross section(RCS) for the large sphere with high dielectric constant is calculated.

• The Journal of the Acoustical Society of Korea
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• v.36 no.4
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• pp.238-246
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• 2017

High frequency ultrasound imaging typically suffers from low sensitivity due to the small aperture of high frequency transducers and shallow imaging depth due to the frequency-dependent attenuation of ultrasound. These limitations should be overcome to obtain high-frequency, high- resolution ultrasound images. One practical solution to the problems is a high-performance signal receiver capable of detecting a very small signal and amplifying the signal with minimal electronic noise addition. This paper reports a recently developed low-noise, wideband ultrasound receiver for high-frequency, high-resolution ultrasound imaging. The developed receiver has an amplification gain of up to 73 dB and a variable amplification gain range of 48 dB over an operating frequency of 80 MHz. Also, it has an amplification gain flatness of ${\pm}1dB$. Due to these high performances, the developed receiver has a signal-to-noise ratio of at least 8.4 dB and a contrast-to-noise ratio of at least 3.7 dB higher than commercial receivers.