• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1799-1806
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• 1991

The effect of an elastic intermediate support on the vibration characteristics of a fluid conveying pipe system modeled as simply-simply supported and fixed-fixed supported pipes has been investigated. The approach is based on solving the closed form equation of the 4th order polynomials. The change of natural frequency and critical velocity are also investigated with the fluid density, the fluid velocity, the position and stiffness of the elastic intermediate support varied. The results show that the vibration characteristics of pipe system could be controled by changing the position and/or stiffness of the elastic intermediate support.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.1
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• pp.50-55
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• 2011

In this paper, Intermediate frequency tunable 4th order Switched Capacitor(SC) bandpass Sigma-Delta(${\Sigma}-{\Delta}$) modulator using feedback integrator using feedback integrator coefficients is proposed. The center frequency of the modulator can be easily changed than conventional structure because of a number of integrator coefficients which is decided rate of capacitors in circuit is reduced. In addition additive clocks and additive clock generating circuit are not necessary. The purposed modulator was implemented in $0.18{\mu}m$ CMOS technology. The resolution of the modulator within 200 kHz bandwidth and 80 MHz sampling frequency under fin = 15 MHz, 20 MHz, 25 MHz are over 12 bit.

• Journal of the Korea Society of Computer and Information
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• v.7 no.4
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• pp.115-120
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• 2002

This paper presents the implementation of IS-95 CDMA signal processor, baseband and Intermediate Frequency(IF) digital converter using Field Programmable Gate Array(FPGA) and ADC/DAC and frequency up/down converter IS-95 CDMA channel processor is generated the pilot channel signal with short PN code and Walsh-code generator. The digital If is composed of FPGA. digital transmit/receive signal processor and high speed analog-to-digital converter(ADC) and digital-to-analog converter(DAC). The frequency up/down converter consisted of filter, mixer, digital attenuator and PLL is analog conversion between intermediate frequency(IF) and baseband. This implemented system can be deployed in the IS-95 CDMA base station device etc.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.951-954
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• 2001

본 논문에서는 SDR (Software Defined Radio)시스템을 위한 디지털 IF (Intermediate Frequency)수신기를 구현하였다[1][2]. 구현된 수신기의 하드웨어 구조는 AD변환부, PDC(Programmable Down Converter)부, DSP (Digital Signal Processing)부분으로 이루어졌다. AD변환부는 Analog Devices사의 AD6644를 이용하여 아날로그 신호를14bit의 디지털 신호로 변환된다. PDC부분은 Intersil사의 HSP 50214B를 이용하여 14bit 샘플 된 IF(Intermediate Frequency)입력을 혼합기와 NCO(Numerically Controlled Oscillator)에 의해 기저대역으로 다운 시키는 역할을 한다. PDC는 CIC (Cascaded Integrator Comb)필터, Halfband 필터 그리고 프로그램할 수 있는 FIR필터로 구성되어 있다. 그리고 PDC부분을 제어하고 PDC부분에서 처리할 수 없는 캐리어, 심볼 트래킹을 위해 Texas Instrument사의 16비트의 고정소수점 DSP인 TMS320C5416과 Altera사의 FPGA를 사용하였다. 그러므로 중간주파수 대역과 기저대역 간의 신호변환을 디지털 신호처리를 수행함으로써 일반적인 아날로그 처리방식보다 고도의 유연성과 고성능 동작이 가능하고 시간과 환경 변화에 우수한 동작 특성을 제공한다.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.417-420
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• 2001

In this paper, a transceiver using waveguide modules for 60 GHz band wireless LAN is implemented and analyzed. The characteristics of millimeter-wave transmitter are 0 dbm output power, 10.5 dB gain and 38 dBc spurious emition. The receiver's are 3.16 dB noise figure, 8.8 dB gain, -86dBm sensitivity. Maximum communication distance is more than loom. Intermediate frequency comply with IEEE 802.11b. The transfer of multimedia files is performed. The transceiver's data rate can vary with intermediate frequency bandwidth and the transceiver is designed more than 200 Mbps.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.349-356
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• 1998

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the three span continuous reinforced concrete bridge with elastic intermediate supports in presented. Such bridge represents either concrete or sandwich type three span bridge on polymeric supports for passive control or on actuators for active control. Any method may be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, In this paper. The influence of the modulus of the foundation and $D_{22}$, $D_{l2}$, $D_{66}$ stiffnesses on the natural frequency is thoroughly studied.d.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.341-348
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• 1998

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the subject problem is presented. The structure considered for this report is two span continuous special orthotropic plates with elastic intermediate support. The use of elastic support as one of the passive control means is common. Any method may be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purposa in this paper. The influence of the modulus of the foundation, and $D_{ij}$ stiffnesses on the natural frequency is thoroughly studied.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.220-223
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• 2000

A method of calculating the natural frequency corresponding to the modes of vibration of beams and tower structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the three span continuous reinforced concrete bridge with elastic intermediate supports is presented. Such bridge represents either concrete or sandwich type three span bridge on polymeric supports for passive control or on actuators for active control The concrete slab is considered as a special orthotropic plate. The influence of the modulus of the foundation and $D_{22}$, $D_{12}$, $D_{66}$ stiffnesses on the natural frequency is thoroughly studied.

• Journal of Positioning, Navigation, and Timing
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• v.3 no.3
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• pp.91-97
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• 2014

A direct RF sampling method refers to a technique that directly converts a passband signal to an intermediate band or a baseband without using a mixer. This method is less complicated than an existing RF receiver because a mixer is not used. It uses digital processing after sampling, and thus can flexibly process signals in a number of bands using software. In this process, it is important to select an appropriate sampling frequency so that a number of signals can be converted to an intermediate band that is easy to process. In this study, going beyond previously studied direct RF sampling frequency selection methods, conditions that need to be additionally considered during receiver design were examined, and the structure of a direct RF sampling receiver that satisfies these conditions was suggested.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.6
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• pp.608-615
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• 2008

Recently, research on GNSS signal receiver, aiding system and integrated navigation system approaching to the new satellite navigation system is needed. It it necessary to develop the GNSS simulator not only to understand the new satellite navigation system but also to develop the core technology about the system. In this paper, the simulator of the GPS and Galileo satellite nagivation is developed in IF(intermediate frequency) signal level.