• Title/Summary/Keyword: 코드위상

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Performance Analysis of Modulator using Direct Digital Frequency Synthesizer of Initial Clock Accumulating Method (클록 초기치 누적방식의 직접 디지털 주파수 합성기를 이용한 변조기의 성능해석)

  • 최승덕;김경태
    • Journal of the Korean Institute of Telematics and Electronics T
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    • v.35T no.3
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    • pp.128-133
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    • 1998
  • This paper is study on performance analysis of modulator using direct digital frequency synthesizer of Initial Clock Accumulating Method. It has been generally used for PLL or digital frequency synthesizing method to be synthesizd randomly chosen frequency state. In order to improve disadvantage of two methods, we constructed modulator system using DDFS of Initial Clock Accumulating Method. We also confirmed the coherence frequency hopping state and possibility of phase control. The results obtained from the experiments are as follows; First, the synthesized output frequency is proportional to the sampling frequency, according to index, K. Second, the difference of the gain between the basic frequency and the harmonic frequencies was more than 50 [dB], that is, this means facts that is reduced the harmonic frequency factor. Third, coherence frequency hopping state is confirmed by PN code sequence. Here, we confirmed the proposed method cut switching time, this verify facts that is the best characteristic of the frequency hopping. We also verified the fact that the phase varies as the adder is operated set or reset.

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A Fully Integrated Ku-band CMOS VCO with Wide Frequency Tuning (Ku-밴드 광대역 CMOS 전압 제어 발진기)

  • Kim, Young Gi;Hwang, Jae Yeon;Yoon, Jong Deok
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.12
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    • pp.83-89
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    • 2014
  • A ku-band complementary cross-coupled differential voltage controlled oscillator is designed, measured and fabricated using $0.18-{\mu}m$ CMOS technology. A 2.4GHz of very wide frequency tuning at oscillating frequency of 14.5GHz is achieved with presented circuit topology and MOS varactors. Measurement results show -1.66dBm output power with 18mA DC current drive from 3.3V power supply. When 5V is applied, the output power is increased to 0.84dBm with 47mA DC current. -74.5dBc/Hz phase noise at 100kHz offset is measured. The die area is $1.02mm{\times}0.66mm$.

Design of a tracking and demodulation circuit for wideband DDMA in IMT-2000 (IMT-2000 광대역 CDMA의 동기추적 및 데이터 복조 회로구현)

  • 권형철;오현서;이재호;조경록
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.6A
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    • pp.871-880
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    • 1999
  • In this paper, a pseudo-noise(PN) tracking and demodulation circuits are analyzed and designed for a direct-sequence/spread-spectrum multiple access system under a mobile fading channel. We consider noncoherent delay locked loop(DLL) as a PN code tracking loop which has 1/8 PN chip resolution. The tracking performance of DLL is evaluated in terms of locking time from a loose state and tracking jitter. The received signal is demodulated to original data by despreading with PN code locked by DLL. Also the designed circuit supports sound service of 32Kbps and in-band signal with 4.096MHz chip clock. The circuits are implemented and verified with FPGA, which is shown completely data recovery under AWGN 7dB and will be available for IMT-2000.

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THE IMPROVEMENT OF THE RELATIVE POSITIONING PRECISION FOR GPS L1 SINGLE FREQUENCY RECEIVER USING THE WEIGHTED SMOOTHING TECHNIQUES (가중 평활화 기법을 이용한 GPS L1 단일 주파수 수신기의 상대 측위 정밀도 향상)

  • Choi, Byung-Kyu;Park, Jong-Uk;Joh, Jeong-Ho;Lim, Hyung-Chul;Park, Phi-Ho
    • Journal of Astronomy and Space Sciences
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    • v.21 no.4
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    • pp.371-382
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    • 2004
  • To improve the precision of relative positioning for GPS single frequency(L1) receiver, we accomplished the GPS data processing using the weighted smoothing techniques. The weighted phase smoothing technique is used to minimize the measurement error of pseudorange and position domain smoothing technique is adopted to make the complement of cycle-slip affection. we also considered some component errors like as ionospheric error, which are related with baseline length, and processed for several baselines (5, 10, 30, 40, and 150 km) to check the coverage area of this algorithm. This paper shows that weighted phase smoothing technique give more stable results after using this technique and the position domain smoothing technique can reduce the errors which are sensitive to the observational environment. Based on the results, we could find out that this algorithm is available for post-time and real-time applications and these techniques can be substitution methods which is able to get the high accuracy and precision without resolving the Integer ambiguity.

Numerical Analysis on Aerodynamic Performances and Characteristics of Quad Tilt Rotor during Forward Flight (전진 비행하는 쿼드 틸트 로터의 공력성능 및 특징에 대한 수치적 연구)

  • Lee, Seonggi;Oh, Sejong;Choi, Seongwook;Lee, Yunggyo;Park, Donghun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.3
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    • pp.197-209
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    • 2018
  • In this study, numerical analyses on Quad Tilt Rotor(QTR) are carried out to investigate the interference effect of components and effect of operating condition during forward flight. Actuator Surface Method(ASM) which is implemented in an open source CFD code, OpenFOAM, is used to calculate the flow field around QTR with high computational efficiency. The lift of the front and rear wing is found to increase or decrease depending on the rotation direction of the rotor. At the rear wing, the interference effects of the front and rear rotor appear as a combined manner. Performance change due to the phase difference is found to be insignificant. For both rotors, the locally higher thrust is generated by the blockage effect of the wing. The interference effect of wake from the front nacelle contributes to higher local thrust for the rear rotor compared to the front rotor. And it is observed that the amplitude of thrust oscillation can decrease depending on the phase difference between the rotors. Aerodynamic performances of both rotors and the entire aircraft were compared and analyzed for various operating conditions.

Development of the IRIS Collimator for the Portable Radiation Detector and Its Performance Evaluation Using the MCNP Code (IRIS형 방사선검출기 콜리메이터 제작 및 MCNP 코드를 이용한 성능평가)

  • Ji, Young-Yong;Chung, Kun Ho;Lee, Wanno;Choi, Sang-Do;Kim, Change-Jong;Kang, Mun Ja;Park, Sang Tae
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.13 no.1
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    • pp.55-61
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    • 2015
  • When a radiation detector is applied to the measurement of the radioactivity of high-level of radioactive materials or the rapid response to the nuclear accident, several collimators with the different inner radii should be prepared according to the level of dose rate. This makes the in-situ measurement impractical, because of the heavy weight of the collimator. In this study, an IRIS collimator was developed so as to have a function of controlling the inner radius, with the same method used in optical camera, to vary the attenuation ratio of radiation. The shutter was made to have the double tungsten layers with different phase angles to prevent the radiation from penetrating owing to the mechanical tolerance. The performance evaluation through the MCNP code was conducted by calculating the attenuation ratio according to the inner radius of the collimator. The attenuation ratio was marked on the outer scale ring of the collimator. It is expected that when a radiation detector with the IRIS collimator is used for the in-situ measurement, it can change the attenuation ratio of the incident photon to the detector without replacing the collimator.

Electrical Characteristics Measurement of Eddy Current Testing Instrument for Steam Generator in NPP (원전 증기발생기 와전류검사 장치의 전기적 특성 측정)

  • Lee, Hee-Jong;Cho, Chan-Hee;Yoo, Hyun-Joo;Moon, Gyoon-Young;Lee, Tae-Hun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.33 no.5
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    • pp.465-471
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    • 2013
  • A steam generator in nuclear power plant is a heatexchager which is used to convert water into steam from heat produced in a nuclear reactor core, and the steam produced in steam generator is delivered to the turbine to generate electricity. Because of damage to steam generator tubing may impair its ability to adequately perform required safety functions in terms of both structural integrity and leakage integrity, eddy current testing is periodically performed to evaluate the integrity of tubes in steam generator. This assessment is normally performed during a reactor refueling outage. Currently, the eddy current testing for steam generator of nuclear power plant in Korea is performed in accordance with KEPIC & ASME Code requirements, the eddy current testing system is consists of remote data acquisition unit and data analysis program to evaluate the acquired data. The KEPIC & ASME Code require that the electrical properties of remote data acquisition unit, such as total harmonic distortion, input & output impedance, amplifier linearity & stability, phase linearity, bandwidth & demodulation filter response, analog-to-digital conversion, and channel crosstalk shall be measured in accordance with the KEPIC & ASME Code requirements. In this paper, the measurement requirements of electrical properties for eddy current testing instrument described in KEPIC & ASME Code are presented, and the measurement results of newly developed eddy current testing instrument by KHNP(Korea Hydro & Nuclear Power Co., LTD) are presented.

Performance Analysis of a CE-CPSK modulated code acquisition system for nonlinear amplified DS-CDMA signal (비선형 전력증폭기로 인한 CE-CPSK 변조된 DS-CDMA 초기동기 시스템의 성능분석)

  • Kim Seong-Cheol
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.1
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    • pp.49-56
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    • 2006
  • In this paper, to overcome the effect of nonlinear power amplifier, CE-CPSK(Constant Envelope Continuous Phase Shift Keying)modulation method which has the constant envelope and continuous phase characteristics is proposed. The code acquisition performances of the CE-CPSK modulated system and BPSK system are analyzed. And the performance is evaluated in terms of mean acquisition time and detection probability with the output backoff of the amplifier in multiuser environment. Results performed in a channel having a high degree of AM nonlinearity(AM-to-AM conversion), have shown that the CE-CPSK signal, when passed through class C-nonlinear Amplifier, has a spectrum with greatly reduced sidelobes compared to the conventional BPSK signal. The code acquisition performance of a CE-CPSK modulation system is better than that of BPSK system with nonlinear amplified multiuser environments.

A Novel BOC(n,n) Correlation Function for Maritime Satellite Communications (해양 위성 통신을 위한 BOC(n,n) 신호의 새로운 상관함수)

  • Lee, Youngseok;Lee, Seong Ro;Yoon, Seokho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38C no.3
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    • pp.296-302
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    • 2013
  • The binary offset carrier (BOC) modulation has attracted much attention as a new physical layer implementation for satellite communication and global navigation satellite systems. In this paper, we propose a new correlation function for sine-phased BOC signals. Specifically, we separate a sub-carrier pulse into several rectangular pulses, and then, generate a number of partial correlation functions. Finally we combine the partial correlation functions to yield an unambiguous correlation function with no side-peak. From numerical results, it is demonstrated that the proposed correlation function provides a significant tracking performance improvement over the conventional correlation functions.

Carrier phase recovery algorithm for LDPC coded system (LDPC 코드를 이용한 위상 동기 알고리즘)

  • Lee Juhyung;Kim Namshik;Park Hyuncheol;Kim Pansu;Oh Dukgil;Lee Hojin
    • Proceedings of the IEEK Conference
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    • 2004.06a
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    • pp.43-46
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    • 2004
  • In this paper, we present a carrier phase estimation algorithm for LDPC coded systems. LDPC coded system can not achieve the ideal performance if phase offset is introduced by channel. However, the estimation of phase offset is very hard since the operating point of LDPC is very low SNR. To solve this problem, the algorithm using the tentative soft decision value and based on Maximum Likelihood (ML), was proposed in [2]. But this algorithm has problem which works only under constant phase offset. If phase offset is time variant, it has a severe degradation in performance. To solve this problem. we propose two types of estimators. symbol by symbol estimator: Unidirectional estimator (UDE) and hi-directional estimator (BDE), and sub-block estimator (SBE).

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