• Title/Summary/Keyword: direct spectrum

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PN Code Acquisition Technique using A Pre-Dump Correlation Energy in DS-SS Systems (직접대역확산 시스템에서 프리덤프 상관 에너지를 사용하는 PN코드 획득 기술)

  • Yeom, Soo-Nam;Lee, Seong-Joo
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.48 no.6
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    • pp.22-27
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    • 2011
  • This paper presents an efficient technique to reduce PN code acquisition time considerably by adjusting threshold values in direct sequence spread spectrum (DS-SS) systems. The proposed algorithm employs a pre-dump mode prior to a search mode, and the pre-dump mode determines threshold values of both search and verification modes depending on its correlation energy, which can improve not only the rejection performance of false code phases in the search mode but also that in the verification mode. The proposed method can reduce the mean code acquisition time by about 40% without increase of hardware costs compared with the conventional technique.

Mobility-Spectrum Analysis of an Anisotropic Material System with a Single-Valley Indirect-Band-Gap Semiconductor Quantum-Well

  • Joung, Hodoug;Ahn, Il-Ho;Yang, Woochul;Kim, Deuk Young
    • Electronic Materials Letters
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    • v.14 no.6
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    • pp.774-783
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    • 2018
  • Full maximum-entropy mobility-spectrum analysis (FMEMSA) is the best algorithm among mobility spectrum analyses by which we can obtain a set of partial-conductivities associated with mobility values (mobility spectrum) by analyzing magnetic-field-dependent conductivity-tensors. However, it is restricted to a direct band-gap semiconductor and should be modified for materials with other band structures. We developed the modified version of FMEMSA which is appropriate for a material with a single anisotropic valley, or an indirect-band-gap semiconductor quantum-well with a single non-degenerate conduction-band valley e.g., (110)-oriented AlAs quantum wells with a single anisotropic valley. To demonstrate the reliability of the modified version, we applied it to several sets of synthetic measurement datasets. The results demonstrated that, unlike existing FMEMSA, the modified version could produce accurate mobility spectra of materials with a single anisotropic valley.

The Seismic Response Evaluation of Shear Buildings by Various Approximate Nonlinear Methods (비선형 약산법들에 의한 전단형 건물의 지진응답평가)

  • Kim, Jae-Ung;Kang, Pyeong-Doo;Jun, Dae-Han
    • Journal of the Earthquake Engineering Society of Korea
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    • v.9 no.5 s.45
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    • pp.75-86
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    • 2005
  • In performance-based design methods, it is clear that the evaluation of the nonlinear response is required. Analysis methods available to the design engineer today are nonlinear time history analyses, or monotonic static nonlinear analyses, or equivalent static analyses with simulated inelastic influences. The nonlinear time analysis is the most accurate method in computing the nonlinear response of structures, but it is time-consuming and necessitate more efforts. Some codes proposed the capacity spectrum method based on the nonlinear static analysis to determine earthquake-induced demand. The nonlinear direct spectrum method is proposed and studied to evaluate nonlinear response of structures, without iterative computations, given by the structural linear vibration period and yield strength from pushover analysis. The purpose of this paper is to compare the accuracy and the reliability of approximate nonlinear methods with respect to shear buildings and various earthquakes. The conclusions of this study are summarized as follows: 1) Linear capacity spectrum method may fail to find a convergent answer or make a divergence. Even if a convergent answer is found, it has a large error in some cases and the error varies greatly depending on earthquakes. 2) Although nonlinear capacity spectrum method need much less calculation than capacity spectrum method and find an answer in any case, it may be difficult to obtain an accurate answer and generally large error occurs. 3) The nonlinear direct spectrum method is thought to have good applicability because it produce relatively correct answer than other methods directly from pushover curves and nonlinear response spectrums without additional and iterative calculations.

A study on Design and Performance Evaluation of the BCPFSK Modem (BCPFSK 모뎀 설계 및 성능 평가에 관한 연구)

  • 조형래;김경복
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.5 no.5
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    • pp.869-876
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    • 2001
  • In modern wireless communication, it has been regarded as a important problem for the spectrum efficiency to utilize the limited frequency-resource efficiently. In addition, the system architecture has been designed for low cost, low power consumption and ultra-lightweight. In this paper, we directly modulated the BCPFSK with a superior spectrum efficiency using the DDS and applied the direct conversion to the system architecture. Finally, we designed a transceiver which has the 433 MHz BCPFSK output and evaluated the system performance. In the measured result, we know that as for spectrum and the power efficiency, BCPFSK method is better than conventional one. Also, the results of the designed system is 433.92 MHz in center frequency and about 33 dBc in carrier suppression ratio. And we get the better results in local oscillator leakage and the spurious of the ISM out-band the same as -69dBc and under 60dBc.

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Sea trial results of long range underwater acoustic communication based on direct sequence spread spectrum transmission in the East Sea (동해에서 직접수열 대역확산 전송에 기반한 장거리 수중음향통신의 해상실험 결과)

  • Ra, Hyung-in;An, Jeong-ha;Youn, Chang-hyun;Kim, Ki-man;Kim, In-soo
    • The Journal of the Acoustical Society of Korea
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    • v.40 no.4
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    • pp.304-313
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    • 2021
  • This paper presents the results of a sea trial for long range underwater acoustic communication conducted in the East Sea in November 2020. Signals were collected through a moving transmitter and 16 vertically arranged receivers, and the range between the transmitter and receiver was about 20 km. The signal in the experiment is a conventional Direct Sequence Spread Spectrum (DSSS) method and a superimposed DSSS method that increases data rate by superimposing of multiple circulated Pseudo Noise (PN) sequences for each symbol. The results show that the uncoded bit error rate averaged over 16 channels to which the channel coding technique was not applied was 0.0005 for the conventional direct sequence spreading method, and was 0.00124 for the superimposed direct sequence spreading method.

A Study on Design and Performance Evaluation of the BCPFSK Modem Using the DDS (DDS를 이용한 BCPFSK모뎀 설계 및 성능 평가에 관한 연구)

  • 김경복;최정수;조형래
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2000.10a
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    • pp.166-171
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    • 2000
  • In modem wireless communication it has been regarded as a important problem for the spectrum efficiency to utilize the limited frequency-resource efficiently. In addition, the system architecture has bun designed for low cost, low power consumption and ultra-lightweight. In this paper, we directly modulated the BCPFSK with a superior spectrum efficiency using the DDS and applied the direct conversion to the system architecture. Finally, we designed a transceiver which has the 433 MHz BCPFSK output and evaluated the system performance.

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Construction of Spread Spectrum Power Line Communication Equipment Using Power Line Synchronization (전원동기를 이용한 스펙트럼 확산 전원선 통신장치의 구성)

  • 이동욱;변건식;김명기
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.15 no.6
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    • pp.475-484
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    • 1990
  • This paper proposes a method for the implementation of a power line communication equipment using power line synchronization in a direct-sequence spread spectrum communication system. In order to implement a network using a power line as a transmission channel we have investigated the utilization of direct-sequence speread spctrum which gives such advantages as robustness against narrow-band interference and noise, and realization of multiple access. In a power line, however, complexity of synchronization makes it difficult to realize a multiple access and cost down and system simplification. The proposed technique of power line synchronization makes it possible to get cost down and system size small, and the realization of multiple communication can be achieved by the addition of address setting circuit.

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Research on In-band Spurious Evasion Techniques of Hybrid Frequency Synthesizer

  • Kim, Seung-Woo;Yoo, Woo-Sung
    • Journal of IKEEE
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    • v.19 no.2
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    • pp.176-185
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    • 2015
  • The study aims to a design hybrid frequency synthesizer in spectrum analyzer and to propose new techniques designed for evasion of in-band spurious. The study focuses on calculating the exact location of multiple phase locked loop of hybrid frequency synthesizer and spurious of direct digital synthesizer to evade in-band spurious outside of frequency range that the user wants to see and thereby simulating technique to improve input related spurious of spectrum analyzer for algorithm. The proposed technique is designed to calculate spurious evasion algorithm in central processing system when in-band spurious arises, and to move output frequency of DDS(direct digital synthesizer) into the place where no in-band spurious exists thereby improving performance of frequency synthesizer. The study used simulation and result representation to prove the effectiveness of the proposed technique.

Direct Sequence Spread Spectrum Transmitter using FPGAs

  • Abhijit S. Pandya;Souza, Ralph-D′;Chae, Gyoo-Yong
    • Journal of information and communication convergence engineering
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    • v.2 no.2
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    • pp.76-79
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    • 2004
  • The DS-SS (Direct Sequence Spread Spec1nun) transmitter is part of a low data rate (∼150 kbps - burst rate and 64 bps - average data rate) wireless communication system. It is traditionally implemented using Digital Signal processing chip (DSP). However, with rapid increase in variety of services through cell phones, such as, web access, video transfer, online games etc. demand for higher rate is increasing steadily. Since the chip rate and thereby the sampling rate requirements of the system are fairly high, the transmitter should implemented using Field programmable Gate Arrays FPGAs instead of a DSP. This paper shows the steps taken to get a working prototype of the transmitter unit on a FPGA based platform.

Spectral Estimation of the Pass-by Noise of an Acoustic Source (등속 이동 음원의 통과소음 스펙트럼 추정에 관한 연구)

  • Lim Byoung-Duk;Kim Deok-Ki
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.12 s.243
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    • pp.1597-1604
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    • 2005
  • The identification of a moving noise source is important in reducing the source power of the transport systems such as airplanes or high speed trains. However, the direct measurement using a microphone running with noise source is usually difficult due to wind noise, white the source motion distorts the frequency characteristics of the pass-by sound measured at a fixed point. In this study the relationship between the spectra of the source and the pass-by sound signal is analyzed for an acoustic source moving at a constant velocity. Spectrum of the sound signal measured at a fixed point has an integral relationship with the source spectrum. Nevertheless direct conversion of the measured spectrum to the source spectrum is ill-posed due to the singularity of the integral kernel. Alternatively a differential equation approach is proposed, where the source characteristics can be recovered by solving a differential equation relating the source signal to the distorted measurement in time domain. The parameters such as the source speed and the time origin, required beforehand, are also determined only from the frequency-phase relationship using an auxiliary measurement. With the help of the regularization method, the source signal is successfully recovered. The effects of the parameter errors to the estimated frequency characteristics of the source are investigated through numerical simulations.