• Title/Summary/Keyword: coherent system

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A Comparison with SNR Performance of Coherent Integration and Non-coherent Integration to Estimate Target Detection Range in Radar System (레이더 시스템에서 목표물 탐지 거리 추정을 위한 코히런트 집적과 비 코히런트 집적의 SNR 성능 비교)

  • Ga, Gwan-U;Ham, Sung-Min;Lee, Kwan-Hyeong
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.7 no.2
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    • pp.86-91
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    • 2014
  • This paper compare with SNR performance of coherent integration and non-coherent integration in radar system. This paper to prevent distortion of transmit signal and radar return in radar system is used to pulsed waveform. This paper to estimate target detection range and to compare with SNR performance used to coherent integration performed before the envelope detector and non-coherent integration processed after the envelope detector. Through simulation, SNR performance of coherent integration and non-coherent integration were comparatively analyzed. SNR performance of coherent integration is good proof higher than non-coherent integration.

A Study on Target Direction and Rage Estimation using Radar Single Pulse (레이더 단일 펄스를 이용한 목표물 방향과 거리 추정에 대한 연구)

  • Lee, Kwan-Hyeong
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.14 no.6
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    • pp.107-112
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    • 2014
  • In this paper, we analysed a performance signal to noise ratio about pulse, integration coherent, and integration non coherent system in radar system. It compared existing with proposal method in order to estimation two target direction of arrival. Generally, radar system radiate pulse wave in order to decreasing distortion of return wave and transmission wave. We analysed the performance integration coherent and integration non coherent. Integration coherent is processing system before doing envelop detection, and integration non coherent is processing system after doing envelop detection. Through simulation, we analysed a performance signal to noise ratio to estimation two target range detection and estimated target direction of arrival. We showed that integration coherent system is the most good performance.

Research on the Influence of Polarization Aberration on Heterodyne Efficiency in Space Coherent Laser Communication System

  • Zheng, Yang;Piao, Yu
    • Current Optics and Photonics
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    • v.6 no.1
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    • pp.23-31
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    • 2022
  • Heterodyne efficiency is an indicator to evaluate the performance of space coherent laser communication systems. It is affected by signal light and local oscillator (LO) light amplitude, phase and polarization state. In this paper, based on the common heterodyne efficiency, a heterodyne efficiency model that can reflect polarization aberration of optical system is proposed. The heterodyne efficiency is analyzed when the signal light and the LO light are linearly polarized or circularly polarized. For a coherent communication optical system, when the incident signal light is right-circularly polarized light and the incident LO light is 45° linear polarized light. Based on the three-dimensional ray tracing theory and the heterodyne efficiency proposed in this paper, the change of polarization states and the distribution of heterodyne efficiency of the signal light and LO light influenced by the optical system's polarization aberration are analyzed. Analysis shows that the heterodyne efficiency model proposed in this paper can be used to evaluate coherent communication systems and reflect the influence of optical system polarization aberration.

Performance Comparison of Coherent and Non-Coherent Detection Schemes in LR-UWB System

  • Kwon, Soonkoo;Ji, Sinae;Kim, Jaeseok
    • Journal of Communications and Networks
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    • v.14 no.5
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    • pp.518-523
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    • 2012
  • This paper presents new coherent and non-coherent detection methods for the IEEE 802.15.4a low-rate ultra-wideband physical layer with forward error correction (FEC) coding techniques. The coherent detection method involving channel estimation is based on the correlation characteristics of the preamble signal. A coherent receiver uses novel iterated selective-rake (IT-SRAKE) to detect 2-bit data in a non-line-of-sight channel. The non-coherent detection method that does not involve channel estimation employs a 2-bit data detection scheme using modified transmitted reference pulse cluster (M-TRPC) methods. To compare the two schemes, we have designed an IT-SRAKE receiver and a MTRPC receiver using an IEEE 802.15.4a physical layer. Simulation results show the performance of IT-SRAKE is better than that of the M-TRPC by 3-9 dB.

Pulse Repetition Based Selective Detection Scheme for Coherent IR-UWB Systems (Coherent IR-UWB 시스템을 위한 펄스 반복 전송 기반의 선택적 검출 기법)

  • Kim, Se-Kwon;Kim, Jae-Woon;Shin, Yo-An
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.45 no.3
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    • pp.19-26
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    • 2008
  • We propose a selective detection scheme based on pulse repetition considering the BER (Bit Error Rate) performance and complexity of coherent IR-UWB (Impulse Radio-Ultra Wide Band) systems. To take system complexity into account, the proposed scheme transmits the UWB signals by pulse repetition at the transmitter, like conventional PRC (Pulse Repetition Coding). However, to effectively improve BER performance of the system, the proposed scheme performs selective detection by estimating the SNR (Signal-to-Noise Ratio) of the received pulse-repeated signal at the UWB receiver. Hence, the proposed scheme effectively improves BER performance of the coherent IR-UWB systems without increasing system complexity, as compared to the conventional PRC algorithm.

A Comparison on Coherent Integration and Non-coherent Integration to Estimate Detection Range about Radar Cross Section in Radar System (레이더 시스템에서 레이더 단면적에 따른 탐지 거리 추정을 위한 코히런트 집적과 비 코히런트 집적에 대한 비교)

  • Ham, Sung-min;Ga, Gwan-u;Lee, Kwan-hyeong
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.7 no.2
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    • pp.100-105
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    • 2014
  • This paper comparatively analyze to integration case to have a influence detection range estimation about radar cross section in radar system. This paper estimate detection range used to probability of detection in radar equation that used to swerling case 1 in case of radar cross section is small and used to swerling case 3 in case of radar cross section is large. Through simulation, coherent integration and non-coherent integration about swerling case difference were comparatively analyzed. Through simulation, non-coherent integration case is outstanding detection range and we known that coherent integration don't suitable for detection range estimation.

An Optical Asynchronous Transfer Mode(ATM) Switching System Using Free Space Optics and an Output Buffer Memory (자유공간 광학과 출력 버퍼 메모리를 이용한 광 Asynchronous Transfer Mode(ATM) 교환방식)

  • 지윤규;이상신
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.16 no.4
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    • pp.326-334
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    • 1991
  • We propose an optical Asynchronous Transfer Mode(ATM) switching system using free-space optics and an output buffer memory. The distributor system in the switching fabric was analyzed using the Huygens-Fresnel principle and lens transformation. For monochromatic illumination, a pattern similar to the Fourier transform of the input distribution was observed across the output plane. A spatially broadened intensity distribution across the the output plane can be expected when the system is illminated with a partially coherent, quasimonochromatic beam. Spatially coherent pulses as short as 100fs can propagate through the distributor without severe spatial broadening.

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Experimental Study of Large-amplitude Wavefront Correction in Free-space Coherent Optical Communication

  • Guo, Qian;Cheng, Shuang;Ke, Xizheng
    • Current Optics and Photonics
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    • v.5 no.6
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    • pp.627-640
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    • 2021
  • In a free-space coherent optical communication system, wavefront distortion is frequently beyond the correction range of the adaptive-optics system after the laser has propagated through the atmospheric turbulence. A method of residual wavefront correction is proposed, to improve the quality of coherent optical communication in free space. The relationship between the wavefront phase expanded by Zernike polynomials and the mixing efficiency is derived analytically. The influence of Zernike-polynomial distortion on the bit-error rate (BER) of a phase-modulation system is analyzed. From the theoretical analysis, the BER of the system changes periodically, due to the periodic extension of wavefront distortion. Experimental results show that the BER after correction is reduced from 10-1 to 10-4; however, when the closed-loop control algorithm with residual correction is used, the experimental results show that the BER is reduced from 10-1 to 10-7.

Quantum Interference Effects on Optical Amplification and the Index of Refraction in a Four-Level System

  • Zhang, Hui-Fang;Wu, Jin-Hui;Gao, Jin--Yue
    • Journal of the Optical Society of Korea
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    • v.7 no.3
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    • pp.174-179
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    • 2003
  • We construct a four-level system where a metastable state is included in an $Er^{3+}$ Doped Yttrium aluminum garnet (YAG) crystal. Because of the action of the coherent field, the traditional light amplification with inversion can be exhibited with remarkable variation. As a result, we propose a method to achieve the gain equalization by atomic coherence. At the same time, we find that the high index of refraction accompanied by vanishing absorption can also be reached in this model. We also find that a higher index of refraction with zero absorption can be easily obtained when the coherent field is off resonance.

Design and Noise Figure Analysis of Coherent Transceiver for Airborne Radar (비행탑재용 레이다의 코히어런트 송수신단 설계 및 잡음지수 해석)

  • Woo, Duk-Jae;Kim, Sang-Joong;Lee, Taek-Kyung
    • Journal of Advanced Navigation Technology
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    • v.8 no.1
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    • pp.38-47
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    • 2004
  • To achieve functions of doppler measurement, MTI(Moving Target Indicator), high-resolution, and others in radar system, all circuits of transmitter and receiver are to be performed in coherent system. In this paper, we use TWTA(Traveling Wave Tube Amplifier), STALO(Stable Local Oscillator) and COHO(Coherent Oscillator) to design of coherent radar transceiver, and calculates noise figure of designed receiver. Using radar equation calculated noise figure, maximum detecting range of each transmitting mode can be calculated.

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