共查询到17条相似文献,搜索用时 187 毫秒
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正交频分复用(OFDM)的原理及应用 总被引:7,自引:0,他引:7
OFDM是一种新型的调制方式,称为正交频分复用。阐述了OFDM的原理、系统组成和优良性质及其在数字电视传输和混合光纤电缆网(HFC)中的应用。 相似文献
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航空移动通信中OFDM信道估计方法的研究 总被引:3,自引:0,他引:3
正交频分复用(OFDM)由于其自身的技术优势使其在未来的航空移动通信中将占有重要地位,但航空移动通信中时变的信道环境和多普勒频移造成的严重的子载波之间干扰(ICI),使OFDM在航空移动通信中应用面临着困难。本文在建立航空移动通信通用信道模型的基础上,分析了ICI和噪声对信道估计的干扰机制,采用低通滤波和线性插值的方式对最小平方信道估计方法(LS)加以改进,抑制了ICI和信道噪声对LS〖JP2〗的干扰。经过仿真证明,该方法实现简单,精度高,抗ICI干扰和噪声能力强,满足了移动速度高达1 500 km/h的航空通信的要求。 相似文献
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针对目前的月面定位技术中成本高、观测时间长以及缺少可用定位信息的问题,开展了基于长期演进(LTE)基站的月面定位技术的研究,并引入了LTE技术,通过在月面布设基站为月面巡视器的实时定位提供了可行基础。提出了一种基于因子图优化的月面定位方法,通过融合月面基站的正交频分复用(OFDM)测距信息和巡视器自身的惯性导航信息,利用有限的月面基础设施,在较低成本的硬件条件下实现了月面巡视器的准确定位。仿真实验结果显示,该月面定位方法具有良好的准确性和鲁棒性。 相似文献
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在简要介绍OFDM系统模型的基础上,重点分析并仿真验证了COST 207标准TU衰落信道模型下,基于导频符号的频率选择性OFDM系统信道估计算法,包括块状导频下典型信道估计算法的性能比较,以及梳状导频下插值算法的性能分析比较。仿真结果验证了理论分析的正确性。 相似文献
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针对L波段数字航空通信系统(L-DACS1)反向链路测距仪(DME)信号干扰正交频分复用(OFDM)接收机的问题,提出基于联合压缩感知与接收分集的干扰抑制方法。在地面基站各接收支路中,首先通过压缩感知重构DME干扰信号,随后将重构的DME信号在时域进行干扰消除,消除干扰后各支路信号最终通过最大比值合并提高OFDM解调器输出信噪比,以克服测距仪残留信号的影响。仿真结果表明:该方法可有效抑制DME信号的干扰,提高L-DACS1系统的可靠性。 相似文献
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提出了分析自旋稳定目标RCS(雷达反射截面积)变化周期的FFT(快速傅里叶变换)模型,并分段对特定的多个同类型目标做了算例分析,显示出相对其他目标,自旋稳定目标在起旋前频谱能量主要集中在极低频(0.5Hz以下);在起旋后,除了在极低频部分有集中的能量,在某些频点附近可能会出现相对比较集中的能量。最后给出了该自旋稳定目标RCS变化周期的量化结果和适用性结论。 相似文献
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詹艳艳 《沈阳航空工业学院学报》2008,25(5)
正交频分复用技术(OFDM)具有良好的抗多途特性和带宽利用率高的特点.由于使用并行传输使数据传输速率大大提高,并且通过加循环前缀提高了抗多径干扰的能力,经多径时延信道传输后,接收端通过简单的信道编解码技术即可实现无符号间干扰接收.OFDM技术受到高速率数据传输系统的青睐,在水下通信中具有很好的应用前景. 相似文献
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A novel range-Doppler imaging algorithm with OFDM radar 总被引:1,自引:1,他引:0
《中国航空学报》2016,(2):492-501
Traditional pulse Doppler radar estimates the Doppler frequency by taking advantage of Doppler modulation over different pulses and usually it requires a few pulses to estimate the Doppler frequency. In this paper, a novel range-Doppler imaging algorithm based on single pulse with orthogonal frequency division multiplexing(OFDM) radar is proposed, where the OFDM pulse is composed of phase coded symbols. The Doppler frequency is estimated using one single pulse by utilizing Doppler modulation over different symbols, which remarkably increases the data update rate. Besides, it is shown that the range and Doppler estimations are completely independent and the well-known range-Doppler coupling effect does not exist. The effects of target movement on the performances of the proposed algorithm are also discussed and the results show that the algorithm is not sensitive to velocity. Performances of the proposed algorithm as well as comparisons with other range-Doppler algorithms are demonstrated via simulation experiments. 相似文献
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Carrier loop architectures for tracking weak GPS signals 总被引:8,自引:0,他引:8
Razavi A. Gebre-Egziabher D. Akos D.M. 《IEEE transactions on aerospace and electronic systems》2008,44(2):697-710
The performance of various carrier recovery loop architectures (phase lock loop (PLL), Doppler-aided PLL, frequency lock loop (FLL), and Doppler-aided FLL) in tracking weak GPS signals are analyzed and experimentally validated. The effects of phase or frequency detector design, oscillator quality, coherent averaging time, and external Doppler aiding information on delaying loss of lock are quantified. It is shown that for PLLs the metric of total phase jitter is a reliable metric for assessing low C/N performance of the tracking loop provided the loop bandwidth is not too small (~> 5 Hz). For loop bandwidths that are not too small, total phase jitter accurately predicts carrier-to-noise ratio (C/N) at which loss of lock occurs. This predicted C/N is very close to the C/N predicted by bit error rate (BER). However, unlike BER, total phase jitter can be computed in real-time and an estimator for it is developed and experimentally validated. Total phase jitter is not a replacement for BER, since at low bandwidths it is less accurate than BER in that the receiver loses lock at a higher C/N than predicted by the estimator. Similarly, for FLLs operating at small loop bandwidths, it is found that normalized total frequency jitter is not a reliable metric for assessing loss of lock in weak signal or low C/N conditions. At small loop bandwidths, while total frequency jitter may indicate that a loop is still tracking, the Doppler estimates provided by the FLL will be biased. 相似文献
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OFDM 系统的频率同步技术研究 总被引:1,自引:0,他引:1
频率偏差会导致 OFDM 系统的子载波间干扰,系统性能的下降.本文建立仿真模型,并对不同频率偏差对系统性能的影响进行了仿真研究.结合仿真分析,针对 LTE 下行 OFDM 系统中的频率同步技术给出了一种合适的同频偏估计和补偿的方案,仿真验证了其有效性和可行性 相似文献
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Jack M.A. Grant P.M. Collins J.H. 《IEEE transactions on aerospace and electronic systems》1977,(6):610-619
A prototype real time cepstrum analyzer incorporating surface acoustic wave (SAW), Fourier transform processors is reported. This system offers sophisticated wideband signal processing for radar, sonar, and communications applications. Practical results demonstrate its capabilities when analyzing bandwidths in excess of 10 MHz in a few microseconds with simulated pulsed RF waveforms in the presence of multipath echoes. Pulse duration, repetition interval, and binary code length are resolved and the potential to characterize unknown chirp waveforms is briefly reported. 相似文献