共查询到18条相似文献,搜索用时 109 毫秒
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刘建新 《工程物理研究院科技年报》2004,(1):228-228
脉问二相编码信号不仅满足脉冲多普勒雷达高度表的要求,而且在频域和时域具有较高的分辨率和测量精度,同时能够解决测距和测速模糊。除此之外,距离旁瓣和多普勒旁瓣亦可有效抑制。然而,脉间二相编码和传统的二相编码信号一样,该信号仍属于多普勒敏感信号。要实现对该类信号的匹配处理必须进行多普勒补偿。基于频域滤波、相干积累与相位补偿的一致性原理可采用图1的处理方法。 相似文献
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机载多脉冲激光雷达目标信号模拟器的研究 总被引:4,自引:0,他引:4
研究多脉冲激光雷达目标信号模拟器,用以评估回波数字信号处理算法及其实现平台的性能。结合信号能量与波形关系指出由激光雷达方程建立回波信号波形模型是不充分的。对空中目标回波脉冲展宽进行建模及数值仿真,得到不同倾角、目标距离及目标尺寸下的波形展宽时间数据。根据展宽前后能量保持不变的性质,利用高斯脉冲函数特征参数求解建立回波波形数学模型。基于目标距离误差及目标回波噪声统计特性建立回波仿真模型,提出了依信噪比发生回波观测信号的方法。对比两种模拟器的信噪比误差、最小模拟信噪比、连续工作时间等性能指标,总结了新型模拟器的优势。 相似文献
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由于线性调频信号(LFM)的线性时频调制规律,即其模糊度和Wigner-Ville分布(WVD)图象均具有线性峰脊特性,本文利用LFM信号的这一特性,用对其回波的互模糊度函数和WVD进行分析,着重讨论沿着斜脊方向进行后置积累的检测和识别多目标回波的性能,指出WVD后置积累的检测和分辨性能比通用匹配滤波器优越。 相似文献
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提出一种用于单载波数字相干光通信系统的自适应色散补偿方法.在发射机端,利用强度光调制器在光信号两侧加入脉冲幅度调制导频光信号.搜索信号谱的峰值确定光信号两侧的PAM-PTs线状谱.在色散估计之前,通过其中一个PAM-PTs的频率漂移来估计激光器发射频偏,并将信号谱线沿着频率轴反向平移,补偿发射频偏,实现信号谱频域均衡.在接收机端,利用幅度脉冲调制导频信号脉冲时延估计色散大小,在色散补偿之前通过幅度脉冲调制导频信号频移补偿,并消除接收机本振频偏对频域色散补偿的影响.最终,幅度脉冲调制导频的光场信息被充分用来精确进行色散估计和色散补偿.数值仿真表明:每次色散估计的误差小于±65ps/nm,而且距离从200km到1 000km之间的平均色散估计误差小于±10ps/nm.该方法色散补偿精度高,计算量小. 相似文献
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The technique of coherent echo processing in the approximation of a small number of point scatterers
In this paper, we aim at studying the structure of individual samples of coherent echo signals and determining signal features
that permit one to detect coherent backscatter and also improve the methods of signal processing. We offer a model of the
received signal in the form of a square pulse with duration of the order of the sounding pulse length and filled with a sinusoidal
signal of arbitrary frequency. It is shown that this model is quite effective to interpret coherent echo signals in some cases.
There are two ways of practical use of the model. One is a technique which singles out the sounding sessions in which strong
coherent echo signals are distinguished against the background of other signals received by the Irkutsk incoherent scatter
radar. Another is a technique of the spatial resolution improvement. 相似文献
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线性调频(LFM)信号目标的方位估计是水声探测研究的重要内容,在进行方位估计时,若存在强干扰信号源与强背景噪声,阵元接收信号的信噪比会显著降低,严重影响LFM信号目标方位估计结果的准确性.针对该问题,提出了一种简明分数阶滤波方法,并将其与常规波束形成方法(CBF)相结合来实现低信噪比条件下LFM信号目标的方位估计.简明分数阶傅里叶变换能在正交角度上将LFM信号的能量聚集在特定频点处并形成明显的能量峰,利用该特性,可对阵列各阵元接收的低信噪比LFM信号在简明分数阶域聚集的能量峰进行最佳滤波,以滤除干扰信息及背景噪声.对滤波输出进行逆简明分数阶傅里叶变换可得到增强信干比和信噪比的阵元域信号,进一步用于目标方位估计,就能获得更加准确的目标方位。数值仿真结果和海试实验数据处理结果验证表明,本文所提出的方法可有效抑制干扰和背景噪声,并对低信噪比LFM信号进行准确、稳健的方位估计。 相似文献
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水下回波处理中分数阶傅里叶变换的带通采样实现方法 总被引:1,自引:0,他引:1
利用球形压电陶瓷自身所具有的耐压能力,采用径向极化空气背衬压电球壳换能器作为声学接收敏感元件,设计并制作了一种球形耐压水听器。首先对其低频开路接收灵敏度和谐振频率等声学特性进行了分析和有限元仿真,然后对其强度和稳定性等耐压性能进行了分析和有限元仿真,最后对其声学性能和耐压能力进行了测试。测试表明,该球形耐压水听器的直径为36 mm,工作频段为50 Hz10 kHz,低频接收灵敏度为198:4 dB(0 dB=1 V/Pa),等效自噪声谱级为46.5 dB@1 kHz,其耐压深度可达3000 m。该耐压水听器为大深度水听器设计提供了参考,在深水声学领域具有重要的应用价值。 相似文献
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Acceleration target detection based on LFM radar 总被引:1,自引:0,他引:1
In radar systems, the echo signal caused by an accelerated target can be similarly considered as linear frequency modulation (LFM) signal. In high signal-to-noise ratio (SNR), discrete polynomial-phase transform (DPT) algorithm can be used to detect the echo signal, as it has low computation complexity and high real-time performance. However, in low SNR, the DPT algorithm has a large mean square error of the rate of frequency modulation and a low detection probability. In order to detect LFM signal in low SNR, this paper proposes a detection method, segment discrete polynomial-phase transform (SDPT), which means, at first, dividing the whole echo pulses into several segments with same duration in time domain, and then, using coherent accumulation method of DFT to segments, at last, processing this signal with DPT in intra-segment. In the case of a large number of segments, the SDPT can improve the output SNR. In addition, in a certain SNR, to the target signal with big sampling interval, large acceleration and less segments, this paper proposes an algorithm to detect the LFM signal generated from the combination of an improved DPT (IDPT) and fractional Fourier transform (FRFT). The output SNR of this algorithm is connected with the length of time delay. In the simulation, when the length of the time delay is 0.2 N, the output SNR is 2.5 dB more than that which results from directly using DPT. Finally, the detection performance and algorithm complexity of the proposed algorithm were analyzed, and the simulated and measured data verify the effectiveness of the algorithm. 相似文献
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提出一种基于互逆光纤色散的微波光子雷达系统设计方案,既可以产生宽带线性调频信号,又可以实现线性调频信号的光域脉冲压缩.在发射端利用互逆色散光纤产生线性调频信号.在接收端,雷达回波信号通过马赫-曾德调制器调制到预啁啾的光信号上,然后经过色散光纤的进一步色散.最终在探测器端可以得到目标回波信号脉冲压缩后的结果.该方案无需脉冲压缩过程中数字化和离线处理,且具有脉冲压缩比的调谐作用.理论、数值仿真和实验证明了该设计方案能有效进行线性调频信号的光域脉冲压缩.实验产生了C波段下时宽1.2ns,带宽3.2GHz的线性调频信号,并通过互逆色散光纤将该信号压缩到了0.09ns,脉冲压缩比达13.3. 相似文献
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Wang R Huang J Ma T Zhang Q 《The Journal of the Acoustical Society of America》2010,128(6):EL361-EL365
This letter presents an improved space time prewhitening method for linear frequency modulation (LFM) reverberation. The proposed method transforms the reverberation to fractional Fourier domain to whiten using fractional Fourier transform. The linear varying frequency in LFM reverberation is focused on a stationary frequency, and the adjacent block signal is used as the reference signal of prewhitening. Finally, experiment results with real reverberation data verify that the proposed method improves the detection performance of active sonar in shallow sea significantly. 相似文献
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为了提高超声波多普勒法测量复杂流体流量的精度,针对流体的超声回波频率的复杂性,本文研究多普勒流速测量中的频偏提取方法。以傅里叶分析为理论基础,设计了硬件电路并获得代表回波平均频率的信号,然后以该信号作为输入,以数字鉴频法获得回波多普勒频移。基于该方法设计了一种超声多普勒流量测量系统,实验结果显示:油水混合流体流量的测量误差在3%以内,从而证实了此频偏提取方法的有效性。 相似文献