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星载SAR距离模糊分布规律及其改进设计 总被引:1,自引:0,他引:1
本文提出了一种不加大天线尺寸而又使距离模糊满足要求的新方法,它能够在保持原有天线尺寸不增大的情况下实现宽测绘带的高质量成象。这种方法采用交替发射线性调频斜率完全相反的调频信号,在对回波信号进行距离压缩时,由于主要模糊区回波信号与参考函数失配就被大大地抑制,从而使距离模糊大大改善并得到较宽的测绘带。 相似文献
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本文提出一种临近空间高分辨率宽测绘带快速重复访问模式。发射天线采用线性相控阵列天线,结合合适的接收天线模式,共形成一个主瓣两个栅瓣,对同一成像区域快速重复访问。在方位向高分辨率及距离向宽测绘带的要求下,各子波束方位向回波在方位时域及频域均存在混叠。本文提出一种多通道多子波束重建算法,以对方位向各子波束回波进行分离。采用非线性调频尺度算法对分离后各子波束回波进行成像。并对各子图像的成像性能参数进行研究。本文给出了一个系统设计示例。实验仿真结果表明,本文提出的成像模式及所提出的信号处理流程正确有效。计算所得性能参数表明,各子图像质量可满足实际应用的要求。 相似文献
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传统步进频率波形不模糊距离窗大小受载频步进量制约,将会导致距离像混叠等问题.针对此问题,基于压缩感知理论,研究了一种随机稀疏调频步进信号距离像抗混叠方法.首先对子脉冲进行脉压(Dechirp)处理,将处理后的回波信号看作为具有等效带宽线性调频信号回波的量测数据;其次根据子脉冲随机发射方式构造相应的量测矩阵,得到随机稀疏调频步进信号的压缩感知重构模型,并采用压缩感知重构算法得到高分辨一维距离像.最后,对该方法不模糊距离窗大小进行了分析,并给出了影响不模糊距离窗大小的因素和参数设置原则.所研究方法通过将随机稀疏调频步进信号的距离像合成处理等效为LFM信号的距离像合成过程,既降低了载频步进量对不模糊距离窗大小的限制,克服了距离像混叠问题,又提高了距离像合成性能.仿真实验进一步验证了本文方法的有效性. 相似文献
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一种LFMCW雷达多目标距离-速度配对新方法 总被引:1,自引:1,他引:0
针对线性调频连续波雷达双差拍-傅里叶处理中的多目标配对问题,提出了一种新的多目标距离-速度联合配对法。文中分析了连续波与线性调频连续的雷达回波频谱,描述了雷达系统工作原理;然后,利用单载频回波信号测量多目标的不模糊速度,同时利用锯齿调频波测量多目标的不模糊距离与模糊速度;最后,结合距离-速度配对的方法,实现多目标的配对。仿真结果验证了方法的有效性。 相似文献
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根据线性调频脉冲及其匹配滤波器的时域和频域特性,首先从原理上分析了线性调频雷达脉冲回波信号由于多普勒距离耦合的影响,经过匹配滤波器后产生附加延时而引起的测距误差.然后给出了距离多普勒耦合的雷达距离修正公式,并通过仿真和雷达实际跟踪数据对雷达距离修正公式进行了验证.最后给出了工程应用中校正脉压网络固定延迟、脉压网络输入端线性调频脉冲信号多普勒频率的变化以及正或负斜率线性调频脉冲信号等方面应注意的问题. 相似文献
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荆麟角 《电子科学学刊(英文版)》1995,12(2):160-167
A new approach is proposed which can satisfy the range ambiguity requirement while keep the antenna width not to be enlarged and get the high quality image also. Here the chirp slope of the transmitted linear frequency modulated pulses is reversed alternately. Therefore, during the range compression significant portion of the ambiguous return which is due to the mismatching with the signal reference function is suppressed. The suggested method provides significant improvement in range ambiguity ratio and can be utilized in attaining wider swath. 相似文献
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The presence of stray signals in an antenna measurement range can cause errors in the measured patterns. In order to measure low sidelobe antennas in an antenna range, the stray signals in the range should be very small (at least 8-10 dB below the sidelobe level). It may not be possible to achieve such low level stray signals in a real world antenna range. Thus, alternate methods for reducing these measurement errors are needed. In this paper, such a method is presented. Using simulated examples and experimental data, it is shown that this method significantly reduces the chamber related measurement errors. The method can also be used to identify the angular regions along which the stray signal errors are most significant. Thus, the range can be qualified and, if possible, improved 相似文献
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距离模糊一直是影响合成孔径雷达(SAR)成像质量的重要因素之一。方位向相位编码(APC)技术是一种有效抑制距离模糊的方法,但是由于APC技术高度依赖于高过采样率,对于多通道SAR系统,APC技术的距离模糊抑制效果很有限。该文提出一种新的基于APC技术的多通道系统距离模糊抑制方法。该方法首先通过APC技术将部分距离模糊信号产生方位平移,通过额外增加接收通道数提供的额外信号自由度,能够在方位向上通过合适的数字波束形成(DBF)技术同时滤去距离模糊和重建方位向信号,因此距离模糊信号可以被很好地抑制。该文最后给出仿真结果,证明该方法的有效性。 相似文献
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Ishtiaq Rasool Khan 《Signal, Image and Video Processing》2016,10(5):921-926
Two-layer schemes provide an effective method of encoding high dynamic range images with backward compatibility. The first layer is the tone-mapped low dynamic range version of the original image, used for visualization. The residual information that cannot be preserved in the first layer is stored in the second layer, which itself is generally encoded as an image of a fixed bit-depth. Any further details that cannot be preserved in the second layer are discarded. In this paper, we present a nonlinear quantization algorithm that can significantly enhance the amount of details that can be preserved in the second layer, and therefore improve the encoding efficiency. The proposed technique can be incorporated in any existing two-layer encoding method and leads to significant improvement in their performance. 相似文献
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Hsueh-Jyh Li Yung-Deh Wang Long-Huai Wang 《Antennas and Propagation, IEEE Transactions on》1996,44(4):444-452
In this paper, how the statistical properties of the matching scores are affected by the carrier frequency, the aspect variation, the range resolution, and the target complexity are studied. The statistical parameters (mean and standard deviation) of the matching scores among range profiles of independent objects are derived, and their values are used as references to determine the threshold values for target identification. It is found that the range profile obtained at a certain carrier frequency can also be used as the feature vector for radars operated at shifted frequencies if the range resolution is fine enough or the target is simple. It is also found that a radar with higher range resolution can tolerate more aspect variation, yielding a significant advantage in saving memory space for establishing the data base. The results obtained can have several applications such as target identification, data association in multiple target tracking, and target direction determination when widely-spaced high-resolution radars are employed 相似文献
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《Circuits and Systems II: Express Briefs, IEEE Transactions on》2009,56(2):147-151
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Starikov E. Shiktorov P. Gruzinskis V. Reggiani L. Varani L. Vaissiere J.C. Zhao J.H. 《Electron Devices, IEEE Transactions on》2001,48(3):438-443
The linear and nonlinear analysis of microwave power amplification and generation in the terahertz (THz) frequency range is carried out by the Monte Carlo method in bulk wurtzite GaN. It is shown that a dynamic negative differential mobility persists up to 80 K due to the transit-time resonance associated with optical phonons. The generation frequency depends almost linearly on the static electric field strength and can be tuned in the wide frequency range from 0.2 to 3 THz when the electric field varies from 1 up to 12 kV/cm. The optimum amplitude of the microwave electric field generated by bulk GaN is found to be of the order of the static electric field thus leading to a significant maximum efficiency of about 1 to 1.5% for microwave power generation in the THz frequency range 相似文献
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Miniature electron-optical columns 总被引:1,自引:0,他引:1
Miniaturized electron-optical systems based on a field emission microsource and a microlens for probe forming have been studied. The performance of systems with dimensions (length and diameter) in the submillimeter to millimeter range can exceed that of a conventional system over a wide range of potentials (100 V to 10 kV) and working distances (up to 10 mm). Electron-optical studies show that not only can a significant reduction in size be achieved but the performance in terms of resolution and especially beam current can also be greatly improved. A key component of the miniaturized system is the field emission microsource which provides an improvement of two to three orders of magnitude in effective brightness over the conventional field emission source. Among the options, the STM aligned field emission (SAFE) microsource appears most promising and a selective scaling approach has been developed to allow this source to operate over a wide range of potentials. Preliminary experimental studies of the microsource have been conducted 相似文献
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Theodor A. Prosch 《International Journal of Satellite Communications and Networking》2000,18(6):433-456
Non‐stationary broadcast (BC) satellite systems can provide a continuous, direct‐to‐user, and worldwide BC service. Owing to the improved radio link margin of LEO/MEO systems, one can overcome the problems of blockage and foliage attenuation, which are significant in the alternative GEO/HEO systems. A basic analysis also reveals that the specifications of the standardized ITU A (EUREKA 147) DAB signal are adequate to cope with range and range rate effects due to the satellite motion. It is shown that a continuous, area‐wide high‐quality BC service can be provided by overlapping cellular service areas. Each cell may have an individual uplink station for feeding the BC signal. A system concept is discussed which is based on the exploitation of range, range rate, and angular information onboard the satellites with respect to each individual uplink station in order to compensate for Doppler frequency shifts and for variable signal propagation delay. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
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Numerical simulations of frequency modulated (FM) external cavity semiconductor lasers have been performed and a range of dynamic and spectral phenomena observed. It is shown that FM lasing action can be suppressed due to changes in the FM modulation frequency. Coupled cavity effects are seen to be significant in the development of a broad spectral emission associated with experimentally observed coherence collapse in such a configuration 相似文献