共查询到20条相似文献,搜索用时 125 毫秒
1.
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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Lin Yunsong Huang Yong Xiao Xianci 《电子科学学刊(英文版)》2000,17(2):123-131
The relationship between the discrete Fourier transform (DFT) and the symmetrical/asymmetrical number system (SNS/ANS) is introduced in this paper. And the influence of noise upon the solution to the ambiguity problem in number system is also discussed. The principle of noise insensitive solution to the ambiguity in ANS system is extended to SNS system. The unambiguous bandwidth equations with noise protection in SNS are presented, based on which a real time noise insensitive algorithm in SNS for resolving undersampling ambiguous frequency is proposed. 相似文献
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Fang Zhi Xiao Wan'ang Shi Yin 《电子科学学刊(英文版)》2008,25(1):1-6
A new fine carrier frequency offset estimation algorithm in Orthogonal Frequency Division Multiplexing (OFDM) system is proposed. The correlation item is the training sequence instead of the received signal in the new algorithm. Simulation results show that the performance of the new algorithm is 4dB-9dB better than that of Schmidl's algorithm. Coarse frequency offset estimation is also discussed in this paper, which is the improvement of Zhang's method. The estimation range using the improvement method is twice as that using the Zhang's method. Based on the hardware of the receiver and the improved algorithm, a method using Fast Fourier Transform (FFT) is proposed to implement the coarse frequency estimation. The chip area of OFDM system can be reduced by using the proposed method. 相似文献
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Lu Cewu Liu Xiaojun Kuang Yujun Fang Guangyou Chen Qianbin 《电子科学学刊(英文版)》2007,24(6):760-764
The paper proposes a novel approach for fine frequency synchronization of OFDM syn- chronization systems in multi-path channels. Maximum Likelihood (ML) function of frequency offsets including integral and decimal parts in frequency domain is developed according to the law of great number to eliminate the noise impact of the signal. When the timing delay close to the actual time, the proposed function produces a deep valley indicating frequency offset when large Valley-Square- Error (VSE) appears. Coarse timing offset can also be detected when function’s Valley-Square-Error (VSE) is maximized. Simulation results shows that the proposed algorithm gives very robust estimation of frequency offset, and a coarse timing offset estimation. 相似文献
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Li-Ming Zhang 《中国电子科技》2014,(2):201-205
The attempt to represent a signal simultaneously in time and frequency domains is full of challenges.The recently proposed adaptive Fourier decomposition(AFD)offers a practical approach to solve this problem.This paper presents the principles of the AFD based time-frequency analysis in three aspects:instantaneous frequency analysis,frequency spectrum analysis,and the spectrogram analysis.An experiment is conducted and compared with the Fourier transform in convergence rate and short-time Fourier transform in time-frequency distribution.The proposed approach performs better than both the Fourier transform and short-time Fourier transform. 相似文献
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Tao Ran Shan Tao Zhou Siyong Wang Yue 《电子科学学刊(英文版)》2001,18(2):121-126
The phenomenon of frequency ambiguity may appear in radar or communication systems. S. Barbarossa(1991) had unwrapped the frequency ambiguity of single component uri-dersampled signals by Wigner-Ville distribution(WVD). But there has no any effective algorithm to analyze multicomponent undersampled signals by now. A new algorithm to analyze multicomponent undersampled signals by high-order ambiguity function (HAF) is proposed here. HAF analyzes polynomial phase signals by the method of phase rank reduction, its advantage is that it does not have boundary effect and is not sensitive to the cross-items of multicomponent signals. The simulation results prove the effectiveness of HAF algorithm. 相似文献
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Zhang Guangbin Wang Hongyang Liao Guisheng 《电子科学学刊(英文版)》2006,23(2):200-203
A novel frequency estimation algorithm for wideband signal with sub-Nyquist sampling is proposed in this paper. With the aid of information provided by the auxiliary delayed sampling channel and the aliased frequency estimation for wideband signal with sub-Nyquist sampling, the frequency aliasing due to sub-Nyquist sampling can be solved. This method can reduce the complexity of the overall hardware at the cost of an auxiliary sampling channel. Furthermore, in order to alleviate the computation burden for its practicability, a more simplified algorithm is put forward and its validity is proved by our numerical simulation results. The Cramer-Rao Lower Bound (CRLB) of the frequency estimation is also derived at the end of this paper. 相似文献
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A tracking structure suitable for L6 signal of quasi-zenith satellite system (QZSS) was proposed in order to track the L6 signal without other frequency assistance. Moreover, the tracking structure does not change the receiver's hardware structure. The main difference between the proposed and the traditional tracking structure lies in the generation of local codes of E, P and L branches. The method of local code generation is designed in a two-stage manner. The first stage is the generation of the P branch local code with fast fourier transform (FFT). In the second stage, the local codes of the E and L branches are obtained with the code-chip interval. The tracking structure can track and decode L6 signal separately, and track code shift keying (CSK) modulated signal as well. The structure was verified using both simulation data, generated in different conditions, and actual data obtained from QZSS satellites respectively. The results show that the improved tracking loop is able to track L6 signal without other frequency assitance. Furthermore, the biterror ratio (BER) of L6 tracking algorithm is lower than that of L1C/A assist L6 algorithm, when the Doppler remains a constant and reed solomn (RS) encode are applied. To be more specific, with the proposed structure the BER decreased by 11.40%, 17.07%, 15.00%, 11.15%, 5.19% when carrier to noise ratio (CNR) is 36 -40 dB·Hz. 相似文献
9.
Mu Shanxiang Kong Dechun Li Xingguo He Guodong 《电子科学学刊(英文版)》2000,17(2):153-160
A new radar waveform utilizing Costas sequences and interpulse Frequency Hopping (FH) technique is developed, which is a good high range resolution radar signal. The interpulse Costas FH coherent pulse train is introduced and the system block diagram using the interpulse Costas FH waveform is given. In the paper, ambiguity function is employed to study interpulse Costas FH radar. The mathematical expression of the ambiguity function for this waveform is derived. The advantages of the waveform are interpreted by computer simulation. 相似文献
10.
Real-time digital service and multimedia service upstream transmission in Digital Signal Processing(DSP)-based Orthogonal Frequency Division Multiplexing-Passive Optical Network(OFDM-PON) is experimentally demonstrated with Centralised Light Source(CLS) configuration in this paper.After transmitted over 25 km Standard Single Mode Fibre(SSMF) with-16.5 dBm optical power at receiver,the Bit Error Rate(BER) is 9.5×10~(-11).The implementations of digital domain up-conversion and down-conversion based on Field Programmable Gate Array(FPGA) are introduced,which can reduce the cost of In-phase and Quadrature(1Q) radio frequency mixers utilised at transmitter and receiver.A carrier synchronization algorithm is implemented for compensating carrier offset.A channel equalization algorithm is adopted for compensating the damage of channel.A new structure of Frequency Synchronization Unit(FSU) designed in FPGA is also proposed to cope with the frequency shifting at receiver. 相似文献
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针对宽带宽角扫描相控阵雷达系统高精度测距、测速应用需求,提出了脉间Costas编码跳频、脉内线性调频调制的信号形式。通过对信号建模及距离-多普勒二维模糊度函数的分析表明,该信号形式综合了线性调频信号和Costas编码的优点,具有接近理想图钉型的模糊函数,可实现距离-速度的二维高分辨率。推导了线性调频-Costas频率步进信号宽带合成的处理方法,并通过仿真验证了该算法的有效性。 相似文献
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Costas阵列编码与线性调频SFR信号分析 总被引:2,自引:0,他引:2
线性调频-Costas频率步进雷达信号是一种很有研究价值的雷达信号。针对线性调频-Costas频率步进雷达信号的需要研究总结了一套生成N阶Costas序列的方法,同时结合实际需要生成了多组64阶Costas序列。这些Costas阵列是具有良好相关特性的最佳离散信号,将Costas阵列编码与线性调频频率步进雷达信号结合起来构成了线性调频-Costas频率步进雷达信号。通过对该信号的模糊特性的理论和仿真结果的分析表明,这种信号不仅能够较大地抑制信号的模糊旁瓣的幅度。而且能解决距离-速度的多普勒耦合问题。 相似文献
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雷达对于非合作目标的探测,存在目标微小与速度未知两大困难,而相干积累的方法需要准确探测目标速度,并进行速度补偿,实际应用过程中效果受限。针对此问题提出了一种调频步进编码波形设计方法,可以在速度未知情况下脉间积累,同时在准确测量速度后宽带合成。首先研究线性调频子脉冲的距离速度耦合特性,通过波形设计抵消脉间目标运动成像位置变化;然后研究调频步进编码波形的宽带合成技术,使所得的高分辨一维距离像无距离混叠。最后,数值仿真实验验证了所提出波形的优势与应用价值。 相似文献
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毫米波高分辨率雷达运动补偿研究 总被引:6,自引:0,他引:6
频率步进雷达是一种距离高分辨率雷达,运动补偿是其实现距离高分辨的关键。在波形熵法用于毫米波频率步进雷达运动补偿的研究中,针对步进频率信号波形熵的局部最小值问题,采用Costas编码改进,并对波形熵的定义进行了优化,获得了满意的仿真结果。 相似文献
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频控阵(frequency diverse array)雷达存在角度和距离定位模糊的问题,基于频控阵与早期的多频连续波(multi-frequency continuous wave)雷达相同的测距原理,提出了改进的多频连续波雷达模型,通过采用相控阵接收的方式,克服了传统频控阵角度和距离定位模糊的问题.根据收发阵元数的不同,推导了四种配置下的信号模型,分析了多频连续波雷达相比传统频控阵可解耦角度与距离定位模糊的原因.新的多频连续波雷达实现定位的本质为三维多频估计问题,为此提出了一种基于迭代插值傅里叶系数(iterative interpolation Fourier coefficients))的角度-距离联合估计方法,理论分析了算法的性能.仿真结果验证了所提方案与算法的有效性. 相似文献
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分析了频率编码脉冲信号(FCP)雷达原理,推导了基于自相关函数的步进频率信号的模糊函数,针对常用的FcP信号一步进频率编码信号距离-多普勒旁瓣电平较高,存在“距离.速度”耦合,“距离.速度”联合分辨率低的缺点,提出了优化频率编码的模糊优化度准则,并基于该准则给出了两种编码优化规律不同的频率编码优化方法,仿真结果表明,在保持原有的距离、速度分辨率的情况下,两种方法都能有效地降低“距离.速度”二维耦合,提高“距离,速度”联合分辨率。 相似文献