雷达侦察中LFMCW信号检测与参数估计方法研究

发布时间：2018-07-18 08:52

【摘要】：线性调频连续波(Linear Frequency Modulated Continuous Wave,LFMCW)雷达由于结构简单、体积小、距离分辨率高、无距离盲区、成本低、低功耗和低截获等优点,在军用导航、战场侦察与地面成像等领域得到越来越广泛的应用。由于采用连续波体制,LFMCW雷达的发射功率相比于脉冲多普勒雷达具有更低的发射功率,这就导致更低的信噪比,进而需要更多的采样点数保证信号检测的有效性,因此,高计算复杂度和低信噪比成为制约LFMCW信号有效检测和参数估计的主要因素。降低计算复杂度和提高信噪比成为了LFMCW信号检测与参数估计的核心和关键。本论文从信号处理的角度出发,对LFMCW信号的模型、检测和参数估计等方面做了比较全面的分析和阐述。主要工作概括如下:1.研究了单分量周期LFMCW信号的检测和参数估计方法。首先介绍了两种常用的LFMCW信号的发射模型及其截获模型;然后,针对低信噪比和高计算复杂度的问题,提出一种联合变窗长相干平均法、循环平稳法和解线频调处理的单分量周期LFMCW信号的检测与参数估计方法。该方法首先基于信号的周期性,利用变窗长相干平均法和循环平稳法提高了信噪比增益并实现了调制周期和调频率的估计,然后基于估计的调制周期和调频率,利用解线频调处理完成了起始频率、起始时间、幅度和初相的估计。该方法以较低计算复杂度实现了长时间积累,并有效地提高了信噪比。然而,该方法的检测性能受窗长搜索范围的制约。针对该问题,进一步提出了改进的方法。改进的方法首先对变窗长相干平均法进行了改进,然后利用改进的变窗长相干平均法和循环平稳法估计调制周期和调频率,最后,利用解线频调处理实现了起始频率、起始时间、幅度和初相的估计。改进方法的检测性能不再受搜索窗长的制约,并且仍以较低计算复杂度实现了长时间积累,有效地提高了信噪比。仿真实验验证了所提方法的有效性。2.研究了多分量周期LFMCW信号的检测和参数估计方法。针对在低信噪比条件下如何快速实现多分量周期LFMCW信号的检测和估计问题,提出了一种联合帧间相关法、循环平稳法和解线频调处理的多分量周期LFMCW信号的检测与参数估计方法。该方法首先基于信号的周期性,提出一种帧间相关法及其等价形式,帧间相关法及其等价形式只需简单的复乘和复加就可实现多分量信号能量的线性叠加;其次,根据帧间相关法的线性叠加的特点,提出一种目标剥离方法,目标剥离方法可以将多分量LFMCW信号的调制周期依次估计出来,并实现各信号分量的检测;然后,基于CLEAN算法的思想并结合各信号分量的调制周期的估计,利用循环平稳法和解线频调处理依次将各信号分量的幅度、调频率、起始频率、起始时间和初相估计出来。所提方法以较低计算复杂度实现了信号的长时间积累,有效地提高了信噪比,并且无需二维峰值搜索就可实现各信号分量的检测,因此计算量比较小。仿真实验验证了所提方法的有效性。3.针对在低信噪比下如何快速实现LFMCW信号的检测和参数估计的问题,提出了一种联合零频搜索法、循环平稳法和解线频调处理的LFMCW信号的检测与参数估计方法。该方法首先基于LFMCW信号的瞬时相关特性,给出了一种零频搜索法,零频搜索法可以实现信号的检测和调制周期的估计;其次,针对零频搜索法计算量大的问题,对其进行了改进,改进后的零频搜索法在保持相同检测性能的基础上有效地减小了计算量;然后,结合信号的调制周期,利用循环平稳法实现了信号调频率的估计;最后,基于调制周期和调频率,利用解线频调处理估计信号幅度、起始时间、起始频率和初相。所提方法以较低计算复杂度实现了信号的长时间积累,有效地提高了信噪比。此外,所提方法可以对符合一定限制条件的多分量LFMCW信号进行检测与参数估计。仿真实验验证了所提方法的有效性。4.针对LFMCW信号检测与参数估计所面临的高计算复杂度和低信噪比的问题,提出了一种基于匹配帧间相关法、循环平稳法和解线频调处理的LFMCW信号的检测与参数估计方法。该方法首先基于LFMCW信号周期间的固有规律,给出了一种匹配帧间相关法,匹配帧间相关法可以根据各信号分量的调制周期和起始频率的不同实现其检测和调制周期的估计;然后,基于CLEAN算法的思想并结合各信号分量的调制周期的估计,按照信号幅度由大到小的顺序,利用循环平稳法和解线频调处理实现了各信号分量的调频率、起始时间、起始频率、初相和幅度的估计。该方法可在较低的信噪比下对LFMCW信号进行有效的检测和参数估计,其运算复杂度低,利于工程实现。仿真实验验证了所提方法的有效性。
[Abstract]:Linear Frequency Modulated Continuous Wave (LFMCW) radar is becoming more and more widely used in military navigation, battlefield reconnaissance and ground imaging because of its advantages of simple structure, small size, high distance resolution, low distance blind area, low cost, low power consumption and low interception. The application of continuous wave system, LFMCW The transmission power of radar has lower transmission power than that of pulse Doppler radar, which leads to lower signal to noise ratio and more sampling points to ensure the effectiveness of signal detection. Therefore, high computational complexity and low signal to noise ratio become the main factors that restrict the effective detection and parameter estimation of LFMCW signals. Degree and enhancement of signal to noise ratio have become the core and key of LFMCW signal detection and parameter estimation. From the angle of signal processing, this paper makes a comprehensive analysis and exposition of the LFMCW signal model, detection and parameter estimation. The main work is summarized as follows: 1. the detection and parameter estimation of single component periodic LFMCW signal are studied. Methods. First, two kinds of common LFMCW signal emission models and their intercept models are introduced. Then, for low signal to noise ratio and high computing complexity, a method of detection and parameter estimation of single component periodic LFMCW signals with a joint variable window long phase mean method, a cyclostationary method and a line frequency modulation is proposed. The signal's periodicity is used to improve the signal to noise ratio gain and estimate the modulation period and frequency modulation by using the variable window length average method and the cyclostationary method. Then based on the estimated modulation period and frequency modulation, the initial frequency, the starting time, the amplitude and the initial phase are estimated by the frequency modulation of the solution. A long time accumulation is realized and the signal to noise ratio is improved effectively. However, the detection performance of the method is restricted by the scope of the window length search. In view of the problem, an improved method is proposed. The improved method first improves the dry average method of the variable window, and then uses the improved variable window length average method and the cyclostationary method. The modulation period and frequency modulation are estimated. Finally, the initial frequency, the starting time, the amplitude and the initial phase are estimated by the line frequency modulation. The detection performance of the improved method is no longer restricted by the length of the search window, and the long time accumulation is realized with the lower computational complexity, and the signal to noise ratio is improved effectively. The simulation experiment verifies the proposed method. .2. studies the detection and parameter estimation methods of multicomponent periodic LFMCW signals. Aiming at how to quickly realize the detection and estimation of multicomponent periodic LFMCW signals under low signal to noise ratio, a joint inter frame correlation method, the detection and reference of multicomponent periodic LFMCW signals with cyclic stationary and line frequency modulation are proposed. The method of number estimation is based on the periodicity of the signal, and a frame correlation method and its equivalent form are proposed. The interframe correlation method and its equivalent form only need simple complex multiplying and adding to realize the linear superposition of the multicomponent signal energy. Secondly, a target stripping method is proposed according to the linear superposition of interframe correlation method. The target stripping method can estimate the modulation period of the multicomponent LFMCW signal in turn and realize the detection of the signal components. Then, based on the thought of the CLEAN algorithm and the estimation of the modulation period of each signal component, the amplitude, frequency modulation rate and starting frequency of each signal component are sequentially used by the cyclostationary method and the line frequency modulation. The initial time and initial phase are estimated. The proposed method achieves long time accumulation of signals with a lower computational complexity, effectively improves the signal to noise ratio and does not need a two-dimensional peak search to detect the signal components, so the computation is relatively small. The simulation experiment shows how the effectiveness of the proposed method.3. is directed against the low signal to noise ratio. In order to quickly realize the detection and parameter estimation of LFMCW signals, a method of detection and parameter estimation of LFMCW signals combined with zero frequency search, cyclostationary and line frequency modulation is proposed. Firstly, based on the instantaneous correlation characteristic of LFMCW signal, a zero frequency search method is given, and the zero frequency search method can be used to detect the signal. The estimate and modulation period are estimated. Secondly, in view of the problem of large computation of zero frequency search method, it has been improved. The improved zero frequency search method effectively reduces the computation on the basis of maintaining the same detection performance. Then, combining the modulation period of the signal, the estimation of the signal frequency modulation is realized by using the cyclostationary method. Finally, based on the signal modulation method, the method is used to estimate the frequency of the signal. The modulation period and frequency modulation are used to estimate the amplitude, starting time, starting frequency and initial phase by the frequency modulation of the solution line. The proposed method realizes the long time accumulation of the signal with a lower computational complexity and improves the signal to noise ratio effectively. Furthermore, the proposed method can detect and parameter the multicomponent LFMCW signals which are in accordance with certain limit conditions. It is estimated that the effectiveness of the proposed method.4. is based on the problem of high computing complexity and low signal to noise ratio facing LFMCW signal detection and parameter estimation, and a method of detection and parameter estimation of LFMCW signals based on matched frame correlation, cyclostationary and line frequency modulation is proposed. The method is based on LFMCW first. A matching frame correlation method is given, which can be used to estimate the detection and modulation period according to the modulation period and starting frequency of each signal component. Then, the idea based on the CLEAN algorithm and the estimation of the modulation period of each signal component are based on the amplitude of the signal. In the order of large to small, the frequency modulation rate, starting time, starting frequency and initial phase and amplitude of the signal components are estimated by using the cyclostationary method and the line frequency modulation. The method can detect and estimate the LFMCW signal effectively at a low signal to noise ratio, and its operation complexity is low and it is beneficial to the project. The simulation experiment is proved to be good. The effectiveness of the proposed method.
【学位授予单位】：西安电子科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN957.51

【参考文献】