一种靶弹装配检测雷达系统

位于靶弹弹体内的龙伯球装配正确性与否将直接影响靶弹的使用性能,本文设计一种用于靶弹装配生产线使用的检测雷达系统,该系统采用2.1GHz 频率的连续波体制,结合小型微波暗室的使用,实现靶弹内龙伯球正、反向装配时雷达输出信号电平大小差别10 倍以上,可以有效检测龙伯球装配的正确性,并具有操作简便、体积小、可靠性高、成本低的特点。     

Characterization of optimum polarization for multiple targetdiscrimination using genetic algorithms

A stochastic optimization algorithm is used to characterize the polarization states of a nonpolarimetric radar transmitter and receiver antennas for optimal target classification. Specifically, the optimized solution is sought when a multitude of targets are to be categorized. It is shown that the objective function of the optimization problem is highly nonlinear and discontinuous, hence, classical optimization algorithms fail to provide satisfactory results. The stochastic optimization algorithm used is based on a genetic algorithm (GA) which operates on a discretized form of the parameter space and searches globally for the optimum point. In this process, it is assumed that the polarimetric responses of the targets are known a priori. The optimization algorithm is applied to two sets of data: (1) a synthetic backscatter data for four point targets with similar radar cross sections (RCSs) and (2) a set of polarimetric backscatter measurements of asphalt surfaces under different physical conditions at 94 GHz. The purpose of the latter study is to come up with the optimal design for polarization states of an affordable millimeter-wave radar sensor that can assess traction of road surfaces     

杂波环境下共享频谱恒模波形设计

针对射频频谱环境愈发拥挤问题,深入研究了通过波形设计的手段实现频谱共享的问题。为紧密贴近工程实践,提出了一种新的方法设计恒定幅度信号的问题。该算法首先针对雷达发射端,提出雷达波形满足特定的时域与频谱要求,施加约束,然后考虑雷达接收滤波器接收杂波,以优化最大信干噪比建立优化问题模型,得到了一个非凸的分式规划问题模型。最后,利用分步优化方法分解为两个优化问题,并且将非凸问题松弛为可解的凸问题再利用高斯随机化方法得到优化信号,多次循环优化。仿真结果验证了该算法的有效性,该方法设计得到的探测信号能够实现频谱共存,而且信干噪比性能能够得到保证。      

Capabilities of Dual-Frequency Millimeter Wave SAR With Monopulse Processing for Ground Moving Target Indication

Ground moving target indication (GMTI) for synthetic aperture radar (SAR) provides information on nonstatic objects in radar imagery of a static ground scene. An efficient approach for GMTI is the use of multichannel SAR systems for a space- and time-variant analysis of moving targets. This allows the indication, correction of position displacement, and estimation of radial velocity components of moving targets in a SAR image. All three steps are possible due to a determinable Doppler frequency shift in the radar signal caused by radial target movement. This paper focuses on the millimeter wave (mmW) SAR system MEMPHIS with multichannel amplitude-comparison monopulse data acquisition and the ability to use carrier frequencies of 35 and 94 GHz simultaneously, making it a dual-frequency SAR. This paper includes mmW-specific SAR GMTI considerations, an adaptive algorithm to collect velocity and position information on moving targets with mmW monopulse radar, and a discussion on GMTI blind speed elimination and target velocity ambiguity resolving by dual-frequency SAR. To determine the capabilities of both, system and algorithm, three large-scale experiments with MEMPHIS in different environments are presented     

关于动目标近距的杂波谱中心补偿

杂波谱中心补偿是机载雷达动目标检测的关键步骤.杂波谱中心的估计方法主要有两种:惯导估计法和回波数据估计法.对于机载雷达的动目标检测所运用的估计方法利用回波数据进行估计杂波谱中心,然后利用惯导估计的杂波谱中心进行解模糊操作.但是在5km近距的杂波谱中心发现,传统的回波数据方法—重心法估计、相关法估计,仍然会使动目标检测出...     

一种超宽带10 GHz微波光子雷达包络与相位联合运动误差估计方法

由于运动误差严重的2维空变性,对于10 GHz超宽带微波光子SAR,传统的直接从相位进行运动误差估计的方法估计精度不高。因此,该文提出一种包络与相位联合的超高分辨运动误差估计方法,能够在没有惯导信息时实现运动误差的精确估计。该方法首先在距离徙动矫正(RCMC)之前,通过对包络对齐算法(RAA)提取的包络信息采用最小二乘算法(LSA)与梯度下降算法(GDA)获得近似的3维运动误差。接着,对粗补偿与RCMC之后的数据,先消除方位相位空变,然后采用两维空变的相位误差估计方法获得剩余运动误差的精确估计。仿真和车载微波光子雷达实测数据验证了该方法的有效性。

     

Direct positioning of stationary targets using MIMO radar

MIMO radar is a new concept that has recently been proposed as an extension to the multi-static radar systems. We apply the direct position determination (DPD) approach to MIMO radar and obtain maximum likelihood algorithms for a location estimation of a stationary target. It is shown that under low signal to noise ratio DPD improves the estimation accuracy with respect to the traditional location methods.     

Compact range radar cross-section measurements using a noise radar

This paper discusses the measurement of radar cross section (RCS) with a very low-cost system that transmits band-limited random noise over the band from 1.0 to 4.0 GHz. The received signal is correlated with a delayed version of the transmitted signal. A variable delay line is used to obtain the response at various delay times. This yields the radar target impulse response as a function of delay. This can be transformed to yield both the amplitude and phase of the scattering matrix in the frequency domain     

基于杂波的收发分置MIMO雷达阵列位置误差联合校正方法

针对收发分置多输入多输出(MIMO)雷达发射端和接收端均存在位置误差的问题,该文提出一种基于杂波回波的收发阵列位置误差联合校正方法。该方法以最小化杂波回波数据的重构均方误差为准则,在杂波散射系数l1范数稀疏约束下,利用双迭代与凸优化方法对杂波散射系数和阵列位置误差参数进行联合优化求解,最终完成了对收发阵列位置误差的同时估计与校正。仿真实验表明了所提算法的有效性。     

Surface characterization using frequency diverse scatteringmeasurements and regularity models

Accurate classification and characterization of image regions is often an important goal for the users of coherent imaging systems such as synthetic aperture radar (SAR). Many surfaces measured by remote sensing systems can be stochastically described by a regularity model. This parametric point-process model describes a 1-D surface in terms of the mean and variance of the interscatterer distances. Variations of these parameters can describe scatterer distributions ranging from totally random to nearly periodic. Under certain conditions, a closed-form approximation to the mean power spectrum of finite-length data intervals exists. The estimation of model parameters from measured spectra can then be cast as an optimization problem in which the total squared error between the approximation and the simple periodogram is minimized. We examine the general performance limitations of such an optimization procedure, determining how approximation error, signal-to-noise ratio, and frequency-sampling rate affect the feasibility and accuracy of parameter estimation. We determine under what conditions the approximation may be used. We find that parameter estimation is feasible at a frequency-sampling rate that is well below that suggested by the power spectral density (PSD). This suggests that it is possible to obtain parameter estimates by comparing sparse narrow-band frequency measurements to the PSD of the point-process and thereby obtain information about the surface on subresolution scales     

智能反射面辅助雷达通信双功能系统的多载波波形优化方法

雷达通信一体化是解决频谱资源拥挤问题的有效途径之一,而共享波形设计是同时实现雷达与通信功能的关键技术,该文旨在解决智能反射面(IRS)辅助雷达通信双功能(DRC)系统的多载波波形优化问题.首先,通过最大化传输功率、通信码字错误率(WEP)、旁瓣幅度与IRS反射系数约束下的雷达互信息(RMI),构建了双功能发射波形、IR...     

Scattering of radiowaves by a melting layer of precipitation inbackward and forward directions

A melting layer of precipitation is composed of melting snowflakes (snow particles); the assumption of spherical particles along with mass conservation is used. The melting layer is studied by deriving the size distribution of the melting snow particles, the thickness of a melting layer, the density of a dry snow particle, and the average dielectric constant of a melting snow particle. Vertical profiles of radar reflectivity and specific attenuation are computed at 1-100 GHz by using the Mie theory for five raindrop size distributions at rain rates below 12.5 mm/h. The radar bright band is explained with computed radar reflectivities at 3-10 GHz. It is shown that the radar bright band can be absent in the melting layer at frequencies above 20 GHz. This agrees with radar observations at 35 and 94 GHz. The specific attenuation, as well as the average specific attenuation of the melting layer, is divided into absorption part and scattering part. The latter is increasingly significant with the increase of frequency. The total zenith attenuation due to stratiform rain is divided into the rain zenith attenuation and the additional zenith attenuation, which is the difference between zenith attenuation, due to the melting layer, and attenuation, due to the same path length of the resulting rain. The additional zenith attenuation increases with the increase of rain rate even at frequencies above 20 GHz. This should be taken into account in radar remote sensing and satellite-Earth communications     

一种雷达信号的单样本压缩采样方法

本文提出了一种雷达信号的单样本压缩采样方法。该方法在多相随机子采样FFT的模拟信息转换器（Analog to Information Converter,AIC）方案的基础上进行了改进,利用了雷达信号多个连续脉冲相关性较强的特点,提出了一种单样本压缩采样AIC,单个脉冲通过该AIC压缩得到单个样本值,实现了对稀疏信号的压缩采样。此方法降低了硬件电路复杂度,提高了压缩率,能够实现对雷达目标的位置和速度等参数的准确估计。仿真实验验证了此方法的有效性。      

Statistical characteristics of simulated radar imagery from baresoil surfaces: effects of surface roughness and soil moisturevariability

The potential of high-resolution radar imagery to estimate various hydrological parameters, such as soil moisture, has long been recognized. Image simulation is one approach to study the interrelationships between the radar response and the underlying ground parameters. In order to perform realistic simulations, the authors incorporated the effects of naturally occurring spatial variability and spatial correlations of those ground parameters that affect the radar response, primarily surface roughness and soil moisture. Surface roughness and soil moisture images were generated for a hypothetical 100×100 m bare soil surface area at 1 m resolution using valid probability distributions and correlation lengths. These values were then used to obtain copolarized radar scattering coefficients at 2 GHz (L band) and 10 GHz (X band) frequencies using appropriate backscatter models, which were then converted to a digital number within 0-255 gray scale in order to generate radar images. The effect of surface roughness variability causes variability in the radar image, which is more apparent under smooth soil conditions. On the other hand, the inherent spatial pattern in soil moisture tends to cause similar patterns in the radar image under rougher soil conditions. The maximum difference between contrast-enhanced mean values of the radar image digital number due to moisture variations occurs at surface roughness values in the 1.5-2.0 cm range     

一种超分辨OFDM雷达通信一体化设计方法

传统OFDM雷达通常不考虑传递通信信息,该文设计出一种新的基于OFDM的雷达发射方式以实现雷达和通信的一体化,并提出一种基于通信信息补偿的目标距离速度联合高分辨估计方法。所设计的雷达发射方式,采用脉冲发射,每个脉冲由多个OFDM符号构成,在脉冲内实现通信功能;在雷达相干处理时间内,对回波进行通信信息补偿和解相干处理后,采用子空间投影方法实现对目标距离和速度的联合超分辨估计。理论分析和仿真实验表明,所提方法能够在保证通信功能的条件下,可有效实现雷达目标距离和速度的联合超分辨估计。     

基于24 GHz FMCW 雷达的二维近场成像系统

为进行隐藏危险金属制品的安检,文中提出了一种24 GHz 低成本毫米波成像系统。该系统采用低成 本24 GHz 商用调频连续波(FMCW)雷达作为扫描源,在方位角和仰角上合成大孔径,使用二维十字扫描平台,经 FMCW 雷达信号处理以及合成孔径雷达(SAR)处理使隐藏物体成像。低成本的射频外设只提供了一路中频实信号 供ADC 采样量化,在图像重建中,文中提出将单路ADC 采样量化后的中频数字信号通过希尔伯特变换成复信号,对 复信号加布莱克曼窗优化频谱,再对信号序列补零以减小频域栅栏效应,后采用空间匹配滤波器补偿相位偏差,通 过FMCW 雷达近场成像原理对目标成像。改进后的算法适用于低成本的雷达前端系统,只需一路ADC 采集的中频 数字信号即可使成像系统达到理论的合成孔径成像分辨率。     

A multistatic microwave radar sensor for short range anticollisionwarning

An adequate radar technology for the detection and localization of obstacles before, behind and on the sides of a moving car is of primary importance to realize on-board devices able to perform different tasks such as parking, stop and go, and pre-alarm of the frontal air-bags. In these situations, the radar must acquire the position of the obstacles located at short distances from the car. This acquisition must be carried out with high radial and angular resolution; the former needs large radio frequency bandwidth, the latter requires large antennas and this means that the investigation area of the radar is certainly in the near field of the antenna. It is for this reason that traditional anti-collision systems based on phase array antennas prove to be unsuited to perform these tasks in the short range. The solution that we are proposing is based on several independent microwave radar sensors with wide angle of view connected to a central processing unit able to define the position and the relative velocity of the nearest obstacles. This prototype works in the 13.4-14 GHz frequency range at low power (16 dBm cirp) in accordance with the ETSI and CEPT/ERC Recommendations and it has been realized with microstrip technology so that thanks to its reduced size each device can be embedded easily in a bumper     

利用遗传算法优化阵列改善波达方向估计

利用遗传算法优化线阵波达方向估计性能。优化过程中,不仅优化阵元位置改善方位估计,而且将阵元个数作为优化变量,从而提供了更多的自由度来控制阵列性能。在满足空间谱估计精度的条件下,利用较少的阵元实现超分辨估计。优点是减少信号处理量的同时,简化了设备。仿真实验结果验证了其正确性和有效性。     

复杂地形环境下基于CL-KA-STAP的低空风切变风速估计方法

针对机载气象雷达在复杂的地形环境下探测低空风切变时,地杂波呈现的非均匀特征导致难以准确获得杂波统计特性,进而影响杂波抑制效果,使得风切变风速估计不准的问题,该文提出一种色加载知识辅助STAP(CL-KA-STAP)的低空风切变风速估计方法。该方法首先构造降维联合时空变换矩阵,并对待检测距离单元的回波信号进行降维处理,然后将由数字高程模型(DEM)和国家土地覆盖数据库(NLCD)获取的先验知识融入到组合空时主通道自适应处理器(CMCAP)中,构造色加载系数优化函数求解色加载系数,最后构造滤波器,实现杂波自适应滤波并准确估计风速。后续仿真结果证明了所提方法的有效性。     

利用整体退火遗传算法优化阵列改善方位估计

该文将非比例选择、保证收敛且易于判断收敛的整体退火遗传算法应用于优化线阵方位估计性能。优化过程中,不仅优化阵元位置改善方位估计,而且将阵元个数作为优化变量,从而提供了更多的自由度来控制阵列性能。在满足空间谱估计精度的条件下,利用较少的阵元实现超分辨估计。优点是减少信号处理量的同时,简化了设备。仿真实验结果表明该方法收敛速度快,有极强的避免过早收敛及避免局部极值的全局优化能力。