Super-resolution parameter estimation of monopulse radar by wide-narrowband joint processing

The angular resolution of radar is of crucial signifi-cance to its tracking performance.In this paper,a super-resolu-tion parameter estimation algorithm based on wide-narrowband joint processing is proposed to improve the angular resolution of wideband monopulse radar.The range cells containing resolv-able scattering points are detected in the wideband mode,and these range cells are adopted to estimate part of the target parameters by algorithms of low computational requirement.Then,the likelihood function of the echo is constructed in the narrow-band mode to estimate the rest of the parameters,and the parameters estimated in the wideband mode are employed to reduce computation and enhance estimation accuracy.Simu-lation results demonstrate that the proposed algorithm has higher estimation accuracy and lower computational complexity than the current algorithm and can avoid the risk of model mis-match.

Combining sum-difference and auxiliary beams for adaptive monopulse in jamming

Only in the presence of sidelobe jamming （SLJ）, can the conventional adaptive monopulse technique null the jamming effectively and maintain the monopulse angle estimation accuracy simultaneously. While mainlobe jamming （MLJ） exists, the mainlobe of adaptive pattern will subject to serious distortion, which results in a failure of detecting and tracking targets by monopulse technique. Therefore, a monopulse angle estimation algorithm based on combining sum-difference beam and auxiliary beam is presented. This algorithm utilizes both high gain difference beams and high gain auxiliary beams for cancelling the mainlobe jammer and multiple sidelobe jammers （SLJs） while keeping an adap- tive monopulse ratio. Theoretical analysis and simulation results indicate that the serious invalidation of monopulse technique in MLJ and SLJs scenarios is resolved well, which improves the monopulse angle accuracy greatly. Furthermore, the proposed algorithm is of simple implementation and low computational complexity.

Adaptive monopulse beamforming with partial parallel structure

A new recursive algorithm with the partial parallel structure based on the linearly constrained minimum variance （LCMV） criterion for adaptive monopulse systems is proposed. The weight vector associated with the original whole antenna array is decomposed into several adaptive weight sub-vectors firstly. An adaptive algorithm based on the conventional LCMV principle is then deduced to update the weight sub-vectors for sum and difference beam, respectively. The optimal weight vector can be obtained after convergence. The required computational complexity is evaluated for the proposed technique, which is on the order of O（N） and less than that of the conventional LCMV method. The flow chart scheme with the partial parallel structure of the proposed algorithm is introduced. This scheme is easy to be implemented on a distributed computer/digital signal processor （DSP） system to solve the problems of the heavy computational burden and vast data transmission of the large-scale adaptive monopulse array. Then, the monopulse ratio and convergence rate of the proposed algorithm are evaluated by numerical simulations. Compared with some recent adaptive monopulse estimation methods, a better performance on computational complexity and monopulse ratio can be achieved with the proposed adaptive method.

Research on monopulse forward-looking high-resolution imaging algorithm based on adaptive iteration

In this paper,we proposed a monopulse forward-looking high-resolution imaging algorithm based on adaptive iteration for missile-borne detector.Through iteration,the proposed algorithm automatically selects the echo signal of isolated strong-scattering points from the receiving echo signal data to accurately estimate the actual optimal monopulse response curve(MRC) of the same distance range,and we applied optimal MRC to realize the azimuth self-focusing in the process of imaging.We use real-time echo data to perform error correction for obtaining the optimal MRC,and the azimuth angulation accuracy may reach the optimum at a certain distance dimension.We experimentally demonstrate the validity,reliability and high performance of the proposed algorithm.The azimuth angulation accuracy may reach up to ten times of the detection beam-width.The simulation experiments have verified the feasibility of this strategy,with the average height measurement error being 7.8%.In the out-field unmanned aerial vehicle(UAV) tests,the height measurement error is less than 25 m,and the whole response time can satisfy the requirements of a missile-borne detector.

Monopulse instantaneous 3D imaging for wideband radar system

To avoid the complicated motion compensation in interferometric inverse synthetic aperture(InISAR)and achieve realtime three-dimensional(3 D)imaging,a novel approach for 3 D imaging of the target only using a single echo is presented.This method is based on an isolated scatterer model assumption,thus the scatterers in the beam can be extracted individually.The radial range of each scatterer is estimated by the maximal likelihood estimation.Then,the horizontal and vertical wave path difference is derived by using the phase comparison technology for each scatterer,respectively.Finally,by utilizing the relationship among the 3 D coordinates,the radial range,the horizontal and vertical wave path difference,the 3 D image of the target can be reconstructed.The reconstructed image is free from the limitation in InISAR that the image plane depends on the target's own motions and on its relative position with respect to the radar.Furthermore,a phase ambiguity resolution method is adopted to ensure the success of the 3 D imaging when phase ambiguity occurs.It can be noted that the proposed phase ambiguity resolution method only uses one antenna pair and does not require a priori knowledge,whereas the existing phase ambiguity methods may require two or more antenna pairs or a priori knowledge for phase unwarping.To evaluate the performance of the proposed method,the theoretical analyses on estimation accuracy are presented and the simulations in various scenarios are also carried out.

On a Monopulse Ring-Focus Shaped Reflector Antenna with Arbitrary Polarization

The near field distribution and far field pattern of a monopulse ring focus shaped reflector antenna are studied. The four fold integral appearing in the formulation by using PO method is converted into a triple integral for the near field case and a double integral for the far field case by applying the Fourier series expansion. Good agreements have been achieved between theoretical and experimental results.

Direction estimation for two steady targets in monopulse radar

Traditional monopulse radar cannot resolve two targets present in one range and Doppler cell by means of the monopulse ratio. A novel algorithm is proposed to estimate the directions of two steady targets with two pulses. The algorithm has a closedform expression and its variance is derived at high signal-to-noise ratios（SNRs）. Furthermore, the pulse pair selection criterion and the estimation method with multiple pulses are given. Finally, some numerical results are shown to validate the proposed algorithm and the effect of slight target fluctuations is tested.

STUDY ON MONOPULSE ANGLE MEASUREMENT METHOD BASED ON VIRTUAL POLARIZATION MATCHING

A monopulse angle measurement method for polarization array radar is studied in this paper.The receiving signal model is established and then a monopulse angle measurement method based on virtual polarization matching is proposed.To analyze the estimation performance,the Cramer-Rao Lower Bound(CRLB)of angle estimation is derived.Both theoretical analysis and simulation show that:firstly,the proposed method is superior to the traditional angle measurement methods based on the single polarization.Secondly,the performance of the new method is unrelated to the echo polarization.Thirdly,angle estimation of this method is asymptotically optimal.The results show that this method has great potential to be used in polarization array radar.

Substrate Integrated Waveguide Based Monopulse Slot Antenna Arrays for 60 GHz Applications

Monopulse slot antenna arrays based on substrate integrated waveguide （SIW） are proposed for the application of 60 GHz mono- pulse tracking systems in this paper. The sum-difference monopulse comparator can provide a high amplitude and phase balance over wide frequency band and no phase delay technique is required for the difference channel. Resonant slot antennas are adopted as the radiating elements since they can be integrated with the sum-difference monopulse comparator in a single layer with a compact size. Two monopulse arrays with 2× 4 and 4×4 slot elements are designed, fabricated, and measured. Measured results show that the proposed antenna arrays have wide bandwidth covering the unlicensed 60-GHz band. The peak sum beam gain is 13.85 dBi for the 2 ×4 element array and 16.24 dBi for the 4×4 element array. The peak difference beam gain is 11.20 dBi for the 2×4 element array and 12.11 dBi for the 4×4 element array and the maximum null depth can reach -40 dB.

基于空时级联单脉冲的多目标高效参数估计算法

比幅单脉冲最大似然算法(ACM-ML)在进行目标参数估计时需要进行距离与速度的2维松弛迭代搜索,导致了计算效率低、运算量大的问题。针对上述问题,该文提出一种基于空时级联单脉冲的高效多目标参数估计算法(M-STCMP算法)。该算法将单脉冲概念引入脉冲域,利用时域单脉冲计算目标速度,避免了ACM-ML算法中对速度的迭代搜索,将2维松弛迭代搜索降为1维搜索,有效降低了计算复杂度。考虑时域单脉冲无法同时匹配分布在不同时域主波束的速度各异的多个检测目标,进一步利用目标信号的多普勒信息,在各多普勒单元分别进行时域单脉冲测速,并搜索目标距离值。最后为抑制目标间的信号泄露,将所有目标的估计参数进行级联迭代获得高精度参数估计值。理论分析和仿真结果验证了M-STCMP算法的有效性。

单脉冲测角的二维分级主旁瓣干扰联合抑制方法

针对矩形平面阵列天线同时存在主、旁瓣干扰的单脉冲测角问题,该文设计了2维分级自适应单脉冲波束形成算法(TDHJ-ADBF)。TDHJ-ADBF算法将矩形平面阵分为方位维和俯仰维两个正交维度,采用2维分级处理架构:第1级处理在测角维进行,采用低运算量的压缩多重信号分类法对测角维主瓣干扰进行快速识别与方向估计,构造阻塞矩阵滤除主瓣干扰,获得仅含旁瓣干扰和噪声的协方差矩阵,进而对和、差波束方向图进行指向与鉴角曲线联合约束,完成测角维旁瓣干扰抑制与波束形成处理;第2级在非测角维对残留的测角维主瓣干扰进行抑制。通过2维分级处理实现主、旁瓣干扰联合对抗,并保持单脉冲测角的鉴角曲线线性度。仿真结果表明,TDHJ-ADBF算法实现了对主、旁瓣干扰联合抑制,具有高精度的单脉冲测角性能。

基于间隙波导的低剖面毫米波单脉冲天线设计

针对近些年来单脉冲雷达系统对天线的低剖面、宽频带、高效率的需求,本文设计了一种基于脊间隙波导的圆口面低剖面单脉冲阵列天线,通过去除传统的背腔层,引入双脊形辐射缝隙替代传统的矩形缝隙来拓宽带宽。相比于传统的宽边纵缝串联馈电和背腔缝隙并联馈电单脉冲天线的四层以上的结构,整个天线的层数仅为三层,结构更为紧凑。同时设计了宽带不等功分器,降低了天线副瓣。天线中心频率为35 GHz,覆盖了32.6 GHz~37.4 GHz,约4.8 GHz的频带范围,相对阻抗带宽达到了13.7%,副瓣小于-20 dB,零深优于-35 dB,天线效率大于60%,满足当前单脉冲雷达系统对天线的要求,具有广阔的应用前景。

基于非脉冲矢量网络分析仪的非反向交叉眼干扰实验设计与分析

交叉眼技术是对抗单脉冲雷达最有效的方式之一。针对交叉眼干扰多侧重于仿真建模、实验设计及实施复杂等特点,基于交叉眼干扰原理、单脉冲测角原理和矢量网络分析仪幅相精确测量等特性,设计了基于喇叭天线、微带天线、幅相调节器和非脉冲矢量网络分析仪组成的非反向交叉眼干扰实验系统。在微波暗室环境下,先后开展了基于矢量网络分析仪的测角实验和非反向交叉眼干扰实验,并通过建立干扰天线相位中心电磁仿真模型,对误差展开了分析。实验和仿真结果表明:交叉眼干扰下实验测量的角度值与理论角度值随相位差变化趋势一致,其理论最大角度值与实际最大角度值误差不超过2°,对应的交叉眼增益误差小于0.5;基于矢量网络分析仪设计的非反向交叉眼实验系统可行,可模拟非反向交叉眼干扰对被动单脉冲雷达干扰,亦可部分模拟反向交叉眼干扰应用场景,为交叉眼干扰机设计和测试提供一定的指导。

子阵级单脉冲四通道主瓣干扰对消角度分辨率分析

针对子阵级单脉冲雷达,研究了和差四通道主瓣干扰对消技术。为此,构建了二维子阵级单脉冲四通道干扰对消信号模型,并提出了以有用信号信噪比损失值为指标的定量方法来表征主瓣干扰对消角度分辨率。基于此,进一步推导了干扰对消角度分辨率的解析表达式,并明确了对消角度盲区的理论边界。仿真与暗室实验的结果验证了该解析式的正确性。研究可为四通道主瓣干扰对消技术的理论边界分析和工程实现提供参考。

An angular blinking jamming method based on electronically controlled corner reflectors

Passive jamming is believed to have very good potential in countermeasure community.In this paper,a passive angular blinking jamming method based on electronically controlled corner reflectors is proposed.The amplitude of the incident wave can be modulated by switching the corner reflector between the penetration state and the reflection state,and the ensemble of multiple corner reflectors with towing rope can result in complex angle decoying effects.Dependency of the decoying effect on corner reflectors’radar cross section and positions are analyzed and simulated.Results show that the angle measured by a monopulse radar can be significantly interfered by this method while the automatic tracking is employed.

多源圆阵反向交叉眼干扰技术研究

单脉冲雷达是一种兼顾抗干扰能力和测角精度的雷达,被广泛应用于火炮控制、目标跟踪和导弹制导等军事领域。目前交叉眼干扰是针对单脉冲雷达最为行之有效的干扰方法,其中多源圆阵反向交叉眼干扰(C-MRCJ)从理论上来说可以实现全方位稳定持续的干扰效果。针对C-MRCJ仍然存在特定情况下因测角误差为0而失效的问题,以六阵元的C-MRCJ模型,完成了单脉冲指示角和交叉眼增益的数学推导,并完成仿真验证。

基于收发分置结构的反向交叉眼干扰性能研究

交叉眼干扰是一种能够有效对抗单脉冲雷达的角度欺骗干扰。针对不同收发分置结构的两点源反向交叉眼干扰系统,考虑干扰机平台旋转的影响,建立不同天线结构的干扰信号传播路径模型,通过理论分析和仿真实验研究了不同结构模型对干扰性能的影响,验证了模型分析与实验结果的一致性。仿真实验结果表明:干扰机平台的旋转角度以及干扰机与雷达间的距离等参数对不同天线结构的干扰机性能有着不同的影响,对反向交叉眼干扰系统的工程设计具有一定的参考价值。

Single-Channel Speech Enhancement Based on Improved Frame-Iterative Spectral Subtraction in the Modulation Domain

Aiming at the problem of music noise introduced by classical spectral subtraction,a shorttime modulation domain(STM)spectral subtraction method has been successfully applied for singlechannel speech enhancement.However,due to the inaccurate voice activity detection(VAD),the residual music noise and enhanced performance still need to be further improved,especially in the low signal to noise ratio(SNR)scenarios.To address this issue,an improved frame iterative spectral subtraction in the STM domain(IMModSSub)is proposed.More specifically,with the inter-frame correlation,the noise subtraction is directly applied to handle the noisy signal for each frame in the STM domain.Then,the noisy signal is classified into speech or silence frames based on a predefined threshold of segmented SNR.With these classification results,a corresponding mask function is developed for noisy speech after noise subtraction.Finally,exploiting the increased sparsity of speech signal in the modulation domain,the orthogonal matching pursuit(OMP)technique is employed to the speech frames for improving the speech quality and intelligibility.The effectiveness of the proposed method is evaluated with three types of noise,including white noise,pink noise,and hfchannel noise.The obtained results show that the proposed method outperforms some established baselines at lower SNRs(-5 to +5 dB).

Multi-objective Optimization Based on Unsteady Analysis Considering the Efficiency and Radial Force of a Single-Channel Pump for Wastewater Treatment

A multidisciplinary optimization was conducted to simultaneously improve the efficiency and reduce the radial force of a single-channel pump for wastewater treatment. A hybrid multi-objective evolutionary algorithm was coupled with a surrogate model to optimize the geometry of the single-channel pump volute. Steady and unsteady Reynolds-averaged Navier-Stokes equations with a shear stress transport turbulence model were discretized using finite volume approximations and were then solved on tetrahedral grids to analyze the flow in the single-channel pump. The three objective functions represented the total efficiency, the sweep area of the radial force during one revolution, and the distance of the mass center of sweep area from the origin while the two design variables were related to the cross-sectional area of the internal flow of the volute. Latin hypercube sampling was employed to generate twelve design points within the design space, and response surface approximation models were constructed as surrogate models for the objectives based on the values of the objective function at the given design points. A fast non-dominated sorting genetic algorithm for local search was coupled with the surrogate models to determine the global Pareto-optimal solutions. The trade-off between the objectives was determined and was described in terms of the Pareto-optimal solutions. The results of the multi-objective optimization showed that the optimum design simultaneously improved the efficiency and reduced the radial force relative to those of the reference design.