Integrated sidelobe energy reduction technique using optimalpolyphase codes

For the distributed targets arising in most synthetic aperture radar (SAR) images, it is the integrated sidelobe (ISL) energy rather than the peak sidelobe level (PSL) that governs the performance of the pulse compression processing. A sidelobe cancellation technique is suggested which reduces the ISL energy by eliminating a significant portion of the sidelobe pattern of the pulse compression output, while the PSL is presented at the optimal Barker-code level. The efficiency of this ISL reduction is proportional to the signal code length     

Low sidelobe pattern using Woo filter concepts

This paper presents a new pulse compression technique that can reduce sidelobes significantly. The code used in this is p4, which belongs to the class of polyphase codes. This retains the merit of strong resistance to the Doppler shift effect. This processing technique, which is proposed in this paper, is useful to reduce peak sidelobe level (PSL) and integrated sidelobe level (ISL) but increases the mainlobe width. The results are compared with the Woo filter.     

Correlation Processor Based Sidelobe Suppression for Polyphase Codes in Radar Systems

Wireless Personal Communications - Peak sidelobe level (PSL), integrated sidelobe level (ISL) and signal to noise ratio (SNR) are the main performance indices in pulse compression radar. Pulse...     

Sequence Sets With Optimal Integrated Periodic Correlation Level

Sequence sets with low periodic correlations are used in many areas, such as asynchronous code-division multiple access (CDMA) systems, medical imaging, radar and sonar. Lower bounds on the integrated sidelobe level (ISL) and the peak sidelobe level (PSL) of periodic sequence sets, under a power constraint, have been previously derived in the literature. In this letter, we obtain the ISL and PSL lower bounds using a different framework. The main contribution of the letter consists in using this framework to derive closed-form expressions for all power constrained periodic sequence sets that meet the ISL lower bound.      

基于动态交替投影的失配滤波器快速设计算法

雷达脉冲压缩处理中,通常需要使用匹配滤波器以获得最优的输出信噪比.然而,对于常用雷达波形,其匹配滤波器输出距离旁瓣较高,易产生目标遮蔽效应,而通过优化设计失配滤波器可以在牺牲一定输出信噪比的条件下有效抑制距离维旁瓣.另外,在实际应用中一般需要对系统失真进行周期性标校,进而根据经过系统失真后的雷达波形进行失配滤波器设计,...     

平面稀疏阵列天线的约束优化设计

针对有阵元数和阵列口径约束的矩形平面稀疏阵天线的综合问题,提出了一种基于整数编码的差分进化算法。该方法以每个阵元的栅格位置编号作为设计变量,使阵列的稀疏率满足约束条件,避免了优化过程中的不可行解,还减少了优化变量的个数。为了加速优化过程,采用快速傅里叶变化计算阵列的方向图。以改善阵列峰值副瓣电平为目的进行仿真试验,结果表明：优化后的稀疏天线阵峰值旁瓣电平比现有方法相比改善了1.2~1.7 dB,且具有收敛性和稳定性好的优点。     

一种改进窗函数非线性组合法的旁瓣抑制性能研究

为解决在雷达脉冲压缩过程中通过海明窗、汉宁窗等加权方式降低旁瓣而引起主瓣展宽、分辨率下降的问题,提出了一种以常用窗函数为基窗函数的改进窗函数非线性组合法。首先,相较于基窗函数,基于窗函数加权脉冲压缩的原理,证明窗函数线性组合法在主瓣展宽不变时可获得更好的旁瓣抑制能力;并在此基础上进一步证明改进的窗函数非线性组合法具有更优的旁瓣抑制能力。然后,通过对改进的窗函数非线性组合法在三角窗、汉宁窗、海明窗、布莱克曼窗等作为基窗函数时的脉冲压缩性能仿真与分析,验证了该方法使用不同基窗函数均可在主瓣展宽不变、信噪比损失增加低于0.5 dB的前提下,将峰值旁瓣相比凯塞窗降低4 dB以上、相比几种常用窗函数降低7 dB以上。最后,通过多目标的仿真实验验证,相比于不同的基窗函数,改进窗函数非线性组合法具有更优的弱小目标检测能力。     

多相脉压编码在旁瓣抑制下的多普勒性能

由频率调制导出的 P3、P4多相码是一类常见的脉冲压缩信号 ,已提出的几种旁瓣抑制技术可用于降低这类脉压信号的压缩输出旁瓣。本文主要研究在使用这几种旁瓣抑制技术时 ,多普勒频移对 P3、P4多相码压缩输出性能的影响 ,包括多普勒频移对输出峰值旁瓣电平 (PSL )以及信噪比 (SNR)损失的影响。文中给出了计算机仿真结果。     

基于VMD的宽带混沌雷达多生命信号探测方法

提出并实验验证了一种基于变分模态分解（VMD）的宽带混沌雷达多生命信号探测方法。首先基于混沌相关测距获得原始回波矩阵,然后利用VMD方法抑制噪声和杂波并重构多生命信号,包括基于0 dB峰值噪声比（PNR）判决减小VMD运算量,通过中心频率分析优选 K值以及利用3 dB峰值旁瓣水平（PSL）判决自动提取呼吸信号,最后结合快速傅里叶变换（FFT）和恒虚警率（CFAR）等,同时估计墙后多个人体目标的呼吸频率和距离。实验结果表明所提方法可以实现20 cm墙后二至五个人体目标的准确、快速探测,并且具有15 cm的高距离分辨率。      

OFDM MIMO radar waveform design for targets identification

In order to obtain better target identification performance, an efficient waveform design method with high range resolution and low sidelobe level for orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) radar is proposed in this paper. First, the wideband CP-based OFDM signal is transmitted on each antenna to guarantee large bandwidth and high range resolution. Next, a complex orthogonal design (COD) is utilized to achieve code domain orthogonality among antennas, so that the spatial diversity can be obtained in MIMO radar, and only the range sidelobe on the first antenna needs suppressing. Furthermore, sidelobe suppression is expressed as an optimization problem. The integrated sidelobe level (ISL) is adopted to construct the objective function, which is solved using the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm. The numerical results demonstrate the superiority in performance (high resolution, strict orthogonality, and low sidelobe level) of the proposed method compared to existing algorithms.     

An approach for low sidelobe beamforming in uniform concentric circular arrays

In this paper, a new tapered beamforming function for sidelobe reduction in the uniform concentric circular arrays (UCCA) is proposed. This technique is based on tapering the current amplitudes of the rings in the array, where all elements in an individual ring are weighted in amplitude by the same value and the weight values of different rings are determined by a function that has a normalized-gaussian probability density function variation. This novel tapering window is optimized in its parameters to have the lowest possible sidelobe level that may reach 43 dB below the main lobe and these optimum weights are found to be function of the number of elements of the innermost ring and the number of rings in the array. The proposed tapering window can be modified to compensate the gain reduction due to tapering when compared with the uniform feeding case.     

m序列相位编码信号的最小峰值旁瓣滤波器

m序列相位编码信号最小峰值旁瓣滤波器(LP滤波器)的冲激响应序列可以通过解线性规划问题求得。对于15位和31位全部m序列的计算结果表明,LP滤波器对峰值旁瓣有较大的抑制。对[4,3,0]反馈连接的起始状态为1001的15位码,它的长度为15的LP滤波器的峰值旁瓣电平降到—21.47dB,比用匹配滤波器改善7.49dB;对[5,3,2,1,0]反馈连接的起始状态为11101的31位码,它的长度为31的LP滤波器的峰值旁瓣电平降到—23.80dB,比用匹配滤波器改善6.01dB。当滤波器的长度增加时,LP滤波器可把峰值旁瓣抑制到更低电平。     

NOVEL BIPHASE CODE——INTEGRATED SIDELOBE SUPPRESSION CODE

A kind of novel binary phase code named sidelobe suppression code is proposed in this paper.It is defined to be the code whose corresponding optimal sidelobe suppression filter outputs the minimum sidelobes.It is shown that there do exist sidelobe suppression codes better than the conventional optimal codes-Barker codes.For example,the sidelobe suppression code of length 11 with filter of length 39 has better sidelobe level up to 17dB than that of Barker code with the same code length and filter length.     

NOVEL BIPHASE CODE -INTEGRATED SIDELOBE SUPPRESSION CODE

A kind of novel binary phase code named sidelobe suppression code is proposed in this paper. It is defined to be the code whose corresponding optimal sidelobe suppression filter outputs the minimum sidelobes. It is shown that there do exist sidelobe suppression codes better than the conventional optimal codes-Barker codes. For example, the sidelobe suppression code     

Conformal four-beam antenna arrays with reduced sidelobes

Investigations on sidelobe reduction in multibeam conformal antenna arrays are presented. The recently presented concept of sidelobe reduction in planar multibeam antenna arrays in conjunction with the phase compensation technique has been applied for the design of reduced sidelobe multibeam conformal antenna arrays. Six- and eight-element antenna arrays fed by modified Butler matrices have been investigated and minimum radii have been found for which the sidelobe level is comparable to the respective planar multibeam arrays. A novel fully integrated six-element four-beam antenna array has been successfully designed in which sidelobes equal -14 dB for all four beams have been achieved.     

Simplified Sidelobe Reduction Techniques for Concentric Ring Arrays

In this paper, a simplified sidelobe reduction technique for uniform concentric circular antenna arrays (UCCA) is proposed. This technique is based on modifying some conventional windows to control the amplitude feeding instead of using adaptive techniques which require excessive processing and calculations and suffer from the lack of practical application especially for UCCA. The modified windows are applied to individual rings of the array that will taper the corresponding current amplitudes. The resulted sidelobe level, beamwidth and stability for amplitude errors are discussed for the different proposed windows where it shows a sidelobe reduction to about 49 dB as in the case of Binomial UCCA while the Hamming window shows the most immunity to tapered amplitude errors.     

A pair of asymmetric weighting receivers and polyphase codes for efficient aperiodic correlations

Sequences with low autocorrelation levels are highly desirable in digital communication. Conventional sidelobe reduction techniques have suffered from performance degradations in range resolutions and signal-to-noise ratio (SNR) gains. In this paper we propose a way to synthesize amplitude weight correlators for polyphase codes. These weighted codes generate sidelobes that are lower than those found in Barker codes. The sidelobe level is kept uniformly flat over all time delays while the range resolution loss is prevented. Unlike the Barker codes, the proposed technique is not limited by the code length. The technique is easy to implement and incurs a minimal SNR loss.     

非线性调频信号时域旁瓣抑制滤波器设计

本文研究较小时带积的非线性调频信号以 Ｎｙｑｕｉｓｔ速率采样在时域进行压缩处理的数字 ＦＩＲ滤波器设计问题。重新定义目标函数和约束条件,利用迭代加权最小二乘技术,得出了又一种设计算法。模拟和实验表明,设计处理结果在多普勒频移 ｆ_ｄ＝０时,控制 ４ｄＢ主瓣展宽并使失配信噪比损失有限条件下,峰值旁瓣电平抑制较匹配处理提高了６～１０ｄＢ。     

A set of sum-cosine window functions

This paper presents a set of windows, called sum-cosine windows, whose first side-lobe level varies from ?39-30 to ? 67-66dB, while the peak sidelobe offers ?39-30 to ? 6312dB attenuation. The asymptotic decay rate of the sidelobe envelope ranges from 12dB per octave to 36dB per octave. However, the main-lobe width of these windows falls in between Hamming and Blackman windows and Black-man windows and the optimum windows, proposed by Harris and Nuttall. The distinct advantage of these windows is their simple form, resulting in easy implementation, compared to the near-optimum windows proposed by Kaiser.     

一种数字脉压旁瓣抑制滤波器设计方法

本文使用迭代加权最小二乘法设计脉冲压缩滤波器,适用于二相码和多相码,LFM和NLFM等各种信号。由于重新定义了目标函数和约束条件,本文方法较之常用的频域加窗法性能有很大提高。多普勒频移fd=0时,在保持4dB主瓣展宽系数为1,且压缩比较低、滤波器抽头数有限条件下,峰值旁瓣电平低于-40dB。