Random-injection-based two-channel chaos with enhanced bandwidth and suppressed time-delay signature by mutually coupled lasers: Proposal and numerical analysis

Simultaneous bandwidth(BW) enhancement and time-delay signature(TDS) suppression of chaotic lasing over a wide range of parameters by mutually coupled semiconductor lasers(MCSLs) with random optical injection are proposed and numerically investigated. The influences of system parameters on TDS suppression(characterized by autocorrelation function(ACF) and permutation entropy(PE) around characteristic time) and chaos BW are investigated. The results show that, with the increasing bias current, the ranges of parameters(detuning and injection strength) for the larger BW(> 20 GHz) are broadened considerably, while the parameter range for optimized TDS(< 0.1) is not shrunk obviously.Under optimized parameters, the system can simultaneously achieve two chaos outputs with enhanced BW(> 20 GHz)and perfect TDS suppression. In addition, the system can generate two-channel high-speed truly physical random number sequences at 200 Gbits/s for each channel.

Effects of time-delayed vibration absorber on bandwidth of beam for low broadband vibration suppression

The effects of time-delayed vibration absorber(TDVA) on the dynamic characteristics of a flexible beam are investigated. First, the vibration suppression effect of a single TDVA on a continuous beam is studied. The first optimization criterion is given,and the results show that the introduction of time-delayed feedback control(TDFC) is beneficial to improving the vibration suppression at the anti-resonance band. When a single TDVA is used, the anti-resonance is located at a specific frequency by the optimum design of TDFC parameters. Then, in order to obtain low-frequency and broad bands for vibration suppression, multiple TDVAs are uniformly distributed on a continuous beam,and the relationship between the dynamic responses and the TDFC parameters is investigated. The obtained relationship shows that the TDVA has a significant regulatory effect on the vibration behavior of the continuous beam. The effects of the number of TDVAs and the nonlinearity on the bandgap variation are discussed. As the multiple TDVAs are applied, according to the different requirements on the location and bandwidth of the effective vibration suppression band, the optimization criteria for the TDFC parameters are given, which provides guidance for the applications of TDVAs in practical projects such as bridge and aerospace.

Review of Infrared signature suppression systems using optical blocking method

With rapid advancements in Infra-Red (IR) detection techniques, the range from where the IR-guided missiles are able to lock the target aircraft has increased. To avoid the detection and tracking by modern IR-guided missiles, the aircraft and helicopters also demand progress in its stealth techniques. Hence, study of Infra-Red Signature Suppression (IRSS) systems in aircraft and helicopters has become vital even in design stage. Optical blocking (masking) is one of the effective IRSS techniques used to block the Line- Of-Sight (LOS) of the hot engine parts of the exhaust geometry. This paper reviews the various patents on IR signature suppression systems based on the optical blocking method or a combination of IRSS techniques. The performance penalties generated due to installation of various IRSS methods in aircraft and helicopters are also discussed.

柴油机湿式排气系统红外抑制效果研究

[目的]舰船湿式舷侧排气系统在一些隐身护卫舰上广泛应用,有必要对湿式舷侧排气系统的红外抑制效果进行研究。[方法]分析湿式舷侧排气系统红外抑制原理,以某船为研究对象,建立主推进柴油机舷侧排气系统数学模型,对红外抑制效果进行仿真计算和理论分析,结合航行试验开展实船红外测量。[结果]仿真计算结果表明,采用湿式舷侧排气后,排气出口温度可降低至约60℃,相比于采用烟囱空气引射红外抑制装置的方式,湿式舷侧排气系统红外辐射强度可大幅降低;实船红外测量结果表明,经过喷水降温,排气出口温度降低至约66.7~70.0℃,3~5μm红外辐射强度约1.39 W/sr,具有较好的红外辐射抑制效果。[结论]研究结果对湿式舷侧排气系统在舰船红外抑制中的应用具有借鉴意义。

Experimental investigation on the time-delay signature of chaotic output from a 1550 nm VCSEL subject to FBG feedback

The time-delay signature(TDS) of chaos output in a 1550 nm vertical-cavity surface-emitting laser(VCSEL) subject to fiber Bragg grating(FBG) feedback is investigated experimentally. Autocorrelation function(ACF) and mutual information(MI) are used for quantitatively identifying the TDS of chaos. For various bias currents, the TDS evolution with the feedback strength is different, as the FBG provides wavelength-selective feedback. Furthermore,based on the TDS map of the FBG feedback VCSEL(FBGF-VCSEL) in the parameter space of feedback strength and bias current, the optimal TDS suppression regions, where the dominant polarization mode of FBGF-VCSEL locates at the edge of the main lobe of FBG reflection spectrum, have been determined. Finally, for comparative purpose,the TDS of chaos in mirror feedback VCSEL(MF-VCSEL) also has been presented, and the results show that an FBGF-VCSEL possesses better TDS suppression performance than an MF-VCSEL.

Time-delay signature concealment of polarizationresolved chaos outputs in vertical-cavity surface-emitting lasers with variable-polarization filtered optical feedback

Through employing permutation entropy and the self-correlation function, the time-delay signature （TDS） of a vertical-cavity surface-emitting laser （VCSEL） with variable-polarization filtered optical feedback （VPFOF） is evaluated theoretically. The work shows that the feedback rate η, polarizer angle Op, and filter bandwidth A have an obvious influence on the TDS. The evolution maps of the TDS in parameter space （η, A） and （ηθp） are simulated for searching the chaos with weak TDS. Furthermore, compared with a VCSEL with polarization-preserved filtered optical feedback and a VCSEL with variable-polarization mirror optical feedback, this VPFOF-VCSEL shows superiority in TDS suppression.

Time-delay signature characteristics of the chaotic output from an optoelectronic oscillator by introducing an optical feedback

In this work,via autocorrelation function(ACF)and permutation entropy(PE)methods,we numerically investigate the time-delay signature(TDS)characteristics of the chaotic signal output from an optoelectronic oscillator(OEO)after introducing an extra optical feedback loop.The results demonstrate that,for such a chaotic system,both the optoelectronic feedback with a delay time of T1 and the optical feedback with a delay time of T2 contribute to the TDS of generated chaos.The TDS of the chaotic signal should be evaluated within a large time window including T1 and T2 by the strongest peak in the ACF curve of the chaotic signal,and the strongest peak may locate at near T1 or T2.Through mapping the evolution of the TDS in the parameter space of the optical feedback strength and time,certain optimized parameter regions for achieving a chaotic signal with a relatively weak TDS can be determined.

直升机排气系统红外抑制器的模型实验研究

对直升机排气系统红外抑制器进行了一系列的模型试验研究,旨在分析引射混合和遮挡隔热对降低目标红外辐射特征的作用机制和抑制效果,并对缩比模型的红外辐射相似关系进行探讨.结果表明: (1)引射冷气掺混具有降低排气温度和混合管壁面温度的双重作用,其降温效果在大引射流量比下非常显著;当遮挡间距大于 20mm,遮挡隔热可以使遮挡罩壁温接近于环境温度. (2)引射混合对总体红外辐射强度抑制约 85%;在此基础上进行隔热遮挡可以再抑制 10%. (3)在保持主流速度、温度和压力均相同的条件下,不同缩比模型的辐射亮度基本相当;红外辐射强度基本上与模型的几何模化比平方成正比.

粉末气溶胶抑制热喷流红外辐射特性实验

针对红外制导武器的快速发展和应用，降低飞行器热喷流红外辐射特征是有效的应对措施。为获得粉末气溶胶对热喷流红外抑制效果及基本规律，就3-5μm和8-14μm两个红外测试波段，在不同角度、不同气固质量比下对比研究了两种粉末气溶胶对热喷流的红外抑制特性。实验结果证明喷射粉末气溶胶可有效抑制热喷流红外辐射，B材料在3～5μm遮蔽效果显著，抑制率达到80％，A材料在两个测试波段均有较好的遮蔽效果。

直升机排气系统用波瓣喷管引射-混合式红外抑制器研究

在针对直升机排气系统用波瓣喷管引射-混合式红外抑制器开展的一系列数值计算和模型实验研究基础上,对其内流气动特性和红外辐射特性进行较为系统的综合总结。揭示并分析了这种形式的红外抑制器内部混合流动特征,引射混合和隔热遮挡的红外抑制作用效果,以及红外抑制器缩比模型红外辐射模化关系;同时也指出了需进一步研究的一些问题。

模化比对船用排气红外抑制装置红外辐射特性的影响及修正

在两种典型船用燃气轮机排气系统红外抑制装置数值计算和试验测量的基础上 ,根据相似理论 ,分析讨论了模化比对气流和壁面温度场分布以及红外辐射强度的影响 .根据实物排气红外抑制系统的相应参数和模化比影响的量级 。

基于空间特征的MIMO穿墙雷达墙杂波抑制

在穿墙成像中,墙体反射波相对于目标回波具有很强的能量,因此对目标的成像及检测造成严重干扰。传统的空域滤波方法基于单发单收阵列体制,利用墙体空间特征不变性有效地抑制墙体杂波。随着MIMO技术越来越多的应用于穿墙雷达,墙体空间特征发生变化,该方法不再适用于MIMO穿墙雷达回波。为解决这一问题,该文分析了MIMO穿墙雷达回波中墙体与目标回波的空间特征,参数化建模结果表明,墙体回波的空间特征与天线阵列的位置无关且具有对称性,而目标回波不具有该特性。根据两者的这一差异,该文提出对称消去法来消除墙体回波。仿真结果表明该方法能够有效地消除墙体杂波,且能够保留目标的全部信息。

相干干扰对基于特征空间分解算法性能的影响

分析干扰信号的互相关性和方向矢量正交性对接收信号自相关矩阵的特征值和特征向量分布的影响。干扰相关时,会有信号特征矢量发散到噪声空间,采用基于特征空间分解的自适应算法,只有在相干干扰的来向相同时才能实现干扰抑制,否则不能抑制此相干干扰;干扰不相关时,如果干扰来向相同,只能检测到一个干扰,但此时基于特征空间分解的自适应算法可实现干扰抑制。对MUSIC(multiple signal classification)和最小范数算法的仿真结果,与理论推导一致。

直升机红外隐身技术研究

本文主要分析讨论了直升机红外隐身技术措施和一体化红外抑制器方案,通过对一体化红外抑制器主喷管和混合管缩比模型试验件进行热态试验,测量了在不同下洗气流速度下出口截面的排气温度场和红外辐射特性,得到了一体化红外抑制器的性能情况,试验结果表明,所提出的一体化红外抑制器具有很好的红外抑制效果。

双通道视频信息处理数据融合技术

“飞鱼”类掠海反舰导弹已对水面大型舰艇的生存构成重大威胁,而近程反导舰炮武器系统是反“飞鱼”类掠海反舰导弹的最后防线。因此,实现成功拦截掠海反舰导弹,精确稳定地自动跟踪目标,是近程反导舰炮武器系统的关键技术之一。阐述了适合自动跟踪高速飞行掠海导弹的双通道视频处理器的构成。对工作原理、去噪预处理、图像分割、特征抽取、识别和位置检测等技术作了简要说明,并对核心部分——双通道视频信息的资源利用和数据融合处理作了较详细的论述。双通道并行处理数据融合技术在国内首次应用于××近程反导舰炮武器系统光电跟踪仪中,在海上定型试验中取得了很好的跟踪效果。

气体引射器型红外抑制器的结构及性能研究

通过介绍红外抑制器的工作原理 ,用实验和数值方法分析了由不同的抑制器结构引起的不同红外抑制效果。通过对多组参数的数值计算和实验测量 ,得出了有关结构参数对红外抑制装置工作性能的影响规律 ,为以后抑制器的设计提出了最佳的组合方案和取值范围。实验结果表明 ,装置有较好的红外抑制效果。

几何参数对S弯喷管红外辐射特性的影响

为了深入理解和掌握S弯喷管的红外辐射特性,采用数值模拟的方法着重研究了轴向长度比和中心线变化规律这两个几何参数对S弯喷管红外辐射特性的影响。结果表明,S弯喷管在水平探测面上的燃气红外辐射强度比垂直探测面上的低61.1%。同时,在垂直探测面上,下方的壁面红外辐射强度高于上方的。轴向长度比和中心线不同的S弯喷管,总红外辐射强度的变化在2.2%~6.3%。虽然S弯喷管轴向长度比和中心线变化规律对喷管性能有显著的影响,但其对红外辐射特性的影响较小。因此,仅从红外辐射的角度,在S弯喷管的设计过程中轴向长度比和中心线变化规律可不作为主要考虑因素。

弹用航空发动机尾喷流红外抑制技术研究

详细介绍了弹用航空发动机红外抑制技术开展的一系列试验和数值分析。这些工作均取得了较好的结果，为今后此项技术的进一步深入研究直至工程应用打下了良好的基础。

军用飞机特征信号抑制要求研究

分析了国内外现有标准规范对军机特征信号的抑制要求,指出其不足之处。根据周边国家和地区装备的雷达和光学探测装置的主要性能,研究了我国现阶段军机面临的主要威胁及其特点;提出了我国现阶段新型战斗机雷达与红外隐身设计的主要要求,包括隐身频段、隐身姿态及应具有的隐身性能。

一种基于慢时域盲分离的欺骗干扰抑制方法

针对单脉冲比幅雷达的距离假目标欺骗干扰,研究了一种基于慢时域盲分离的欺骗干扰抑制方法。该方法在慢时域上建立雷达信号接收模型,首先验证了回波与干扰的可分离性,然后采用二阶统计盲源分离技术完成了回波和干扰的分离,最后通过微多普勒频率特征完成对真假目标的鉴别。仿真结果表明,该算法对欺骗干扰具有较好的抑制性能。当SNR>0dB时,回波相似系数大于98%,延迟时间测量误差小于0.03μs。