Beidou receiver based on anti-jamming antenna arrays with self-calibration for precise relative positioning

Unmanned aerial vehicles(UAVs)may be subjected to unintentional radio frequency interference(RFI)or hostile jamming attack which will lead to fail to track global navigation satellite system(GNSS)signals.Therefore,the simultaneous realization of anti-jamming and high-precision carrier phase difference positioning becomes a dilemmatic problem.In this paper,a distortionless phase digital beamforming(DBF)algorithm with self-calibration antenna arrays is proposed,which enables to obtain distortionless carrier phase while suppressing jamming.Additionally,architecture of high precision Beidou receiver based on anti-jamming antenna arrays is proposed.Finally,the performance of the algorithm is evaluated,including antenna calibration accuracy,carrier phase distortionless accuracy,and carrier phase measurement accuracy without jamming.Meanwhile,the maximal jamming to signal ratio(JSR)and real time kinematic(RTK)positioning accuracy under wideband jamming are also investigated.The experimental results based on the real-life Beidou signals show that the proposed method has an excellent performance for precise relative positioning under jamming when compared with other anti-jamming methods.

Anti-Jamming Null Space Projection Beamforming Based on Symbiotic Radio

With the development of information technology,more and more devices are connected to the Internet through wireless communication to complete data interconnection.Due to the broadcast characteristics ofwireless channels,wireless networks have suffered more and more malicious attacks.Physical layer security has received extensive attention from industry and academia.MIMO is considered to be one of the most important technologies related to physical layer security.Through beamforming technology,messages can be transmitted to legitimate users in an offset direction that is as orthogonal as possible to the interference channel to ensure the reception SINR by legitimate users.Combining the symbiotic radio(SR)technology,this paper considers a symbiotic radio antijamming MIMO system equipped with a multi-antenna system at the main base station.In order to avoid the interference signal and improve the SINR of the signal received by the user.The base station is equipped with a uniform rectangular antenna array,and using Null Space Projection(NSP)Beamforming,Intelligent Reflecting Surface(IRS)can assist in changing the beam’s angle.The simulation results show that NSP Beamforming could make a better use of the null space of interference,which can effectively improve the received SINR of users under directional interference,and improve the utilization efficiency of signal energy.

Studies on Novel Anti-jamming Technique of Unmanned Aerial Vehicle Data Link

Based on the M-ary spread spectrum （M-ary-SS）, direct sequence spread spectrum （DS-SS）, and orthogonal frequency division multiplex （OFDM）, a novel anti-jamming scheme, named orthogonal code time division multi-subchannels spread spectrum modulation （OC-TDMSCSSM）, is proposed to enhance the anti-jamming ability of the unmanned aerial vehicle （UAV） data link. The anti-jamming system with its mathematical model is presented first, and then the signal formats of transmitter and receiver are derived. The receiver＇s bit error rate （BER） is demonstrated and anti-jamming performance analysis is carded out in an additive white Ganssian noise （AWGN） channel. Theoretical research and simulation results show the anti-jamming performance of the proposed scheme better than that of the hybrid direct sequence frequency hopping spread spectrum （DS/FH SS） system. The jamming margin of the OC-TDMSCSSM system is 5 dB higher than that of DS/FH SS system under the condition of Rician channel and full-band jamming, and 6 dB higher under the condition of Rician channel environment and partial-band jamming.

含J-C损伤的前吸能装置低速碰撞多目标优化

为提升前吸能装置整体碰撞性能,建立了含防撞梁、吸能盒和刚性墙的100%正面低速碰撞有限元显式动力学模型,及前吸能装置多目标优化模型。采用Johnson-Cook损伤本构模拟铝合金材料碰撞损伤特性,以整车最大质心加速度、最大质心位移和吸能装置总质量等评价指标为优化目标,以防撞梁和吸能盒截面的宽度、长度和厚度等7个结构尺寸作为设计变量,以吸能装置最大吸收能量为约束条件。采用NSGA-Ⅱ算法对前吸能装置多目标优化模型进行求解,优化结构与初始设计结构进行40%偏置碰撞对比验证。通过分析100%低速正面碰撞多目标优化结果可知,在整车最大质心位移增加约3%的情况下,最大质心加速度和最大防撞梁碰撞力下降35%以上,前吸能装置减重达23%。由40%低速偏置碰撞对比验证结果可知,整车最大质心加速度、最大质心位移和防撞梁碰撞力峰值等性能参数较优化前下降10%以上。研究结果为前吸能装置碰撞性能优化提供设计参考。

CYP2J2通过激活Notch1途径改善慢性间歇性低氧后心血管损伤的实验研究

目的:探讨细胞色素P450表氧化酶2J2(CYP2J2)对慢性间歇性低氧(CIH)模型大鼠心血管损伤的影响及机制。方法:将50只SD大鼠随机分为对照组、CYP2J2组、CIH组、CIH+CYP2J2组、CIH+CYP2J2+DAPT组,每组10只。CIH组、CIH+CYP2J2组及CIH+CYP2J2+DAPT组大鼠均构建CIH模型;造模成功后,CYP2J2组、CIH+CYP2J2组、CIH+CYP2J2+DAPT组大鼠一次性尾静脉注射携带CYP2J2基因的重组腺病毒;CIH+CYP2J2+DAPT组再通过腹腔注射DAPT。2周后,采用高分辨率小动物超声影像系统测定各组大鼠左室缩短分数(FS)、射血分数(EF)、左室收缩末期容积(LVESV)和左室舒张末期容积(LVEDV);自动生化分析仪检测血清肌酸激酶同工酶(CK-MB)与心肌肌钙蛋白I(cTnI)含量;硝酸还原酶法测定血清一氧化氮(NO)含量;酶联免疫吸附法(ELISA)测定血浆内皮素-1(ET-1)含量;苏木精-伊红(HE)染色观察主动脉及心肌组织形态学变化;末端DNA转移酶dUTP缺口末端标记法(TUNEL)染色观察心肌细胞凋亡情况;生化指标检测试剂盒测定心肌组织超氧化物歧化酶(SOD)活性与丙二醛(MDA)含量;蛋白免疫印迹法(Western Blot)测定心肌组织Notch受体1(Notch1)信号途径相关蛋白表达水平。结果:与CIH组比较,CIH+CYP2J2组大鼠FS和NO水平升高,LVESV、LVEDV及CK-MB、cTnI、ET-1水平均降低,主动脉结构基本清晰,细胞肿大、脱落及血管壁增厚等现象均有所改善,心肌纤维断裂、心肌细胞肿大等现象减轻,心肌组织TUNEL阳性细胞比例减少,SOD活性升高,MDA含量下降,Notch1和Hes1蛋白相对表达量上调,差异均有统计学意义(P<0.05)。与CIH+CYP2J2组比较,CIH+CYP2J2+DAPT组大鼠FS和NO水平降低,LVESV、LVEDV及CK-MB、cTnI、ET-1水平均升高,主动脉组织及心肌组织病理损伤现象显著,心肌组织TUNEL阳性细胞比例增加,SOD活性下降,MDA含量升高,Notch1和Hes1蛋白相对表达量下调,差异均有统计学意义(P<0.05)。结论:CYP2J2可改善CIH大鼠心血管损伤,减少心肌细胞凋亡,并抑制氧化应激水平,该机制可能与激活Notch1途径有关。

腺病毒载体介导编辑chNHE1基因对J亚群禽白血病病毒抗性研究

鸡Na~+/H~+离子交换蛋白-1(chNHE1)是J亚群禽白血病病毒(ALV-J)的细胞受体,是ALV-J感染的细胞靶点。为了探索鸡抗禽白血病的育种目标,试验构建了定点编辑chNHE1基因的CRISPR/Cas9腺病毒系统,并对编辑后细胞抗ALV-J感染能力进行评价。结果显示:使用CRISPR/Cas9腺病毒载体介导的ssODNs同源重组方案可以在chNHE1中引入突变,其中36%单克隆细胞株存在W38缺失;T37缺失的细胞对ALV-J感染具备极显著的抗性;W38缺失的细胞对ALV-J感染具有完全抗性,同时具有E35A替换、P36缺失、T37缺失的细胞对ALV-J感染也具有完全抗性。研究表明,CRISPR/Cas9腺病毒载体可以有效地编辑鸡DF-1细胞,W38缺失或E35A替换P36、T37缺失都可以使DF-1对ALV-J感染具有抗性,该方案为培育抗ALV-J感染的基因编辑鸡提供技术储备。

海南省文昌鸡主要养殖地区A、B和J亚群禽白血病的血清学调查和分析

为了解海南省文昌鸡A、B和J亚群禽白血病病毒(ALV)的感染情况,于2021年12月—2022年12月分别从海南省文昌鸡主要养殖地区(海口市、文昌市、儋州市、琼海市和澄迈县)的鸡场随机采集鸡血清样品1746份,采用酶联免疫吸附试验(ELISA)进行ALV-J和ALV-A/B抗体检测,并统计分析不同地区、不同生长阶段、不同季节、不同规模鸡场、不同类型鸡血清ALV-J和ALV-A/B的抗体阳性率。结果显示,1746份血清样品中共检出ALV-J抗体阳性样品182份,总抗体阳性率为10.42%(95%CI:8.99%~11.86%);共检出ALV-A/B抗体阳性样品5份,总抗体阳性率为0.29%(95%CI:0.04%~0.54%);5个地区的鸡场均有不同程度的ALV-J感染,其中儋州市ALV-J抗体阳性率最高,达到50.00%(30/60)(95%CI:37.24%~62.76%);ALV-A/B抗体阳性样品仅在海口市检出,抗体阳性率为0.49%(5/1011)(95%CI:0.06%~0.93%);成年鸡ALV-J抗体阳性率显著高于育成鸡和雏鸡(P<0.05),达到14.60%(138/945)(95%CI:12.35%~16.86%);ALV-J在一年四季均有感染,以冬季感染率最高,抗体阳性率为23.12%(86/372)(95%CI:18.83%~27.41%);ALV-A/B抗体阳性样品仅在夏秋两季检出;小型和中型鸡场的ALV-J抗体阳性率明显高于大型鸡场(P<0.05),分别为20.42%(88/431)(95%CI:16.61%~24.23%)和21.48%(29/135)(95%CI:14.52%~28.44%);商品代肉鸡的ALV-J抗体阳性率最高,为20.13%(61/303)(95%CI:15.61%~24.65%)。结果表明,在海南省文昌鸡养殖地区存在ALV-J感染,ALV-A/B仅在海口市零星发生;ALV-J感染在冬季和成年文昌鸡群中较多,以商品代肉鸡感染最为严重,因此,应针对性地加强对海南省文昌鸡ALV-J的防控。

GNSS array receiver faced with overloaded interferences:anti-jamming performance and the incident directions of interferences

Anti-jamming solutions based on antenna arrays enhance the anti-jamming ability and the robustness of global navigation satellite system(GNSS)receiver remarkably.However,the performance of the receiver will deteriorate significantly in the overloaded interferences scenario.We define the overloaded interferences scenario as where the number of interferences is more than or equal to the number of antenna arrays elements.In this paper,the effect mechanism of interferences with different incident directions is found by studying the anti-jamming performance of the adaptive space filter.The theoretical analysis and conclusions,which are first validated through numerical examples,reveal the relationships between the optimal weight vector and the eigenvectors of the input signal autocorrelation matrix,the relationships between the interference cancellation ratio(ICR),the signal to interference and noise power ratio(SINR)of the adaptive space filter output and the number of interferences,the eigenvalues of the input signal autocorrelation matrix.In addition,two simulation experiments are utilized to further corroborate the theoretical findings through soft anti-jamming receiver.The simulation results match well with the theoretical analysis results,thus validating the effect mechanism of overloaded interferences.The simulation results show that,for a four elements circular array,the performance difference is up to 19 dB with different incident directions of interferences.Anti-jamming performance evaluation and jamming deployment optimization can obtain more accurate and efficient results by using the conclusions.

An Active Anti-Jamming Approach for Frequency Diverse Array Radar with Adaptive Weights

Due to the rapid development of electronic countermeasures(ECMs),the corresponding means of electronic counter countermeasures(ECCMs)are urgently needed.In this paper,an act-ive anti-jamming method based on frequency diverse array radar is proposed.By deriving the closed form of the phase center in a uniform line array FDA,we establish a model of the FDA signal based on adaptive weights and derive the effect of active anti-jamming in this regime.The pro-posed active anti-jamming method makes it difficult for jammers to detect or locate our radar.Fur-thermore,the effectiveness of the two frequency increment schemes in terms of anti-jamming is ana-lyzed by comparing the deviation of phase center.Finally,the simulation results verify the effective-ness and superiority of the proposed method.

Space-borne antenna adaptive anti-jamming method based on gradient-genetic algorithm

A novel space-borne antenna adaptive anti-jamming method based on the genetic algorithm （GA）, which is combined with gradient-like reproduction operators is presented, to search for the best weight for pattern synthesis in radio frequency （RF）. Combined, the GA＇s the capability of the whole searching is, but not limited by selection of the initial parameter, with the gradient algorithm＇s advantage of fast searching. The proposed method requires a smaller sized initial population and lower computational complexity. Therefore, it is flexible to implement this method in the real-time systems. By using the proposed algorithm, the designer can efficiently control both main-lobe shaping and side-lobe level. Simulation results based on the spot survey data show that the algorithm proposed is efficient and feasible.

Put Others Before Itself:A Multi-Leader One-Follower Anti-Jamming Stackelberg Game Against Tracking Jammer

This paper mainly investigates the coordinated anti-jamming channel access problems in multiuser scenarios where there exists a tracking jammer who senses the spectrum and traces the channel with maximal receiving power.To cope with the challenges brought by the tracking jammer,a multi-leader onefollower anti-jamming Stackelberg(MOAS)game is formulated,which is able to model the complex interactions between users and the tracking jammer.In the proposed game,users act as leaders,chose their channel access strategies and transmit firstly.The tracking jammer acts as the follower,whose objective is to find the optimal jamming strategy at each time slot.Besides,the existence of Stackelberg equilibriums(SEs)is proved,which means users reach Nash Equilibriums(NEs)for each jamming strategy while the jammer finds its best response jamming strategy for the current network access case.An active attraction based anti-jamming channel access(3ACA)algorithm is designed to reach SEs,where jammed users keep their channel access strategies unchanged to create access chances for other users.To enhance the fairness of the system,users will adjust their strategies and relearn after certain time slots to provide access chances for those users who sacrifice themselves to attract the tracking jammer.

Throughput Analysis of Dynamic Spectrum Anti-Jamming Multiple-Access in HF Communication Systems

A multiple-access networking scheme based on the new dynamic spectrum anti-jamming system is proposed in this paper. The network consists of a center node and multiple user nodes. The center node detects spectrum holes in the operation band periodically according to the user performance target. Detected spectrum holes are allocated to users who request communication. Throughput of this networking scheme is analyzed over a high-frequency(HF) interference channel. The effect of error correction coding and spectrum hole information transmission error is discussed. Throughput of this scheme and conventional frequency-hopping multiple-access(FHMA) scheme are compared. Results show that user performance increase leads to throughput decrease, which can be offset by error correction coding. If spectrum hole information transmission is in error, the throughput is not affected much as long as the bit error rate is below 10-2. Furthermore, throughput of this scheme is obviously superior to the throughput of FHMA scheme.

Cognitive anti-jamming receiver under phase noise in high frequency bands

This paper investigates the jamming sensing performance of the simultaneous transmit and receive based cognitive anti-jamming(SCAJ) receiver impaired by phase noise in local oscillators(LO) over fading channels. Firstly, energy detection(ED)based on the jamming to noise ratio(JNR) of the high frequency bands SCAJ receiver with phase noise under different channels is analyzed. Then, the probabilities of jamming detection and false alarm in closed-form for the SCAJ receiver are derived. Finally,the modified Bayesian Cramer-Rao bound(BCRB) of jamming sensing for the SCAJ receiver is presented. Simulation results show that the performance degradation of the SCAJ system due to phase noise is more severe than that due to the channel fading in the circumstances where the signal bandwidth(BW) is kept a constant. Moreover, the signal BW has an effect on the phase noise in LO, and the jamming detection probability of the wideband SCAJ receiver with lower phase noise outperforms that of the narrowband receiver using the same center frequency. Furthermore,an accurate phase noise estimation and compensation scheme can improve the jamming detection capability of the SCAJ receiver in high frequency bands and approach to the upper bound.

Combined algorithm of acquisition and anti-jamming based on SFT

A communication and navigation receiver is required to remove hostile jamming signals and synchronize receiving signals effectively especially for satellite communication and navigation whose resources are becoming more and more limited. This paper proposes a novel signal receiving method by combining the pro- cesses of anti-jamming and synchronization to reduce the overall computationa~ complexity at the expense of slightly affecting the detection probability, which is analyzed in detail by derivations. Furthermore, this paper introduces sparse Fourier transformation （SFT） into the proposed algorithm to replace fast Fourier transfor- mation （FFT） so as to further reduce the calculation time especially in large frequency offset environments.

Anti-Jamming Algorithm Based on Spatial Blind Search for Global Navigation Satellite System Receiver

A novel subspace projection anti-jamming algorithm based on spatial blind search is proposed,which uses multiple single-constrained subspace projection parallel filters.If the direction of arrival(DOA)of a satellite signal is unknown,the traditional subspace projection anti-jamming algorithm cannot form the correct beam pointing.To overcome the problem of the traditional subspace projection algorithm,multiple single-constrained subspace projection parallel filters are used.Every single-constrained anti-jamming subspace projection algorithm obtains the optimal weight vector by searching the DOA of the satellite signal and uses the output of cross correlation as a decision criterion.Test results show that the algorithm can suppress the jamming effectively,and generate high gain toward the desired signal.The research provides a new idea for the engineering implementation of a multi-beam anti-jamming algorithm based on subspace projection.

基于Neo4j和Django的天人相应知识图谱构建研究

目的通过Neo4j图数据库和Django框架构建天人相应知识图谱,探析天人相应理论在中医临床中的实际应用。方法以《河洛精蕴》《淮南子》《五行大义》《素问》《灵枢》《说文解字》《周易》为数据来源,通过人工标注、专家筛选的方法抽取结构化数据,采用图数据库技术构建知识图谱,并搭建以Django框架为核心的Web系统。结果共抽取得到天干、地支、八卦等18种实体,节点151个;阴阳、五脏、五行等12种关系,连线206条,完成天人相应知识图谱构建,并实现天人相应理论的知识可视化及知识查询功能。结论天人相应理论在中医理论中占据关键地位,天人相应知识图谱可有效解决领域内知识孤岛问题,为研究人员从天人相应角度解决中医临床问题提供新思路。

基于手机拍照结合Image J软件对干辣椒外观品质的分级研究

干辣椒外观形状和色泽是其品质分类的重要指标。目前GB 10465—1989《辣椒干》中对干辣椒外观形状和色泽的检测方式还停留在人工检测阶段,通常受到主观感知、误差、视觉生理等多种因素影响,未形成科学标准化的检测方法。该研究利用手机拍照对干辣椒获取图像,通过Image J软件进行图像处理,提出了一种便捷、快速、准确的干辣椒外观形状相关特征量的测定方法。与游标卡尺法、剪纸法等人工测量相比,该方法更方便快速,可用于干辣椒的长度、宽度、面积等表型指标的测量。同时,通过构建红绿蓝(RGB)色彩模型获得干辣椒的外观颜色特征参数,色泽分选采用R/(G+B)比率为分级依据,结合干辣椒宽长比和面积可以将干辣椒分为优质、合格、不合格3个等级。

Dynamic Spectrum Anti-Jamming with Distributed Learning and Transfer Learning

Physical-layer security issues in wireless systems have attracted great attention.In this paper,we investigate the spectrum anti-jamming(AJ)problem for data transmissions between devices.Considering fast-changing physical-layer jamming attacks in the time/frequency domain,frequency resources have to be configured for devices in advance with unknown jamming patterns(i.e.the time-frequency distribution of the jamming signals)to avoid jamming signals emitted by malicious devices.This process can be formulated as a Markov decision process and solved by reinforcement learning(RL).Unfortunately,stateof-the-art RL methods may put pressure on the system which has limited computing resources.As a result,we propose a novel RL,by integrating the asynchronous advantage actor-critic(A3C)approach with the kernel method to learn a flexible frequency pre-configuration policy.Moreover,in the presence of time-varying jamming patterns,the traditional AJ strategy can not adapt to the dynamic interference strategy.To handle this issue,we design a kernelbased feature transfer learning method to adjust the structure of the policy function online.Simulation results reveal that our proposed approach can significantly outperform various baselines,in terms of the average normalized throughput and the convergence speed of policy learning.

Anti-jamming channel access in 5G ultra-dense networks: a game-theoretic learning approach

This paper investigates the Quality of Experience(QoE)oriented channel access anti-jamming problem in 5th Generation Mobile Communication(5G)ultra-dense networks.Firstly,considering that the 5G base station adopts beamforming technology,an anti-jamming model under Space Division Multiple Access(SDMA)conditions is proposed.Secondly,the confrontational relationship between users and the jammer is formulated as a Stackelberg game.Besides,to achieve global optimization,we design a local cooperation mechanism for users and formulate the cooperation and competition among users as a local altruistic game.By proving that the local altruistic game is an Exact Potential Game(EPG),we further prove the existence of pure strategy Nash Equilibrium(NE)among users and Stackelberg Equilibrium(SE)between users and jammer.Thirdly,to obtain the equilibrium solutions of the proposed games,we propose an anti-jamming channel selection algorithm and improve its convergence speed through heterogeneous learning parameters.The simulation results validate the convergence and effectiveness of the proposed algorithm.Compared with the throughput optimization scheme,our proposed scheme obtain a greater network satisfaction rate.Finally,we also analyze user fairness changes during the algorithm convergence process and get some interesting conclusions.

Comparison of the Radar Receiver Anti-Jamming Circuits Performance

This paper researches on some key technologies of anti-jamming of an air-borne radar receiver, the automatic testing of AGC, IAGC and multi-filtering under one million noisy pulses by the computer simulation system. The system tests the width of the jamming pulse whose width is 100% bigger, 60% bigger and 100% smaller than the Radar signal’s respectively and show the SNR curve.