The m series with 511 bits is taken as an example being applied in non-coherent integra- tion algorithm. A method to choose the bi-phase code is presented, which is 15 kinds of codes are picked out of 511 kinds of m s...The m series with 511 bits is taken as an example being applied in non-coherent integra- tion algorithm. A method to choose the bi-phase code is presented, which is 15 kinds of codes are picked out of 511 kinds of m series to do non-coherent integration. It is indicated that the power in- creasing times of larger target sidelobe is less than the power increasing times of smaller target main- lobe because of the larger target＇ s pseudo-randomness. Smaller target is integrated from larger tar- get sidelobe, which strengthens the detection capability of radar for smaller targets. According to the sidelobes distributing characteristic, a method is presented in this paper to remove the estimated sidelobes mean value for signal detection after non-coherent integration. Simulation results present that the SNR of small target can be improved approximately 6. 5 dB by the proposed method.展开更多
Worldwide Interoperability for Microwave Access(WiMAX)trusts Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing(MIMO-OFDM)combination for the deployment of physical layer functions and for conne...Worldwide Interoperability for Microwave Access(WiMAX)trusts Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing(MIMO-OFDM)combination for the deployment of physical layer functions and for connecting the medium access control to the wireless media.Even though Orthogonal Frequency Division Multiplexing(OFDM)facilitates reliable digital broadband transmission in the fading wireless channels,the presence of synchro-nization errors in the form of Carrier Frequency Offset(CFO)and Time Offset(TO)adversely affect the performance of OFDM based physical layers.The objective of this work is to improve the accuracy of the frequency and the time offset estimation in the WiMAX physical layer.A method to enhance the synchro-nization accuracy byfine-tuning the merit factor of the preamble sequence is sug-gested in this paper.Also,a new preamble with improved synchronization accuracy is proposed for the WiMAX system.The performance of the proposed preamble is evaluated in a Rayleigh fading channel and the results of simulations show that the Mean Square Error(MSE)in offset estimation is significantly reduced and it outperforms the standard WiMAX preamble.展开更多
针对雷达射频隐身波形设计中的复杂调制问题,本文提出脉间复合调频与脉内多相码调相的复合策略。在脉间采用非线性的调频特征调制Costas信号各恒定频率,并在脉内采用多相位编码方式调制信号的相位特征,进而得到IPNC-PC信号。采用脉间复...针对雷达射频隐身波形设计中的复杂调制问题,本文提出脉间复合调频与脉内多相码调相的复合策略。在脉间采用非线性的调频特征调制Costas信号各恒定频率,并在脉内采用多相位编码方式调制信号的相位特征,进而得到IPNC-PC信号。采用脉间复合调频增加了信号的时频复杂度,脉内多相码调相增加了信号的相位随机性。仿真结果表明:IPNC-PC信号具备近似“图钉型”的模糊图,自相关旁瓣电平达到-41dB、主瓣宽度变窄率最高达到39%、功率谱峰值低于-10 d B。IPNC-PC信号具有低截获性,射频隐身性能良好,在现代电子战中有良好的应用前景。展开更多
工作于高频(HF)、甚高频(VHF)和超高频(UHF)拥塞频段的宽频带雷达,面临频带使用限制以及多种无线通讯系统同频窄带干扰的问题.对此,该文以峰均功率比(peak-to-average power ratio,PAR)为约束条件,建立联合优化功率谱密度(power spectru...工作于高频(HF)、甚高频(VHF)和超高频(UHF)拥塞频段的宽频带雷达,面临频带使用限制以及多种无线通讯系统同频窄带干扰的问题.对此,该文以峰均功率比(peak-to-average power ratio,PAR)为约束条件,建立联合优化功率谱密度(power spectrum density,PSD)和积分旁瓣电平(integrated sidelobe level,ISL)的波形设计目标函数,提出了一种基于快速傅里叶变换和子空间分解的循环迭代算法求解目标函数的方法.仿真实验结果表明,经过优化的波形在提高多频段限制中频谱利用率的同时,有效地抑制了窄带干扰且具有较低的旁瓣.展开更多
基金Supported by the National Natural Science Foundation of China(Youth Science Fund)(61001190)
文摘The m series with 511 bits is taken as an example being applied in non-coherent integra- tion algorithm. A method to choose the bi-phase code is presented, which is 15 kinds of codes are picked out of 511 kinds of m series to do non-coherent integration. It is indicated that the power in- creasing times of larger target sidelobe is less than the power increasing times of smaller target main- lobe because of the larger target＇ s pseudo-randomness. Smaller target is integrated from larger tar- get sidelobe, which strengthens the detection capability of radar for smaller targets. According to the sidelobes distributing characteristic, a method is presented in this paper to remove the estimated sidelobes mean value for signal detection after non-coherent integration. Simulation results present that the SNR of small target can be improved approximately 6. 5 dB by the proposed method.
文摘Worldwide Interoperability for Microwave Access(WiMAX)trusts Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing(MIMO-OFDM)combination for the deployment of physical layer functions and for connecting the medium access control to the wireless media.Even though Orthogonal Frequency Division Multiplexing(OFDM)facilitates reliable digital broadband transmission in the fading wireless channels,the presence of synchro-nization errors in the form of Carrier Frequency Offset(CFO)and Time Offset(TO)adversely affect the performance of OFDM based physical layers.The objective of this work is to improve the accuracy of the frequency and the time offset estimation in the WiMAX physical layer.A method to enhance the synchro-nization accuracy byfine-tuning the merit factor of the preamble sequence is sug-gested in this paper.Also,a new preamble with improved synchronization accuracy is proposed for the WiMAX system.The performance of the proposed preamble is evaluated in a Rayleigh fading channel and the results of simulations show that the Mean Square Error(MSE)in offset estimation is significantly reduced and it outperforms the standard WiMAX preamble.
文摘针对雷达射频隐身波形设计中的复杂调制问题,本文提出脉间复合调频与脉内多相码调相的复合策略。在脉间采用非线性的调频特征调制Costas信号各恒定频率,并在脉内采用多相位编码方式调制信号的相位特征,进而得到IPNC-PC信号。采用脉间复合调频增加了信号的时频复杂度,脉内多相码调相增加了信号的相位随机性。仿真结果表明:IPNC-PC信号具备近似“图钉型”的模糊图,自相关旁瓣电平达到-41dB、主瓣宽度变窄率最高达到39%、功率谱峰值低于-10 d B。IPNC-PC信号具有低截获性,射频隐身性能良好,在现代电子战中有良好的应用前景。
