The Shenzhou -4 spaceborne （SZ -4） altimeter waveforms were processed, and then the significant wave heights （SWH） was retrieved on the basis of waveform fitting and waveform retracking. Waveforms processing inclu...The Shenzhou -4 spaceborne （SZ -4） altimeter waveforms were processed, and then the significant wave heights （SWH） was retrieved on the basis of waveform fitting and waveform retracking. Waveforms processing includes the waveform ls averaging, the elimination of thermal noise and the waveforms normalization. Double peaks were found on each SZ - 4 waveform, and it was pointed out that the region of waveforms with the second peak is abnormal and its effects on the whole waveform in the waveform fit should be taken into consideration. To obtain the width of the waveform leading-edge, a method was proposed to find the starting point of waveform, and the half-power point of waveform was found by retracking the waveform. The normalized wavefornis were fitted with the Haynes model by using the weighting least square fit method. Then the selections of the weighting coefficients and their effects on significant wave hight retrieving were discussed, and the optimal five-region weighting method was proposed. At last, the SWH data of SZ -4 altimeter retrieved by using the proposed method were compared with those of ERS -2 and Jason - 1 altimeter, and it was concluded that the SZ -4 altimeter can detect significant wave height.展开更多
针对双功能雷达通信(Dual-Functional Radar-Communication,DFRC)系统中雷达峰均比(Peak-to-Average Power Ratio,PAPR)导致的通信误码率高及通信信号的调制方式导致的雷达分辨率降低的问题,在总功率和PAPR约束下对下行链路多用户通信...针对双功能雷达通信(Dual-Functional Radar-Communication,DFRC)系统中雷达峰均比(Peak-to-Average Power Ratio,PAPR)导致的通信误码率高及通信信号的调制方式导致的雷达分辨率降低的问题,在总功率和PAPR约束下对下行链路多用户通信与目标探测的双功能雷达通信一体化波形设计进行了简要介绍。首先,以总功率与PAPR为约束条件,以多用户干扰(Multi-User Interference,MUI)能量与雷达波形相似度加权和为目标函数,并引入加权因子ρ动态调整通信雷达性能偏好。其次,采用标准交替方向乘子(Alternating Direction Multiplier Method,ADMM)算法,并引入增广拉格朗日函数,通过变量分裂实现优化求解。最后,对所提方法的通信误码率和雷达分辨率等性能进行了仿真。结果表明,所提方法相较于传统方法实现了动态场景下通信和速率的提升,且与恒模约束相比和速率增幅达4.5%,雷达探测概率在低信噪比时达到0.8以上,并最终趋于稳定值1。展开更多
频谱兼容波形利用多段离散寂静带宽合成大带宽,在满足带宽要求的同时有效对抗频域密集干扰。为了抑制频谱兼容波形的峰值旁瓣水平,提出一种低峰值旁瓣频谱兼容波形设计方案。所提方案综合考虑波形的自相关峰值旁瓣性能和抗干扰性能,构...频谱兼容波形利用多段离散寂静带宽合成大带宽,在满足带宽要求的同时有效对抗频域密集干扰。为了抑制频谱兼容波形的峰值旁瓣水平,提出一种低峰值旁瓣频谱兼容波形设计方案。所提方案综合考虑波形的自相关峰值旁瓣性能和抗干扰性能,构建加权目标函数。在波形恒模约束下,该问题为非确定多项式难(non-deterministic polynomial-hard,NP-hard)问题。为此,首先利用指数对数平滑技术逼近目标函数,进而提出基于快速傅里叶变换的共轭梯度(conjugate gradient method based on fast Fourier transformation,CGFFT)法求解该问题。此外,波形设计中需要根据性能指标要求选择合适的加权值,为此提出一种加权值自适应确定方法,最后通过数值仿真验证了所提方法的有效性。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
文摘The Shenzhou -4 spaceborne （SZ -4） altimeter waveforms were processed, and then the significant wave heights （SWH） was retrieved on the basis of waveform fitting and waveform retracking. Waveforms processing includes the waveform ls averaging, the elimination of thermal noise and the waveforms normalization. Double peaks were found on each SZ - 4 waveform, and it was pointed out that the region of waveforms with the second peak is abnormal and its effects on the whole waveform in the waveform fit should be taken into consideration. To obtain the width of the waveform leading-edge, a method was proposed to find the starting point of waveform, and the half-power point of waveform was found by retracking the waveform. The normalized wavefornis were fitted with the Haynes model by using the weighting least square fit method. Then the selections of the weighting coefficients and their effects on significant wave hight retrieving were discussed, and the optimal five-region weighting method was proposed. At last, the SWH data of SZ -4 altimeter retrieved by using the proposed method were compared with those of ERS -2 and Jason - 1 altimeter, and it was concluded that the SZ -4 altimeter can detect significant wave height.
文摘针对双功能雷达通信(Dual-Functional Radar-Communication,DFRC)系统中雷达峰均比(Peak-to-Average Power Ratio,PAPR)导致的通信误码率高及通信信号的调制方式导致的雷达分辨率降低的问题,在总功率和PAPR约束下对下行链路多用户通信与目标探测的双功能雷达通信一体化波形设计进行了简要介绍。首先,以总功率与PAPR为约束条件,以多用户干扰(Multi-User Interference,MUI)能量与雷达波形相似度加权和为目标函数,并引入加权因子ρ动态调整通信雷达性能偏好。其次,采用标准交替方向乘子(Alternating Direction Multiplier Method,ADMM)算法,并引入增广拉格朗日函数,通过变量分裂实现优化求解。最后,对所提方法的通信误码率和雷达分辨率等性能进行了仿真。结果表明,所提方法相较于传统方法实现了动态场景下通信和速率的提升,且与恒模约束相比和速率增幅达4.5%,雷达探测概率在低信噪比时达到0.8以上,并最终趋于稳定值1。
文摘频谱兼容波形利用多段离散寂静带宽合成大带宽,在满足带宽要求的同时有效对抗频域密集干扰。为了抑制频谱兼容波形的峰值旁瓣水平,提出一种低峰值旁瓣频谱兼容波形设计方案。所提方案综合考虑波形的自相关峰值旁瓣性能和抗干扰性能,构建加权目标函数。在波形恒模约束下,该问题为非确定多项式难(non-deterministic polynomial-hard,NP-hard)问题。为此,首先利用指数对数平滑技术逼近目标函数,进而提出基于快速傅里叶变换的共轭梯度(conjugate gradient method based on fast Fourier transformation,CGFFT)法求解该问题。此外,波形设计中需要根据性能指标要求选择合适的加权值,为此提出一种加权值自适应确定方法,最后通过数值仿真验证了所提方法的有效性。
