针对当前地面测距机(DME)导航台的作用范围一般为200 n miles左右[3],飞机在航行过程中往往需要经过多个DME导航台,而传统的机载DME设备只能工作在单频率下,这就需要飞行员手动切换对应地面台的频率,从而增加了飞行员工作量的问题。本...针对当前地面测距机(DME)导航台的作用范围一般为200 n miles左右[3],飞机在航行过程中往往需要经过多个DME导航台,而传统的机载DME设备只能工作在单频率下,这就需要飞行员手动切换对应地面台的频率,从而增加了飞行员工作量的问题。本文从实际工程应用出发,通过对机载DME设备工作过程进行分析,提出多台轮询技术,研究并实现直接扫描和自由扫描两种模式情况,该技术可提高航路定位的精准性,减少飞行员工作量。展开更多
针对测距仪(distance measure equipment,DME)信号严重干扰L频段数字航空通信系统(L-band digital aviation communication system,L-DACS)前向链路接收机的问题,提出基于相关稀疏变分贝叶斯(correlated sparse variational Bayesian,cS...针对测距仪(distance measure equipment,DME)信号严重干扰L频段数字航空通信系统(L-band digital aviation communication system,L-DACS)前向链路接收机的问题,提出基于相关稀疏变分贝叶斯(correlated sparse variational Bayesian,cSVB)算法的DME脉冲干扰抑制方法。所提方法利用L-DACS系统正交频分复用(orthogonal frequency division multiplexing,OFDM)接收机的空子载波信息构建接收信号的压缩感知方程;然后,根据cSVB算法进行三层次贝叶斯信号建模,最后选择了两种变体算法重构DME干扰信号,并将其从时域接收信号中去除。理论分析与仿真结果表明,所提出的干扰抑制方法可以充分利用信号先验信息,进一步降低DME干扰信号估计的归一化均方误差,有效改善L-DACS系统的误码性能,提高传输可靠性。展开更多
Mathematical simulation was performed on tube-shell reactor for dimethyl ether （DME） synthesis from coal-based syngas. The model was established based on kinetics of dimethyl-ether synthesis from syngas over a bifun...Mathematical simulation was performed on tube-shell reactor for dimethyl ether （DME） synthesis from coal-based syngas. The model was established based on kinetics of dimethyl-ether synthesis from syngas over a bifunctional catalyst, which is mixed by methanol synthesis catalyst and dehydration catalyst as 1：1 mass ratio. Methanol synthesis from CO and CO2 and methanol dehydration were selected as three-independent reactions, CO, CO2, and DME as key components to estab- lish the one-dimensional mathematical model of the reactor. The gas concentration and temperature profiles inside the reactor tubes were obtained. The operating conditions affecting DME synthesis were also discussed based on the model. The simula- tions indicate that higher pressure and lower temperature at the inlet and rich hydrogen in the reactant are favorable in direct DME synthesis in fixed-bed process, and the temperature of boiling water affect the reactor performance seriously.展开更多
针对L波段数字航空通信系统(L-band digital aeronautic communication system,LDACS)可用频谱资源有限且易受大功率测距仪(distance measuring equipment,DME)信号干扰的问题,提出一种基于降维循环谱和残差神经网络的频谱感知方法。首...针对L波段数字航空通信系统(L-band digital aeronautic communication system,LDACS)可用频谱资源有限且易受大功率测距仪(distance measuring equipment,DME)信号干扰的问题,提出一种基于降维循环谱和残差神经网络的频谱感知方法。首先理论推导分析了DME信号的循环谱特征;然后利用Fisher判别率(Fisher discriminant rate,FDR)提取循环频率能量最大的向量,通过主成分分析(principal component analysis,PCA)进行预处理特征增强;最后给出数据处理后的循环谱向量与卷积神经网络相结合的实现过程,实现了DME信号的有效检测。仿真结果表明,该方法对噪声不敏感,当信噪比不低于-15 dB时,平均检测概率大于90%。当信噪比不低于-14 dB,检测概率接近100%。展开更多
L波段数字航空通信系统(L band digital aeronautical communication system,LDACS)是未来航空宽带通信重要的基础设施之一,针对LDACS信号容易受到相邻波道大功率测距仪(distance measuring equipment,DME)信号干扰的问题,提出了联合正...L波段数字航空通信系统(L band digital aeronautical communication system,LDACS)是未来航空宽带通信重要的基础设施之一,针对LDACS信号容易受到相邻波道大功率测距仪(distance measuring equipment,DME)信号干扰的问题,提出了联合正交投影干扰抑制与单快拍稀疏分解的波达方向(direction of arrival,DOA)估计方法。通过子空间投影抑制DME干扰,然后使用单快拍数据构建伪协方差矩阵,对伪协方差矩阵求高阶幂,之后进行奇异值分解,并利用约束条件求解稀疏解得到期望信号来向的估计值。所提方法使用高阶伪协方差矩阵降低了噪声影响,仅用单快拍就可以准确估计LDACS信号的入射方向。仿真结果表明,改进单快拍高级幂(improved single snapshot high order power,ISS-HOP)L1-SVD算法的估计精度优于ISS-HOP-MUSIC算法。该方法可以有效抑制DME干扰,提高OFDM接收机性能。展开更多
文摘针对当前地面测距机(DME)导航台的作用范围一般为200 n miles左右[3],飞机在航行过程中往往需要经过多个DME导航台,而传统的机载DME设备只能工作在单频率下,这就需要飞行员手动切换对应地面台的频率,从而增加了飞行员工作量的问题。本文从实际工程应用出发,通过对机载DME设备工作过程进行分析,提出多台轮询技术,研究并实现直接扫描和自由扫描两种模式情况,该技术可提高航路定位的精准性,减少飞行员工作量。
文摘针对测距仪(distance measure equipment,DME)信号严重干扰L频段数字航空通信系统(L-band digital aviation communication system,L-DACS)前向链路接收机的问题,提出基于相关稀疏变分贝叶斯(correlated sparse variational Bayesian,cSVB)算法的DME脉冲干扰抑制方法。所提方法利用L-DACS系统正交频分复用(orthogonal frequency division multiplexing,OFDM)接收机的空子载波信息构建接收信号的压缩感知方程;然后,根据cSVB算法进行三层次贝叶斯信号建模,最后选择了两种变体算法重构DME干扰信号,并将其从时域接收信号中去除。理论分析与仿真结果表明,所提出的干扰抑制方法可以充分利用信号先验信息,进一步降低DME干扰信号估计的归一化均方误差,有效改善L-DACS系统的误码性能,提高传输可靠性。
文摘Mathematical simulation was performed on tube-shell reactor for dimethyl ether （DME） synthesis from coal-based syngas. The model was established based on kinetics of dimethyl-ether synthesis from syngas over a bifunctional catalyst, which is mixed by methanol synthesis catalyst and dehydration catalyst as 1：1 mass ratio. Methanol synthesis from CO and CO2 and methanol dehydration were selected as three-independent reactions, CO, CO2, and DME as key components to estab- lish the one-dimensional mathematical model of the reactor. The gas concentration and temperature profiles inside the reactor tubes were obtained. The operating conditions affecting DME synthesis were also discussed based on the model. The simula- tions indicate that higher pressure and lower temperature at the inlet and rich hydrogen in the reactant are favorable in direct DME synthesis in fixed-bed process, and the temperature of boiling water affect the reactor performance seriously.
文摘L波段数字航空通信系统(L band digital aeronautical communication system,LDACS)是未来航空宽带通信重要的基础设施之一,针对LDACS信号容易受到相邻波道大功率测距仪(distance measuring equipment,DME)信号干扰的问题,提出了联合正交投影干扰抑制与单快拍稀疏分解的波达方向(direction of arrival,DOA)估计方法。通过子空间投影抑制DME干扰,然后使用单快拍数据构建伪协方差矩阵,对伪协方差矩阵求高阶幂,之后进行奇异值分解,并利用约束条件求解稀疏解得到期望信号来向的估计值。所提方法使用高阶伪协方差矩阵降低了噪声影响,仅用单快拍就可以准确估计LDACS信号的入射方向。仿真结果表明,改进单快拍高级幂(improved single snapshot high order power,ISS-HOP)L1-SVD算法的估计精度优于ISS-HOP-MUSIC算法。该方法可以有效抑制DME干扰,提高OFDM接收机性能。
