To improve the transmission performance of XCTD channel, this paper proposes a method to measure directly and fit the channel transmission characteristics by using frequency sweeping method. Sinusoidal signals with a ...To improve the transmission performance of XCTD channel, this paper proposes a method to measure directly and fit the channel transmission characteristics by using frequency sweeping method. Sinusoidal signals with a frequency range of 100 Hz to 10 k Hz and an interval of 100 Hz are used to measure transmission characteristics of channels with lengths of 300 m, 800 m, 1300 m, and 1800 m. The correctness of the fitted channel characteristics by transmitting square wave, composite waves of different frequencies, and ASK modulation are verified. The results show that when the frequency of the signal is below 1500 Hz, the channel has very little effect on the signal. The signal compensated for amplitude and phase at the receiver is not as good as the uncompensated signal.Alternatively, when the signal frequency is above 1500 Hz, the channel distorts the signal. The quality of signal compensated for amplitude and phase at receiver is better than that of the uncompensated signal. Thus, we can select the appropriate frequency for XCTD system and the appropriate way to process the received signals. Signals below1500 Hz can be directly used at the receiving end. Signals above 1500 Hz are used after amplitude and phase compensation at the receiving end.展开更多
现有单载波传输方式下,深海走航投弃式剖面仪的信号幅值会随信号速率增大而剧烈衰减,从而使得信号传输准确性降低,严重影响了信号传输速率的提高。提出了对抗信道衰落和窄带干扰的正交频分复用(Orthogonal Frequency Division Multiplex...现有单载波传输方式下,深海走航投弃式剖面仪的信号幅值会随信号速率增大而剧烈衰减,从而使得信号传输准确性降低,严重影响了信号传输速率的提高。提出了对抗信道衰落和窄带干扰的正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术,以增加载波数量来提高信道带宽利用率,在保证准确性的同时提高投弃式温盐深剖面仪(Expendable Conductivity-Temperature-Depth profiler,XCTD)信号传输速率。设计了基于SIMULINK平台的OFDM算法仿真系统,从XCTD信道模型入手,针对不同的传输频率、探测深度和噪声量级,分析了OFDM算法与ASK、DPSK单载波的传输方式。通过OFDM算法与单载波传输方式对比的仿真结果表明,OFDM算法对于提高XCTD信号传输速率具有较高的可行性和有效性,对提高深海走航投弃式剖面仪信号传输速率的研究提供了一种新的思路。展开更多
结合CTD/LADCP(Conductivity-Temperature-Depth/Lowed Acoustic Doppler Current Profiler)观测实例,从作业海况、水下单元架构、水下姿态三方面分析研究下放式海洋观测中同轴铠装缆自缠绕/打结状况发现,仪器观测架在布放过程中存在旋...结合CTD/LADCP(Conductivity-Temperature-Depth/Lowed Acoustic Doppler Current Profiler)观测实例,从作业海况、水下单元架构、水下姿态三方面分析研究下放式海洋观测中同轴铠装缆自缠绕/打结状况发现,仪器观测架在布放过程中存在旋转现象,旋转产生的扭力作用于同轴铠装缆;扭力得不到释放,在海况较差的情况下极易造成同轴铠装缆的自缠绕/打结。为解决这些问题,本文进一步提出了一套实用的改进方案,在既保证能够在较差海况下作业、又不减少观测仪器的前提下,改进仪器观测架和同轴铠装缆的连接结构,同时增加机械转环及附属结构。观测实践证明,该方案可以有效避免与CTD/LADCP观测类似的下放式观测中同轴铠装缆因自缠绕造成的“打结”现象的出现,大大提高了现场观测效率,保证了仪器安全和数据顺利传输。该技术源自基本海洋观测实践,可为广大海洋调查工作者提供有益的借鉴。展开更多
基金financially supported by the National Key Research and Development Program of China(Grant No.2016YFC1400400)
文摘To improve the transmission performance of XCTD channel, this paper proposes a method to measure directly and fit the channel transmission characteristics by using frequency sweeping method. Sinusoidal signals with a frequency range of 100 Hz to 10 k Hz and an interval of 100 Hz are used to measure transmission characteristics of channels with lengths of 300 m, 800 m, 1300 m, and 1800 m. The correctness of the fitted channel characteristics by transmitting square wave, composite waves of different frequencies, and ASK modulation are verified. The results show that when the frequency of the signal is below 1500 Hz, the channel has very little effect on the signal. The signal compensated for amplitude and phase at the receiver is not as good as the uncompensated signal.Alternatively, when the signal frequency is above 1500 Hz, the channel distorts the signal. The quality of signal compensated for amplitude and phase at receiver is better than that of the uncompensated signal. Thus, we can select the appropriate frequency for XCTD system and the appropriate way to process the received signals. Signals below1500 Hz can be directly used at the receiving end. Signals above 1500 Hz are used after amplitude and phase compensation at the receiving end.
文摘结合CTD/LADCP(Conductivity-Temperature-Depth/Lowed Acoustic Doppler Current Profiler)观测实例,从作业海况、水下单元架构、水下姿态三方面分析研究下放式海洋观测中同轴铠装缆自缠绕/打结状况发现,仪器观测架在布放过程中存在旋转现象,旋转产生的扭力作用于同轴铠装缆;扭力得不到释放,在海况较差的情况下极易造成同轴铠装缆的自缠绕/打结。为解决这些问题,本文进一步提出了一套实用的改进方案,在既保证能够在较差海况下作业、又不减少观测仪器的前提下,改进仪器观测架和同轴铠装缆的连接结构,同时增加机械转环及附属结构。观测实践证明,该方案可以有效避免与CTD/LADCP观测类似的下放式观测中同轴铠装缆因自缠绕造成的“打结”现象的出现,大大提高了现场观测效率,保证了仪器安全和数据顺利传输。该技术源自基本海洋观测实践,可为广大海洋调查工作者提供有益的借鉴。
