通信中的正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术具有频带利用率高、抗多径衰落强等优点,但是OFDM通信存在高峰值平均功率比(Peak to Average Power Ratio,PAPR)的问题,如果不加抑制,在输出时会导致信号失...通信中的正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术具有频带利用率高、抗多径衰落强等优点,但是OFDM通信存在高峰值平均功率比(Peak to Average Power Ratio,PAPR)的问题,如果不加抑制,在输出时会导致信号失真,降低通信效率。提出了一种通过给OFDM符号不同信道的导频和信号添加固定相位偏移因子来抑制发射信号PAPR的方法。首先介绍了信道相位偏移因子的添加方法和解调过程,其次仿真分析表明随机产生的相位偏移因子可以将任意传输信号的PAPR抑制在小于11 dB的水平。此技术不需要消耗额外带宽和计算资源,且对系统的误码率几乎没有影响。最后采样低成本的功放和声源作为发射换能器,用光纤水听器作为接收换能器进行实际通信试验,验证了该方法的有效性。展开更多
A fiber Bragg grating (FBG) hydrophone with high sensitivity was demonstrated. This hydrophone used a rubber diaphragm and a copper hard core as the sensing element. To compensate the hydrostatic pressure, a capilla...A fiber Bragg grating (FBG) hydrophone with high sensitivity was demonstrated. This hydrophone used a rubber diaphragm and a copper hard core as the sensing element. To compensate the hydrostatic pressure, a capillary tube was fixed at the end of the hydrophone. Theoretical analysis of the acoustic pressure sensitivity was given in this letter. Experiments were carried out to test the frequency response of the hydrophone. The result shows that when the Young's modulus of the diaphragm is higher, a flatter frequency response will be obtained.展开更多
文摘通信中的正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术具有频带利用率高、抗多径衰落强等优点,但是OFDM通信存在高峰值平均功率比(Peak to Average Power Ratio,PAPR)的问题,如果不加抑制,在输出时会导致信号失真,降低通信效率。提出了一种通过给OFDM符号不同信道的导频和信号添加固定相位偏移因子来抑制发射信号PAPR的方法。首先介绍了信道相位偏移因子的添加方法和解调过程,其次仿真分析表明随机产生的相位偏移因子可以将任意传输信号的PAPR抑制在小于11 dB的水平。此技术不需要消耗额外带宽和计算资源,且对系统的误码率几乎没有影响。最后采样低成本的功放和声源作为发射换能器,用光纤水听器作为接收换能器进行实际通信试验,验证了该方法的有效性。
基金Key Projects Program of Chinese Acadelny of Sciences under Grant No.CXJJ-177.
文摘A fiber Bragg grating (FBG) hydrophone with high sensitivity was demonstrated. This hydrophone used a rubber diaphragm and a copper hard core as the sensing element. To compensate the hydrostatic pressure, a capillary tube was fixed at the end of the hydrophone. Theoretical analysis of the acoustic pressure sensitivity was given in this letter. Experiments were carried out to test the frequency response of the hydrophone. The result shows that when the Young's modulus of the diaphragm is higher, a flatter frequency response will be obtained.