The technology of DDS-driven PLL is introduced and a new scheme of frequency synthesizer which is suitable for SW SFH/MFSK System is presented in this paper. Based on the special requirement of SW communication, a mod...The technology of DDS-driven PLL is introduced and a new scheme of frequency synthesizer which is suitable for SW SFH/MFSK System is presented in this paper. Based on the special requirement of SW communication, a model of the scheme is given and the results show that the frequency synthesizer has small frequency insteval (≤0.1 Hz), short switch pierod (<200 ms) and high frequency stability as crystal oseillator.展开更多
目的 观察听力正常青年人独立调幅调频（independent amplitude and frequency modulation，IAFM）反应与言语识别率（word recognition score，WRS）的关系，探讨采用IAFM反应预估WRS的可能性。方法 21名听力正常青年受试者（21耳）以0...目的 观察听力正常青年人独立调幅调频（independent amplitude and frequency modulation，IAFM）反应与言语识别率（word recognition score，WRS）的关系，探讨采用IAFM反应预估WRS的可能性。方法 21名听力正常青年受试者（21耳）以0．5、1．0、2．0和4．0kHz为载波，振幅调制频率分别为79、87、95和103Hz，调幅深度分别为55％、50％、45％及35％；频率调制频率分别为85、93、101和109Hz，调制深度分别为35％、30％、20％及35％，四个IAFM声同时给出，单耳给声。分别测试20、30、40、50、60、70、80和90dB SPL的IAFM有意义反应数和WRS，观察两者之间的相关性。结果 IAFM反应数与强度的线性相关系数为0．844（P〈0．01），WRS与强度的线性相关系数为0．785（P〈0．01），IAFM反应数与WRS的线性相关系数为0．785（P〈0．01）；IAFM反应数与WRS的偏相关系数（强度为控制因素）为0．371（P〈0．01）。结论 调制频率在70～110Hz的IAFM反应能够反映耳蜗和脑干对频率和振幅变化的分辨能力，与WRS有显著的相关性，有可能成为评价言语感知所必需的声学信息分辨能力的客观工具。从而成为评价和预估言语识别功能的措施之一。展开更多
文摘The technology of DDS-driven PLL is introduced and a new scheme of frequency synthesizer which is suitable for SW SFH/MFSK System is presented in this paper. Based on the special requirement of SW communication, a model of the scheme is given and the results show that the frequency synthesizer has small frequency insteval (≤0.1 Hz), short switch pierod (<200 ms) and high frequency stability as crystal oseillator.
