Based on the theory of the passive hydrogen maser, along with the technology of frequency modulation and modulation transfer spectroscopy, the theoretical expression of the single frequency modulation for the passive ...Based on the theory of the passive hydrogen maser, along with the technology of frequency modulation and modulation transfer spectroscopy, the theoretical expression of the single frequency modulation for the passive hydrogen maser and the function of the cavity and H line error signals separation are derived, which are basically coincident with the experiment. The absorption and dispersion spectrum curves with different resonance widths show that the cavity and hydrogen transition serve as discriminators, and the two error signals can be separated. Through the calculations of the two error signals in the passive hydrogen maser, it analyzes the traditional method of the two error signals separation, and then describes a new improved method for the passive hydrogen servo loops consisting in the use of a single modulation frequency and frequency discrimination. A null interaction of the two error signals for the new selection of the phase setting is deduced theoretically and validated by the simulation. The preliminary experimental result confirms the feasibility of this new approach, which can reduce the influence from the cavity frequency variety on the crystal oscillator and contribute significantly to the long term performance of the passive hydrogen maser.展开更多
The multi-tone frequency modulation （FM） signal transferred through track circuit in automatic train control （ATC） system is analyzed. A digital filter with ideal sloping shape in frequency domain is designed for ...The multi-tone frequency modulation （FM） signal transferred through track circuit in automatic train control （ATC） system is analyzed. A digital filter with ideal sloping shape in frequency domain is designed for frequency discrimination. With this filter, the FM signal is converted into AM-FM signal by frequency-to-amplitude conversion. The modulating signal is finally extracted from the envelope of the AM-FM signal. Simulations show that the digital demodulation method could accurately recover the modulating signal in low signal noise ratio （SNR） circumstance, and has good performance in suppressing interference of harmonies of traction current frequency. The feasibility of the proposed method is proved in a hardware system based on SHARC DSP.展开更多
目前对刺激速率是否影响电子耳蜗纯音频率分辨尚不清楚。分别开启基部和顶部4个电极,测试了刺激速率分别为250、720、900、1 200和2 400pps/ch(pulses per second per channel,pps/ch)的频率分辨率。共有11位佩戴Nucleus的ESPrit 3G言...目前对刺激速率是否影响电子耳蜗纯音频率分辨尚不清楚。分别开启基部和顶部4个电极,测试了刺激速率分别为250、720、900、1 200和2 400pps/ch(pulses per second per channel,pps/ch)的频率分辨率。共有11位佩戴Nucleus的ESPrit 3G言语处理器、并采用ACE(advanced combined encoder,ACE)处理策略的语后聋电子耳蜗植入者参与了实验。结果表明:1kHz以下纯音的频率分辨率要显著高于1kHz以上;刺激速率对纯音频率分辨率无显著影响。另外,与正常耳蜗对声刺激的响应不同,开启基部电极时高频段频率分辨率较低。进一步验证了刺激速率对无调语音识别无影响的相关研究结果。展开更多
文摘振动信号在触觉通信中常用来承载快速信息.深入研究触觉的频率分辨机制和能力,可以为设计触觉通信中的振动信号提供理论指导.对13名自愿者触觉的频率分辨精度和分辨速度进行了6个月的训练,并记录下不同阶段的分辨能力.结果表明:触觉根据周期差异来分辨不同振动信号,分辨功能在大脑皮层内完成;经过6个月训练后能够分辨开的振动信号间的最小周期差为1 ms,能分辨的最高振动频率为250～322 Hz,分辨时所需的振动信号最短保持时间为0.2 s.
基金supported by the Next Generation of Beidou Navigation Satellite(GFZX0301020104)
文摘Based on the theory of the passive hydrogen maser, along with the technology of frequency modulation and modulation transfer spectroscopy, the theoretical expression of the single frequency modulation for the passive hydrogen maser and the function of the cavity and H line error signals separation are derived, which are basically coincident with the experiment. The absorption and dispersion spectrum curves with different resonance widths show that the cavity and hydrogen transition serve as discriminators, and the two error signals can be separated. Through the calculations of the two error signals in the passive hydrogen maser, it analyzes the traditional method of the two error signals separation, and then describes a new improved method for the passive hydrogen servo loops consisting in the use of a single modulation frequency and frequency discrimination. A null interaction of the two error signals for the new selection of the phase setting is deduced theoretically and validated by the simulation. The preliminary experimental result confirms the feasibility of this new approach, which can reduce the influence from the cavity frequency variety on the crystal oscillator and contribute significantly to the long term performance of the passive hydrogen maser.
文摘The multi-tone frequency modulation （FM） signal transferred through track circuit in automatic train control （ATC） system is analyzed. A digital filter with ideal sloping shape in frequency domain is designed for frequency discrimination. With this filter, the FM signal is converted into AM-FM signal by frequency-to-amplitude conversion. The modulating signal is finally extracted from the envelope of the AM-FM signal. Simulations show that the digital demodulation method could accurately recover the modulating signal in low signal noise ratio （SNR） circumstance, and has good performance in suppressing interference of harmonies of traction current frequency. The feasibility of the proposed method is proved in a hardware system based on SHARC DSP.
文摘目前对刺激速率是否影响电子耳蜗纯音频率分辨尚不清楚。分别开启基部和顶部4个电极,测试了刺激速率分别为250、720、900、1 200和2 400pps/ch(pulses per second per channel,pps/ch)的频率分辨率。共有11位佩戴Nucleus的ESPrit 3G言语处理器、并采用ACE(advanced combined encoder,ACE)处理策略的语后聋电子耳蜗植入者参与了实验。结果表明:1kHz以下纯音的频率分辨率要显著高于1kHz以上;刺激速率对纯音频率分辨率无显著影响。另外,与正常耳蜗对声刺激的响应不同,开启基部电极时高频段频率分辨率较低。进一步验证了刺激速率对无调语音识别无影响的相关研究结果。
