A new FM transmitter is reported. It adopts a fractional-N PLL synthesizer to realize the FM modulator. An extra offset current has also been applied to eliminate the effects of the mismatch in CP. The chip is fabrica...A new FM transmitter is reported. It adopts a fractional-N PLL synthesizer to realize the FM modulator. An extra offset current has also been applied to eliminate the effects of the mismatch in CP. The chip is fabricated with CSMC 0.5μm DPTM CMOS technology. Experiments show that it achieves THD≤0.08% and SNR≤ 82dB,and the maximum outband emission energy ≤ 90dBc/Hz. Furthermore,it also uses an auto frequency adjusting method to avoid tuning up the external inductances. All these merits are very suitable for FM transmission.展开更多
The vibration signals of multi-fault rolling bearings under nonstationary conditions are characterized by intricate modulation features,making it difficult to identify the fault characteristic frequency.To remove the ...The vibration signals of multi-fault rolling bearings under nonstationary conditions are characterized by intricate modulation features,making it difficult to identify the fault characteristic frequency.To remove the time-varying behavior caused by speed fluctuation,the phase function of target component is necessary.However,the frequency components induced by different faults interfere with each other.More importantly,the complex sideband clusters around the characteristic frequency further hinder the spectrum interpretation.As such,we propose a demodulation spectrum analysis method for multi-fault bearing detection via chirplet path pursuit.First,the envelope signal is obtained by applying Hilbert transform to the raw signal.Second,the characteristic frequency is extracted via chirplet path pursuit,and the other underlying components are calculated by the characteristic coefficient.Then,the energy factors of all components are determined according to the time-varying behavior of instantaneous frequency.Next,the final demodulated signal is obtained by iteratively applying generalized demodulation with tunable E-factor and then the band pass filter is designed to separate the demodulated component.Finally,the fault pattern can be identified by matching the prominent peaks in the demodulation spectrum with the theoretical characteristic frequencies.The method is validated by simulated and experimental signals.展开更多
The present study was built upon a previous study on the new generation video game, exergame, in elementary school physical education (PE). The purpose of the study was to examine the effect of exergames on elementa...The present study was built upon a previous study on the new generation video game, exergame, in elementary school physical education (PE). The purpose of the study was to examine the effect of exergames on elementary children's in-class physical activity (PA) intensity levels and perceived situational interest over time. The results indicated that students' situational interest dropped dramatically over two semesters, but their PA intensity increased over time. The results showed that boys and girls were equally active in the exergaming lessons, but boys perceived their gaming experiences more enjoyable than girls did. The findings suggest that exergames may be a possible means to enhance PA in PE. However, whether exergaming is a sustainable way to motivate children in PA is questionable.展开更多
Based on the good time-frequency localization of the wavelet packet modulation (WPM) system and the analysis of the muhitone (MT) interference, an improved WPM narrow band interference (NBI) rejection system usi...Based on the good time-frequency localization of the wavelet packet modulation (WPM) system and the analysis of the muhitone (MT) interference, an improved WPM narrow band interference (NBI) rejection system using an adaptive least mean square (LMS) algorithm is discussed in this paper. In the WPM interference rejection system, according to the structure of the wavelet packet tree (WFF) and the characteristic of the MT interference, the demodulated WPM signal which contains the interference component is filtered using an adaptive LMS filtering implementation. Theoretical analysis and simulation resuits show that the proposed method improves the bit error rate (BER) performance of the WPM system in the presence of MT interference.展开更多
Based on the Gauss linear frequency modulated wavelet transform, a new characteristic index is presented, namely time frequency energy attenuation factor which can reflect the difference features of waveform in earthq...Based on the Gauss linear frequency modulated wavelet transform, a new characteristic index is presented, namely time frequency energy attenuation factor which can reflect the difference features of waveform in earthquake focus mechanism, wave traveling path and its attenuation characteristics in focal area or near field. In order to test its validity, we select the natural earthquakes and explosion or collapse events whose focus mechanisms vary obviously,and some natural earthquakes located at the same site or in a very small area. The study indicates that the time frequency energy attenuation factors of the natural earthquakes are obviously different with that of explosion or collapse events, and the change of the time frequency energy attenuation factors is relatively stable for the earthquakes under the normal seismicity background. Using the above mentioned method, it is expected to offer a useful criterion for strong earthquake prediction by continuous earthquake observation.展开更多
Under free field conditions, we used single unit extracellular recording to study the detection of acoustic signals by neurons in the ventral nucleus of the lateral lemniscus(VNLL) in Kunming mouse(Mus musculus). The ...Under free field conditions, we used single unit extracellular recording to study the detection of acoustic signals by neurons in the ventral nucleus of the lateral lemniscus(VNLL) in Kunming mouse(Mus musculus). The results indicate two types of firing patterns in VNLL neurons: onset and sustained. The first spike latency(FSL) of onset neurons was shorter than that of sustained neurons. With increasing sound intensity, the FSL of onset neurons remained stable and that of sustained neurons was shortened, indicating that onset neurons are characterized by precise timing. By comparing the values of Q10 and Q30 of the frequency tuning curve, no differences between onset and sustained neurons were found, suggesting that firing pattern and frequency tuning are not correlated. Among the three types of rate-intensity function(RIF) found in VNLL neurons, the proportion of monotonic RIF is the largest, followed by saturated RIF, and non-monotonic RIF. The dynamic range(DR) in onset neurons was shorter than in sustained neurons, indicating different capabilities in intensity tuning of different firing patterns and that these differences are correlated with the type of RIF. Our results also show that the best frequency of VNLL neurons was negatively correlated with depth, supporting the view point that the VNLL has frequency topologic organization.展开更多
A minimum mean-squared error (MSE) beamforming algorithm employing the optimum fractional Fourier transform (Opt-FrFT) domain second-order cyclostationarity is proposed. This method can efficiently filter out the ...A minimum mean-squared error (MSE) beamforming algorithm employing the optimum fractional Fourier transform (Opt-FrFT) domain second-order cyclostationarity is proposed. This method can efficiently filter out the compact desired chirp signal, with a consequence that the cyclically uncorrelated interferences and stationary (colored) Gaussian noise are greatly suppressed in the Opt- FrFT domain. This improves the MSE minimization cyclic beamformer by reducing effectively the Opt-FrFY domain signal-noise cross terms in the presence of finite data length de-correlation operation. Simulation results show that the new method works well under a wide range of signal-to-noise ratio (SNR) and signal-to-interference ratio (SIR).展开更多
A new type of despreader for direct sequence spread spectrum signal is proposed. Compared with traditional despreaders, the new despreader does not contain hard decision ware or handle binary sequence any more, and th...A new type of despreader for direct sequence spread spectrum signal is proposed. Compared with traditional despreaders, the new despreader does not contain hard decision ware or handle binary sequence any more, and the locally stored spread spectrum signals are pre-modulated baseband signals (such as Gaussian minimum shift keying (GMSK) signals), which are much more similar to the received spread spectrum signals. Moreover, the missed detection probability of the despreader is about one order of magnitude lower than that of traditional ones. Based on the maximum likelihood criterion and phase probability density function of demodulated signal, a new method of ana- lyzing the despreaders’ performance is put forward, which is proved to be more accurate than traditional methods according to the numerical results. Finally, an adaptive despreader under different signal-to-noise ratios is given.展开更多
Constellation mapping has provided a great convenience to measure the performance of digital signal modulation in Euclid space. However, traditional in-phase and quadrature(IQ) plane is difficult to express the freque...Constellation mapping has provided a great convenience to measure the performance of digital signal modulation in Euclid space. However, traditional in-phase and quadrature(IQ) plane is difficult to express the frequency modulation scheme such as minimum shift keying(MSK) and the time domain modulation such as cyclic code shift keying(CCSK). How to represent the digital signal modulation visually through constellation mapping is an attractive problem. To address this issue, in this paper, the combined frequency and phase modulation are utilized to define a new kind of constellation mapping, where the phase and frequency are quantized to the same elements. The uniform geometric construction for combined phase and frequency modulation is redefined in the 3D cylindrical coordinate system based on frequency(f), in-phase component(I) and quadrature component(Q). In the new coordinates, the quadrature frequency-phase shift keying(QFPSK) is produced by the QPSK with dimensional rotation matrix and denoted by the reduced dual quaternion. Furthermore, the spatial extension from QFPSK to chirp cyclic shift keying(Chirp CSK) is analyzed with bandwidth efficiency and energy efficiency. At last, the QFPSK is combined with the 2D OFDM, yielding the image OFDM system.Experimental results verify the effectiveness of QFPSK in the proposed system with the time-varying wireless channel and frequency selective fading channel respectively.展开更多
文摘A new FM transmitter is reported. It adopts a fractional-N PLL synthesizer to realize the FM modulator. An extra offset current has also been applied to eliminate the effects of the mismatch in CP. The chip is fabricated with CSMC 0.5μm DPTM CMOS technology. Experiments show that it achieves THD≤0.08% and SNR≤ 82dB,and the maximum outband emission energy ≤ 90dBc/Hz. Furthermore,it also uses an auto frequency adjusting method to avoid tuning up the external inductances. All these merits are very suitable for FM transmission.
基金Project(2018YJS137)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(51275030)supported by the National Natural Science Foundation of China
文摘The vibration signals of multi-fault rolling bearings under nonstationary conditions are characterized by intricate modulation features,making it difficult to identify the fault characteristic frequency.To remove the time-varying behavior caused by speed fluctuation,the phase function of target component is necessary.However,the frequency components induced by different faults interfere with each other.More importantly,the complex sideband clusters around the characteristic frequency further hinder the spectrum interpretation.As such,we propose a demodulation spectrum analysis method for multi-fault bearing detection via chirplet path pursuit.First,the envelope signal is obtained by applying Hilbert transform to the raw signal.Second,the characteristic frequency is extracted via chirplet path pursuit,and the other underlying components are calculated by the characteristic coefficient.Then,the energy factors of all components are determined according to the time-varying behavior of instantaneous frequency.Next,the final demodulated signal is obtained by iteratively applying generalized demodulation with tunable E-factor and then the band pass filter is designed to separate the demodulated component.Finally,the fault pattern can be identified by matching the prominent peaks in the demodulation spectrum with the theoretical characteristic frequencies.The method is validated by simulated and experimental signals.
文摘The present study was built upon a previous study on the new generation video game, exergame, in elementary school physical education (PE). The purpose of the study was to examine the effect of exergames on elementary children's in-class physical activity (PA) intensity levels and perceived situational interest over time. The results indicated that students' situational interest dropped dramatically over two semesters, but their PA intensity increased over time. The results showed that boys and girls were equally active in the exergaming lessons, but boys perceived their gaming experiences more enjoyable than girls did. The findings suggest that exergames may be a possible means to enhance PA in PE. However, whether exergaming is a sustainable way to motivate children in PA is questionable.
基金Supported by the National Natural Science Foundation of China (No. 60532030).
文摘Based on the good time-frequency localization of the wavelet packet modulation (WPM) system and the analysis of the muhitone (MT) interference, an improved WPM narrow band interference (NBI) rejection system using an adaptive least mean square (LMS) algorithm is discussed in this paper. In the WPM interference rejection system, according to the structure of the wavelet packet tree (WFF) and the characteristic of the MT interference, the demodulated WPM signal which contains the interference component is filtered using an adaptive LMS filtering implementation. Theoretical analysis and simulation resuits show that the proposed method improves the bit error rate (BER) performance of the WPM system in the presence of MT interference.
文摘Based on the Gauss linear frequency modulated wavelet transform, a new characteristic index is presented, namely time frequency energy attenuation factor which can reflect the difference features of waveform in earthquake focus mechanism, wave traveling path and its attenuation characteristics in focal area or near field. In order to test its validity, we select the natural earthquakes and explosion or collapse events whose focus mechanisms vary obviously,and some natural earthquakes located at the same site or in a very small area. The study indicates that the time frequency energy attenuation factors of the natural earthquakes are obviously different with that of explosion or collapse events, and the change of the time frequency energy attenuation factors is relatively stable for the earthquakes under the normal seismicity background. Using the above mentioned method, it is expected to offer a useful criterion for strong earthquake prediction by continuous earthquake observation.
基金This study was supported by the National Natural Science Foundation of China (31000493) and the Central China Normal University Independent Scientific Research Project Fund for Youth Scholars (11A01025)
文摘Under free field conditions, we used single unit extracellular recording to study the detection of acoustic signals by neurons in the ventral nucleus of the lateral lemniscus(VNLL) in Kunming mouse(Mus musculus). The results indicate two types of firing patterns in VNLL neurons: onset and sustained. The first spike latency(FSL) of onset neurons was shorter than that of sustained neurons. With increasing sound intensity, the FSL of onset neurons remained stable and that of sustained neurons was shortened, indicating that onset neurons are characterized by precise timing. By comparing the values of Q10 and Q30 of the frequency tuning curve, no differences between onset and sustained neurons were found, suggesting that firing pattern and frequency tuning are not correlated. Among the three types of rate-intensity function(RIF) found in VNLL neurons, the proportion of monotonic RIF is the largest, followed by saturated RIF, and non-monotonic RIF. The dynamic range(DR) in onset neurons was shorter than in sustained neurons, indicating different capabilities in intensity tuning of different firing patterns and that these differences are correlated with the type of RIF. Our results also show that the best frequency of VNLL neurons was negatively correlated with depth, supporting the view point that the VNLL has frequency topologic organization.
基金Supported by the National Natural Science Foundation of China ( No. 60672084, 60602037, 60736006).
文摘A minimum mean-squared error (MSE) beamforming algorithm employing the optimum fractional Fourier transform (Opt-FrFT) domain second-order cyclostationarity is proposed. This method can efficiently filter out the compact desired chirp signal, with a consequence that the cyclically uncorrelated interferences and stationary (colored) Gaussian noise are greatly suppressed in the Opt- FrFT domain. This improves the MSE minimization cyclic beamformer by reducing effectively the Opt-FrFY domain signal-noise cross terms in the presence of finite data length de-correlation operation. Simulation results show that the new method works well under a wide range of signal-to-noise ratio (SNR) and signal-to-interference ratio (SIR).
基金Supported by National Natural Science Foundation of China (No. 60572147) National "111" Program of Introducing Talents of Discipline to Universities (No. B08038)
文摘A new type of despreader for direct sequence spread spectrum signal is proposed. Compared with traditional despreaders, the new despreader does not contain hard decision ware or handle binary sequence any more, and the locally stored spread spectrum signals are pre-modulated baseband signals (such as Gaussian minimum shift keying (GMSK) signals), which are much more similar to the received spread spectrum signals. Moreover, the missed detection probability of the despreader is about one order of magnitude lower than that of traditional ones. Based on the maximum likelihood criterion and phase probability density function of demodulated signal, a new method of ana- lyzing the despreaders’ performance is put forward, which is proved to be more accurate than traditional methods according to the numerical results. Finally, an adaptive despreader under different signal-to-noise ratios is given.
基金supported in part by National Natural Science Foundation of China(Grant Nos.61501051,61421001)Ph.D.Programs Foundation of Ministry of Education of China(Grant No.20121101130001)
文摘Constellation mapping has provided a great convenience to measure the performance of digital signal modulation in Euclid space. However, traditional in-phase and quadrature(IQ) plane is difficult to express the frequency modulation scheme such as minimum shift keying(MSK) and the time domain modulation such as cyclic code shift keying(CCSK). How to represent the digital signal modulation visually through constellation mapping is an attractive problem. To address this issue, in this paper, the combined frequency and phase modulation are utilized to define a new kind of constellation mapping, where the phase and frequency are quantized to the same elements. The uniform geometric construction for combined phase and frequency modulation is redefined in the 3D cylindrical coordinate system based on frequency(f), in-phase component(I) and quadrature component(Q). In the new coordinates, the quadrature frequency-phase shift keying(QFPSK) is produced by the QPSK with dimensional rotation matrix and denoted by the reduced dual quaternion. Furthermore, the spatial extension from QFPSK to chirp cyclic shift keying(Chirp CSK) is analyzed with bandwidth efficiency and energy efficiency. At last, the QFPSK is combined with the 2D OFDM, yielding the image OFDM system.Experimental results verify the effectiveness of QFPSK in the proposed system with the time-varying wireless channel and frequency selective fading channel respectively.