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小调频发射点(站)的设计和建设 被引量:3
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作者 李韶文 《广播与电视技术》 北大核心 2008年第2期109-111,共3页
近年来,为适应城市经济发展形势的需要,各地广播电台纷纷利用原有的调频频率建立调频同步广播网。同步广播网络是由多个小功率调频发射点同步发射而组成,设计和建设每个小调频发射点(站)尤为重要。本文以广东电台股市台为例,介绍了小调... 近年来,为适应城市经济发展形势的需要,各地广播电台纷纷利用原有的调频频率建立调频同步广播网。同步广播网络是由多个小功率调频发射点同步发射而组成,设计和建设每个小调频发射点(站)尤为重要。本文以广东电台股市台为例,介绍了小调频发射点(站)的设计和建设。 展开更多
关键词 小调频发射点 经济 有效覆盖
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小调频发射点(站)的设计和建设
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作者 杨柳 《数字技术与应用》 2015年第11期150-151,共2页
多个小功率调频发生点同步发射是同步广播网络形成的基础,设计与建设好各小调频发射点(站)对促进我国调频广播的发展十分重要。因此,文章以调频同步广播产生的背景为切入点,结合某电台小调频发射点(站)的设计与建设,从小调频发射点选址... 多个小功率调频发生点同步发射是同步广播网络形成的基础,设计与建设好各小调频发射点(站)对促进我国调频广播的发展十分重要。因此,文章以调频同步广播产生的背景为切入点,结合某电台小调频发射点(站)的设计与建设,从小调频发射点选址、发射杆设计、机房设计等方面进行了系统分析,以期实现同步广播网的无缝隙同步覆盖。 展开更多
关键词 小调频 发射点(站) 设计与建设
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A New High Performance FM Transmitter 被引量:1
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作者 曹政新 李学初 +3 位作者 李振 吴岳 宋树贵 熊绍珍 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2007年第5期655-660,共6页
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
关键词 FM fraction N frequency synthesizer in-band phase noise
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广播电台现场直播系统
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作者 韩明 郑存良 《内蒙古广播与电视技术》 2000年第2期41-42,共2页
利用小调频发射机或电话线路进行台外现场直播
关键词 现场直播系统 小调频发射机 电视台
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Demodulation spectrum analysis for multi-fault diagnosis of rolling bearing via chirplet path pursuit 被引量:1
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作者 LIU Dong-dong CHENG Wei-dong WEN Wei-gang 《Journal of Central South University》 SCIE EI CAS CSCD 2019年第9期2418-2431,共14页
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
关键词 rolling bearing demodulation spectrum multi-fault detection NONSTATIONARY chirplet path pursuit
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Impact of exergames on physical activity and motivation in elementary school students: A follow-up study 被引量:4
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作者 Haichun Sun 《Journal of Sport and Health Science》 SCIE 2013年第3期138-145,共8页
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
关键词 Active video game Calorie expenditure GENDER Physical education Situational interest
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An improved WPM interference rejection system using an adaptive LMS algorithm
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作者 Zhong Weizhi Guo Qing +1 位作者 Guo Yan Xiao Liping 《High Technology Letters》 EI CAS 2010年第3期241-246,共6页
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
关键词 WPM interference rejection system adaptive LMS algorithm MT interference
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The Time-Frequency Energy Attenuation Factor and Its Application on the Basis of Gauss Linear Frequency-Modulated Continuous Wavelet Transform
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作者 LiuXiqiang ShenPing +4 位作者 LiHong ShanChanglun JiAidong ZhangPing CaiMingjun 《Earthquake Research in China》 2004年第1期42-53,共12页
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
关键词 Continuous wavelet transform Time frequency energy attenuation factor The space difference characteristics The time change characteristics
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Acoustic signal characteristic detection by neurons in ventral nucleus of the lateral lemniscus in mice
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作者 Hui-Hua LIU Cai-Fei HUANG Xin WANG 《Zoological Research》 CAS CSCD 北大核心 2014年第6期500-509,共10页
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
关键词 Ventral nucleus of the lateral lemniscus Firing pattern Frequency tuning Intensity tuning MOUSE
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Cyclic beamforming using fractional Fourier transform domain cyclostationarity
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作者 Muhammad Ishtiaq Ahmad Liu Zhiwen Xu Yougen 《High Technology Letters》 EI CAS 2011年第1期57-63,共7页
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
关键词 BEAMFORMING fractional Fourier transform chirp signal CYCLOSTATIONARITY
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Despreader for Direct Sequence Spread Spectrum System and Its Performance Analysis
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作者 何先灯 裴昌幸 易运晖 《Transactions of Tianjin University》 EI CAS 2010年第4期275-278,共4页
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
关键词 spread spectrum communication matched filter digital matched filter PROBABILITY
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Generalized spatial representation for digital modulation and its potential application 被引量:1
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作者 Hao HUAN Pengfei SHI +1 位作者 Xiaodong YAN Ran TAO 《Science China Earth Sciences》 SCIE EI CAS CSCD 2016年第12期47-58,共12页
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
关键词 quadrature frequency-phase shift keying (QFPSK) chirp cyclic shift keying spatial constellation mapping image OFDM system wireless communication
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