With reference to the air target detection of ultra-wide band (UWB)/impulse radar(IR), the transient signal processing techniques was discussed. In weak UWB signal detection, the wavelet transforms and high order spec...With reference to the air target detection of ultra-wide band (UWB)/impulse radar(IR), the transient signal processing techniques was discussed. In weak UWB signal detection, the wavelet transforms and high order spectrum estimation techniques were preferred. In target characteristic analysis, a time domain bispectrum estimation algorithm was used to analyze the target impulse response, which could estimate accurately local scattering distribution of complex target. A free field IR experimental system installed in an anechoic chamber was used. With this system, experiments to several target models were made. The results of these experiments verified the signal processing method efficiency.展开更多
This analysis focuses on PIM interference under multi-band multi-signal input in mobile communication system.Unlike single band system that only odd order PIM(especially 3rd order) should be concerned,in multi-band mu...This analysis focuses on PIM interference under multi-band multi-signal input in mobile communication system.Unlike single band system that only odd order PIM(especially 3rd order) should be concerned,in multi-band multi-signal case,both odd and even order PIM could be interference source because of more complicated intermodulation,more IMPs generated and more receive bands.Especially,the 2nd order PIM may interfere more serious to receiving channel for its strong magnitude.In duplex indoor distribute system,the PIM interference is a potential problem to GSM900,DCS1800,CDMA,and even 3G system wireless services,because the PIM frequencies may fall in receive bands and interfere to the receiving channels.In radio system design and wireless channel assignment,precautions must be taken to minimize the PIM level and to avoid interfere to receiving channels.For practical use,the lower order possible PIM interference to 2G and 3G systems is calculated.展开更多
This paper analyzes mathematically the crucial aspects of signal processing in a Multi-Band (MB) Orthogonal Frequency Division Multiplexing (OFDM) based system considering Ultra-Wideband (UWB) channel environment. In ...This paper analyzes mathematically the crucial aspects of signal processing in a Multi-Band (MB) Orthogonal Frequency Division Multiplexing (OFDM) based system considering Ultra-Wideband (UWB) channel environment. In the process of analysis, it emphasizes the significant features of UWB receiver design in comparison with ‘conventional’ narrow-band system. The analysis shows that the high dispersive nature of a frequency selective UWB channel effects the design of different signal processing blocks like pre-select filter, low noise amplifier (LNA) and analog-to-digital (A/D) converter in the receiver front end. The characteristic functions of each of these stages are now dominated by the channel characteristics and it needs to be modified accordingly. This analysis is extended further with the study of frequency offset error and its correction. The unbiased Cramer Rao Lower Bound (CRLB) of estimation error is calculated and supported by computer simulation. The performance of an MB-OFDM system with frequency offset correction in terms of Bit-Error-Rate (BER) is also reported.展开更多
The evaluation of System Performance of UWB (ultra-wide band) jointing in MC (multi-carrier) signaling in correlated environments is presented in the report. The correlated Nakagami-m statistical distribution for the ...The evaluation of System Performance of UWB (ultra-wide band) jointing in MC (multi-carrier) signaling in correlated environments is presented in the report. The correlated Nakagami-m statistical distribution for the multipath fading model is assumed in this scenario. In fact to establish the model for analyzing in this article is using MC-CDMA (multi-carrier code-division multiple-access) system characterization combined with a UWB scheme. The average BER (bit error rate) is calculated and compared to a special case of previously published results. Studied results from this paper can be implied to approve the system performance for a UWB system combined with a MC-CDMA wireless communication system. It is worth noting that the Nakagami-m distributed fading parameter significantly dominates UWB system performance when it cooperates with MC signaling under a fading environment. Finally, it is worthy of noting that when the SNR (signal-to-noise ratio) at system’s receiver reaches a preset high threshold value, the parameter of power decay ratio effect could be not included.展开更多
A novel compression method for mechanical vibrating signals,binding with sub-band vector quantization(SVQ) by wavelet packet transformation(WPT) and discrete cosine transformation(DCT) is proposed.Firstly,the vibratin...A novel compression method for mechanical vibrating signals,binding with sub-band vector quantization(SVQ) by wavelet packet transformation(WPT) and discrete cosine transformation(DCT) is proposed.Firstly,the vibrating signal is decomposed into sub-bands by WPT.Then DCT and adaptive bit allocation are done per sub-band and SVQ is performed in each sub-band.It is noted that,after DCT,we only need to code the first components whose numbers are determined by the bits allocated to that sub-band.Through an actual signal,our algorithm is proven to improve the signal-to-noise ratio(SNR) of the reconstructed signal effectively,especially in the situation of lowrate transmission.展开更多
随着物联网技术的飞速发展,窄带物联网(Narrow Band Internet of Things,NB-IoT)作为一种低功耗、广覆盖、大连接的无线通信技术,逐渐成为连接物理世界与数字世界的桥梁。然而,在实际应用中,NB-IoT信号面临着诸如信号衰减、干扰、覆盖...随着物联网技术的飞速发展,窄带物联网(Narrow Band Internet of Things,NB-IoT)作为一种低功耗、广覆盖、大连接的无线通信技术,逐渐成为连接物理世界与数字世界的桥梁。然而,在实际应用中,NB-IoT信号面临着诸如信号衰减、干扰、覆盖不均等挑战。这些挑战不仅影响用户体验,还限制了物联网应用的进一步发展。因此,研究面向物联网的NB-IoT信号优化方法具有重要意义。文章深入研究面向物联网的NB-IoT信号优化方法,提出多种有效的优化策略和技术手段。展开更多
目的:分析脑干带状高信号的软脑膜转移病例的临床特征。方法:收集海南医学院第一附属医院及检索知网、万方、维普、PubMed、Web of Science等数据库中报道磁共振表现为脑干带状高信号的患者,收集并整理纳入患者的既往病史、症状、体征...目的:分析脑干带状高信号的软脑膜转移病例的临床特征。方法:收集海南医学院第一附属医院及检索知网、万方、维普、PubMed、Web of Science等数据库中报道磁共振表现为脑干带状高信号的患者,收集并整理纳入患者的既往病史、症状、体征、基因检查结果、脑脊液表现、治疗及预后等。结果:共纳入28例患者,其中26例有肺腺癌病史,2例发现肺部占位性改变,磁共振均表现为T2‐FLAIR上脑干腹侧呈带状高信号,两侧对称,可延伸至小脑脚,DWI呈高信号,ADC呈低信号,T1加权成像为长T1信号,T2加权成像为长T2信号,增强扫描未见强化。结论:识别肺癌继发软脑膜转移很重要,T2‐FLAIR和DWI上脑干无强化带状高信号很可能是非小细胞肺癌继发软脑膜转移的特征性表现。展开更多
随着无线电通信的迅速发展,频谱资源日益紧张,各种干扰问题也越来越严重。其中,900 M Hz频段的干扰问题尤为突出。该文提出了一种基于信号特征分析和机器学习技术的900 MHz频段干扰自动定位方法,通过对干扰信号的频谱、时域、调制等特...随着无线电通信的迅速发展,频谱资源日益紧张,各种干扰问题也越来越严重。其中,900 M Hz频段的干扰问题尤为突出。该文提出了一种基于信号特征分析和机器学习技术的900 MHz频段干扰自动定位方法,通过对干扰信号的频谱、时域、调制等特征进行分析,建立干扰信号特征库,并利用机器学习算法对信号进行分类和定位。实验结果表明,该文提出的方法具有较高的干扰定位准确率和稳定性,能够有效地提高频谱资源利用效率的闭环。展开更多
文摘With reference to the air target detection of ultra-wide band (UWB)/impulse radar(IR), the transient signal processing techniques was discussed. In weak UWB signal detection, the wavelet transforms and high order spectrum estimation techniques were preferred. In target characteristic analysis, a time domain bispectrum estimation algorithm was used to analyze the target impulse response, which could estimate accurately local scattering distribution of complex target. A free field IR experimental system installed in an anechoic chamber was used. With this system, experiments to several target models were made. The results of these experiments verified the signal processing method efficiency.
文摘This analysis focuses on PIM interference under multi-band multi-signal input in mobile communication system.Unlike single band system that only odd order PIM(especially 3rd order) should be concerned,in multi-band multi-signal case,both odd and even order PIM could be interference source because of more complicated intermodulation,more IMPs generated and more receive bands.Especially,the 2nd order PIM may interfere more serious to receiving channel for its strong magnitude.In duplex indoor distribute system,the PIM interference is a potential problem to GSM900,DCS1800,CDMA,and even 3G system wireless services,because the PIM frequencies may fall in receive bands and interfere to the receiving channels.In radio system design and wireless channel assignment,precautions must be taken to minimize the PIM level and to avoid interfere to receiving channels.For practical use,the lower order possible PIM interference to 2G and 3G systems is calculated.
文摘This paper analyzes mathematically the crucial aspects of signal processing in a Multi-Band (MB) Orthogonal Frequency Division Multiplexing (OFDM) based system considering Ultra-Wideband (UWB) channel environment. In the process of analysis, it emphasizes the significant features of UWB receiver design in comparison with ‘conventional’ narrow-band system. The analysis shows that the high dispersive nature of a frequency selective UWB channel effects the design of different signal processing blocks like pre-select filter, low noise amplifier (LNA) and analog-to-digital (A/D) converter in the receiver front end. The characteristic functions of each of these stages are now dominated by the channel characteristics and it needs to be modified accordingly. This analysis is extended further with the study of frequency offset error and its correction. The unbiased Cramer Rao Lower Bound (CRLB) of estimation error is calculated and supported by computer simulation. The performance of an MB-OFDM system with frequency offset correction in terms of Bit-Error-Rate (BER) is also reported.
文摘The evaluation of System Performance of UWB (ultra-wide band) jointing in MC (multi-carrier) signaling in correlated environments is presented in the report. The correlated Nakagami-m statistical distribution for the multipath fading model is assumed in this scenario. In fact to establish the model for analyzing in this article is using MC-CDMA (multi-carrier code-division multiple-access) system characterization combined with a UWB scheme. The average BER (bit error rate) is calculated and compared to a special case of previously published results. Studied results from this paper can be implied to approve the system performance for a UWB system combined with a MC-CDMA wireless communication system. It is worth noting that the Nakagami-m distributed fading parameter significantly dominates UWB system performance when it cooperates with MC signaling under a fading environment. Finally, it is worthy of noting that when the SNR (signal-to-noise ratio) at system’s receiver reaches a preset high threshold value, the parameter of power decay ratio effect could be not included.
基金Supported by the National Natural Science Foundation of China(No.51135001)
文摘A novel compression method for mechanical vibrating signals,binding with sub-band vector quantization(SVQ) by wavelet packet transformation(WPT) and discrete cosine transformation(DCT) is proposed.Firstly,the vibrating signal is decomposed into sub-bands by WPT.Then DCT and adaptive bit allocation are done per sub-band and SVQ is performed in each sub-band.It is noted that,after DCT,we only need to code the first components whose numbers are determined by the bits allocated to that sub-band.Through an actual signal,our algorithm is proven to improve the signal-to-noise ratio(SNR) of the reconstructed signal effectively,especially in the situation of lowrate transmission.
文摘随着物联网技术的飞速发展,窄带物联网(Narrow Band Internet of Things,NB-IoT)作为一种低功耗、广覆盖、大连接的无线通信技术,逐渐成为连接物理世界与数字世界的桥梁。然而,在实际应用中,NB-IoT信号面临着诸如信号衰减、干扰、覆盖不均等挑战。这些挑战不仅影响用户体验,还限制了物联网应用的进一步发展。因此,研究面向物联网的NB-IoT信号优化方法具有重要意义。文章深入研究面向物联网的NB-IoT信号优化方法,提出多种有效的优化策略和技术手段。
文摘目的:分析脑干带状高信号的软脑膜转移病例的临床特征。方法:收集海南医学院第一附属医院及检索知网、万方、维普、PubMed、Web of Science等数据库中报道磁共振表现为脑干带状高信号的患者,收集并整理纳入患者的既往病史、症状、体征、基因检查结果、脑脊液表现、治疗及预后等。结果:共纳入28例患者,其中26例有肺腺癌病史,2例发现肺部占位性改变,磁共振均表现为T2‐FLAIR上脑干腹侧呈带状高信号,两侧对称,可延伸至小脑脚,DWI呈高信号,ADC呈低信号,T1加权成像为长T1信号,T2加权成像为长T2信号,增强扫描未见强化。结论:识别肺癌继发软脑膜转移很重要,T2‐FLAIR和DWI上脑干无强化带状高信号很可能是非小细胞肺癌继发软脑膜转移的特征性表现。
文摘随着无线电通信的迅速发展,频谱资源日益紧张,各种干扰问题也越来越严重。其中,900 M Hz频段的干扰问题尤为突出。该文提出了一种基于信号特征分析和机器学习技术的900 MHz频段干扰自动定位方法,通过对干扰信号的频谱、时域、调制等特征进行分析,建立干扰信号特征库,并利用机器学习算法对信号进行分类和定位。实验结果表明,该文提出的方法具有较高的干扰定位准确率和稳定性,能够有效地提高频谱资源利用效率的闭环。