双驱动(对扣)带通扬声器系统分析

给出了双驱动（对扣）带通扬声器系统的声学类比线路，在此基础上详细讨论了系统特性和工作模式，并与四阶带通扬声器系统的特性作了比较，最后描述系统参数变化对系统特性的影响。

语音信号模拟传输系统实验设计与实现

针对通信原理授课案例的不足,考虑到近距离传输模拟系统的优势设计了语音信号模拟带通传输系统实验案例。以录制的语音为信号源,在模拟调制原理的基础上结合语音信号特性,构建了基于幅度调制的信号传输系统。实验结果表明:模拟带通系统可以有效地实现语音信号传输且直观性强,易于学生深入理解模拟调制解调原理,很大程度上激发了学生的学习兴趣和学习积极性。

基于“Bennia-Riad”准则频域反卷积

文中首先简介了“Bennia-Riad”准则和扩展的“Bennia-Riad”准则;其次介绍了基于扩展的“Bennia-Riad”准则的高通系统的反卷积问题;最后介绍了基于“Bennia-Riad”

Admission Control Based on QoS for Third Generation Broadband Mobile Communication Systems

In this paper, a novel admission scheme is proposed which provides high degrees of quality of service (QoS) guarantees for multimedia traffic carried in mobile networks. The proposed scheme combines the admission control and bandwidth reservation to guarantee QoS requirements. It considers both local information and remote information to determine whether to accept or reject a connection. In order to embody the characteristics of the algorithms proposed in the article, two traditional algorithms of admission control are used for comparison. In the end of the paper the simulation analyses are given and the results show that the proposed algorithm can adjust the bandwidth according to the current status of networks and decrease the probability of connections forcibly dropped. The most important thing is that the algorithm is based on the multimedia communications and can guarantee the QoS of real time connections through decreasing the bandwidth of non real time connections.

Low-Density Parity-Check Codes for Noncoherent UWB Communication Systems

In order to guarantee reliable data transmission, powerful channel coding techniques are usually required in noncoherent ultra-wideband(UWB) communication systems. Accordingly, several forward error correction(FEC) codes, such as Reed-Solomon and convolutional codes have been used in noncoherent UWB systems to improve the bit error rate(BER) performance. In this paper, low-density parity-check(LDPC) codes are further studied as more powerful FEC candidates for noncoherent UWB systems. Two LDPC codes and the corresponding decoding procedures are presented for noncoherent UWB systems. Moreover, performance comparison between the LDPC codes and other FEC codes are provided for three major noncoherent UWB communication systems, namely, noncoherent pulse position modulation(NC-PPM), transmitted reference(TR) and transmitted reference pulse cluster(TRPC). Both theoretical analysis and simulation results show that the two investigated LDPC codes outperform other existing FEC codes with limited penalty in terms of complexity and therefore they are promising FEC candidates for noncoherent UWB systems with low-cost and low-power consumption.

A NEW MODULATION SCHEME FOR IR-UWB COMMUNICATION SYSTEMS

Since the poor performance of orthogonal binary Pulse Position Modulation (PPM) compared with binary Pulse Amplitude Modulation (PAM), this paper presents a new modulation scheme named Pulse Width Modulation (PWM) for Impulse Radio Ultra-WideBand (IR-UWB) communication systems. This modulation scheme uses pulses with equal amplitude and different widths to carry different information. The receiver employs differences between similarity coefficients among these pulses to distinguish different information. Both theoretical analysis and simulation results verify that this novel scheme has a Signal to Noise Ratio (SNR) gain of about 1.75 dB compared with or- thogonal binary PPM, and has an SNR loss of about 1.4 dB compared with binary PAM. Although both the theoretical analysis and simulations are based on time-hopping multiple access, this modulation scheme can also be applied to other accessing techniques of UWB communication systems.

Simulation Study and Probe on UWB Wireless Communication in Underground Coal Mine

From an analysis of the status of coal mine underground wireless communication, the application of UWB wireless communication system to underground coal mine is proposed. The basic composition of an UWB communication system and application in underground coal mines are introduced. The analyses show that, because of the transmission power being non-limitted in underground coal mines, the use of UWB in coal mines cannot only realize wireless access services of short distance high rate application for transmission of video monitoring signals, but also realize wireless access services of long distance low rate applications for mobile telephones in underground coal mines and parameters of working conditions monitoring, etc. It is emphasized on the simulation of a TH-PPM UWB communication system with traditional underground broadband model and ground CM1, CM3 model. It is shown that the traditional underground broadband model and ground CM1, CM3 models are not applicable to the UWB communication system in underground coal mines. It is necessary to conduct research on the propagation characteristics of UWB in coal mine tunnels, given the characteristics of the underground environment and to find the appropriate UWB model for underground coal mines.

Forecasting promising technology using analysis of patent information:Focused on next generation mobile communications

In order to forecast promising technologies in the field of next generation mobile communication, various patent indicators were analyzed such as citation per patent, patent family information, patent share, increase rate, and patent activity. These indicators were quantified into several indexes and then integrated into an evaluation score to provide promising technologies. As a result of the suggested patent analysis, four technologies out of twenty two in details classification were selected, which showed outstanding technology competitiveness, high patent share and increasing rates as well as high recent-patent-ratios and triad-patent-family-ratios. Each of the selected technologies scored more than 10 points in total, and the following four technologies were suggested as promising ones in the field of next generation mobile communication: 1) 3GPP based mobile communication, 2) beyond 4G mobile communication, 3) IEEE 802.16 based mobile communication, which are in medium classification of broadband mobile communication system, and 4) testing/certification system of mobile communication, which is in medium classification of mobile communication testing/certification system.

A UWB communication system based on dechirp pulse compression and OOK modulation

In this paper,a novel UWB communication system structure is proposed.The transmitted signal uses OOK modulation and chirp spread spectrum.The received signal first goes through a dechirp pulse compression process,and then is processed with a two-level sliding correlation algorithm for coarse timing synchronization and fine timing synchronization.After the SNR estimation,the signal is demodulated by an energy detection method.An integrated system level simulation model is established,and the performance of this system is evaluated over the AWGN channel,IEEE 802.15.3a CM1 and CM4 channels.The theoretical analysis and simulation results show that this UWB communication system can effectively reduce the sampling rate and signal processing speed at the receiver,and it is more suitable for long-distance and low-rate UWB communications with high spreading gain.

Performance analysis model for real-time Ethernet-based computer numerical control system

In order to optimize the embedded system implementation for Ethernet-based computer numerical control （CNC） system, it is very necessary to establish the performance analysis model and further adopt the codesign method from the control, communication and computing perspectives. On the basis of analyzing real-time Ethemet, system architecture, time characteristic parameters of control-loop ere, a performance analysis model for real-time Ethemet-based CNC system was proposed, which is able to include the timing effects caused by the implementation platform in the simulation. The key for establishing the model is accomplished by designing the error analysis module and the controller nodes. Under the restraint of CPU resource and communication bandwidth, the experiment with a case study was conducted, and the results show that if the deadline miss ratio of data packets is 0.2%, then the percentage error is 1.105%. The proposed model can be used at several stages of CNC system development.

A SYNCHRONIZATION ALGORITHM FOR HF(HIGH FREQUENCY) BROADBAND OFDM SYSTEM

In this letter,a kind of associated synchronization algorithm which is suitable for HF(High Frequency) broadband OFDM(Orthogonal Frequency Division Multiplexing) system is presented based on describing and constructing the GMW(Gorden,Mills and Welch) sequence. The algorithm is based on the Schmidl and Minn's symbol timing principle,the constructed GMW sequence is trans-mitted and disposed,and the synchronization is adjudicated using the correlation of GMW sequence. The simulation result indicates that this algorithm has high performance synchronization ability under the low SNR(Signal to Noise Ratio) at two different kinds of channel models.

Generalized bounds on the partial periodic correlation of complex roots of unity sequence set

In this paper,the generalized bounds are derived on the partial periodic correlation of complex roots of unity sequence set with zero or low correlation zone(ZCZ/LCZ)as the important criteria of the sequence design and application.The derived bounds are with respect to family size,subsequence length,maximum partial autocorrelation sidelobe,maximum partial cross-correlation value and the ZCZ/LCZ.The results show that the derived bounds include the previous periodic bounds,such as Sarwate bound,Welch bound,Peng-Fan bound and Paterson-Lothian bound,as special cases.

China's First HTS Broadband Satellite Communications System Construction Initiated

China Aerospace Science and Technology Corporation（CASC）and the People’s Government of Shenzhen Municipality co-hosted a ceremony for the contract signing of the high-throughput broadband satellite project and for the establishment of a joint venture on July23,marking the formal start of the construction of China’s first high-throughput broadband satellite communication system.

电声元件、器件

2002408浅谈扬声器单元[刊]/陈坚强//电声技术.—1999.(10).—24～33(L)2002409双驱动(对扣)带通扬声器系统分析〔刊)/胡新//电声技术一1999,(10)一18一21(L) 给出了双驱动(对扣)带通扬声器系统的声学类比线路,在此基础上详细讨论了系统特性和工作模式,并与四阶带通扬声器系统的特性作了比较,最后描述系统参数变化对系统特性的影响。