通信卫星有效载荷的现状与发展趋势

介绍了目前国内外通信卫星有效载荷的现状,在简要地分析和总结了国内外通信卫星有效载荷的现状的基础上,详细列举了通信卫星载荷的发展趋势,以及发展过程中出现的新技术,最后提出了我国卫星有效载荷发展的一些建议。     

Digital signal processing

Markets have always influenced the central thrust of the semiconductor industry. Beginning in the early eighties, the personal computer (PC) market has been the dominant market influencing the semiconductor industry. Single-chip microprocessors (MPUs) enabled what became the huge PC market, which ultimately overshadowed the earlier minicomputer and mainframe computer markets. The popularity of PCs led to investments in increasingly more powerful MPUs and memory chips of ever-growing capacity. MPUs and DRAMs became the semiconductor industry technology drivers for the data processing needs of the PC. But now, DSP, as opposed to conventional data processing, has become the major technology driver for the semiconductor industry as evidenced by its market growth and the fervour of chip vendors to provide new products based on DSP technology. The increasing need to digitally process analog information signals, like audio and video, is causing a major shift in the semiconductor business. Since DSP is the mathematical manipulation of those digitized information signals, specialized math circuitry is required for efficient signal processing-circuitry that was previously confined to classical DSP chips     

Digital signal processors in cellular radio communications

Contemporary wireless communications are based on digital communications technologies. The recent commercial success of mobile cellular communications has been enabled in part by successful designs of digital signal processors with appropriate on-chip memories and specialized accelerators for digital transceiver operations. This article provides an overview of fixed point digital signal processors and ways in which they are used in cellular communications. Directions for future wireless-focused DSP technology developments are discussed     

Advanced signal processing for power line communications

In this article, signal processing techniques to combat the adverse communications environment on power lines are addressed, so as to enable reliable high speed data communications over low-voltage power distribution networks for Internet access and in-home/office networking. It is seen that multicarrier code-division multiple access, multiuser detection, and turbo decoding, having demonstrated their limit-approaching capacity in DSL and wireless communication systems, are readily applied to power line communications. In particular, it is argued that these methods can successfully mitigate the influence of the principal impairments in PLC channels: time-varying channel attenuation, multipath frequency-selective fading, multiple access interference, and background noise. Strategies to deal with the most unfavorable noise source, the impulse noise, are also discussed.     

Optical signal processing for lightwave communications networks

A number of optical signal processing functions that might be potentially important for future lightwave communication networks are described. An optical network with a distribution capacity of 100 HDTV channels is considered along with how such a network can be implemented using the following functional subsystems: frequency converters; transmitter banks; modified (wavelength division multiplexing) WDM demultiplexers; and tunable optical receivers. Discussed are the key network-level issues: the power budget, the channel separation, and the overall rationale for selection of multiplexing techniques. A hardware implementation of the functional subsystems using three basic building blocks-tunable amplifiers/filters, phase locked loops, and comb generators-is discussed     

电视接收机中的数字信号处理

本文从全电视信号的频谱特征出发,讨论了各种数字梳状滤波器的分析设计。这些数字梳状滤波器,使亮度和色度信号达到了最大限度的分离,从而大大地降低了亮—色交调失真及相互串扰,提高了电视接收机的观看效果。文章在最后给出了进一步彩电观看效果的方法,如降低大面积场间闪烁和局部行间闪烁。总之,所有这些对未来视频系统的分析设计提供了不少启迪和借鉴。     

Low earth orbit satellite communications experiments using the digital signal processing payload on the PoSAT-1 microsatellite

There is a growing interest in using networks of small satellites in low Earth orbit (LEO) to provide a variety of communications services in conjunction with small ground terminals. The only ’little LEO’ microsatellite digital store-and-forward communications network (HealthNet) in commercial operation at the time of writing uses microsatellites, communications payloads, and protocols designed and built at the University of Surrey, U.K. In order to provide an in-orbit research test-bed for improving communications with microsatellites in LEO by optimizing modulation and demodulation techniques, an advanced DSP payload, the digital signal processing experiment (DSPE), was included on board the latest Surrey microsatellite (PoSAT-1). In-orbit experiments using the PoSAT-1 DSPE first optimized the existing non-coherent CPFSK communication systems and then investigated the use of coherent MSK to provide a potential 3dB advantage while remaining compatible with the spacecraft systems. A novel DSP implementation of the Hodgart-Massey coherent MSK demodulator/decoder was developed by the authors and its behaviour compared with the classical de Buda demodulator undertypical LEO conditions through a sequence of rigorous computer simulations and laboratory bench tests. The simulations and bench tests quantified a practical 2dB improvement in BER performance when compared with non-coherent CPFSK, while also exhibiting considerable tolerance to the frequency and amplitude variations which are encountered in an LEO environment. These characteristics were subsequently confirmed by in-orbit demonstrations using the PoSAT-1 DSPE. The microsatellite, payload, modems and experimental results are presented in this paper and discussed with a view towards implementing an adaptable DSP-based communications system capable of optimizing data throughput with LEO microsatellites.     

Digital signal processing in measurement microsystems

A digital signal processing (DSP) based stand-alone measurement system is capable of making decisions in control. This article explains the applications of DSP measurand reconstruction and defines and illustrates three classes of elementary problems: scalar nonlinear problems of static reconstruction, scalar linear problems of dynamic reconstruction, and scalar nonlinear problems of quasi-dynamic reconstruction.     

An on-board processing satellite payload for european mobile communications

The paper considers the application of satellite on-board processing (OBP) technology for land mobile applications for possible introduction in the late 1990s. Initially a system outline is presented followed by a discussion considering the merits of OBP over conventional transparent payloads. The paper then presents an overview of the work being carried out as part of an ESA study. Some details on the critical parts of the system are also included.     

Optical technologies for signal processing in satellite repeaters

The evolution of modern communications satellites from the older cable-in-the-sky concept toward more intelligent architectures, exploiting onboard processing (OBP) techniques involving various technologies to improve the system performance and flexibility, is addressed. The key components in advanced communications satellite repeaters compatible with integrated optical device implementation are presented. The relevant device technologies and fabrication techniques are examined, and integrated optical circuit configurations that can be applied to OBP are described with reference to recent experimental data. Particular attention is given to optical beamforming networks. Areas for further research and development are suggested     

Digital signal processing for sonar

This paper is a tutorial which describes "main stream" sonar digital signal processing functions along with the associated implementation considerations. The attempt is to promote further cross-fertilization of ideas among digital signal processing applications in sonar, radar, speech, communications, seismology, and other related fields.     

Digital signal processing for video

Applications of the digital signal processing of video signals in broadcasting, communication, and consumer electronics are reviewed. These include: digital encoding systems, digital video effect equipment, and the television standards converter for broadcasting; videoconferencing and video telephone equipment; and TV receivers, including those for extended definition and high-definition television (EDTV and HDTV). Performance requirements for video signal processing (VSP) are discussed, and an example of a video signal processor comprising a parallel processor system composed of multiple VSP modules is examined. Future trends in VSP are predicted     

Multichannel signal processing for data communications in thepresence of crosstalk

Transceiver designs for multiple coupled channels typically treat the crosstalk between adjacent twisted pairs as random noise uncorrelated with the transmitted signal. The authors propose a transmitter/receiver pair that compensates for crosstalk by treating an entire bundle of twisted pairs as a single multi-input/multi-output channel with a (slowly varying) matrix transfer function. The proposed transceiver uses multichannel adaptive FIR filters to cancel near- and far-end crosstalk, and to pre- and postprocess the input/output of the channel. Linear pre- and postprocessors that minimize mean squared error between the received and transmitted signal in the presence of both near- and far-end crosstalk are derived. The performance of an adaptive near-end crosstalk canceller using the stochastic gradient (least-mean-square) transversal algorithm is illustrated by numerical simulation. Plots of mean squared error versus time and eye diagrams are presented, assuming a standard transmission line model for the channel. A signal design algorithm that maps a vector input bit stream to a stream of channel symbol vectors is also presented and illustrated explicitly for s simple model of two coupled channels     

Statistical reference criteria for adaptive signal processing indigital communications

A general criterion for the design of adaptive systems in digital communications called the statistical reference criterion is proposed. The criterion is based on imposition of the probability density function of the signal of interest at the output of the adaptive system, with its application to the scenario of highly powerful interferers being the main focus of this paper. The knowledge of the PDF of the wanted signal is used as a discriminator between signals so that interferers with differing distributions are rejected by the algorithm. Its performance is studied over a range of scenarios. Equations for gradient-based coefficient updates are derived, and the relationship with other existing algorithms like the minimum variance and the Wiener criterion are examined