数字电视地面广播COFDM传输中的软判决技术

深入研究了数字电视地面广播COFDM解调方案中的解映射软判决技术,提出了适用于该系统的信道状态信息CSI提取方法。在此基础上通过算法仿真分析,进一步提出一种新的克服单频和PAL模拟电视同频干扰的消除法并给出计算公式。本设计基于国家数字高清晰度电视总体组的多载波BDB-T传输方案,方案样机采用FPGA实现其相应的硬件电路,经过在实际无线环境中传输测试,证明了所提方法的易实现性和其良好性能。     

基于FPGA的Camera Link转HD-SDI接口转换系统

由于Camera Link相机具有接口复杂、传输距离近等局限性,设计并实现了一种基于FPGA的Camera Link转HD-SDI接口转换系统。该系统采用Altera公司的EP2S60F1020高性能FPGA完成图像数据的采集并按SMPTE274M标准编码;为解决Camera Link相机输出数据同HD-SDI输出图像行、场时间不同的问题,采用3片SDRAM作为帧缓存模块,延迟1帧输出;编码完成的数据输出到并串转换芯片LMH0030,从而得到HD-SDI格式的视频输出。由于Camera Link相机输出数据同HD-SDI输出图像的帧频并不绝对相同,每隔708帧必须丢去一帧数据,从而导致输出时固定丢帧,但FPGA对图像的处理并不会丢帧。实验结果表明,本系统能够将Camera Link相机输出的图像数据转换成HD-SDI输出,并用采集卡采集到图像数据。     

新型DVI数字视频接口电路的研究

随着各种平板显示器的广泛应用,高画质视频接口技术的研究凸显重要.采用基于DVI接口解码芯片SiI161硬件电路设计方案,进行了高分辨率平板显示嚣视频接口电路的试验研究,实现了平板显示器可用高质量数字视频 数据的解码输出.该设计方案已在液晶显示器等接口电路系统中得到验证,为系统提供优质稳定的数字视频源,最高图像显示分辨率...     

A low power and small area digital self-calibration technique for pipeline ADC

A digital self-calibration implementation with discontinuity-error and gain-error corrections for a pipeline analog-to-digital converter (ADC) is presented. In the proposed calibration method, the error owing to each reference unit capacitor of the multiplying D/A converter is measured separately using a calibration capacitor and an enhanced resolution back-end pipeline ADC acting as an error quantizer. The offset and finite open loop DC-gain of the operational amplifier and capacitor mismatches, the reference voltage mismatch can all be calibrated. The calibration can be achieved by that only used addition and subtraction. Hence, it needs low power and area consuming. A prototype ADC with the proposed calibration was fabricated on a 0.5 μm double-poly triple-metal CMOS process. The power consumption and area of the calibration circuit are only 10.1 mW and 1.05 mm², respectively. At a sampling rate of 30 MS/s, the calibration improves the DNL and INL from 2.59 LSB and 14.98 LSB to 0.72 LSB and 1.82 LSB, respectively. For a 1.25 MHz sinusoidal signal, the calibration improves the signal-to-noise-distortion ratio and spurious-free dynamic range from 43.1 dB and 52.1 dB to 75.51 dB and 83.61 dB, respectively. The 12.25 effective number of bits at 30 MS/s ADC consumes a total power of 136 mW.     

数字视频监控中的远端摄像仪控制系统

以基于网络的数字视频监控为基础，论述了数字视频监控中远端摄像仪控制系统的工作原理、帧编码以及软件和硬件的实现方法。实际应用表明，系统具有操作灵活、误码率低的特点，可达到实时控制目的。     

Fiber-optic digital video multiplexing using optical CDMA

The use of laser pulsing in the form of code-division multiple access (CDMA) to multiplex a set of digital video signals over a fiber network is proposed. The laser pulsing is used to generate unique code sequence addresses which identify each source, and the video data are modulated on these sequences. Digital encoding using pulse position modulation (PPM) is proposed, having advantages that permit efficient integration of optical and electronic processing. Data recovery is achieved by optical correlation for sequence recognition, followed by standard electronic PPM decoding. The relation between key system parameters of the encoding, decoding, and optics is derived, and indicates that compressed video rates between 5 and 20 Mb/s/channel, with 25-50 channels, is possible with relatively standard hardware. Experimental breadboard results being carried out at USC on this system indicate the feasibility of the CDMA concept for fiber multiplexing     

3D scanning-based compression technique for digital hologram video

In this paper, we proposed an efficient coding method for digital hologram video using a three-dimensional (3D) scanning method and two-dimensional (2D) video compression technique. It consists of separation of the captured 3D image into R, G, and B color space components, localization by segmenting the fringe pattern in to M×N [pixel²], frequency-transform by 2D discrete cosine transform (2D DCT), 3D-scanning the segments to form a video sequence, classification of coefficients, and hybrid video coding with H.264/AVC, differential pulse code modulation (DPCM), and lossless coding method. The experimental results with this method showed that the proposed method has compression ratios of 8–16 times higher than the previous researches. Thus, we expect it to contribute to reduce the amount of digital hologram data for communication or storage.     

数字视频混合系统的设计

介绍了利用Philips的一款视频芯片SAA71 99B实现的数字视频混合系统.该系统可以将一路PAL制彩色复合视频信号编码进入另一路PAL制彩色复合视频信号中,以取代第二路视频中用户指定的颜色,从而实现了两路视频的混合.另外还介绍了如何利用单片机的I/O口模拟I 2C总线以及如何利用单片机进行彩色空间变换的算法.     

Fiber-optic digital video distribution system for usinghigh-definition television signals using laser-diode optical switch

A fiber-optic high-definition television (HDTV) distribution system is discussed, which economically distributes HDTV signals to customers at a bit rate of about 100 Mb/s. The subscriber network is formed in a star topology to facilitate bidirectional connection. The distribution system uses digital video transmission at 1.3 μm wavelength using single-mode fiber. The video channel selection is made by an optical video selector. The optical selector consists of laser diode optical switch modules, which have a gain in the `ON' state and two-input, two-output 3 dB couplers. The authors describe the bit error rate characteristics of a signal-mode fiber digital distribution system using a four-input, one-output optical selector     

A novel digital predistorter technique using an adaptive neuro-fuzzy inference system

This letter presents a novel digital predistorter technique using an adaptive neuro-fuzzy inference system (ANFIS). The proposed approach employs real-time input and output signals of a nonlinear power amplifier as inputs to the ANFIS, so as to approximate the inverse functions of the power amplifier. The antecedent and consequent parameters of the FIS constructed by the ANFIS are tuned using backpropagation and least squares algorithms. Simulation shows that this novel technique has improved the linearity of a WCDMA signal by a further 4 dBc compared to a conventional look-up table (secant) approach. Moreover, this proposed technique is capable of adapting to instantaneous variation in the power amplifier response through time, which is a topic often omitted by researchers in this area.     

Closed-form approximations for link loss in a UWB radio system using small antennas

A critical need in the evaluation of an ultrawideband (UWB) radio system is the calculation of the energy link loss between the source at the transmit antenna and the receiver load. While the rigorous calculation of link loss in a wideband pulsed system requires a full transient electromagnetic solution for the transmit and receive antennas, we show in this paper that accurate approximations for link loss can be obtained for the special cases of electrically small dipole or loop antennas, with Gaussian or Gaussian doublet (monocycle) generator waveforms. We also consider the error involved with applying the much simpler narrowband Friis transmission formula. It is found that the use of the basic Friis formula can result in link loss errors of more than 60 dB for a UWB system having severely (impedance) mismatched antennas, but may give results correct to within a few dB for well-matched narrowband antennas, or if the formula is augmented with an impedance mismatch correction factor. It appears that the dominant limitation of the Friis formula, when applied to UWB systems, is the broadband effect of mismatch between the transmit/receive antennas and their source or load impedances. Numerical examples are presented for electrically short dipoles, resonant dipoles, and broadband lossy dipoles for both Gaussian and monocycle input pulse waveforms.     

Satellite-based distance learning using digital video and theInternet

The Boston University College of Engineering Distance Learning Initiative (DLI) integrates computers, digital video, and the Internet to deliver graduate degree courses in engineering to students in companies distant from the Boston University campus. A key objective of the DLI is to support learning wherever it is most convenient, whether by groups in a classroom, at the workplace desk, or at home. The article describes the motivation, technology, and experiences in integrating a satellite-based digital video distance learning system coupled with Web technology     

LVDS技术在数字视频传输系统中的应用

提出一种基于LVDS技术的视频传输系统,该系统是以APA150和DS92LV18为核心,考虑到长距离图像传输的需要,增加了LVDS差分信号预加重和均衡功能.实践证明,该系统能够满足视频图像的远距离实时传输要求,结构简单且扩展性强.     

A digital video system for the CATV industry

A ditigal pulse code modulator (PCM) system is proposed to implement long-haul video system for the CATV industry. A comparison is made between PCM system and wide-band FM system in terms of repeaterability versus additional occupied signal bandwidth. This is followed by a noise analysis of coaxial cable to determine the correct PCM format and bit information rate. An 80- megabit system is selected, which uses an 8-bit code in a four-level, eight-level, eight-level pulse sequence per video sample. The selected PCM system is then evaluated for its performance on both a long-haul cable system and a long-haul microwave system. Performance calculations are made on a 500-mile cable system in terms of error rate and its related video signal-to-noise ratio. Repeater spacings are computad for various configurations, including the replacement of the digital regenerators with analog amplifiers. Additional performance calculations are then made on a 3000-mile microwave system, including the effect of simultaneous Rayleigh fading.     

数字视频系统接口应用

随着技术发展,数字视频接口逐步替代模拟视频接口,成为视频产生、传输、显示、存储的主要方式.列举了常用的模拟和数字接口,阐述了视频系统前端与后端数字视频接口的特点及应用情况.通过分析各个端口的性能和实际军事需要,得出Camera Link接口是现在军用光电产品中的主要发展和应用方向.并且从接口的发展趋势来看,未来的数字接口是向摄取速度更高、传输带宽更宽、分辨率更高的方向发展.     

Analogue multiplexing using a digital technique

A digital technique of multiplexing analogue signals is described whereby improved isolation between channels and negligible equivalent-channel `on? resistance is achieved. It is also suggested that the proposed method may find application in analogue?digital conversion     

A 20-channel optical communication system using subcarriermultiplexing for the transmission of digital video signals

Microwave subcarriers have been used to demonstrate an optical communication system suitable for the distribution of digital video channels. The design, performance, and optical link requirements are discussed for a 2-Gb/s subcarrier-multiplexed (SCM) system with 20 microwave subcarriers modulated at 100 Mb/s and using a frequency-shift-keyed format. The system uses the 2-6-GHz bandwidth and represents the first example of an SCM system using more than one octave of bandwidth. The bit error rate was measured for all 20 channels; results for five typical channels are shown and discussed. The performance results show that a digital SCM approach is attractive in an optical link for a multichannel wide bandwidth video distribution system made from standard microwave components     

FCO sampling of digital video using perfect reconstruction filterbanks

Three-dimensional nonseparable perfect reconstruction filter banks using three-dimensional nonseparable sampling by two, FCO, are proposed. Filter structures are derived and applied to digital video. Separation into two bands is obtained, and it is shown to perform better from the perceptual point of view than interlaced sequences resulting from the quincunx sampling of a progressively scanned signal in time-vertical dimensions.     

基于无线的数字式船舶视频监控系统

根据船舶视频监控系统对系统结构和功能的新需求,采用TI公司的TMS320DM6446作为系统的主控部分,提出了基于EVDO的无线数据传输方案,设计了摄像机前端采集输出和主控模块等硬件电路,给出了通信控制等软件流程,并成功实现云台调节控制等功能。实际分析测试表明,该系统操作简便,创新性较高,可广泛应用于民用船舶的视频监控需求。     

Terrestrial digital video broadcasting for mobile reception using OFDM

Performance of a system design for digital video broadcasting is examined with emphasis on mobile reception. Orthogonal frequency division multiplexing (OFDM) is used to achieve good bandwidth efficiency and to mitigate the intersymbol interference resulting from the channel delay spread. The resulting equivalent channel including OFDM can be modeled as a flat Rayleigh fading channel plus an interchannel interference (ICI) term due to the channel Doppler spread. This ICI term is analyzed and shown to result in an error floor. Performance improvements due to antenna diversity and trellis-coded modulation (TCM) are given. Finally, multiresolution modulation is discussed as a means of achieving graceful degradation and giving degrees of freedom for further performance improvement.This research was supported by the Multimedia Systems R & D Laboratory, Hitachi, Ltd.