数字电视机顶盒高清接口解析

有线电视网络的发展进入了数字时代,原先的模拟接收电视方式正在向新一代数字化接收过渡,由此新型交互式多媒体电视接收系统应运而生,数字电视机顶盒成为一个交互式数字电视系统中必不可少的重要组成部分,它在模拟电视和今天主流的数字电视二者间起连接的桥梁的作用。     

The HDTV Grand Alliance System

Broadcast television in the United States has remained essentially unchanged in the last 50 years except for the addition of color and stereo sound. Today, personal computers are meeting the need for random access of high-resolution images and CD-quality audio. Furthermore, advances in digital video compression and digital communication technology have cleared the way toward offering high-resolution video and audio services to consumers using traditional analog communications channels. In 1987, the US Federal Communications Commission (FCC) chartered an advisory committee to recommend an advanced television system for the United States. From 1990 to 1992, the Advanced Television Test Center (ATTC) tested four all-digital systems, one analog high-definition television (HDTV) system, and one enhancement NTSC system using broadcast and cable television environment simulators. The formation of the HDTV Grand Alliance in May 1993 resulted from the withdrawal of the only analog HDN system from the competition and a stalemate between the other four all-digital systems. The HDTV Grand Alliance system is composed of the best components from previously competing digital systems demonstrated to the FCC. The Moving Pictures Experts Group (MPEG-2) syntax is used with novel encoding techniques to deliver a set of video scanning formats for a variety of applications. This article describes the important features and concepts embodied in the HDTV Grand Alliance system     

Precoded Modulo-Precanceling Systems for Simulcasting Analog FM and Digital Data

We present techniques for simulcasting low-power digital data and analog FM over fading channels. Our methods have strong connections to what are referred to as dirty paper coding techniques in that a low-power digital data signal is modulo-added to the host analog FM signal. Due to the low power levels of the digital data and the suppression capability of analog FM, a standard analog FM receiver can be used to reliably recover the analog audio signal. We develop digital receivers that work reliably over fading channels given imperfect channel state information. Spreadresponse precoding is exploited to not only provide rate-1 temporal diversity benefits, but also to simplify the design of the modulo-precanceler and the receiver. Our theoretical and simulation-based performance analysis of the digital receivers and our MSE-based analog FM distortion analysis suggest that precoded modulo-precanceling schemes provide substantially higher data rates than existing precanceling strategies at the cost of transmission delay and transmitter and receiver complexity. The systems we present are also readily compatible with conventional channel coding techniques as well as with analog FM postcancelers, which can improve the digital receiver bit-error-rate performance at the expense of receiver complexity.     

Digital audio broadcasting in the FM band by means of contiguous band insertion and precanceling techniques

A low-complexity method of linearly combining an analog frequency-modulation (FM) signal with a low-level multitone signal for simultaneous broadcasting of digital data and analog FM is proposed and evaluated. The analog FM signal can be recovered with a standard FM receiver. The digital multitone signal is added symmetrically at the band edges of the 200-kHz FM signal in contiguous bands with variable width. To maximize the data rate, the digital bandwidth is maximized subject to a maximum allowed distortion of the demodulated analog FM signal. The impact of the analog FM signal on, digital reception is cancelled by means of transmitter precanceling techniques. Conditions for precanceling techniques for multipath channels are formulated. The main advantage of the contiguous band insertion method is that the rate of the control channel is considerably lower compared to previously proposed methods of carrier insertion without significant reduction in data rate. We present a number of numerical results for acoustical signals.     

ASTRA Digital Radio: high‐quality digital audio transmissions via satellite

ASTRA Digital Radio (ADR) is a satellite audio transmission technology which has been designed to be compatible with analogue radio and television transmissions via satellite. It uses QPSK modulated subcarriers above the video spectrum. For source coding, the internationally standardized MPEG 1 Layer II digital audio compression has been selected. Owing to its backward compatibility with the existing analogue audio transmission technology, ADR provides a maximum operational flexibility for both the broadcasters and the satellite operator. For the consumer this technology allows for a very high number of near CD quality radio programmes which may be received with a low‐cost receiver connected to a standard 60 cm satellite reception antenna. ADR was officially launched in August 1995 during the Internationale Funkausstellung in Berlin and currently allows for the reception of over 85 radio programmes in digital quality. Copyright © 2000 John Wiley & Sons, Ltd.     

A Flexible, Ultra-Low-Energy 35 pJ/Pulse Digital Back-End for a QAC IR-UWB Receiver

A low-energy, flexible digital back-end for the quadrature analog correlating (QAC) IR-UWB receiver, implemented in 0.13 m CMOS technology, is presented. The built-in flexibility allows the receiver to operate over a wide range of frequency bands, pulse rates, code lengths, acquisition modes, etc. This ability to dynamically trade power consumption, system performance and system reliability is crucial for application in sensor networks where energy is scarce. To avoid the large power penalty, that often accompanies the introduction of flexibility, the chip's architecture is based on nested FLEXmodules. These are small configurable modules with a local controller, that can be slowed down and clock gated individually. Communicating at 40 Mpulses/s, the resulting digital back-end consumes as little as 3.5 mW in acquisition mode and 1.5 mW during data reception. This is equivalent to an energy consumption of 35 pJ per received pulse.     

Digital television

It is now recognized worldwide that all television services, including HDTV, will eventually become digital, but there is wide disagreement about the optimum timing for transforming existing analog systems. A major driving force is the ongoing partial merging of television and digital computers in interactive multimedia services involving digital television and applications in areas like information (news), education, medical, entertainment, etc. A major target is to maximize interoperability of video services at all levels, including various resolutions, different transmission and storage mechanisms, as well as bit rates. This paper provides an overview of the current status in digital television, techniques used, future prospects, and research areas that need to be investigated. The maturity of compression techniques needed for digital video storage and transmission, and the establishment of international standards for digital television representation, like MPEG-2, have greatly contributed in this transformation. Recent developments are mentioned, including the American “Grand Alliance” FCC effort for digital terrestrial HDTV broadcasting, and also other efforts for digital television by cable and DBS. The concept of hierarchical multiresolution coding is also explained, and some of its techniques are briefly described     

一种用于DVB-C的全数字QAM解调器结构

该文提出了一种适用于数字有线电视的全数字QAM解调器结构,对解调器的载波恢复、符号同步、自动增益控制和自适应均衡等进行研究分析,通过仿真给出了相应的参数,最后给出整个解调器在AWGN信道条件下的误码性能,从仿具结果可以看出,该文提出的解调器具有较好的性能,且易于全数字实现。     

Adaptive Hybrid Beamformer for Mobile Reception of ATSC DTV

An adaptive hybrid beamformer is proposed to improve the reception performance of the advanced television system committee (ATSC) digital television (DTV) in a mobile environment. Dynamic multipaths and Doppler shifts severely degrade the reception performance of the ATSC DTV receiver. Accordingly, a hybrid beamformer, called a Capon and least mean square (CLMS) beamformer, is presented that uses direction of arrival (DOA) information and the least mean square (LMS) beamforming algorithm. The proposed CLMS algorithm efficiently removes dynamic multipaths and compensates for the phase distortion caused by Doppler shifts in mobile receivers. When the CLMS beamformer has an insufficient degree of freedom (DOF), the subsequent use of an equalizer removes any residual multipath effects, thereby significantly improving the performance of DTV receivers. The performances of the proposed CLMS, Capon, and LMS beamformers are compared based on computer simulations. In addition, the overall performance of the CLMS beamformer followed by an equalizer is also considered.     

A Low-Voltage Low-Power CMOS Analog Adaptive Equalizer for UTP-5 Cables

An analog adaptive equalizer based on a feed-forward architecture is implemented in 0.18-mum digital CMOS process. The equalizer is implemented with only digital core devices and operates at 125 Mbps over unshielded-twisted-pair category-5 cable of up to 100 m. Novel low-power circuit and system techniques resulted in 3.7-mW total power consumption and supply voltage operation as low as 1.6 V. The maximum peak-to-peak jitter at the output of the equalizer (including the transmit path driver) under all cable length is 0.33 UI. The total area of the equalizer is 27738 mum².     

An ADPCM Receiver for NTSC Composite Video Signals

An ADPCM codec for carrying one broadcast quality NTSC color TV channel at a bit rate of 42.9 Mb/s has been proposed. The system uses 3 fsc sampling, adaptive intrafield contour prediction, adaptive quantization., 4/8-bit dual length coding, and horizontal blanking interval suppression techniques. The receiver of.the video codec is designed and implemented in ECL for recovery of the original signal. The receiver accepts.a 42.9 Mb/s serial data stream with a synchronous clock from the transmitter. The receiver detects the line synchronization code, demultiplexes the audio signal and video signal, and generates the horizontal blanking patterns which have been removed at the transmitter side. The 4/8-bit dual length code is decoded and fed to the ADPCM reconstruction loop to obtain the reconstructed active video signal. The generated horizontal blanking pattern is multiplexed with the reconstructed video=signal and sent through a D/A converter to form the reconstructed analog NTSC composite video signal.     

A single-chip tuner for DVB-T

A new architecture is presented for a single-chip tuner for digital terrestrial television, based on existing double conversion and direct conversion topologies. The new design forms part of a mixed-signal Digital Video Broadcasting-Terrestrial (DVB-T) receiver system, employing digital signal processing at baseband to ensure minimal performance requirements for the analog circuitry. To evaluate the potential performance of this new tuner/receiver system, high-level system simulations have been performed, followed by the construction of a prototype DVB-T receiver using a custom-designed analog ASIC which integrates all analog tuner blocks (including channel filtering) on one chip. Measured results from this chip, implemented in a 20-GHz bipolar technology, show an overall third-order input referred intercept point of 116 dB/spl mu/V, a noise figure of 14 dB and an automatic gain control range of 71.4 dB, drawing 250 mA at a 5-V supply.     

Digital Broadcasting Television Channel Measurements and Characterization for SIMO Mobile Reception

This paper presents propagation measurement results in the UHF Digital Television (DTV) band using an ATSC DTV signal as a channel sounding signal to investigate the characteristics of a wideband single-input multiple-output (SIMO) under mobile reception conditions. A series of DTV dual channel signal measurements were conducted in the Ottawa region to characterize the transmission of ATSC 8-VSB signals under different propagation environments. A dual channel receiver was used to record SIMO signals: these were used to provide channel impulse response estimates. From the recorded time-varying impulse responses and their correlation functions, average power delay profiles, scattering functions were computed to analyse the joint spatial fluctuations of the received signals. The DTV channel characterization study is aimed at broadcast system designers involved in data transmission of terrestrial digital television signals over mobile channels with diversity reception     

Digital TV Receiver for NTSC Color TV Signals with Dual Word-Length DPCM Coding

A video codec system for carrying one broadcast quality NTSC color TV channel at a rate of 42.935 Mbits/s has been proposed. The receiver of the video codec system is developed for recovery of the original signal. The receiver accepts a 42.935 Mbits/s serial TDM data stream with a synchronous clock from the Transmitter. The receiver detects the unique sync code and inserts a horizontal blanking pattern which has been removed from the transmitting data. The audio and video data are separated at the outputs of the demultiplexer. The 4/8 bit dual length code word of the video data is smoothed out by a buffer memory and fed to the DPCM reconstruction loop. The analog NTSC color video signal as well as the audio signal are reconstructed after the D/A conversion. This paper describes the design and development of the receiver portion (Fig. 1) of the codec which is capable of transmitting'one color signal at broadcast standards on a T3 digital link.     

Simultaneous broadcasting of analog FM and digital audio signals bymeans of adaptive precanceling techniques

A method for broadcasting digital audio simultaneously with existing analog frequency modulation (FM) radio is presented. The method is based on precomputing the response of the host analog FM signal at the digital receiver and precanceling it at the transmitter. As a result, the digital transmission is free from interference from analog FM. We select the rate and power level of the digital transmission in a manner that the interference the digital data incur on the analog FM signal remains at acceptably low levels. The digital transmission is based on adaptive orthogonal frequency-division multiplexing (OFDM) (adaptive multicarrier). The frequencies and number of carriers of the digital multicarrier modem are judiciously selected in a time-varying fashion so as to cause a negligible distortion in a standard receiver for analog FM. Simulations based on conservative nonoptimized signal design indicate that data rates up to about 130 kb/s inside the 200-kHz FM channel are achievable for acoustic test signals. We present a number of numerical examples where the average digital data use up to 50% of the 200-kHz power spectrum with digital signal power levels 25-35 dB below the analog signal. Due to the resulting variable-rate digital transmission, a control channel is required. A method of precanceling with multiple orthogonal direct-sequence spread-spectrum schemes is also presented     

HDTV Mobile Reception in Automobiles

Mobile reception of digital terrestrial broadcasting carrying an 18-Mb/s digital HDTV signals is achieved. The effect of diversity reception in moving automobiles for a 64 quadrature amplitude modulation-orthogonal frequency division multiplexing (QAM-OFDM) signal is investigated by prototype hardware. There are two methods for diversity reception of OFDM signals. The first is the Doppler compensation directivity control system. For this method, high-performance on-glass antennas and new diversity reception systems for OFDM reception have been developed to verify HDTV service availability in mobile reception environments. Novel horizontally polarized on-glass antennas suitable for DTV were developed. The antenna elements were printed on the inside surface of the rear window glass of a passenger van. OFDM signals received by the four antenna elements were weighted and combined using maximal ratio combining (MRC). The experiments were conducted in urban areas and they showed that employing diversity techniques would make HDTV mobile reception possible in many areas. The other method is post-FFT diversity. In the receiver, MRC is performed after an FFT operation on each branch signal. Experimental results show that accurate HDTV mobile reception can be achieved by using a four-branch MRC system. Also, the minimum usable electric field strength could be reduced compared with that of a single dipole antenna.     

Source coding, channel coding and modulation techniques used in thedigital spectrum-compatible HDTV system

The digital spectrum-compatible high-definition television (DSC-HDTV) system, a digital HDTV simulcast system designed for United States terrestrial broadcasting on currently unassignable channels, is described. The system uses progressively scanned source signals and is characterized by an effective, high-performance video compression system. Compression includes motion compensation with hierarchical block matching and block transform coding with adaptive quantization according to perceptual criteria. Video compression is designed to simplify the receiver decoding; only a few VLSI chips and only one full frame memory are required. The source signal, source coding, channel coding, modulation, and performance of the system are discussed     

The US HDTV standard

This standard for digital high-definition television has been submitted to the Federal Communications Commission for its approval. Based as it is on the MPEG-2 video compression and transport protocol, multiple transmission formats, Dolby AC-3 digital audio, and vestigial sideband digital modulation, this HDTV system will supply the home with superb images and spectacular sound while also, as part of the National Information Infrastructure (NII), relaying digital data. An HDTV system employing multiple transmission formats, digital compression, packetization, and modulation techniques is a marked advance over current world television standards such as NTSC, PAL, or SECAM     

数字卫星电视接收天线仰角方位角极化角调试探讨

数字电视正以迅猛之势发展,目前数字电视信号主要是通过卫星传输,数字卫星电视信号的接收方法与模拟卫星电视信号的接收方法相同,利用室外抛物面状天线将数字卫星电视信号——电磁波接收下来,但由于数字电视信号的特点,接收数字电视卫星信号时的“寻星”过程远比接收模拟卫星电视信号困难得多,为此对数字卫星电视接收天线仰角、方位角、极化角的调试进行探讨。     

Joint VSB terrestrial digital TV indoor reception project

The reliability and efficacy of indoor reception of 8VSB digital terrestrial television (DTV) in four major U.S. cities was studied in an initial field measurement survey program and a subsequent data capture and processing program. Measurements from the initial survey identified problem sites for reliable DTV reception using currently available 2nd generation DTV receivers. Subsequent field dual channel data captures made at the identified problem sites provided data for testing and verification of new antenna diversity receiver algorithms destined for future generation DTV receivers. From data captures at selected problem sites of sufficient signal strength, but where currently available 2nd generation DTV receivers failed, it was found that in 70% of the cases DTV reception performance was satisfactory when using new antenna diversity receiver algorithms. These measurements and data captures corroborate the claim that the VSB DTV indoor reception problem may be less severe than implied from surveys using less advanced current 2nd generation receivers with a single antenna. For sites with severe multipath, 8VSB DTV reception could be potentially superior to NTSC, which would experience an unwatchable picture.