应用于数字广播系统的高线性下变频器

An integrated downconverter with high linearity for digital broadcasting system receivers is implemented in a 0.13 m CMOS process with an active area of 0.1 mm2. The current-mode scheme is adopted to improve linearity performance by avoiding voltage fluctuation. A passive CMOS switching pair is utilized to improve the even-order linearity of the downconverter. A current amplifier is used to provide low input impedance which will easily lead to a wide operating bandwidth and high linearity. Moreover, a current-mode Sallen-Key low-pass filter is adopted for effective rejection of out-of-band interferers and also low input impedance. The digital-assisted DC offset calibration improves the second-order distortion of the downconverter. This design achieves a maximum gain of 40 d B and a dynamic range of 10 d B. Measured noise figure is 8.2 d B, an IIP2 of 63 d Bm, an IIP3 of 17 d Bm at the minimum gain of 30 d B. The downconverter consumes about 7.7 m A under a supply of 1.2 V.     

A digital rights management system for digital broadcasting based on home servers

This paper presents a digital rights management (DRM) system for digital broadcasting based on home servers (DBHS) using receivers with large-capacity storage devices. DBHS will enable viewers to enjoy 'television anytime/anywhere' by utilizing these storage functions. Our proposed DRM system is suitable for broadcasting, and allows both rights protection and advanced access to content held on home storage devices (in terms of validity, usage and charge conditions, and so on). We developed a prototype DRM system using a Pentium3 personal computer (1 GHz) in order to evaluate the nonlinear playback and 'trick-play' modes of encrypted content on the hard disk drive (HDD). Using this prototype, we confirmed that the nonlinear playback of content encrypted using the proposed DRM system could be processed in real time. The functionality in terms of trick-play modes was equal to that of commercially available hard disk recorders. In addition, we developed a security module for the DRM system in the form of a smart card with a built-in processor. We confirmed that the proposed DRM system utilizing the new smart card could be applied to DBHS.     

A concept of digital terrestrial television broadcasting

The future terrestrial television broadcasting system should support the transmission of a digital HDTV signal with a high spectral efficiency. In addition, this system should maintain graceful degradation as the actual analog systems, and should be compatible with the SDTV. The system compatibility can be achieved by using a hierarchical HDTV source-coding scheme that can provide at least two (HDTV, SDTV) or three (HDTV, EDTV, SDTV) hierarchy levels: SDTV image quality will be expected for portable receivers, and HDTV/EDTV image quality will destinate to stationary receivers with roof-top antennas. Taking into account the receivers' antenna gains and the different channel conditions, there will be a difference of 25–30 dB between the received powers of the stationary and the portable receivers. Therefore, the design of a powerful and a suitable transmission scheme for the future broadcasting of the digital HDTV signal will be a technological challenge. In this article we describe a concept of a flexible reconfigurable hierarchical digital terrestrial TV broadcasting system for clear and taboo channels. The flexibility of the proposed scheme easily permits the receivers to support different reconfigurable modes: One HDTV program or multi-programming EDTV or SDTV (for fixed receivers up to 5 × SDTV in clear and up to 2 × SDTV in taboo channels; for portable receivers up to 2 × SDTV.) The system achieves a high interoperability with the Satellite Baseline system. It maintains a graceful degradation and provides a hierarchical complexity. It is based on a concatenated coding scheme. The inner code of the concatenated coding scheme is combined with multi-resolution modulation. The basic constellation is a 64-QAM, which will be operated in clear channels. It can be reconfigured to a 16-QAM in the case of taboo channels. The principle of OFDM with very rugged frequency/time synchronization mechanisms is used to combat the frequency selectivity and the co-channel interference (CCI) in the channel. Known pilot symbols are sent regularly in order to perform coherent detection.The authors are within the RACE-dTTb and the German HDTV-T project.     

数字音频广播浅谈

本文介绍了数字音频广播的一些关键技术、优点、系统组成、应用情况。     

Multicarrier modem for digital HDTV terrestrial broadcasting

A digital modulation system using orthogonal frequency division and multiplexing (OFDM) is addressed in this paper. Such a system presents the advantage of coping with echoes more easily than classical single-carrier modems, thanks to the insertion of a guard interval between two symbols. The signal equalization is then achieved in the frequency domain. This OFDM modem is improved by using dual polarizations. In this configuration, it can convey a 70 Mbits/s (HDTV) bit stream in an 8 MHz UHF channel. Some experimental results relate field trials carried out in several countries with such equipment.     

On-channel repeater for digital television broadcasting service

This paper presents the results of tests performed by the Communications Research Center Canada (CRC) to investigate the on-channel repeater (OCR) for digital television broadcasting services using the ATSC-8VSB transmission standard. The focus has been to study the areas where the coverage of the OCR overlaps with the main transmitter. The factors involved in successful reception in these areas and their impact on the design and configuration of this kind of repeater are identified and discussed.     

Transmission techniques for digital terrestrial TV broadcasting

The authors discuss the potential of OFDM signaling, with its limitations and inherent problems, as well as another potential technique that has so far been overlooked: single-carrier transmission with frequency-domain equalization. The carrier synchronisation issue is dealt with before the authors introduce coded-OFDM (COFDM), which makes use of channel coding and frequency-domain interleaving     

Modulation for terrestrial broadcasting of digital HDTV

The digital modulation methods used by the DigiCipher, DSC-HDTV, ADTV, and ATVA-P digital high-definition television (HDTV) systems are discussed. Three of the systems use a quadrature amplitude modulation method and the fourth uses a vestigial sideband modulation method. The channel equalization and spectrum sharing of the digital HDTV systems is discussed     

数字电视地面广播系统的三种标准制式

1引言数字电视以其卓越的画质和音响、多功能、多用途及与信息高速公路互联互通的特点,成为广播电视发展的必然趋势。与之相应,数字电视传输系统的研究与开发也取得了长足的进展。根据国际电信联盟（ITU）无线电通信部的规定,数字电视系统可由三个子系统组成,见图1。目前,全球数字电视广播有三个相对成熟的标准制式：欧洲的DVB、美国的AThC和日本的ISDB,其中美国的AThC与欧洲的DVB占主导地位,而DVB制式应用最广泛、最灵活。DVB制式主要包括数字卫星电视（DVB－S）、数字有线电视（DVB－C）和数字地面广播电视（DVB－T…     

Subband-multipulse digital audio broadcasting for mobile receivers

The audio quality, robustness and implementational complexity of a novel mobile digital audio broadcast scheme are addressed. The audio codec proposed is based on an efficient combination of subband coding (SBC) and multipulse excited linear prediction coding (MPLPC). The bit allocation is dynamically adapted according to both the signal power in different subbands and a perceptual hearing model. Typically a segmental signal to noise ratio (SEGSNR) in excess of 30 dB associated with high fidelity subjective quality was achieved for 2.67-b/sample transmissions at a bit rate of 86 kb/s. Perceptually unimpaired audio quality was achieved for a bit error rate (BER) of about 10^-4, when injecting random errors, which was degraded for increased BERs. In order to provide robust error protection, the audio codec was also subjected to a rigorous bit sensitivity analysis. Four different forward error correction schemes were investigated in order to explore the complexity, bit rate, and robustness tradeoffs     

Source coding for digital HDTV terrestrial broadcasting

It is claimed that an all-digital system will provide true high-definition television quality and coverage area equivalent to NTSC without noise and interference. Less transmission power may be required, and the signal will be easy to encrypt. The proposed source coding algorithms are reviewed, and the methods by which they are used in the proposed digital HDTV terrestrial broadcasting systems are discussed     

Channel coding for digital HDTV terrestrial broadcasting

In order to transmit the HDTV signal in 6 MHz, the four United States digital HDTV proponents, the DigiCipher, DSC-HDTV, ADTV and ATVA-P systems, are reducing the video data rate of HDTV to 15-17 Mb/s, a compression ratio of approximately 60-70 times. The high compression dictates that channel coding be used to avoid block errors and multiframe error propagation. High efficiency in channel utilization required by the 6-MHz limitation means that the channel must be properly equalized and that the multipath and interfering signals must be severely limited. The channel coding techniques used for error reduction include data interleaving, error detection and replacement, and error correction at different levels of protection for bits and blocks of unequal importance     

Transmitter linearity considerations for digital TV broadcasting

An introduction is given to the principles of digital modulation as it is being applied to advanced television by comparison with the way in which chrominance information modulates the NTC color subcarrier. The concept of the unit circle in constellation diagrams is explained for both signal-to-noise ratio and signal-to-interference. Using constellation diagrams, the effects of AM/AM and AM/PM and their combined effects are shown in terms of reducing noise/interference margins. it is seen that the dynamic range of the ATV transmitter must be sufficient to handle the transient peak power which results from filtering to constrain the data to the 6-MHz channel. Out-of-channel spectral components are generated by intermodulation in the high-power amplifier, as are in-channel intermodulation components which are responsible for reducing the eye opening. This results in reduction in noise/interference margins. It is shown that nonlinear amplification of the transient peaks results in intermodulation products that may cause interference to a signal on adjacent channels and reduce expected coverage     

数字视频广播卫星传送标准中的RS码

在数字卫星电视信号传送中的ＦＥＣ中,常采用ＲＳ码,讨论了ＲＳ码的三个问题;１）伽罗华域ＧＦ（２＾８）;２）ＲＳ的码的编码;３）ＲＳ码的检错和纠错。     

Performance of cofdm for satellite digital audio broadcasting

This paper analyses the performance of a coded orthogonal frequency division multiplexing (COFDM) based system for digital audio broadcasting using a highly inclined orbit satellite constellation. The sources of performance degradation considered are non-linear amplification in the satellite transponder and multipath propagation for mobile reception. Despite its strong peak-to-mean amplitude variation, COFDM has been found to be very robust against non-linear amplification. In the multipath channel, practical cases demonstrate low performance losses even in highly populated areas when highly inclined elliptical orbits (HEO) are used.     

Analysis of satellite broadcasting systems for digital television

The concept of digital direct satellite broadcasting (D-DBS), which allows unprecedented flexibility by providing a large number of audio-visual services, is introduced. The concept assumes an information rate of about 40 Mb/s, which is compatible with practically all present-day transponders. After discussion of the general system concept, the optimization procedure is introduced, and results of the transmission system optimization are presented. Channel distortion and uplink/downlink interference effects are taken into account by means of a time domain system computer simulation approach. It is shown, by means of link budget analysis, how a medium-power direct-to-home TV satellite can provide multimedia services to users equipped with small (60-cm) dish antennas     

Complementary punctured-pair convolutional codes for digital audio broadcasting

Hybrid in-band on-channel (IBOC) broadcasting systems for digital audio radio have the capability of simultaneously transmitting analog FM and digital audio of CD-like quality. Due to fading and interference in the already-crowded FM band, the signal design for the hybrid IBOC system is very challenging. It has been proposed to use a method of double sideband transmission where the digital information is transmitted by means of orthogonal frequency-division multiplexing (OFDM) on both sides of the analog host FM and where the digital information can be recovered when one sideband is partially or even totally lost. This leads to an interesting channel coding problem, where we search for optimal pairs of high-rate codes that form good combined low-rate codes, which are better than classic code combining techniques. Furthermore, we also search for rate-compatible punctured convolutional codes which can be used for two-level unequal error protection (UEP) of digital audio. Since some of the tones in the multitone modem (OFDM) are more exposed to interference than others, optimal assignments of convolutional code bits to tones depending on their spectral position are also found. A large number of new codes with memory 6 and 8 are presented both for equal error protection and UEP.