Achievements in rotary head magnetic recording

The principal achievements since 1980 in rotary head recording on magnetic tape are outlined. These developments are related to fundamental improvements in recording media, heads, the design of tape transports, and signal processing. The D-1 and D-2 video tape recorders (VTRs), the Hi-Band 8-mm video cassette recorder (VCR), and the rotary digital audio tape (R-DAT) recorders are discussed. The future of rotary head recorders for consumer digital VCRs, professional high-definition TV (HDTV) VTRs, and consumer HDTV VCRs is assessed     

An Experimental HDTV Digital VTR with a Bit Rate of 1.188 Gbps

This paper describes the technical details of an experimental HDTV digital VTR with a bit rate of 1.188 Gbps. This newly developed machine satisfies the proposed parameter values in the CCIR Report 801. The basic technologies developed to achieve such an ultra-high speed recording are: metal particle tape and Sendust sputtered type head, a high performance head assembly, and parallel signal processing. Using 8 recording heads, the recording rate per channel is 148.5 Mbps and the minimum recording wavelength is 0.69 pm. The error control mechanism, based on Reed-Solomon product code, worked sufficiently well with the overhead for parity, sync code and ID code in the blanking period. Even after 20th generation dubbing, no picture quality degradation has been observed.     

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     

1/2-inch cassette VTR for baseband HDTV signal recording

Technical details are reported for a 1/2-inch cassette videotape recorder (VTR) developed for recording the baseband high-definition TV (HDTV) signal. A recording time of 63 min was achieved by using metal-particle tape and laminated amorphous video heads. The frequency bandwidths used for luminance and chrominance signals were 20 and 7 MHz, respectively. A novel two-channel, three-segment recording method was developed for the purpose. Four-channel digital audio recording with a sampling frequency of 48 kHz and 16-b linear quantization was used. The digital audio signal was recorded on the overlapped area succeeding to the video track by using the same heads used for video recording     

High definition television systems

High definition television (HDTV) services will play the most important role in the digital television systems for the future. HDTV is already broadcast daily in Japan and advanced television (ATV) standards will soon be established in the US. The hardware systems for two HDTV systems, the 1125/60 and 1250/50 systems, have already been developed. Their outlines are described in the paper. Signal processing of HDTV is mainly carried out by digital methods on both the studio and receiver sides. The principles of processing are the same as for conventional television but the higher clock frequency and larger quantity of information require more sophisticated hardware. Digital signal processing methods are the key technology in HDTV broadcasting systems regardless of whether modulation is analog or digital. Some broadcasting systems are already practical use while others, are experimental. The author discusses these systems. The aim of the article is to present a global scope of the HDTV technology     

HDTV集成解码芯片的一种总线设计

本文给出了HDTV集成解码芯片的一种总线设计方案。通过分割总线时间片静态调度DMA传输，并将部分HDTV解码同步控制嵌入到总线调度中，使总线数据传输与解码流程相配合，有效地分配和使用总线带宽，在确保满足系统实时处理性能的条件下，尽可能降低系统对总线带宽的需求，减少片内数据缓冲区容量以降低系统硬件开销。     

Subband HDTV coding using high-order conditional statistics

An HDTV coding scheme that is capable of achieving high quality below 20 Mb/s is presented. The system employs motion estimation/compensation followed by four-band subband splitting. The band signals are then subject to quantization and coded by an innovative high-order entropy coder. It is shown that this high-order entropy coder generates a bit rate nearly 30% lower than that of run-length/Huffman coding for motion-compensated frame differences. About 15% improvement is observed for the intrafield coded data. To reduce the complexity of the high-order entropy coder for high-speed implementation, two techniques, codebook reduction and nonuniform quantization of conditioning samples, are developed. A method for selecting conditioning samples and their order, based on mutual information between samples, is proposed and shown to outperform several other systematic and intuitive approaches. Simulations show that the new system, at about 20 Mb/s, achieves picture quality comparable to that of a 120-Mb/s six-band intrafield coding system previously investigated     

全数字化HDTV传输系统图像信源编码的研究

本文研究了一种全数字化HDTV传输系统图像信源编码方案。将运动补偿帧间预测,离散余弦变换编码和二维熵编码技术结合起来,通过对码率的自适应调节,实现HDTV图像信号的压缩编玛。在14.38Mb/s和20Mb/s码率,取得了良好的图像质量。应用数字调制技术,如16-QAM,能够实现在一个基带8MHz射频信道中传输全数字化HDTV。     

Digital transmission of high bit rate signals using 16DAPSK-OFDMmodulation scheme

Radio transmission signals are distorted by multipath propagation and signal level fading in the channel. In the case of digital transmission systems, the distortion of signals causes a degradation of bit error performance. It is an especially severe problem with digital outside-broadcasting-link (OBL) which has to transmit, for example, digital HDTV signals at more than about 45 Mbps. The OFDM modulation scheme can mitigate the adverse effects of multipath fading. An experimental OFDM modem has been developed to enable stable transmission of digital HDTV sources in an OBL. The experimental modem distributes transmitting digital data to 688 carriers in a bandwidth of about 13.5 MHz using the 16DAPSK for each OFDM carrier. A combination of 8DPSK and 2DASK is adopted as the 16DAPSK and another combination of 8DPSK and coherent 2ASK instead of 2DASK is also considered. Indoor transmission experiments confirmed that the 16DAPSK-OFDM is feasible for transmitting high bit rate signals, even under severe propagation conditions     

HDB-MAC A New Proposal for High Definition TV Transmission

During the last few years there has been increasing interest in the use of high-definition television (RDTV) equipment to reduce costs in programme production. It is also clear that the wider aspect-ratio of HDTV, and the absence of picture impairments, would be very attractive to many consumers if delivered at the right price. In fact, it is not unreasonable to suggest that a successful system for the delivery of HDTV to the public could both differentiate and enhance the value-of the programming supplied, and give rise to the next generation of consumer TV sets. Moreover, the opportunity for HDTV distribution extends beyond broadcast and cable technologies to VCR tape and video disc. Therefore the possibility exists that these distribution industries might be bypassed unless a practical HDTV signal format is devised.     

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     

基于高清晰度数字电视机顶盒的硬盘节目录放功能实现

首先简述本实验室开发的高清晰度数字电视机顶盒结构，然后提出基于该机顶盒的硬盘节目录放功能的实现方法。方法被证明是成功的，满足了高清晰度电视硬盘节目录放功能的性能指标。     

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.     

Loose composite constraint codes and their application in DVD

Constrained coding is used in recording systems to translate an arbitrary sequence of input data to a channel sequence with special properties required by the physics of the medium. Very often, more than one constraint is imposed on a recorded sequence; typically, a run-length constraint is combined with a spectral-null constraint. We introduce a low-complexity encoder structure for composite constraints, based on loose multimode codes. The first channel constraint is imposed strictly, and the second constraint is imposed in a probabilistic fashion. Relaxing the second constraint is beneficial because it enables higher code rates and simplifies the encoder. To control the second constraint a multimode encoder is used. We represent a set of multimode coded sequences by a weighted trellis and propose using a limited trellis search to select optimal output. Using this method, we modify the EFM+ code used in digital versatile disk (DVD). We combine EFM+'s run-length constraint with the first- and second-order spectral-null constraints. The resulting EFM++ code gives more than 10-dB improvement in suppression of low-frequency spectral content in the servo bandwidth over the original EFM+ code with the same complexity     

The implementation of digital echo cancellation in codecs

The architecture of a codec in which the echo cancellation is done in two stages, an analog hybrid to reduce the echo level at the input of the A/D converter and a programmable digital balance filter, is presented. The design problems connected with this architecture, such as the signal-to-noise performance of the A/D converter and the limiting effects of the variation of the analog components on the echo cancellation performance of the device and on the structure of the digital balance filters, are discussed. These results were used in the design of a single-power-supply CMOS device implemented in 1.5-μm technology using ΣΔ modulation techniques for A/D and D/A conversion. Its echo cancellation performance is sufficiently high that only one set of coefficients per national standard is necessary     

A comparison of nondeterministic and deterministic switchingmethods for DC-DC power converters

An analysis and experimental results of the random pulsewidth modulation (RPWM) and random pulse-position modulation (RPPM) methods for DC-DC converters are presented. The characteristics and performance of power converters under two randomized modulations are evaluated. The theoretical relationships of discrete harmonics, continuous noise, and output-voltage ripple of the RPWM and RPPM schemes are established and compared with those of a standard deterministic pulsewidth modulation (PWM) scheme in a buck converter. Limitations in the randomly switched DC-DC converters, which have not been addressed before, are highlighted. Randomized schemes generally have inherent problems in achieving low-output-voltage ripple due to the low-frequency continuous noise within the passband of the converter filter. The inherent low-frequency noise-induced voltage ripple problems of nondeterministic switching methods for DC converters are confirmed experimentally. The performance of the RPPM method is found to be closer to the standard PWM method than that of the RPWM method. For DC-DC power conversion, the RPPM method offers much better output-voltage performance than the RPWM method     

Video recording goes digital

The author begins by mentioning the obstacles which had to be overcome to implement video recording. The evolution of digital processes into video recording is then considered with emphasis on its relevance for HDTV. Mention is then made of digital video on disk and data compression     

毫米波发射端中频调制的实现

通信事业的发展使得频率低端无线频谱已十分拥挤,同时对大容量、远距离、高可靠性提出较高要求,毫米波以其频段宽、空间分辨率高、干扰和截获概率低等特点被应用到各个领域。在研究毫米波发射机原理的基础上提出一种采用两次变频法的上变频设计方案,将中频70 MHz上变频至31 GHz,并利用FPGA完成了基带数字信号处理,控制AD9857实现了中频调制设计。     

Extreme value theory applied to multichannel communication systems

Results from the branch of statistics known as extreme value theory are applied to the problem of calculating the probability of occurrence of large peaks in the signals produced by communication systems employing multichannel angle modulation. Results are obtained in the specific case of digital audio broadcasting (DAB), and a scheme for reducing the probability of large peaks is briefly discussed