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ACTIVE RC LOWPASS FILTERS FOR FDM AND PCM SYSTEMS

PROCEEDINGS OF THE INSTITUTION OF ELECTRICAL ENGINEERS-LONDON 1973年第9期120卷 945-953页

作者： JEFFERS, R HAIGH, DG GEC LTD TELECOMMUN RES LABS HIRST RES CTR WEMBLEY ENGLAND

Various techniques of active RC realisation of lowpass filters are discussed, and two methods which are considered to have engineering relevance are investigated in detail. The design of lowpass filters suitable for use in f.d.m. and p.c.m. systems is presented. The results of tests carried out on microelectronics models of these filters show that they meet the requirements for use in practical systems.

关键词： audio equipment active RC lowpass filters FDM systems active filters Filters and other networks pulse-code modulation PCM systems frequency division multiplexing

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ADAPTIVE PREDICTIVE IMAGE-CODING USING LOCAL CHARACTERISTICS

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IEE PROCEEDINGS-I COMMUNICATIONS SPEECH AND VISION 1989年第6期136卷 385-390页

作者： HSIEH, CH LU, PC LIOU, WG Department of Electrical Engineering Chung Cheng Institute of Technology Ta-Hsi Republic of China

The paper presents an efficient adaptive predictive coding method using the local characteristics of images. In this method, three coding schemes, namely, mean, subsampling combined with fixed DPCM, and ADPCM/PCM, are used and one of these is chosen adaptively based on the local characteristics of images. The prediction parameters of the 2-d linear predictor in the ADPCM/PCM are extracted on a block by block basis using the 2-d lattice filtering method. The order update 2-d lattice model proposed by Parker and Kayran is extended into order update and time update recursion for more efficient computation. Simulation results show that the proposed method is effective in reducing the slope overload distortion and the granular noise at low bit rates, and thus it can improve the visual quality of reconstructed images. Other advantages of this method are the low computational burden and the suitability for the VLSI implementation.

关键词： PCM adaptive differential pulse code modulation DPCM Pattern recognition VLSI implementation granular noise slope overload distortion codes picture processing filtering and prediction theory adaptive predictive image coding encoding pulse-code modulation local characteristics Optical information, image and video signal processing 2D linear predictor low bit rates prediction parameters visual quality reconstructed images differential pulse code modulation adaptive filters 2D lattice filtering time update recursion order update recursion ADPCM/PCM

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PERIODIC OSCILLATIONS IN pulse-MODULATED SYSTEMS

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IEE PROCEEDINGS-D CONTROL THEORY AND APPLICATIONS 1981年第4期128卷 129-136页

作者： RAO, UM ATHERTON, DP UNIV SUSSEX SCH ENGN & APPL SCIBRIGHTON BN1 9QTENGLAND

Feedback systems employing pulse-modulated actuators are gaining increasing popularity. In the paper, using the A-locus method, general equations have been obtained to solve for limit cycles of various modes in feedback systems employing σPFM, IPFM and combined pulse modulation (pulse frequency and pulse width). Several theorems have also been presented to find the region of system parameters within which particular oscillations are absent. In addition, some examples have been given to illustrate the results derived, and the solutions have been compared with those obtained by other methods.

关键词： Discrete control systems A-locus method IPFM sampled data systems pulse-code modulation oscillations closed loop systems feedback systems SIGMA PFM pulsemodulated actuators limit cycles Stability in control theory

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REED-SOLOMON codeD HOMODYNE DIGITAL pulse POSITION modulation

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IEE PROCEEDINGS-I COMMUNICATIONS SPEECH AND VISION 1992年第2期139卷 140-146页

作者： CRYAN, RA UNWIN, RT Electronics and Communication Group School of Engineering Huddersfield Polytechnic Huddersfield UK

Digital pulse-position modulation (PPM) is a scheme whereby the abundance of bandwidth available in monomode fibres may be exchanged for improved receiver sensitivity. As this format relies on the position of the pulse to convey information, it is subject to a positional error as well as to the familiar false-alarm and erasure errors. A performance and optimisation analysis for both uncoded homodyne digital PPM and digital PPM employing Reed-Solomon error-correction codes is presented. System performance for a range of fibre bandwidths and PPM symbol sizes is analysed, and it is shown how the predetection filter may be configured in order to minimise the three error sources and achieve maximum transmission efficiency (nats/photon). Results are presented at a bit rate of 565 Mbit/s and a wavelength of 1.5-mu-m, comparing both uncoded and coded homodyne digital PPM with shot-noise-limited coherent PCM. It is shown that there are optimum PPM symbol sizes, fibre bandwidths and Reed-Solomon code rates at which to operate. The conclusion is that uncoded digital PPM offers an improvement of 5 dB over homodyne PSK PCM, and that the Reed-Solomon error-correction coded system offers a 4 dB improvement over uncoded PPM, when operating at the optimum 3/4 code rate.

关键词： pulse-code modulation FILTERS AND FILTERING OPTICAL TRANSMISSION

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HIGH-QUALITY SUBBAND codeC FOR HDTV TRANSMISSION

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 1994年第2期4卷 195-199页

作者： IRIE, K OKUMURA, Y SAKURAI, N KISHIMOTO, R Optical Subscriber Networks Laboratory NTT Transmission Systems Laboratories Yokosuka Kanagawa Japan

High Definition Television (HDTV) is expected to be one of the major services offered in future Broadband Integrated Services Digital Networks (B-ISDN). Transmitting HDTV signals over digital networks requires sophisticated compression techniques to limit bit-rate requirements and to provide high-quality, reliable services to customers. To transmit image signals within a studio and between studios or broadcasting stations, multiple encoding and decoding of signals without visible degradation is required. In this paper, we describe a high-quality HDTV codec that can encode original 1.2 Gb/s HDTV signals at 600 Mb/s. A subband DPCM (Differential pulse-code modulation) coding algorithm capable of distortion-free encoding is used. Input signals are decomposed into four bands in the horizontal and vertical directions. A new architecture of perfect reconstructive short-kernel subband filters that reduces subband signal entropy has been adopted. Three bands are coded with adaptive DPCM and one band is coded with PCM. The performance of the codec is evaluated using true video signals. Experimental results show that a very high percentage of samples of component signals can be transmitted distortion free. A Signal-to-Noise Ratio (SNR) of over 45 dB is obtained with signals transmitted after the quantization process. Degradation after nine encoding and decoding processes is only 2 dB in terms of SNR.

关键词： B-ISDN codecs data compression digital communication systems high definition television image coding pulse-code modulation television networks video equipment video signals 1.2 Gbit/s 600 Mbit/s HDTV transmission PCM bit-rate requirements broadban Broadband integrated services digital network differential pulse code modulation Digital communication systems video equipment image coding Television networks Data compression Video signals signals Studios codecs

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NEW STRUCTURE FOR DIGITAL SWITCHING NETWORK

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ELECTRONICS LETTERS 1989年第3期25卷 209-211页

作者： JAJSZCZYK, A Inst. of Electron. & Commun. Tech. Univ. of Poznan Poland

Methods for the design of cost-effective one-stage PCM switching networks composed of digital switching matrices are proposed. These one-stage networks have, in many cases, a more regular structure and contain fewer elements than networks currently known. The proposed one-stage networks can also be used as submodules for multistage networks.

关键词： PCM cost-effective design digital communication systems digital switching network multistage networks one-stage networks pulse code modulation pulse-code modulation regular structure submodules switching matrices switching networks

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EMBEDDED ADPCM WITH NOISE SPECTRAL SHAPING FOR PACKET VOICE TRANSMISSION

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ELECTRONICS LETTERS 1987年第5期23卷 239-241页

作者： KIM, HD UN, CK Communications Research Laboratory Department of Electrical Engineering Korea Advanced Institute of Science & Technology Seoul Korea

An embedded adaptive differential pulse code modulation (EADPCM) that may be used for speech coding in a packet network is proposed. In this scheme the quantisation nosie of an ADPCM is reduced significantly by employing an instant-aneously adaptive PCM (ADPCM) as a second-stage coder, and is shaped further to reduce the subjectively annoying effects by a noise-shaping filter. By computer simulation using real speech we show a significant performance improvement (3 to 10dB at rates of 16 to 48 kbit/s) with the proposed scheme.

关键词： EADPCM speech coding adaptive differential pulse code modulation noise spectral shaping modulation and coding methods 16 to 48 kbit/s computer simulation using real speech packet switching subjectively annoying effects instantaneously adaptive PCM voice communication noise-shaping filter pulse-code modulation quantisation noise APCM embedded ADPCM second-stage coder performance improvement packet network packet voice transmission Communication system theory digital simulation

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ERROR BURST AND GUARD SPACE OBSERVATIONS ON CCITT PCM CHANNELS

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ELECTRONICS LETTERS 1988年第12期24卷 739-740页

作者： HOPE, JF FERREIRA, HC Lab for Cybernetics Rand Afrikaans Univ. Johannesburg

The results of a series of experimental measurements on CCITT type primary PCM channels are presented, with special emphasis on statistics of error bursts and related error-free guard spaces

关键词： CCITT PCM channels digital communication systems error statistics error-free guard spaces experimental measurements primary PCM channels pulse-code modulation statistics of error bursts

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CONDITIONAL ENTROPY ENCODING OF LOG-PCM SPEECH

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ELECTRONICS LETTERS 1985年第11期21卷 475-476页

作者： GHARAVI, H STEELE, R UNIV SOUTHAMPTON DEPT ELECTRSOUTHAMPTON SO9 5NHHANTSENGLAND

The conditional dependence between the current and previously quantised samples in 64 kbit/s ??-law PCM speech is exploited to noiselessly reduce the average transmitted bit rate. From the conditional probabilities, the conditional entropy and average Huffman code word lengths were computed. The average data rate reduction for the first-order noiseless encoder was found to be 12 kbit/s.

关键词： 64 kbit/s speech analysis and processing log-PCM speech pulse-code modulation encoding data reduction average Huffman code word lengths probabilities average data rate reduction logarithmic pulse code modulation codes first-order noiseless encoder conditional entropy Speech and audio signal processing analogue-digital conversion quantised samples

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BANDWIDTH AND SIGNAL-DATA COMPRESSION USING MAXIMUM SPECIFIED ERROR AS CONTROL

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ELECTRONICS LETTERS 1985年第16期21卷 673-674页

作者： SANDMAN, AM Centre for Information Engineering City University London UK

A technique for bandwidth compression is described which is based on the principle of having an interpolation function between `important points?? and ensuring that the maximum error between the original function and the interpolation function is closely approached but never exceeded. The maximum error controls the placing of the `important points??.

关键词： interpolation function maximum specified error as control data compression bandwidth compression pulse-code modulation PCM Information theory signal-data compression Signal processing and detection modulation and coding methods

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