Showing papers in "Radio and Electronic Engineer in 1980"
TL;DR: The transmission-line modelling method presents a new approach to the solution of lumped networks by providing discrete models for components and the concept of numerical parasitic components as a means of assessing errors is introduced.
Abstract: The transmission-line modelling (t.l.m.) method presents a new approach to the solution of lumped networks by providing discrete models for components. Errors become due to the modelling process only and not due to the approximate solution of an approximate calculus model. The correspondence between stub models and existing implicit methods is shown and the concept of numerical parasitic components as a means of assessing errors is introduced. The paper then describes the entirely new explicit routines resulting from transmission-line modelling and explains their use in non-linear circuits. Finally, examples of mixed implicit and explicit working are given for the solution of non-linear transistor circuits.
154 citations
TL;DR: The NICAM 3 (Near-Instantaneously Companded Audio Multiplex, Mark 3) as discussed by the authors was developed by the BBC for the transmission of sound programs on digital circuits designed for multi-channel telephony.
Abstract: The paper describes a system, known as NICAM 3 (Near-Instantaneously Companded Audio Multiplex, Mark 3), which is being developed by the BBC for the transmission of sound programmes on digital circuits designed for multi-channel telephony.Subjective tests which led to the choice of this system are referred to, and the system design, which is based on a compromise between efficiency and flexibility, is discussed in some detail.Various applications are mentioned, the main one being for six channels in a dedicated bit-stream of 2048 kbit/s, but other arrangements are possible, including mixed telephony and sound-programme working.
31 citations
TL;DR: This introductory paper provides an entry to the systems concepts that underlie systems engineering, and then illuminates the practice through the perspectives of systems organization, design and planning.
Abstract: Since World War II the magnitude and complexity of technological enterprise has increased dramatically. So too have the costs of development, mistakes and failures. The old-style project engineer who could often be his own designer and project manager has been replaced by a team—the systems engineering staff—who integrate, co-ordinate and evaluate the realization of a project through all its evolutionary phases. In particular, systems engineering has produced an approach to design and project appraisal that integrates and balances the various technical, economic, reliability, safety, logistic, support criteria oriented towards future market and operational requirements evaluated over the whole-life of the system.This introductory paper provides an entry to the systems concepts that underlie systems engineering, and then illuminates the practice through the perspectives of systems organization, design and planning.
25 citations
TL;DR: Some of the considerations and comparison criteria presented, even though not completely general because extracted from experimental results, can be useful in selecting and defining the more pertinent data compression system for the different practical applications.
Abstract: Several data compression methods are reviewed for signal and image digital processing and transmission, including both established and more recent techniques. Methods of prediction-interpolation, differential pulse code modulation, delta modulation and transformations are examined in some detail. The processing of two-dimensional data is also considered.Results of the application of these techniques to space telemetry and biomedical digital signal processing and telemetry systems are presented.Some of the considerations and comparison criteria presented, even though not completely general because extracted from experimental results, can be useful in selecting and defining the more pertinent data compression system for the different practical applications.
21 citations
TL;DR: In this paper, a radio receiver system for frequency-modulated signals is described which uses a direct conversion (zero intermediate frequency) technique and the characteristics of the system are developed especially in areas of difference from conventional methods.
Abstract: A radio receiver system for frequency-modulated signals is described which uses a direct conversion (zero intermediate frequency) technique. The characteristics of the system are developed especially in areas of difference from conventional methods. The realization is shown of the complete receiver in two integrated circuits which form part of a synthesized 30 to 88 MHz equipment. The conclusion is drawn that the combination of direct conversion and large-scale integration is a very powerful means for future development of radio receiver techniques.
19 citations
TL;DR: In this article, the results of a c.w. chemical hydrogen/deuterium fluoride laser and a pulsed TEA CO2laser for monitoring of atmospheric trace constituents and process control are reported.
Abstract: Applications of a c.w. chemical hydrogen/deuterium fluoride laser and a pulsed TEA CO2laser for monitoring of atmospheric trace constituents and process control are reported. The c.w. HF/DF laser has been used for field measurements of the HF concentration in the exhaust of an aluminium plant. The laser has also been operated as a DF laser for measurements of the HDO concentration in natural water samples. In addition, using a pulsed TEA CO2 laser in connection with the differential absorption technique, range-resolved ambient air measurements of the water vapour distribution in the vicinity of a cooling tower as well as measurements of the ethylene concentration over the area of a refinery have been performed. The results have been further evaluated using simple and reasonable propagation models. From this both the diffusion parameters and the total mass emission of a source could be obtained.
15 citations
TL;DR: The evolution of the technique of remote sensing of the sea surface by dekametric radar is traced from the original observation of the Bragg resonant scattering phenomenon by D. D. Crombie in 1955 to its present applications to the measurement of surface wind-direction and wind-speed, wave height spectrum, wave-directional spectrum and surface current.
Abstract: The evolution of the technique of remote sensing of the sea-surface by dekametric radar is traced from the original observation of the Bragg resonant scattering phenomenon by D. D. Crombie in 1955 to its present applications to the measurement of surface wind-direction and wind-speed, wave-height spectrum, wave-directional spectrum and surface-currents. The central role played by the Doppler spectrum of the radar echoes is illustrated. The generation and spectral properties of wind-driven waves on the sea-surface are discussed including wave-wave interactions and the nature of electromagnetic scattering by first and second-order processes is described.An account is given of the techniques used for UK experiments on ground-wave radar surveying the Celtic Sea from West Wales. Synthetic aperture experiments using a moving vehicle permitted the directional spectrum of the sea-surface to be determined. Sky-wave experiments from a radar in Southern England permitted comparisons with sea-state and surface winds measured in the Rockall Bank area of the North Atlantic by oceanographic vessels and buoys.Finally, work in progress in the US and UK on improved narrow beam and interferometer radars and new methods for inversion of measured Doppler spectra to yield seawave spectra are reviewed.
13 citations
TL;DR: The development of large area c.c.d. image sensors is described and illustrated with the example of a frame-transfer array with 385 × 576 image elements intended for 625-line television applications.
Abstract: The development of large area c.c.d. image sensors is described and illustrated with the example ofa frame-transfer array with 385 × 576 image elements intended for 625-line television applications. The problems that still exist in meeting more demanding applications such as broadcast television are discussed and the various possible solutions are described.
12 citations
TL;DR: Advances in analogue-to-digital speech conversion providing acceptable quality at bit rates below 9.6 k bit/s should eventually enable a simple digital output coder to be as effective as a cryptovocoder for audio band high security applications.
Abstract: This paper surveys some past and present principles of speech coding. The advent of digital logic systems and integrated circuit components is seen as a major turning point in the implementation of effective coding principles that could not previously be used satisfactorily.Various coding methods are discussed, covering frequency domain, time domain and analogue and digital output systems. The problems of key generator integrity, synchronization, received voice quality and recognizability, and channel bandwidth restrictions, and the security offered by different systems are considered.The author concludes that in the immediate future high security speech encipherment systems will be of the digital output crypto-vocoder type, with audio bandwidth analogue output coders offering an increasingly secure alternative for the majority of applications. Digital output coders will continue to be used effectively in those applications where the communication equipment and transmission path have the necessary characteristics to carry low-error-rate digital signals. Advances in analogue-to-digital speech conversion providing acceptable quality at bit rates below 9.6 k bit/s should eventually enable a simple digital output coder to be as effective as a cryptovocoder for audio band high security applications.
9 citations
TL;DR: In this article, the use of the acoustic sounder to monitor the height of low level layer cloud and the depth of radiation fog is discussed as well as the detection and tracking of plumes of methane gas.
Abstract: Acoustic sounder design and performance parameters are described. Various atmospheric features as recorded by the acoustic sounder, including thermal plumes, inversions and waves, are presented and their interpretation given. The use of the acoustic sounder to monitor the height of low level layer cloud and the depth of radiation fog is discussed as well as the detection and tracking of plumes of methane gas.
8 citations
TL;DR: In this paper, the authors examined the conditions which would allow land mobile radio systems using spread-spectrum techniques to share certain r.f. channel allocations on a mutual noninterference basis with the existing users of these channels, namely the television broadcasters.
Abstract: This paper examines the conditions which would allow land mobile radio systems using spread-spectrum techniques to share certain r.f. channel allocations on a mutual non-interference basis with the existing users of these channels, namely the television broadcasters. An experimental spread-spectrum communication system has been developed and this has been used to examine the feasibility of bandsharing from the point of view of establishing protection for the television signal from the spread-spectrum interference for imperceptible visual interference on the screen, whilst still allowing adequate reception of the spread-spectrum signal under conditions of high television interference. The results indicate that the spread-spectrum signal must be at least 42 dB below the peak television carrier level at the television carrier frequency for picture quality to be unaffected, and under these conditions an output signal with at least 25 dB signal-to-noise ratio can be obtained from the spread-spectrum receiver.
TL;DR: A circuit is proposed which transforms a delta sequence (d.s.) of a signal into another delta sequence of a double amplitude signal, which increases the flexibility of the realization of digital filters with delta input-output sequences.
Abstract: A circuit is proposed which transforms a delta sequence (d.s.) of a signal into another delta sequence of a double amplitude signal. With the proposed circuit, it is possible to transform the d.s. of half-sums obtained from the conventional delta-adders into a d.s. of the corresponding full sums. This increases the flexibility of the realization of digital filters with delta input-output sequences.
TL;DR: An alternative method, based on the Boolean matrix approach, is suggested here, which is simpler and faster compared to existing methods and can be easily programmed on a computer.
Abstract: Many algorithms have been suggested1−5in the past to design combinational logic circuits using multiplexers. An alternative method, based on the Boolean matrix approach, is suggested here. The method is simpler and faster compared to existing methods and can be easily programmed on a computer. Finally, the proper selection of multiplexers is suggested by applying simple empirical rules.
TL;DR: The paper deals briefly with a few widely-used image signal processing algorithms and discusses how these can be incorporated on the same silicon chip as that of the c.c.d. scanner.
Abstract: The paper deals briefly with a few widely-used image signal processing algorithms and discusses how these can be incorporated on the same silicon chip as that of the c.c.d. scanner. Recent work on c.c.d. scanners is reviewed and solid-state scanners which include on-chip signal processing functions are described. Future trends are towards `smart? scanners; these are scanners with on-chip real-time processing functions, such as analogue-to-digital conversion, thresholding, data compaction, edge enhancement and other real-time image processing functions.
TL;DR: The Multi-Role Combat Aircraft Tornado is probably the most spectacular example to date of a complex man-machine system in which design and manufacture are widely dispersed as discussed by the authors, which makes life extremely difficult for an engineer involved in the procurement of the sub-assembly, especially as the overall objective can soon be submerged in a mass of detail.
Abstract: The Multi-Role Combat Aircraft Tornado is probably the most spectacular example to date of a complex man-machine system in which design and manufacture are widely dispersed. Even sub-assemblies of this system are extremely complex relative to the technology of just a few years ago. This makes life extremely difficult for an engineer involved in the procurement of the sub-assembly, especially as the overall objective can soon be submerged in a mass of detail. Starting with a review of desirable dynamic properties of the machine, as seen by the man, typical human operator transfer functions which have found use in closed-loop control system design are presented. Some ways in which microelectronics can reduce pilot work load are then discussed with the object of conveying to the design engineer some of the reasoning behind the performance specification he is trying to meet. Examples include helicopter stability augmentation systems and spacecraft terminal phase control.
TL;DR: In this paper, a frequency-independent phase-shift network was constructed using field effect transistors as variable resistors, and the operation was shown to be similar to that of a phase lock loop with a self-generating v.c.o.
Abstract: A frequency-independent phase-shift network has been designed and constructed using field effect transistors as variable resistors. The operation of the system is shown to be similar to that of a phase lock loop with a self-generating v.c.o. Analysis of the system is given assuming linear operation. Phase difference outputs have been obtained in the frequency range 20–80 kHz. The phase error introduced in any set phase difference is ±2° in this frequency range. Theoretical predictions indicate this error could be reduced by an order of magnitude.
TL;DR: An unusual class of digital frequency synthesizers is presented capable of very high frequency-resolution and the complexity of the hardware may be reduced by up to 50% compared with earlier approaches.
Abstract: An unusual class of digital frequency synthesizers is presented capable of very high frequency-resolution. Construction may be made very simple. In typical applications the complexity of the hardware may be reduced by up to 50% compared with earlier approaches. A standard circuit is defined which may be used in a variety of applications, several of which have been outlined as illustrations of the flexibility of the technique.
TL;DR: In this article, several techniques are described for ensuring a constant loop gain and hence a good overall performance for the synthesizer over a wide frequency range of operation, which is not the integral part of the loop gain in a simple phase lock loop type of frequency synthesizer.
Abstract: In a simple phase lock loop type of frequency synthesizer the closed-loop dynamic performance dictates the settling time after a frequency step, the close-in noise spectrum, the achievable cancellation of microphony in the output oscillator, and the flatness of the frequency modulation characteristic. The dynamic performance is controlled mainly by the proportional and not the integral part of the loop gain. Several techniques are described for ensuring a constant loop gain and hence good overall performance for the synthesizer over a wide frequency range of operation.
TL;DR: It is shown that relatively few general classifications are necessary to encompass all the codes, and that, within each classification, it is often possible to say which code is optimum.
Abstract: A detailed comparison of recording codes, using superposition, is used to show that there is little to choose between the popular ones, as regards maximum achievable data density. It is shown that relatively few general classifications are necessary to encompass all the codes, and that, within each classification, it is often possible to say which code is optimum. A guide to the selection of an efficient code for some common conditions of use is presented.
TL;DR: In this article, the authors investigate the effect of displacement of a magneto-resistive element on replayed pulse shapes, and show that the amount of asymmetry decreasing with increasing head-to-medium separation.
Abstract: This paper is concerned with shielded magneto-resistive replay head structures in which the sensitive magneto-resistive elements are displaced to be either nearer to one shield than the other or deep into the gap between the shields. These structures are analysed experimentally using a resistive paper analogue and theoretically using standard potential theory. It is found that ‘sideways’ displacement of the element has the effect of causing asymmetry in replayed pulse shapes, the amount of asymmetry decreasing with increasing head-to-medium separation. Shifting of the elements back into the gap is shown to result in significant reductions in signal amplitude but only minor increases in pulse width. Theory and experiment show reasonable agreement.
TL;DR: The operational features and performance of a fully-integrated programmable transversal filter, using c.c.d./m.o.m.t.f. technology, and the potential of this miniature integrated filter for sonar-type applications is reviewed against new developments.
Abstract: This paper describes the operational features and performance of a fully-integrated programmable transversal filter (p.t.f.), using c.c.d./m.o.s.t. technology. The choice of filter architecture for a prototype realization is discussed with particular reference to a novel multiplier array implementation using a single, time-multiplexed m.o.s. transistor. The performance characteristics of a prototype, 64-point filter design based on this approach are detailed with reference to frequency- and matched- filtering. Techniques for optimizing the performance of this analogue filter structure under microprocessor control are suggested, through the iterative adaption of the filter impulse response, and equivalent results are given to show the improvement gained. An alternative technique for improving the filter characteristics which enables it to optimize the processing of signals under certain conditions has also been demonstrated. This adaptive filter configuration is based on the linear Widrow least-mean-square (W.l.m.s.) algorithm, and has been realized using the p.t.f. with minimal additional circuitry, without the requirement for a microprocessor.A general signal-processing module of 256-points using four cascaded filters is described; and results are presented when it is used in a sonar, matched-filtering experiment. Also a 64-point adaptive filter based on a prototype p.t.f. is described and its application to inverse filtering and self-tuning filtering is demonstrated.Finally, the potential of this miniature integrated filter for sonar-type applications is reviewed against new developments. In particular, a 256-point monolithic p.t.f.currently in development, and the concept of a dedicated adaptive filter in single chip form.
TL;DR: Pulse code modulation systems as used in telephony networks are briefly described with particular regard to the inherent quantizing distortion (q.d.) and test methods for the evaluation of signal to q.d. ratio, from analogue input to analogue output are reviewed.
Abstract: Pulse code modulation systems as used in telephony networks are briefly described with particular regard to the inherent quantizing distortion (q.d.). Test methods for the evaluation of signal to q.d. ratio, from analogue input to analogue output, are reviewed. Three test stimuli are considered and their advantages and disadvantages discussed. The three stimuli are a sinusoid, a band-limited noise signal and a band-limited pseudo-random noise signal.
TL;DR: In this paper, the feasibility of transmitting high integrity data via a leaky coaxial feeder at much higher rates than are normally considered possible over a mobile radio channel is established.
Abstract: This paper establishes the feasibility of transmitting high integrity data, via a leaky coaxial feeder, at much higher rates than are normally considered possible over a mobile radio channel. Both signal variations and error rates are examined. The use of diversity techniques to improve performance are considered and possible system layouts are presented.
TL;DR: In this article, a system for detecting and attenuating impulsive noise on gramophone records is described, which uses a detector which uses these characteristics to distinguish between the noise and the recorded signal.
Abstract: The paper describes a system for detecting and attenuating impulsive noise on gramophone records. Fast transitions and short duration are shown to be the essential characteristics of the impulsive noise waveform and a detector which uses these characteristics to distinguish between the noise and the recorded signal is described. Several methods of producing a noise-free approximation to the recorded signal are discussed and compared. A simple attenuation technique is shown to be as subjectively acceptable as more complex techniques. The designs of delay line and attenuator for optimum performance are considered and the subjective performance of the system is assessed.
TL;DR: The error performance of multi-transmitter data systems is described for mobile and stationary users in overlap areas, as a function of carrier frequency and modulation timing difference, and the conclusion is reached that performance is comparable to single transmitter systems at the same signal level.
Abstract: The error performance of multi-transmitter data systems is described for mobile and stationary users in overlap areas, as a function of carrier frequency and modulation timing difference. Plots of bit error rate and error distribution are given, and the conclusion is reached that performance is comparable to single transmitter systems at the same signal level. The constraints on the choice of data modulation are discussed
TL;DR: In this paper, a long cylindrical reentrant cavity having dimensions similar to those used for Gunn oscillators and for studies on semiconductors is presented for experimentally-determined tuning characteristics.
Abstract: Experimentally-determined tuning characteristics are presented for a long cylindrical re-entrant cavity having dimensions similar to those used for Gunn oscillators and for studies on semiconductors. The results indicate the simultaneous existence of the dominant TEM and the fundamental TE modes of resonance. A perturbation technique is given for the identification of the modes. Theoretical calculations of the resonant frequencies using simple models are presented. Experimental values of the Q-factors of the resonator for both the modes of resonance are also given.
TL;DR: In this paper, various ways in which c.c.d.s can be employed in i.r.t. sensing systems are reviewed. And the relative merits of these different approaches are compared and recent experiment results for many of them are quoted.
Abstract: The paper reviews the various ways in which c.c.d.s can be employed in i.r. sensing systems. These include: (i) monolithic structures fabricated using narrow band semiconductors such as HgCdTe or InSb, extrinsic silicon structures doped with deep-level impurities, and silicon Schottky barrier devices; (ii) hybrid structures in which the c.c.d. is used as the read-out mechanism from an array of, for example HgCdTe, PbTe, or pyroelectric detectors. The relative merits of these different approaches are compared and recent experiment results for manystructures are quoted.
TL;DR: In this paper, the effects of base width modulation (Early effect) on the d.c. and low-frequency incremental output characteristics of a bipolar junction transistor are reviewed critically, using only a basic consideration of the physical electronics of device operation.
Abstract: The effects of base width modulation (‘Early effect’) on the d.c. and low-frequency incremental output characteristics of a bipolar junction transistor are reviewed critically, using only a basic consideration of the physical electronics of device operation. Attention is focused on the dependence on collector-base voltage of the majority carrier charge in the base of a device having an arbitrary base doping distribution. The conditions under which a single voltage parameter (‘Early voltage’) can be used to describe the output characteristics, independent of baseemitter drive conditions, are examined and some implications of the results to the circuit engineer outlined.
TL;DR: A holographic recording system, based on the use of lowpower laser sources and high-resolution photographic film, is briefly outlined, and the results of some initial experiments are given which illustrate various problems that have been encountered, particularly with regard to the recording medium.
Abstract: A holographic recording system, based on the use of lowpower laser sources and high-resolution photographic film, is briefly outlined. It was devised principally for the archival storage of high-quality digital television signals and these requirements are reviewed. The development of suitable electro-optic transducers is difficult, largely because of the high data-transfer rates involved, but some progress has been made. Experimental versions of the transducers have been assembled to form a recording apparatus for writing and reading investigations at realtime rates. The results of some initial experiments are given which illustrate various problems that have been encountered, particularly with regard to the recording medium.