Advanced Digital Signal Processing Research Articles

Transients computation for relay testing in real-time

This paper discusses characteristics of a new digital simulator for protection relay testing. The most demanding design requirement is computation of fault transients under the condition of real-time change of power system configuration due to relay operation. This problem is solved using EMTP computational techniques enhanced with novel numerical solutions for dynamic power system configuration change and nonlinear element modeling. An advanced computer architecture is utilized to achieve further optimization of the execution time for the transients computation code. The main advantage of this design is the use of conventional single processor computer architecture in combination with advanced digital signal processors (DSPs). This makes this simulator an off-the-shelf product with all the benefits of commercially available computers priced at a relatively low cost. >

The Evolution of U.S. Naval Satellite Systems Antenna Control Technology

As advances in digital signal processing continue and new algorithms materialize for correctional coding, the requirement for robust and accurate satellite antenna control systems continues to be downplayed. This paper develops the requirement for advanced control concepts based upon an analysis of U.S. Navy SATCOM systems from the earliest UHF system to the most recent member, EHF. Link and gain equations are used to show the effect of pointing error on the various SATCOM systems. Various problems and errors associated with accurate positioning of satellite communication antennas are presented. Methods currently used to minimize pointing error in Navy SATCOM systems are described. Also discussed are advanced control system techniques to negate pointing error in very narrow beamwidth communication systems.

Use of a single chip fixed-point DSP for multiple speech channel vocoders

In this paper, the use of an advanced digital signal processor (DSP) makes possible the parallel real-time implementation of more than one speech coder on a single-chip DSP. Thus, many speech channels can share a single digital communications channel at low cost. Besides the hardware requirements, the algorithms' implementation is considered for multi-channel single-pitch excited LPC vocoders. The Motorola DSP56000/DSP56001 is selected and the execution times are presented. A variable length coding scheme for reduced bit-rate is also described. Up to 10 vocoders are simultaneously implemented on a single DSP and the algorithms can be used as the basis for the implementation of more sophisticated speech coders.

A radio system proposal for widespread low-power tetherless communications

It is suggested that low-power digital radio as an access technology could be integrated into a local exchange network to provide a ubiquitous personal communications network (PCN). High-quality tetherless communications services that could be provided by such an exchange-network-based PCN are described. A possible low-power exchange access digital radio system for providing these exchange-network based PCS services is discussed. The radio system uses a spectrum-efficient time-division multiple-access (TDMA) architecture made possible by advanced digital signal processing techniques. Control of the frequency reuse system is described, and frequency spectrum needs are indicated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Location and characterization of partial discharge sites in shielded power cables

An instrument capable of detecting and locating partial discharge sites and faults in shielded power cables was developed on behalf of a group of US electric utilities. The instrument uses state-of-the-art electronic hardware and advanced digital signal processing techniques. The partial discharge signals are reconstructed using the cable traveling wave characteristics (transfer function), and noise is reduced both through choice of hardware and by modern signal enhancement techniques. An adjunct instrument was also developed to correlate the location of a partial discharge site along the cable to the position along the surface of the cable burial trench. The principle and the implementation of the instrumentation package are described, and results obtained in the laboratory on a 175 m, 15 kV URD cable are discussed. >

Active field control in auditoria

In this paper, technology for the control of the sound field in an auditorium by electro-acoustic means, A-SF (Assistance of Sound Field), is described. The A-SF is one of the AFC (Active Field Control) technologies which have made rapid progress due to the latest advances in digital signal processing, and is characterized by an acoustic feedback loop in the system. Methods for handling loop gain, G c (ω), to increase loudness, reverberance, spatial impression, etc., as well as technological problems, are presented on the basis of actual examples and reference to the various existing systems. In particular, the AAS (Assisted Acoustics System), developed by the Yamaha group, is used in a detailed discussion on the validity of A-SF system with an FIR filter in the feedback loop. Finally, the possibility of using an adaptive filter in A-SF is touched on.

The Meteosat-P2 radiation effects experiment

The Radiation Effects or “Latch-Up Experiment” flown on Meteosat-P2 is an excellent example of the technology demonstration concept. It was implemented as an experiment-of-opportunity in a 10-month timescale following the late withdrawal of another experiment. It is comprised of a radiation dosimeter using ‘RadFET’ detectors to measure cumulative radiation dose; and two separate experiments to measure the latch-up and single-event-upset (SEU) performance of an advanced digital signal processor and a variety of memory chips. It was conceived by ESTEC and Meteosat Project personnel; implemented by a small consortium of European companies; and has been operating faultlessly since the Meteosat-P2 launch in June 1988. The radiation data show strong correlations between the accumulated dose data and solar geophysical data obtained from external sources. A number of SEU events have been observed, but no latch-ups to date. The paper presents a summary of the results for the first year, and goes on to describe the further development of the dosimeter into a standard spacecraft housekeeping instrument.

DSP-Based Multipurpose Instrumentation

The paper illustrates the development of low cost multichannel digital instrumentation for real-time control applications. The realization is based on the use of an advanced digital signal processing chip, providing the necessary computing power and processing throughput. Algorithms perform Discrete Fourier Transform spectral analysis of the incoming signals and further process data to compensate for the effects of spectral leakage. A variety of parameters can be obtained with good accuracy from the knowledge of signal spectra simply by adopting different computing routines. The application of a two channel instrument in the monitoring of electrical power under nonsinusoidal conditions is considered, and results are given for the case of linear loads. Absolute measurement errors are of the order of 10-4-10-5, while a sampling rate in excess of 200kHz per channel is achieved.The structure of the instrument is very simple, and only standard devices are needed to realize it. As a result, it is well suited as a low cost and flexible measurement block in control systems.

The search for hidden periodicities in biological time series revisited

In the study of rhythmicity in biological systems, two critical questions must be addressed: whether the process under investigation is significantly cyclic, and if so, what is the best estimate of the period of the oscillation. The Whittaker-Robinson “periodogram” has been used extensively to answer both of these questions, Fourier Analysis to a lesser extent. Advances in digital signal processing have produced techniques superior to both, and we have applied one of these (Maximum Entropy Spectral Analysis or MESA) to biological data. We have additionally developed a novel method for analyzing signal-to-noise ratios in biological rhythm data using the autoregressive model underlying MESA. We review here the current methodology for the analysis of biological time series and describe our application of these techniques. The superior performance of this combination of techniques is demonstrated using previously published data. In addition, employing an empirical approach, we have demonstrated that cyclic but aperiodic (i.e. chaotic) systems may be distinguished from noisy periodic or stochastic ones using a combination of these analyses. The implications of this for work on ultradian and circadian rhythms are discussed.

Digital Signal Processor Based Measurement System in a Control Application

This paper provides a brief review of a research and development program that is to investigate the technical feasibility of using digital signal processors(DSP) for measurement functions in the voltage regulator aspect of excitation systems. An advanced digital signal processor measurement and control system provides special features for control of a turbogenerator unit. The independent measurement system composed of analog and digital input modules, controlled by a digital signal processor, samples voltages, currents and digital information necessary to drive the machine. It also processes these values, to produce all the quantities necessary to control the system. A package of software, which includes three dala piucessiug algorithm, has been used with the system. This allows a variety of control algorithms to be tested to improve performance of the power generator unit.

An analog speech scrambling system using the FFT technique with high-level security

A full-duplex analog speech-scrambling system is proposed for application to mobile communication systems and public switched telephone networks. The scrambling algorithm is based on the rearrangement of the fast Fourier transform (FFT) coefficients accompanied by adaptive dummy spectrum insertion and companding operation. The simulation results indicate that the scrambled speech has no residual intelligibility and the descrambled speech quality is satisfactory. The hardware unit is implemented by using seven advanced digital signal processor chips, including those for an adaptive equalizer and an echo canceller for full-duplex operation. The performance is proven to be satisfactory. >

A Navstar GPS C/A Code Digital Receiver

This paper describes one method of implementing a GPS C/A code digital receiver. Digital designs promise exceptionally low-power, low-cost, and miniaturized receivers in the near future. This has been made possible through recent advances in digital signal processing and very large scale integration (VLSI) techniques. The receiver described here attempts to minimize analog circuitry, which is difficult to integrate, and maximize the use of digital signal processing hardware and techniques. The digital signal processing has been carried out with a combination of standard integrated circuits and a commercially available digital signal processor. The signal processor is used to control digital code- and carrier-tracking loops via numerically controlled oscillators (NCOs). Hardware and software implementations of these and other receiver functions, including correlation, 50 baud data extraction, and pseudoranging, are described in detail. All receiver software and hardware was designed and developed using a desk-top computer as the host development system.

Design of a full-featured, solid-state telephone answering device

The authors discuss the use of advanced digital signal processing (DSP) algorithms to implement sophisticated audio processing functions and microcontroller tasks on a low-cost digital signal processor, enabling OEM (original equipment manufacturer) vendors to build cost-effective solid-state telephone answering devices. Sophisticated data compression algorithms and a low-cost programmable DSP processor were used to develop a powerful set of telephone-answering-machine chips. The DSP-based chip sets have been integrated in devices that offer incoming message recording times from 5 to 25 min, outgoing messages, time/date voice stamping and many other advanced features. A key to the project was finding application areas where DSP software could replace the traditional hardware while providing higher performance at lower cost. Speech processing along with telephony provided that environment. Aspects of hardware and software design are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A Three-Axis Monolithic Ring Laser Gyro

Evolution of the inertial sensor element for aircraft navigation applications over the last three decades has happened in many areas. Volume/weight has decreased, performance/reliability has increased, and support electronics capability has increased by an order of magnitude. A rotating wheel iron gyro-based sensor element now weighs 8 lb and performs to an accuracy of 0.1 to 0.8 nmi/h. The Ring Laser Gyro-based sensor element has been introduced over the last decade. The first generation Ring Laser Gyro sensor element weighs 20 lb and performs better than 0.8 nmi/h. Significant reliability improvements are projected for this technology. This paper describes a second generation Ring Laser Gyro that will reduce weight to that of the iron gyro-based system. A brief description of the instrument is provided along with flight test data accumulated on the unit. Use of an advanced digital signal processor electronics architecture is discussed as a companion development to reduce system weight/volume and to further increase reliability.

Book Review: Advanced Digital Communication Systems and Signal Processing Techniques

Book Review: Advanced Digital Communication Systems and Signal Processing Techniques

The distribution of conduction velocities (DCV) in peripheral nerves: a review.

Recent advances in digital signal processing have permitted the development of clinically relevant, noninvasive, computer-based methods for estimating the distribution of conduction velocities (DCV) in motor, sensory, and mixed populations of large myelinated nerve fibers. All currently available methods incorporate explicit and implicit assumptions about the nature of the unit impulses under study. Preliminary investigations using DCV methods have clarified some issues concerning conduction of impulses in the different fiber subpopulations of normal and diseased human nerves. In the presence of severe nerve disease, DCV analysis is usually either impractical or superfluous; additional studies are needed to define its range of clinical applicability. Extension of this technology to clinical analysis of small myelinated and unmyelinated fiber populations will require improvements in the techniques of nerve stimulation and recording.