Reflection of electromagnetic wave from a time-varying medium

For the purpose of radiowave propagation in the ionosphere, in a plasma and in other media, the reflection and transmission of an electromagnetic wave from a suddenly changed conductivity, when a plane wave is normally incident upon an interface separating two conducting media, are studied. The field expressions are exactly obtained through the use of the Laplace transform. The discussion is primarily on the time behaviour of the reflected wave.     

Signal processing hardware in a radio LAN demonstrator

In order to demonstrate the practicality of high speed radio LANs, such as HIPERLAN, a hardware demonstrator has been built. To overcome the inter-symbol interference caused by the dispersive nature of the indoor radio channel, a decision feedback equaliser has been included in the system. No central synchronisation is provided in a network and a node must be able to derive all synchronisation from a received packet. This paper describes all of the signal processing hardware built for the demonstrator. The demonstrator is not standards compliant but the physical layer parameters are very similar and the signal processing required in HIPERLAN equipment will be very similar to that in the demonstrator.     

Signal processing forum

Asymptotic analyses are abundant in the literature. However, some people (practitioners or not) question their usefulness. Others argue that they are useful. We do the same here. More exactly, we try to explain briefly why “asymptomania” is not a “dangerous disorder”, but rather an addiction to a useful tool. One can readily identify the following possible goals of an asymptotic (in N or SNR, etc.) analysis [where N is the number of available data samples, and SNR is the signal-to-noise ratio]: (a) derivation (or estimation) of the theoretical performance of a parameter estimator or detector; (b) analytical comparisons of the detection or estimation performance of a number of methods; and (c) the optimal choice of the user's variables of a detection or estimation method     

Signal processing in acoustic imaging

A review of signal processing methods which can be used to improve the effectiveness of systems designed for acoustic imaging and bearing estimation is presented. Topics covered include a) signal processing for increased resolution, b) the processing of stochastic acoustic signals, c) image processing, enhancement, and pattern recognition. The discussion of resolution processing includes lateral resolution improvement by both superresolution techniques and aperture synthesis, and improvement of both range and Doppler resolution. The stochastic signal-processing section addresses adaptive processing, as well as methods of imaging in the case of incoherent, noisy signals.     

Signal processing in random access

In this paper, a cross-layer view for roles of signal processing in random access network and vice versa is presented. The two cases where cross-layer design has a quantifiable impact on system performance are discussed. The first case is a small network (such as wireless LAN) where a few nodes with bursty arrivals communicate with an access point. The design objective is to achieve the highest throughput among users with variable rate and delay constraints. The impact of PHY layer design on MAC protocol is examined and illustrates a tradeoff between allocating resources to the PHY layer and to MAC layer. The second case, in contrast, deals with large-scale sensor networks where each node carries little information but is severely constrained by its computation and communication complexity and most importantly, battery power. This paper emphasizes that the design of signal processing algorithms must take into account the role of MAC and the nature of random arrivals and bursty transmissions.     

Signal processing and standardization

Because in many instances signal processing is geared to communication, the attitude of the signal processing community regarding standardisation has always been very positive, leading to successful exploitation of its findings in the marketplace. Such standards as A-law/μ-law PCM, Group 3 facsimile, the Compact Disc, G.721, H.261, JPEG, MPEG-1, and MPEG-2 are all fine examples of how the signal processing technology available at a certain point in time was exploited to make successful signal processing standards. The fact that different standards were defined by different is just proof of the strategic value of a standard to favour or limit communications     

Signal processing for a digital HDTV chromakey mixer

The quality requirements on HDTV are much higher compared to standard TV. For this reason sophisticated methods of signal processing are necessary within the HDTV studio. This paper compares different methods of key signal generation with respect to the resulting picture quality. Furthermore, an automatic set-up procedure for a digital chromakey mixer is described.     

Signal processing in digital fiber communications

Transmission of pcm signals over optical fibers is limited in transmission rate by the inherent imperfections of the carrier medium. The paper discusses the model for an optical telecommunications system (signal and noise models), simulation in base-band (stressing the rational approximation made for the fiber’s transfer function) pulse equalization, encoding and synchronization. Equalizers, whether linear or not, recursive or not, adjustable or not, reduce intersymbol interference, by compensation of distortion in compliance with certain criteria with a view to improving the error rate. The encoding used is a trade-off between bandwidth, tolerance to intersymbol interference and acquisition and tracking of the signal.     

SIGNAL PROCESSING IN SATELLITE-BORNE RADAR ALTIMETER

A new Suboptimal Maximum Likelihood Estimation (SMLE) algorithm based on full-deramp model and its implementation in satellite-borne radar altimeter are presented, with emphasis on the influence of both the return fluctuation and the receiver noise on height and slope estimation precision. Some conclusions are obtained and verified by computer simulation.     

Signal processing in acoustic surface-wave devices

The Rayleigh surface-wave mode propagates on the surface of suitable elastic solids with velocity independent of frequency at about 10-5 times the speed of light and an attenuation of about 1.5 dB for 104 wavelengths. Thus as a delay line it is far more compact, has much less attenuation, and can be much cheaper than electromagnetic delay lines. Piezoelectric elastic solids permit the launching and detection of the waves by electrodes on the surface. Fabrication technology is similar to that used for monolithic semiconductors and amplification is possible by interaction with carriers in a semiconductor surface layer. Parametric interactions can be used to perform convolution of two signals. The feasibility of deflecting and modulating light beams also has been demonstrated. This rapidly developing art can today produce delay lines, filters, pulse compressors and expanders, and pulse-sequence generators and decoders, and in the future may perform convolution, correlation, and light-beam manipulation in small, economical, low-power structures.     

Signal processing techniques in genomic engineering

Now that the human genome has been sequenced, the measurement, processing, and analysis of specific genomic information in real time are gaining considerable interest because of their importance to better the understanding of the inherent genomic function, the early diagnosis of disease, and the discovery of new drugs. Traditional methods to process and analyze deoxyribonucleic acid (DNA) or ribonucleic acid data, based on the statistical or Fourier theories, are not robust enough and are time-consuming, and thus not well suited for future routine and rapid medical applications, particularly for emergency cases. In this paper, we present an overview of some recent applications of signal processing techniques for DNA structure prediction, detection, feature extraction, and classification of differentially expressed genes. Our emphasis is placed on the application of wavelet transform in DNA sequence analysis and on cellular neural networks in microarray image analysis, which can have a potentially large effect on the real-time realization of DNA analysis. Finally, some interesting areas for possible future research are summarized, which include a biomodel-based signal processing technique for genomic feature extraction and hybrid multidimensional approaches to process the dynamic genomic information in real time.     

Signal processing for networked multimedia

Real-time transmission of multimedia data over packet networks poses several interesting problems for signal processing research. Although the range of these problems covers a large variety of topics, currently two groups appear to attract the most attention. The first group concerns adapting the signal compression techniques to address the special requirements imposed by the packet networks, including accommodating for packet losses, delays, and jitter; providing capability for multipoint; and coping with the heterogeneous nature of today's networks. The second group of problems is related to protecting the intellectual property rights associated with the transmitted multimedia data. The increasing availability of high-bandwidth networking makes it extremely easy to illegally duplicate and disseminate digital information. Unless a mechanism can be established to protect the rights of the content providers, commercial use of networked multimedia will remain extremely limited     

Signal processing with charge-coupled devices

The purpose of this paper is to discuss applications of charge-coupled devices in signal processing systems. Both analog and digital CCD concepts are considered. Recent developments in high-speed (∼100 MHz) CCD's are discussed, and the uses of high-speed CCD and surface-acoustic wave (SAW) devices together are considered. Examples of the applications of CCD's in electro-optical systems, secure voice communication systems, sonar systems and radar systems are given. Finally, projections for future uses of CCD's in signal processing systems are presented.     

Signal processing for optical communication

Optical communication plays a significant and increasing role in our society. The public demand for higher network speed requires an optical backbone network with larger capacity. Accompanying high transmission-rate optical communications system are severe technical specifications for optical devices and systems. Many popular optical devices could be represented with a digital filter model as described in this article. Use of well-developed signal processing techniques and algorithms to design these optical devices is a wise use of existing technology. The wavelength division multiplexing (WDM) system, which is the dominating optical communication system, is introduced in this article. Three signal processing application examples for optical communications are presented: optical wavelength interleaver, an all-pass filter for chromatic dispersion compensation, and an electronic equalizer. As demonstrated in this article, signal processing could play an important role in the development of advanced optical communication systems. However, as demonstrated in the case of an electronic equalizer, some optical system characteristics may require special attention if signal processing techniques are to be applied successfully. Therefore, interdisciplinary cooperation between researchers in optics and signal processing will be crucial for optical communications to fully benefit from signal processing.     

Signal processing with higher-order spectra

The strengths and limitations of correlation-based signal processing methods are discussed. The definitions, properties, and computation of higher-order statistics and spectra, with emphasis on the bispectrum and trispectrum are presented. Parametric and nonparametric expressions for polyspectra of linear and nonlinear processes are described. The applications of higher-order spectra in signal processing are discussed     

Signal processing hardware and software

The explosive growth of digital signal processing techniques has given way to a myriad of high performance DSP devices and tools for today's hardware designer and software specialist. The charts and tables presented reflect up-to-date information on the most widely used programmable DSP chips, DSP board products, major software tools in wide use, types of commercial A-D converters, advanced A-D converters in research, available FIR filters (standard and weighted), IC frequency synthesizers, and integrated FFT chipsets