Showing papers on "Bandwidth (signal processing) published in 1991"

A reliable data-based bandwidth selection method for kernel density estimation

Abstract: We present a new method for data-based selection of the bandwidth in kernel density estimation which has excellent properties It improves on a recent procedure of Park and Marron (which itself is a good method) in various ways First, the new method has superior theoretical performance; second, it also has a computational advantage; third, the new method has reliably good performance for smooth densities in simulations, performance that is second to none in the existing literature These methods are based on choosing the bandwidth to (approximately) minimize good quality estimates of the mean integrated squared error The key to the success of the current procedure is the reintroduction of a non- stochastic term which was previously omitted together with use of the bandwidth to reduce bias in estimation without inflating variance

An improved lattice-based adaptive IIR notch filter

Abstract: A novel lattice-based adaptive infinite impulse response (IIR) notch filter is developed which features independent tuning of the notch frequency and attenuation bandwidth. The internal structure is based on planar rotators, ensuring reliable numerical behaviour and high processing rates in CORDIC environments. A simple update law allows a simpler implementation than previously proposed designs. Rather than minimizing an output error cost function, the algorithm is designed to achieve a stable associated differential equation, resulting in a globally convergent unbiased frequency estimator in the single sinusoid case, independent of the notch filter bandwidth. Using a second-order structure in the multiple sinusoid case, unbiased estimation of one of the input frequencies is achieved by thinning the notch bandwidth. The tracking behavior is superior to conventional output error designs, and the estimation of extremal frequencies is less prone to overflow instability than previously reported structures. >

Effective bandwidths for the multi-type UAS channel

Abstract: The Uniform Arrival and Service (UAS) model is one of several appropriate to modelling traffic offered to a multi-service communication channel. We exhibit, via asymptotics and a range of specific examples, that it is possible to assign a notionaleffective bandwidth to each source, dependent not only on its mean bandwidth but also on its burstiness and on the channel. The effective bandwidth can be calculated quickly and efficiently using the results of Anick, Mitra and Sondhi and reduces the multi-service network to the more familar, and well understood, form of a traditional circuit-switched network.

On optimal data-based bandwidth selection in kernel density estimation

Abstract: A bandwidth selection method is proposed for kernel density estimation. This is based on the straightforward idea of plugging estimates into the usual asymptotic representation for the optimal bandwidth, but with two important modifications. The result is a bandwidth selector with the, by nonparametric standards, extremely fast asymptotic rate of convergence of n−½ where n → ∞ denotes sample size. Comparison is given to other bandwidth selection methods, and small sample impact is investigated.

A multi-band approach to arterial traffic signal optimization

Abstract: Progression schemes are widely used for traffic signal control in arterial streets. Under such a scheme a continuous green band of uniform width is provided in each direction along the artery at the desired speed of travel. A basic limitation of existing bandwidth-based programs is that they do not consider the actual traffic volumes and flow capacities on each link in their optimization criterion. Consequently they cannot guarantee the most suitable progression scheme for different traffic flow patterns. In this paper we present a new optimization approach for arterial progression that incorporates a systematic traffic-dependent criterion. The method generates a variable bandwidth progression in which each directional road section can obtain an individually weighted bandwidth (hence, the term multi-band). Mixed-integer linear programming is used for the optimization. Simulation results indicate that this method can produce considerable gains in performance when compared with traditional progression methods. It also lends itself to a natural extension for the optimization of grid networks.

ISDN-Mixes: Untraceable Communication with Very Small Bandwidth Overhead

Abstract: Untraceable communication for services like telephony is often considered infeasible in the near future because of bandwidth limitations. We present a technique, called ISDN-Mixes, which shows that this is not the case.

Method and apparatus for digital audio broadcasting and reception

Abstract: A radio broadcasting system is provided for transmitting and receiving through free space a composite signal consisting of a frequency modulated (fm) analog signal and a multicarrier modulated digital signal which is especially adapted to be resistive to multipath degradation. The fm signal and the digital multicarrier modulated signal are fully coherent. Further according to the invention, the digital signal comprises a plurality of carriers having a maximum amplitude at least 20 dB below the unmodulated fm signal and preferably, 30 dB below the analog signal. The multicarrier modulated signal is phase locked according to the invention to the recovered analog fm pilot tone at 19 kHz in the composite baseband spectrum of the fm signal which is at least 20 dB above the multicarrier modulated signal, which enables rapid and reliable acquisition of signal for coherent detection. In a specific embodiment, the multicarrier modulated signal is a synthesized vector-modulated signal which is a quadrature phase shift keyed (QPSK) modulated set of synthesized carriers each occupying 9.5 kHz of spectrum replicated twenty-one times within a 199.5 kHz bandwidth with no more than two bits per vector. The broadcast system is designed to be used in support of compressed digital audio programming material. In a demodulation process according to the invention, a demodulator is operative to phase lock to the recovered high-amplitude analog pilot tone, to coherently demodulate the digital signal, and to format the recovered data stream for source decoding.

Improved assessment of interference limits in cellular radio performance

Abstract: Reuse distance aid cluster size are evaluated for cellular mobile radio systems. Rayleigh fading, log-normal shadowing, and area mean power (which is inversely proportional to the fourth power of propagation distance) are considered, using the technique of Schwartz and Yeh (1982) for determining the probability density function of the sum of several log-normal variables in order to obtain the cochannel interference probabilities. These results are used for analyzing the radio spectrum efficiency, taking traffic intensity into consideration. Different modulation methods, namely, analog FM with 30 kHz and 12.5 kHz channel spacing, SSB (single sideband) with 5 kHz spacing, and digital modulation with 25 kHz channel spacing, with adequate protection ratios are compared. An example of the calculation of system bandwidth and cluster size using this procedure is presented. >

Bandwidth Selection for Kernel Density Estimation

Abstract: The problem of automatic bandwidth selection for a kernel density estimator is considered. It is well recognized that the bandwidth estimate selected by the least squares cross-validation is subject to large sample variation. This difficulty limits the application of the cross-validation estimate. Based on characteristic functions, an important expression for the cross-validation bandwidth estimate is obtained. The expression clearly points out the source of variation. To stabilize the variation, a simple bandwidth selection procedure is proposed. It is shown that the stabilized bandwidth selector gives a strongly consistent estimate of the optimal bandwidth. Under commonly used smoothness conditions, the stabilized bandwidth estimate has a faster convergence rate than the convergence rate of the cross-validation estimate. For sufficiently smooth density functions, it is shown that the stabilized bandwidth estimate is asymptotically normal with a relative convergence rate $n^{-1/2}$ instead of the rate $n^{-1/10}$ of the cross-validation estimate. A plug-in estimate and an adjusted plug-in estimate are also proposed, and their asymptotic distributions are obtained. It is noted that the plug-in estimate is asymptotically efficient. The adjusted plug-in bandwidth estimate and the stabilized bandwidth estimate are shown to be asymptotically equivalent. The simulation results verify that the proposed procedures perform much better than the cross-validation for finite samples.

Superresolution techniques for time-domain measurements with a network analyzer

Abstract: Superresolution techniques for time delay estimation are proposed and applied to frequency-domain data measured with a network analyzer. A MUSIC (multiple signal classification) algorithm preprocessed by spatial smoothing is used. The spatial smoothing preprocessing is performed to destroy signal coherence, and the decorrelation performance is examined in detail. The expression which gives an individual response is given. Using this expression, it is possible to eliminate unwanted signals that appear as ripples in the frequency domain. Experimental results show that the frequency bandwidth required by the MUSIC algorithm to resolve distinct time-domain responses and eliminate unwanted signals is much narrower than that required by the FFT (fast Fourier transform). Thus, the MUSIC algorithm is applicable to the time-domain measurements with the network analyzer and has much higher resolution capability than the conventional FFT techniques. The MUSIC algorithm is one of the most promising methods of enhancing the accuracy of measurement for narrowband devices such as antennas. >

Active high resolution time delay estimation for large BT signals

Abstract: Two different high-resolution time-delay estimation (HRTDE) methods, a temporal method and a frequency method, specially adapted to large bandwidth duration (BT) product time-resolvent signals, are described. The performance gain of these methods is shown to be about four times better in comparison with the classical time-delay resolution methods. The frequency HRTDE method is applied to real data obtained from an ocean acoustic experiment. Although classic methods cannot distinguish close signal components, the method presented yields estimates of the delay differences and the attenuation associated with each propagation path. >

A simple root n bandwidth selector

Abstract: The asymptotically best bandwidth selectors for a kernel density estimator currently require the use of either unappealing higher order kernel pilot estimators or related Fourier transform methods. The point of this paper is to present a methodology which allows the fastest possible rate of convergence with the use of only nonnegative kernel estimators at all stages of the selection process. The essential idea is derived through careful study of factorizations of the pilot bandwidth in terms of the original bandwidth.

Lower bounds for bandwidth selection in density estimation

Abstract: This paper establishes asymptotic lower bounds which specify, in a variety of contexts, how well (in terms of relative rate of convergence) one may select the bandwidth of a kernel density estimator. These results provide important new insights concerning how the bandwidth selection problem should be considered. In particular it is shown that if the error criterion is Integrated Squared Error (ISE) then, even under very strong assumptions on the underlying density, relative error of the selected bandwidth cannot be reduced below ordern −1/10 (as the sample size grows). This very large error indicates that any technique which aims specifically to minimize ISE will be subject to serious practical difficulties arising from sampling fluctuations. Cross-validation exhibits this very slow convergence rate, and does suffer from unacceptably large sampling variation. On the other hand, if the error criterion is Mean Integrated Squared Error (MISE) then relative error of bandwidth selection can be reduced to ordern −1/2, when enough smoothness is assumed. Therefore bandwidth selection techniques which aim to minimize MISE can be much more stable, and less sensitive to small sampling fluctuations, than those which try to minimize ISE. We feel this indicates that performance in minimizing MISE, rather than ISE, should become the benchmark for measuring performance of bandwidth selection methods.

A digital DS spread-spectrum receiver with joint channel and Doppler shift estimation

Abstract: A digital spread-spectrum receiver design is presented for communication over multipath channels with severe Doppler shifts. The characteristics of the underwater channel relevant to spread-spectrum system design are discussed, and a channel model for short-range communications (less than 10 km) is defined. The receiver considered uses a digital coherent RAKE combiner, coupled with an extended Kalman filter (EKF)-based estimator for channel parameters and pseudonoise code delay. Receiver performance is evaluated by computing average bit-error rate (BER) versus iterations of the EKF joint estimator, using both fixed and time-varying channels. It is shown that the BER obtained using the EKF joint estimator closely tracks the optimum BER obtained when the channel, delay, and Doppler parameters are known exactly. Finally, the Cramer-Rao lower bound for time-invariant joint channel, delay, and Doppler estimation is derived, and compared with the ensemble averaged mean-squared error of the EKF estimator. >

Wide bandwidth solid state optical source

Abstract: A phosphor is placed on a light emitting surface of a solid state optical source. The phosphor absorbs the narrow bandwidth light from the optical source, and emits light that has a wide bandwidth. A lens is used to collect and focus the wide bandwidth light.

Theoretical model for a Faraday anomalous dispersion optical filter

Abstract: A model for the Faraday anomalous dispersion optical filter is presented. The model predicts a bandwidth of 0.6 GHz and a transmission peak of 0.98 for a filter operating on the Cs (D2) line. The model includes hyperfine effects and is valid for arbitrary magnetic fields.

Apparatus useful in radio communication of digital data using minimal bandwidth

Abstract: Apparatus useful for communicating digital data using a steady stream of pulses which achieve very high ratios of bit rate per occupied bandwidth using digital signal synthesis techniques to produce a stream of constant phase tone pulses having exceptional spectral compactness. An optimal pulse is formed having either no sidelobe energy in the frequency spectrum and few to no sidelobes in the time domain, or no sidelobes in the time domain and minimal sidelobe energy in the frequency spectrum. Each optimal pulse has a specially shaped, non-constant amplitude envelope. The embodiment having no sidelobes in the time domain uses both a pulse envelope corresponding to a Dolph-Chebychev function and more than one frequency of tones with offset timing of overlapping tone pulses so that their envelopes go to zero at different times. The invention is particularly well suited for single sideband radio communication at frequencies below 30 MHz.

Coherent optical transversal filter using silica-based waveguides for high-speed signal processing

Abstract: A coherent optical transversal filter with a tapped delay-line structure is described. Utilizing phase information this filter can express arbitrary tap coefficients (including general complex numbers) by coherently combining tapped signals. Experimental filters using silica-based single-mode optical waveguides, monolithically integrated on silicon substrates were developed for stable and high-speed operation. Experimental results demonstrate the operating capabilities of the filters for high-speed signal processing. The operating bandwidth was experimentally estimated. Degradation of the frequency characteristics due to both deviation of fiber fabricating parameters and errors in setting tap-coefficients has been estimated theoretically. >

Full-duplex, sub-band spread spectrum communications system

Abstract: An improved spread spectrum communications system is provided for establishing full-duplex voice/data radio communications within a single specified FCC ISM band. Spectrum spreading is performed relative to a plurality of sub-bands respectively defined about the lower and upper band-edges of the prescribed ISM band and having spectral roll-off characteristics which satisfy FCC requirements for radio frequency radiation outside the ISM bands on the corresponding band-edges thereof. Full-duplex operation is implemented by the use of digital MSK modulation and associated filtering in order to conserve available bandwidth and accommodate the filtered, modulated signal within the sub-bands defined in the prescribed ISM frequency band, and the system is capable of being easily interfaced to related digital communications services.

A LINC transmitter

Abstract: The LINC (linear amplification using nonlinear components) transmitter shows considerable potential for use in future mobile radio systems employing spectrally efficient linear modulation formats. An experimental LINC transmitter that utilizes modern digital signal processing techniques to perform accurately the necessary signal component separation within the transmitter is described. A technique for significantly reducing the bandwidth required for this digital signal processing is outlined, and practical results which demonstrate that the linearity of the transmitter compares favorably with established linearizing techniques such as Cartesian feedback are presented. >

Narrow-band distributed feedback reflector design

Abstract: The theory is developed for a narrowband distributed feedback reflector that reflects at the center of the grating stopband and transmits at frequencies to either side. A perturbational method of analysis is presented which simplifies the algebra and provides helpful insight. The approximate analysis is compared with the exact results. It is shown that the approximate solution is good in the operating region of practical devices. The proposed tunable narrowband reflector can perform well at a reasonable bandwidth of about 40 GHz. >

Performance of an RCPC-coded OFDM-based digital audio broadcasting (DAB) system

Abstract: A system proposal for DAB is investigated. The kernel is orthogonal frequency division multiplexing (OFDM) with 4-DPSK (differential phase shift keying) modulation, rectangular pulse-shaping, and a guard interval to reject multipath distortions. Emphasis is on the use of source-adapted channel coding with rate-compatible punctured convolutional (RCPC) codes. Based on analytical and simulated BER (bit error rate) curves for several propagation conditions and on preliminary source significance information (SSI), a static code design with unequal error protection (UEP) is presented that also takes auxiliary data services into account. The gain due to UEP is on the order of 8dB in signal power or 25% in bandwidth. >

AM radio receiver with switchable IF bandwidth

Abstract: A method for IF bandwidth switchover and an IF bandwidth switchover apparatus in an AM radio receiver are described. This kind of switchover is appropriate if radio transmitters not only transmit at the normal modulation bandwidth but also broadcast programs with an expanded bandwidth. To obtain optimal reception, the switchover is performed as a function of the reception conditions. To this end, the error rate of supplemental AM information, adjacent-channel interference and the signal strength can be evaluated. These criteria can be used either individually or in various combinations.

High-T/sub c/ superconductive microwave filters

Abstract: Four-pole microstrip bandpass filters have been fabricated using both postannealed and in-situ-grown thin films of Y-Ba-Cu-O. The 4-GHz, 3% bandwidth filters exhibit, at 77 K, a passband insertion loss as low as 0.3 dB, compared with the 2.8-dB loss of similar gold metallic filters at the same temperature. These results demonstrate that complex passive microwave devices can be designed and implemented using high-temperature superconducting (HTS) material. More aggressive filter designs utilizing many more poles will result in much greater performance advantages for an HTS filter technology over a normal metal technology. Ultimately, ultrasharp-skirt filters can be produced, which would allow for more closely spaced communication channels and more efficient use of microwave communication bands than is currently possible with conventional filters.

Self-tuning adaptive bandwidth regulator

Abstract: Methods and apparatus for automatically identifying and adapting to changes in the overall gain of the mechanical plant in a digital servo control system to maintain a constant bandwidth.

Modulator/demodulator for compatible high definition television system

Abstract: An HDTV receiver comprises means (114, 116) responsive to a composite modulated signal having a bandwidth compatible with standard definition TV for separating first and second carriers modulated with compressed digital TV information, signal processing means (120-128) for recovering the information, means for decompressing the information, and means (140-148) for developing an image signal from the decompressed information. The composite signal may include suppressed carrier components with the information.

Low drive-power integrated acoustooptic filter on X-cut Y-propagating LiNbO/sub 3/

Abstract: The authors fabricated very low power integrated acoustically tunable optical filters using walkoff-compensated miniature interdigital transducers, coupled to narrow-width acoustic waveguides. Nearly 100% transverse electric-transverse magnetic (TE-TM) polarization conversion efficiency was achieved using only 8 mW of applied RF power in a 1550-nm filter of 1.8-nm optical bandwidth. A power handling capacity of almost 100 channels was demonstrated by driving these transducers with 760 mW of RF power. These devices suffer little performance degradation in terms of filter width and sidelobe spectrum. >

Reduction of spectral distortion in class D amplifiers by an enhanced pulse width modulation sampling process

Abstract: An enhanced sampling process which can be used to reduce spectral distortion in the output of digital pulse width modulated class D amplifiers is presented. This process arises from a generalisation of the concepts of natural and uniform sampling and can be adjusted such that the spectra produced by the process can take a number of forms for the same signal. Analytical expressions for the spectra produced by the sampling process are derived for both single and double sided modulation. The performance of the process is assessed by case studies on full bandwidth and bass to midrange audio class D amplifiers. It is shown that at carrier frequencies around 88 kHz in a full bandwidth amplifier and 44 kHz in a bass to midrange amplifier the new sampling process will result in significantly lower distortion when compared with either natural or uniform sampling.

Near-lossless bandwidth compression for radiometric data

Abstract: We present a bandwidth compression scheme suitable for transmission of radiometric data collected bytoday's sensitive and high-resolution sensors. Specific design constraints associated with this application are requirements for (1) near-lossless coding, (2) handling of a high dynamic range, and (3) placement of an upper bound on maximum coding error, as opposed to the average or rms coding error. In this approach both the spectral and spatial correlations in the data are exploited to reduce its bandwidth. Spectral correlation is first removed via the Karhunen-Loeve (KL) transformation. An adaptive discrete cosine transform coding technique is then applied to the resulting spectrally decorrelated data. Because the actual coding is done in the transform domain, each individual coding error spreads over an entire block of data when reconstructed. This helps to reduce significantly the maximum error and, as such, makes this approach very suitable for this application. A useful by-product of this approach is that it readily provides some feature classification capability, such as cloud typing, through the interpretation of KL-transformed images. Since each KL-transformed image is a linear combination of all the spectral images, it represents a blend of information present in the entire spectral image set. As such, it could solely render some useful information not readily detectable from the ensemble of spectral images. This may be of particular utility for situations in which a photo interpreter may not have the time or the opportunity to inspect the entire set of images.

Adaptive Robust Control: On-Line Learning

Abstract: A method of on-line adaptation and learning is pro- posed which des use of a probing signal whose frequency content b concentrated at the bandwidth of the current controller. As the plant is learned the procedure naturdyincreases the learning band- width.