Efficient analog communication over quantum channels
Axioms of quantum measurements incorporated into communication estimation theory for optical communication
Personick, S. D.↗
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Estimation of nonlinear pilot model parameters including time delay.
Investigation of the feasibility of using a Kalman filter estimator for the identification of unknown parameters in nonlinear dynamic systems with a time delay. The problem considered is the application of estimation theory to determine the parameters of a family of pilot models containing delayed states. In particular, the pilot-plant dynamics are described by differential-difference equations of the retarded type. The pilot delay, included as one of the unknown parameters to be determined, is kept in pure form as opposed to the Pade approximations generally used for these systems. Problem areas associated with processing real pilot response data are included in the discussion.
Schiess, J. R.↗
The digital phase-locked loop as a near-optimum FM demodulator.
This paper presents an approach to the optimum digital demodulation of a continuous-time FM signal using stochastic estimation theory. The primary result is a digital phase-locked loop realization possessing performance characteristics that approach those of the analog counterpart. Some practical considerations are presented and simulation results for a first-order message model are presented.
Kelly, C. N.↗
Near optimum digital phase locked loops.
Near optimum digital phase locked loops are derived utilizing nonlinear estimation theory. Nonlinear approximations are employed to yield realizable loop structures. Baseband equivalent loop gains are derived which under high signal to noise ratio conditions may be calculated off-line. Additional simplifications are made which permit the application of the Kalman filter algorithms to determine the optimum loop filter. Performance is evaluated by a theoretical analysis and by simulation. Theoretical and simulated results are discussed and a comparison to analog results is made.
Polk, D. R.↗
Multipath modeling for aeronautical communications.
One of the fundamental technical problems in aeronautical digital communications is that of multipath propagation between aircraft and ground terminal. This paper examines in detail a model of the received multipath signal that is useful for application of modern detection and estimation theories. The model treats arbitrary modulation and covers the selective and nonselective cases. The necessarily nonstationary statistics of the received signal are determined from the link geometry and the surface roughness parameters via a Kirchhoff solution.
Painter, J. H.↗
Lunar satellite techniques applicable to earth satellite geodesy
The techniques considered are related to gravity profiling from Doppler residuals, a solution for a surface mass distribution, and a dynamical approach for the estimation of random forces at each data point. The dynamical approach makes use of a new filtering method which uses sequential estimation theory to determine unknown and somewhat correlated forces which randomly perturb the orbit. It is concluded that lunar data reduction methods would be suitable for applications in connection with the GEOS-C/ATS-F mission.
Sjogren, W. L.↗
The chemical composition and distribution of interstellar grains
The chemical composition of interstellar grains is derived here on the basis of (1) the cosmic abundance of the elements; (2) the wavelength dependence of extinction and polarization; (3) the average total extinction; (4) the ratio of polarization to extinction; (5) the predominantly dielectric character of grains in the visible spectral region; and (6) infrared spectral characteristics of grains. Inferences of the core-mantle model with respect to spatial distribution are consistent with the proposition that growth of the mantles occurs in the galactic shock region predicted by the density-wave theory. Estimates of the total visual extinction toward the galactic center and the consequent estimates of the total amount of far infrared radiation are shown to depend critically on the grain model. Variations of the ratio of far ultraviolet to visual extinction are correlated with the conditions for growth of mantles on the bare small particles which are generally prevented from accreting mantles primarily because of their extreme temperature fluctuations produced by the ultraviolet photons in the radiation field.
Greenberg, J. M.↗
Tracking performance of symbol synchronizers for Manchester coded data
The implementation and tracking performance of symbol synchronizers for Manchester coded data is presented with motivation provided by maximum a posteriori (MAP) estimation theory. Certain physically relizable closed-loop structures, readily implemented in practice, are suggested by the theory for uncoded data symbols with arbitrary data transition probabilities. The tracking performance of these loops is optimized and comparisons are made among the various configurations over a wide range of system parameters. Although not the major intent of the paper, the acquisition problem is briefly addressed.
Simon, M. K.↗
Signal detection in l/f noise of SQUID magnetometers
It is shown that the variance on the SQUID power spectrum in the l/f low frequency region is well behaved, i.e., any small frequency band may be treated as white noise in standard power spectrum estimation theory. Specifically a calibration signal is examined at 0.017 Hz with an equivalent energy referred to the SQUID input coil of 1 times 10 to the -30th J and a digitally recorded and analyzed record of 140 hr duration obtained an optimum S/N better than 400. The results are in good agreement with theory. In addition no deviation from the l/f dependence of the noise energy spectrum is seen down to frequencies below 10 to the -5th Hz. A commercially available SQUID and electronics system were used.
Cabrera, B.↗
Spatial and temporal variations of monthly mean total columnar ozone derived from 7 years of BUV data
Ninth-degree spherical harmonic models are used to represent monthly mean total columnar ozone fields, with spatial spectra defined in terms of simple analytic expressions representing the rms value of each spherical harmonic coefficient. The spectra are combined with estimation theory techniques to develop a realistic error analysis accounting for errors due to nonglobal coverage. Amplitude and phase variations for longitudinal waves one, two and three are presented, and it is shown that these waves reinforce in space and time in the period of high poleward ozone transport in the northern hemisphere. In the southern hemisphere, the wave two and three components are much smaller, with wave one maximum amplitude occurring in September and October.
Tolson, R. H.↗
Two-channel Costas loop tracking performance for UQPSK signals with arbitrary data formats
Previous results on the tracking performance of two-channel Costas-type carrier synchronization loops are generalized and corrected, in order that they may be applied to several mixed-format cases. In particular, the mean-square phase jitter performance of these loops with active arm filters, synchronous or asynchronous symbol clocks, and arbitrary data formats on the two channels is examined. It is demonstrated that for each case, selection of the channel gain ratio, as motivated by the MAP estimation theory, does not guarantee optimum loop tracking performance: in some instances, a conventional single-channel Costas loop would outperform the two-channel version with the MAP choice of gain ratio. It is suggested that the gain ratio be chosen to directly minimize the mean-square phase tracking jitter which is equivalent to minimizing the loop's 'squaring loss'. This can, in some cases, improve the performance measure, although in all cases, the two-channel loop will still outperform the single-channel version.
Simon, M. K.↗
Development of rotation sample designs for the estimation of crop acreages
The idea behind the use of rotation sample designs is that the variation of the crop acreage of a particular sample unit from year to year is usually less than the variation of crop acreage between units within a particular year. The estimation theory is based on an additive mixed analysis of variance model with years as fixed effects, (a sub t), and sample units as a variable factor. The rotation patterns are decided upon according to: (1) the number of sample units in the design each year; (2) the number of units retained in the following years; and (3) the number of years to complete the rotation pattern. Different analytic formulae for the variance of (a sub t) and the variance comparisons in using a complete survey of the rotation patterns.
Lycthuan-Lee, T. G.↗
Optimal interpolation and the Kalman filter
The estimation theory of stochastic-dynamic systems is described and used in a numerical study of optimal interpolation. The general form of data assimilation methods is reviewed. The Kalman-Bucy, KB filter, and optimal interpolation (OI) filters are examined for effectiveness in performance as gain matrices using a one-dimensional form of the shallow-water equations. Control runs in the numerical analyses were performed for a ten-day forecast in concert with the OI method. The effects of optimality, initialization, and assimilation were studied. It was found that correct initialization is necessary in order to localize errors, especially near boundary points. Also, the use of small forecast error growth rates over data-sparse areas was determined to offset inaccurate modeling of correlation functions near boundaries.
Cohn, S.↗
Applications of Sequential Estimation to Numerical Weather Prediction
The main objective of this cooperative research with NASA's Goddard Laboratory for Atmospheric Sciences (GLAS) is to use information about the atmosphere acquired from new types of observations, especially from satellites, in order to deepen our understanding of its behavior on time scales from hours to years. This is achieved by: (1) improving the methods for processing point observations into complete fields in space and time, using sequential estimation theory; and (2) analyzing low-frequency atmospheric variability by the methods of dynamical system theory, suitably modified to enhance practical predictability.
Ghil, M.↗
Research on optimal control, stabilization and computational algorithms for aerospace applications
The research carried out in the areas of optimal control and estimation theory and its applications under this grant is reviewed. A listing of the 257 publications that document the research results is presented.
Athans, M.↗
Research on optimal control, stabilization and computational algorithms for aerospace applications
The research carried out in the areas of optimal control and estimation theory and its applications under this grant is reviewed. A listing of the 257 publications that document the research results is presented.
Athans, M.↗
Variability of rainfall over small areas
A preliminary investigation was made to determine estimates of the number of raingauges needed in order to measure the variability of rainfall in time and space over small areas (approximately 40 sq miles). The literature on rainfall variability was examined and the types of empirical relationships used to relate rainfall variations to meteorological and catchment-area characteristics were considered. Relations between the coefficient of variation and areal-mean rainfall and area have been used by several investigators. These parameters seemed reasonable ones to use in any future study of rainfall variations. From a knowledge of an appropriate coefficient of variation (determined by the above-mentioned relations) the number rain gauges needed for the precise determination of areal-mean rainfall may be calculated by statistical estimation theory. The number gauges needed to measure the coefficient of variation over a 40 sq miles area, with varying degrees of error, was found to range from 264 (10% error, mean precipitation = 0.1 in) to about 2 (100% error, mean precipitation = 0.1 in).
Runnels, R. C.↗
Spatially recursive filtering and smoothing for multibody dynamics
Methods developed recently by the author to solve the problem of forward dynamics for nonlinear joint-connected multibody systems are summarized. Solution of this problem is of interest in such application areas as robotics, deploying structures, ground vehicles, and pointing of antennas and instrumented platforms. The problem is solved by the recursive filtering and smoothing techniques of state estimation theory. The filtering stage takes the applied joint moments as inputs to produce a sequence of spatial constraint forces acting at the joints of the system. The smoothing stage takes the innovations process resulting from the filter as an input and produces a set of spatial accelerations and a corresponding set of joint-angle accelerations.
Rodriguez, G.↗