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Aerospace and Electronic Systems, IEEE Transactions on

Issue 6 • Date Nov. 1988

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Displaying Results 1 - 20 of 20
  • Discrete-time state estimation of analog double integrators

    Publication Year: 1988 , Page(s): 670 - 677
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (549 KB)  

    The problem of minimum variance discrete-time state estimation of a continuous-time double integrator via noisy continuous-time measurements is considered. The error covariance matrices of this estimation are calculated and analyzed. The relations between these covariance matrices and the error covariance matrix of the optimal continuous-time filter are obtained, and a way for determining the required sampling period is proposed. A commonly used approximated model is investigated; it is shown to be inappropriate unless a specific improvement is introduced in the model.<> View full abstract»

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  • Aircraft vertical profile implementation using directed-graph methods

    Publication Year: 1988 , Page(s): 682 - 692
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (863 KB)  

    Aircraft vertical profile simulation is realized using a demand-driven minimal-calculation directed graph structure to reduce calculation time and to force synchronization of the performance measurement functions with the system state variables. Performance-directed model adaptation makes dynamic vertical profile path corrections, in the presence of fixed drag variations, possible. Drag variations ranging from +10% to -10% yielded fuel consumption improvements of less than 1% in the majority of the cases. Calculation time improvement for path simulation ranges from a factor of 1.19 in the worst case to 1.5 in the best case.<> View full abstract»

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  • Distributed computation with communication delay (distributed intelligent sensor networks)

    Publication Year: 1988 , Page(s): 700 - 712
    Cited by:  Papers (51)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (807 KB)  

    A linear network of communicating processors is examined. The objective is to solve a computational problem in a minimal amount of time. The processors in the networks may be equipped either with or without front-end processors for communication off-loading. The cases of equal division of processing load and optimal division of processing load are discussed for both the network with front-end processors and the network without front end processors. An example of the inclusion of solution time, the time taken for processors to report the solution back to the problem originator, is also presented.<> View full abstract»

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  • A parallel computer architecture for continuous simulation

    Publication Year: 1988 , Page(s): 719 - 725
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    A parallel computer specifically designed for the solution of ordinary differential equations is described. The first version of the machine contains thirty-two processors, running in an asynchronous multiple-instruction/multiple-data mode, communicating with high-speed parallel busses. Synchronization is accomplished by a microprogrammable communication controller. A number of processors have been designed and built for the machine. The processor types offer a wide variation in solution speed and accuracy. To permit easy comparisons with analog and hybrid systems, performance is measured by finding the highest frequency sine wave which can be integrated in real time with an accuracy of 0.1% or higher. Using this performance measure the performance limit of the current machine is 2000 Hz. The structure is capable of solving systems described by differential equations up to order sixty-four at these performance limits.<> View full abstract»

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  • Generation and classification of PWM DC-to-DC converters

    Publication Year: 1988 , Page(s): 743 - 754
    Cited by:  Papers (36)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (836 KB)  

    A method is presented by which generation and classification of pulsewidth-modulated (PWM) DC-to-DC converters can be effected. Fundamental blocks known as converter cells can be used to generate a plethora of converters leading to a number of useful new converter topologies. A classification of basic converters is proposed in terms of converter-cell generated families.<> View full abstract»

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  • Some practical strategies for reducing intermodulation in satellite communications

    Publication Year: 1988 , Page(s): 755 - 765
    Cited by:  Papers (8)  |  Patents (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (945 KB)  

    Various heuristic procedures for obtaining practical solutions to the general one-level carrier frequency assignment problem are described. The problem treated is general in the sense that it accommodates the case where L of the N slots may be explicitly designated as prohibited and unavailable for assignment. This problem occurs in satellite transmission with many small carriers accessing the same transponder where, due to multipath and TV interference from crosspolarized transponders of the same satellite and from copolarized transponders of the adjacent satellites, some portions of the bandwidth of the considered transponder cannot be used. To permit comparison with respect to the intermodulation advantage and central-processing-unit time required, the case without prohibited slots is considered. The sequential insertion procedure in which, starting with two carriers at the two end slots, one additional carrier at a time is optimally inserted into one of the unassigned slots is found best when the ratio between the available bandwidth and the total carrier bandwidth is greater than about 125%. All the heuristic procedures produced assignments whose intermodulation advantages are all greater than the bandwidth ratio.<> View full abstract»

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  • Mixed graphic architecture for radar displays

    Publication Year: 1988 , Page(s): 791 - 799
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (778 KB)  

    The current state of the art in designing radar displays is first analyzed. An advanced architecture is proposed that overcomes the previous display limitations by using the mixed vector-raster concept. Design tradeoffs are identified, and feasible solutions are given. A simplified prototype that realizes these concepts is presented.<> View full abstract»

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  • Efficient numerical algorithm for steady-state Kalman covariance

    Publication Year: 1988 , Page(s): 815 - 817
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    A stable, quadratically convergent numerical algorithm is presented for computing the steady-state covariance and gain matrices of the Kalman filter. The method is more rapidly convergent than standard Riccati integration techniques and is easier to implement than existing eigenvalue-eigenvector algorithms. The quadratic convergence is proved analytically and illustrated by a numerical example View full abstract»

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  • Buck-flyback DC-DC converter

    Publication Year: 1988 , Page(s): 800 - 807
    Cited by:  Papers (8)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    It is difficult to obtain a large input/output voltage ratio with a DC-DC converter, because the duty factor d may not reach very small values. For the same reason, it is difficult to obtain an output voltage that is adjustable in a large range. A DC-DC converter circuit is proposed that overcomes this limitation by performing a voltage ratio d2/(1-d) in the best operating mode. Circuit operation is analyzed, operating modes are evidenced, and the voltage ratio is deduced in each operating mode as a function of output current, duty factor, and circuit component values. Boundary conditions between different operating modes are obtained; consequently, it is concluded that these conditions do not occur for some operating modes. Component ratings are summarized, to facilitate circuit design. The buck-flyback DC-DC converter is very suitable for low-voltage (e.g. computer) power supplies and for power supplies with the output voltage (adjustable in a large range) supplied from the mains without a mains voltage transformer View full abstract»

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  • Control of nearly singular decoupling systems and nonlinear aircraft maneuver

    Publication Year: 1988 , Page(s): 775 - 784
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    The author treats the question of control of a class of nonlinear systems using state variable feedback whose input/output map is nearly singular. Although the existing decoupling theory is applicable to such systems, this requires a large amount of control, which may not be permissible. A decoupling approach using state variable feedback in an approximate sense, but requiring a small control magnitude is considered. A decoupling scheme is presented that gives rise to a singularly perturbed system describing the fast dynamics of the control vector. The quasi-steady-state solution of the system gives a control law that decouples the system in an approximate way. The controller includes a servocompensator and a reference trajectory generator. Based on this result, a control law for approximate decoupling of roll angle, angle of attack, and sideslip in rapid, nonlinear airplane maneuvers is derived. Simulated responses of the closed-loop system show that large, simultaneous lateral and longitudinal maneuvers can be accurately performed in spite of uncertainty in stability derivatives View full abstract»

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  • Further results on radar pointing error reduction using discrete extended Kalman filtering

    Publication Year: 1988 , Page(s): 817 - 820
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    A recently proposed method of reducing target glint errors in radar systems using extended Kalman filtering is further extended with the inclusion of and compensation for clutter effects. A discrete target model and discrete Kalman filter (DKF) are used. Simulation results demonstrating the DKF are presented, and the limits on the effectiveness of the method are investigated. The major advantage of the DKF is that it can be implemented in software in the digital processor of the radar, offering flexibility over continuous time filters. The ability of the filter to reduce clutter effects further demonstrates the usefulness of this technique for radar pointing error reduction View full abstract»

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  • Detection loss due to interfering targets in ordered statistics CFAR

    Publication Year: 1988 , Page(s): 678 - 681
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    The ordered-statistics (OS) constant false-alarm rate (CFAR) is relatively immune to the presence of interfering targets among the reference cells used to determine the average background. OS CFAR performance in a multitarget environment was previously studied by simulation. The author obtains analytic expressions for the added detection loss, assuming strong interfering targets. The real target is assumed to be a Rayleigh fluctuating target. Numerical examples are included View full abstract»

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  • The early history of pulse compression radar-the development of AN/FPS-17 coded-pulse radar at Lincoln Laboratory

    Publication Year: 1988 , Page(s): 833 - 837
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (668 KB)  

    The development of pulse compression radar at MIT Lincoln Laboratory is related on the basis of the author's personal recollections. He describes the formation of the Radar Techniques Group, the development of the concept, the first system constructed, and the selection of an appropriate code for the transmitted waveform View full abstract»

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  • OS-CFAR theory for multiple targets and nonuniform clutter

    Publication Year: 1988 , Page(s): 785 - 790
    Cited by:  Papers (14)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    The performance of a cell averaging constant false-alarm rate (CA-CFAR) detector degrades rapidly in nonideal conditions caused by multiple targets and nonuniform clutter. The ordered-statistic CFAR (OS-CFAR) is an alternative to the CA-CFAR. The OS-CFAR trades a small loss in detection performance relative to the CA-CFAR in ideal conditions for much less performance degradation in nonideal conditions. A formula is given for the detection probability of the OS-CFAR when there are multiple Swerling I targets in the CFAR window, and a formula is given for the probability of false alarm in nonuniform Raleigh clutter View full abstract»

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  • Noise analysis of a digital tanlock loop

    Publication Year: 1988 , Page(s): 713 - 718
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    The noise performance analysis of a nonuniform digital phase-locked loop (DPLL), called the digital tanlock loop (DTL), is investigated by both analytic and computer-simulation methods. The results are presented in terms of phase error probability mass function and mean time to skip cycle versus input signal-to-noise ratio (SNR). These results are compared to the ones obtained with the conventional sinusoidal DPLL loop (DPLL). It is found that, for low-to-moderate input SNR, the DTL has only a slight improvement over the DPLL. The DTL, however, has larger linear characteristics than the conventional DPLL, which makes it attractive for applications that require an increased tracking range or as a first stage in carrier tracking systems based on optimum estimation procedures such as a Kalman smoother View full abstract»

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  • Time-frequency hop codes based upon extended quadratic congruences

    Publication Year: 1988 , Page(s): 726 - 742
    Cited by:  Papers (16)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1100 KB)  

    Time-frequency hop codes are developed that can be used for coherent multiuser echolocation and asynchronous spread spectrum communication systems. They represent a compromise between Costas codes, which have nearly ideal autoambiguity but not so good cross-ambiguity properties, and linear congruential codes, which have nearly ideal cross-ambiguity but unattractive autoambiguity properties. Extended quadratic congruential code words are shown to have reasonably good autoambiguity and cross-ambiguity properties across the whole class of code sets considered. A uniform upper bound is placed on the entire cross-ambiguity function surface, and bounds are placed on the position and amplitude of spurious peaks in the autoambiguity function. These bounds depend on the time/bandwidth product and code length exclusively and lead naturally to a discussion of the design tradeoffs for these two parameters. Examples of typical autoambiguity and cross-ambiguity functions are given to illustrate the performance of the new codes View full abstract»

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  • SAR resolution in the presence of phase errors

    Publication Year: 1988 , Page(s): 808 - 814
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    The author analyzes the effects of phase errors on synthetic aperture radar (SAR). The theory is applied to the following question: how does the achievable resolution vary with the carrier frequency when optimum quadratic focus and/or optimum processing interval (synthetic aperture length) are used? Numerous related results are given, so that much of the material is tutorial. For phase errors corresponding to uncompensated motion, the best achievable RMS resolution with any phase error spectrum satisfies the derived equation. For motion-induced phase errors it is seen that resolution improves with increasing carrier frequency when the first term in the expression applies (e.g. for phase errors concentrated at low frequencies) and resolution is independent of carrier frequency when R δ/v/v is the smaller term (e.g. with broad band or high frequency phase errors) View full abstract»

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  • Analysis of interference effects on monopulse radars

    Publication Year: 1988 , Page(s): 766 - 774
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    The complete numerical analysis of angle-tracking performance of a coherent amplitude-comparison monopulse radar system in a two-target situation is described. This system, equipped with automatic gain control (AGC) and phase-locked loop (PLL), was originally invented for improving the target-tracking performance in multiple-target situation. The general behavior depends on Doppler separation of the targets relative to the bandwidths of AGC and PLL. The performance of this system has previously been roughly analyzed by using linear approximation for four extreme cases: wideband and narrowband AGC in combination with wideband and narrowband PLL. In this study, the author performs nonlinear analysis of the same system for all bandwidths of AGC and PLL, because Doppler separation varies over a wide range in actual tracker, and therefore it is indispensable to know the total system behavior. A special numerical technique called the Galerkin method is used. As a result of this analysis, the extensive target-tracking performance for all intermediate bandwidths of AGC and PLL has been clarified. The result is useful for actual target tracker design View full abstract»

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  • The early history of pulse compression radar-the history of pulse compression at Sperry Gyroscope Company

    Publication Year: 1988 , Page(s): 825 - 833
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (980 KB)  

    The development of pulse compression radar at Sperry is related on the basis of the author's personal recollections. He discusses the first experiments, concept improvements, demonstration of the concept, system implementations, dealings with the US Patent Office, and finishing touches View full abstract»

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  • Alpha-beta filters in polar coordinates with acceleration corrections

    Publication Year: 1988 , Page(s): 693 - 699
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    The use of polar coordinates is sometimes computationally advantageous for tracking, but complications arise because the position of constant velocity targets is no longer a linear function of time as it is for cartesian coordinates. However, this difficulty can be avoided by using pseudoacceleration correction factors which are added to the prediction equations to give approximately correct system dynamics, but at the expense of an increase in system noise. For alpha-beta tracking filters, these correction factors can be included with minimal degradation in the steady-state error performance of the filter while simultaneously providing substantial reductions in bias errors View full abstract»

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IEEE Transactions on Aerospace and Electronic Systems focuses on the equipment, procedures, and techniques applicable to the organization, installation, and operation of functional systems designed to meet the high performance requirements of earth and space systems.

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Editor-in-Chief
Lance Kaplan
Army Research Laboratory