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Military Electronics, IEEE Transactions on

Issue 1 • Date Jan. 1965

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Displaying Results 1 - 19 of 19
  • [Front cover]

    Page(s): c1
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  • IEEE Military Electronics Group

    Page(s): c2
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  • Table of contents

    Page(s): 1
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  • 1964 Recipient of the M. Barry Carlton Memorial Award

    Page(s): 2
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  • Foreword

    Page(s): 3
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  • Effects of Phase Errors on Resolution

    Page(s): 4 - 9
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    The mathematical problem consists of determining the spread of the Fourier transform of function when the function is modified by a multiplicative factor exp j¿(t), where ¿ is a stationary random process. Let F(¿) be the Fourier transform of f(t) and Fm(¿) be the transform of f(t) exp j¿(t). For example, f may be the illumination function of a linear antenna and ¿ accounts for imperfect phasing of the antenna. The major results consist of simple formulas for the rms tilting (or shifting) of the pattern |Fm|2 and the rms radius of gyration (or beamwidth) of the pattern. These positional errors and resolution degradations are formulated in terms of the pattern in the absence of phase errors and the power density spectrum of ¿¿. The problem of calculating the best obtainable resolution, i.e., minimizing the mean-square resolution over all possible illumination functions, requires numerical solution; however, it is shown that it is always possible to obtain a rms resolution better than the smaller of rms ¿¿ and ¿rms ¿¿. The actual numerical solution is compared to this simple approximation for the case of sinusoidal phase errors. The general results have a broad scope of applications, and here the spreading of the ambiguity function in time and frequency in the presence of time phase errors and dispersion (frequency phase errors) is described with particular attention to linear FM pulses. Finally, some observations are made about quadratic phase errors, signal-to-noise performance, and mean-square point-target response. View full abstract»

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  • The Amplitude Statistics of Aircraft Radar Echoes

    Page(s): 10 - 16
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    Recorded CW radar echoes from a number of aircraft have been analyzed to determine the characteristics of the amplitude fluctuations and the extent to which these vary among different aircraft. The statistics of the echoes from four targets (two jets and two piston aircraft) were found to exhibit marked similarities; typically, the echo power was exponentially distributed, with a correlation time on the order of 0.05 s. Families of probability-distribution functions were derived which show how the amplitude statistics are affected by integration. View full abstract»

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  • The Effect of Limiting on the Detectability of Partially Time-Coincident Pulse Compression Signals

    Page(s): 17 - 24
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    Analytic approximations are derived to describe the effect of band-pass limiting on the detectability of partially time-coincident pulse compression signals. These are applied to the practical radar case of a fixed threshold decision criterion, which effectively becomes an equivalent variable threshold in any region in which a strong signal controls the limiter action. The suppression and gain control effects of the strong signal cause the detection probability of a weaker signal to deteriorate rapidly as a function of the percentage overlap. A calibrated radar simulator is described. The test equipment operated in either a pulsed CW or a linear FM pulse compression mode. Detection probability curves are presented for different false alarm probabilities in each mode, with and without limiting. Test procedures are described that obtain data in the following areas: 1) The effect of partially time-coincident strong signals on the probability of detection (Pd) of a weaker signal in the pulse compression mode, and 2) The effect of the strong signal on the probability of false alarm (Pfa) in the strong-signal region. The data obtained are in agreement with the analysis, illustrating the degradation of the weaker signal Pd as the overlap factor increased. View full abstract»

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  • Radar Frequency Modulations for Accelerating Targets under a Bandwidth Constraint

    Page(s): 25 - 32
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    An optimum frequency modulation for estimating the range, range rate, and range acceleration of a moving target is derived. The criterion of optimality is based on the estimate variances which are evaluated under the following assumptions: 1) additive white Gaussian observation noise, 2) high signal-to-noise ratio, 3) maximum-likelihood processing (matched filters), 4) RF phase used only for the range rate and range acceleration, and 5) carrier frequency much larger than the signal bandwidth. The choice of frequency modulation is constrained by the bandwidth of the transmitted signal. A large time-bandwidth product is assumed. The optimum frequency modulation consists of three appropriately placed frequency jumps between the limits imposed by the bandwidth constraint. This optimum modulation is compared with a third degree, power law modulation. The derivation of the optimum, originally done using Pontryagin's Maximum Principle, leads to the following very simple design principle; the optimum modulation is orthogonal to the target's motion. View full abstract»

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  • A Technique for the Generation of Highly Linear FM Pulse Radar Signals

    Page(s): 32 - 38
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    Some radar systems employing a linear FM pulse require FM linearity not easily obtainable from present generation methods. A technique is developed whereby average linearities of better than 0.1 per cent may be realized by active generation methods. Two methods of implementation are described that synthesize the waveform by generating a staircase-type stepped FM waveform and "filling in" the steps with a suitable sawtooth FM signal. Coherence, required number of steps, Doppler, and random phase errors are considered. View full abstract»

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  • Measurements of UHF and L-Band Radar Clutter in the Central Pacific Ocean

    Page(s): 39 - 44
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    Measurements of clutter with the TRADEX radar at UHF and L band are described. Clutter is shown to be due to sea return and returns from clouds. Sea clutter predominates at ranges less than 13 nmi, values of ¿0 of -100 dB being typical at both frequencies. Coherent scattering from clouds is postulated, and the observed frequency independence of the cloud retums is offered as supporting evidence. Values of cloud cross section per unit volume are given. Below 15,000 ft altitude, values of -140 dB (reference m-1) are typical at both frequencies. Clutter spectra are presented. View full abstract»

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  • On Detection and Estimation of Wave Fields for Surveillance

    Page(s): 44 - 56
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    This paper considers the detection and estimation of a signal field in the presence of a noise field. The wave field, which is a continuous space-time function, is converted into a discrete set of time functions by an array of transducer elements which convert the physical field quantities into other quantities appropriate for processing. The resulting set of time functions makes up a vector random process. A generalization of the one-dimensional Karhunen-Loeve expansion applied to the vector random process yields a series representation with uncorrelated coefficients. The effects of complex element weighting and of internal noise are considered in describing the noise and signal vector processes. If the noise field is Gaussian, the conditional probability density functions of the vector processes, under the hypotheses of noise alone and of signal pulse noise, are straightforwardly written, leading directly to the likelihood ratio for a completely known signal. The operation to obtain a test statistic based upon the likelihood ratio is interpreted as a set of filtering operations, time-varying in the general case where the noise field is not wide-sense stationary. When the noise field is wide-sense stationary, the field may be described by a spectral density matrix whose elements are the cross-spectral densities of the total noise at the transducers taken in pairs. The operation to obtain the test statistic is now interpreted as a set of filtering operations described by a filtering matrix. View full abstract»

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  • Matched-Filter Theory for High-Velocity, Accelerating Targets

    Page(s): 56 - 69
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    Two modifications of the conventional radar theory of matched filters and ambiguity functions are discussed. The first modification is to make the theory valid for high-velocity targets and wide-band signals, and the second is to include the effects of acceleration. The ability of a radar to measure target acceleration has previously been discussed in terms of measurement accuracy for isolated targets. This paper is concerned with the form of data processing necessary for the measurement and with the effects of acceleration on the clutter problem. View full abstract»

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  • Minimum Variance Angle Estimates

    Page(s): 70
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  • Towards a Laser Radar for Near-Horizon Use

    Page(s): 70 - 72
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  • On Future Trends in Large-Scale Energy Conversion

    Page(s): 72
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  • Author's reply

    Page(s): 72
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  • Contributors

    Page(s): 73 - 74
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  • Information for authors

    Page(s): 74a
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Aims & Scope

This Transactions ceased publication in 1965. The new retitled publication is IEEE Transactions on Aerospace and Electronic Systems.

Full Aims & Scope