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Communications, Radar and Signal Processing, IEE Proceedings F

Issue 7 • Date December 1985

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Displaying Results 1 - 18 of 18
  • Algorithms for frame alignment ¿ some comparisons

    Publication Year: 1985 , Page(s): 529 - 536
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (885 KB)  

    The paper presents a comprehensive analysis of frame alignment strategies for time division multiplexed digital signals. Comparisons are made between algorthims recommended by CCITT and others requiring slightly more sophisticated terminal processing. The principal transition times (misalignment detection, false exit, acquisition and false entry times) form the basis for comparison. The enhanced algorithms are shown to be better able to handle the conflicting requirements of rapid misalignment detection and the need to maintain an aligned condition in the presence of transmission errors. They also result in a significant reduction in acquisition time at high error probabilities, the condition under which alignment equipment is often required to act. View full abstract»

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  • Doppler method for improving tracking accuracy of satellite receiving stations

    Publication Year: 1985 , Page(s): 537 - 540
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (450 KB)  

    A system for extracting Doppler signals from the HRPT data stream transmitted by NOAA satellites is described. These signals are used to improve the accuracy of tracking in a system which relies on satellite ephemeris to predict antenna pointing angles. View full abstract»

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  • Performance of generalised AMF receivers for continuous phase modulation

    Publication Year: 1985 , Page(s): 541 - 547
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (812 KB)  

    Partial-response continuous phase modulation (CPM) signals can in many cases yield power spectra with narrow mainlobe and also low sidelobes. The optimum receiver for these signals is sometimes complex. In the paper the idea of using a smaller signal set in the receiver than used by the transmitter is considered. This is done by means of using a generalised average matched filter (AMF) receiver. Only coherent detection of signals transmitted over an additive white Gaussian noise channel is considered. The multiple-symbol AMF receiver can be implemented with fewer filters than the optimum receiver. These receivers are analysed for various partial-response CPM signals. The analysis is done under the assumption of error-free filter and phase updating. A Euclidean distance for mismatched signal sets is used to give the symbol error probability for large signal/noise ratios conditioned on error-free updating. Under the above assumptions, it is shown that the multiple-symbol AMF receiver performs equally well as the optimum receiver for schemes with low modulation indices and also for large modulation indices for some schemes. This is the case both for binary and quarternary schemes. A simple updatiing method is also simulated. View full abstract»

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  • HF spectral occupancy and frequency planning

    Publication Year: 1985 , Page(s): 548 - 557
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (825 KB)  

    The paper gives measurements of spectral occupancy for each ITU-defined user allocation, across the whole HF spectrum. Such measurements are being made currently during stable ionospheric conditions about midday and midnight, at the times of the winter and summer solstice, over a range of sunspot numbers. An application is given in which the occupancy results for a particular service (fixed in this case), are plotted as contours for direct comparison with the conventional OWF predictions. Thus it is possible to choose a frequency based on expected occupancy, as well as on predicted signal/atmospheric noise. The frequency choice for a particular 1500 km link is considered, when it appears beneficial to operate below the predicted OWF during daytime. View full abstract»

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  • Erratum: Analysis of a multilink system in the presence of noise, cochannel interference and some hardware imperfections

    Publication Year: 1985
    Save to Project icon | PDF file iconPDF (90 KB)  
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  • Spread-spectrum waveforms simplifying transform domain signal processing

    Publication Year: 1985 , Page(s): 558 - 560
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    In the paper a novel class of spread-spectrum waveforms is proposed which is based on spreading operations in the frequency domain. As a main advantage over conventional spread-spectrum waveforms, the proposed waveforms are especially well suited for transform domain correlation at low expense, because their Fourier spectra may be constructed from simple binary pseudonoise sequences. It will be shown that SNR degradation due to time and amplitude limiting requirements in practical spread-spectrum communication systems can be limited to about 1.2 dB by properly choosing the system parameters. The paper is primarily intended to initiate the development of new techniques for obtaining spread-spectrum waveforms in the frequency domain, and does not purport to give a complete recipe for design. View full abstract»

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  • Error propagation in decision feedback receivers

    Publication Year: 1985 , Page(s): 561 - 566
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (710 KB)  

    The problem of assessing error propagation in decision-directed feedback receivers is considered. It is shown that useful bounds on error statistics can be obtained by modelling the error mechanism using stochastic state-transition diagrams and then employing state reduction techniques to enable the complexity of the problem to be contained. This provides a more widely applicable approach to obtaining bounds on performance measures for such receivers than was previously available. The techniques are illustrated for representative error burst statistics of interest in practical applications. View full abstract»

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  • Simplified technique for bounding error statistics for DFB receivers

    Publication Year: 1985 , Page(s): 567 - 575
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (875 KB)  

    A new metric, termed `recovery distance¿¿, is introduced for decision feedback receivsers, and is shown to provide the basis for a simple technique for obtaining bounds on a wide range of error statistics. The error propagation process is modelled using stochastic state transition diagrams with merging of states having the same recovery distance, providing the simplification required to render tractable the derivation of probability generating functions for error random variables of interest. The new technique is illustrated by deriving bounds on error statistics for various signal formats of interest for practical applications. View full abstract»

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  • Class of binary cipher sequences with best possible autocorrelation function

    Publication Year: 1985 , Page(s): 576 - 580
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (674 KB)  

    A new class of binary sequences called here `m-like cipher sequences¿¿ are introduced which have rather interesting properties for use as cipher sequences. These are derived by interleaving the so-called `elementary m-sequences¿¿ along with some null sequences in a particular order. The resulting composite sequences are not m-sequences, but require deciphering and storage of a much larger number of bits for their complete prediction from the observed cipher text than that needed for predicting m-sequences of the same length. At the same time, the method of construction of these sequences ensures that their autocorrelation function is identical to that of an m-sequence of the same length. View full abstract»

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  • New design procedure for digital filters based on a finite-state machine implementation

    Publication Year: 1985 , Page(s): 581 - 588
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1073 KB)  

    The concept of a finite-state machine (FSM) is used in an attempt to cover the deficiencies of the conventional digital filter design procedure with respect to finite-word-length effects. The problem of synthesis is considered in detail and a procedure whereby the FSM mappings are designed to best model a given difference equation is presented. This procedure is based on a well known graph theory algorithm. The FSM digital filter design procedure is evaluated by computer simulation of various small-word-length filters. Several examples are presented to demonstrate the improved performance of the FSM filters with respect to conventional fixed-point designs. The design procedure also allows the construction of limit-cycle-free high-order direct-form filters. This form is compared to the more conventional cascade structure. View full abstract»

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  • Asymptotic results for eigenvector methods

    Publication Year: 1985 , Page(s): 589 - 594
    Cited by:  Papers (15)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (569 KB)  

    Asymptotic results are presented for the MUSIC and Kumaresan and Tufts spectral estimators. The paper makes use of results obtained by Sugiura, which are more accurate than those of Anderson. It is shown that the predictions are in good agreement with simulated results. View full abstract»

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  • Empirical observations of a sonar adaptive array

    Publication Year: 1985 , Page(s): 595 - 597
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (446 KB)  

    The responses of adaptive and conventional acoustic array processors using data acquired from an underwater environment are compared. The data from a horizontal planar array with omnidirectional elements are processed using frequency-domain and element-space techniques to estimate the azimuthal noise anisotropy and to contrast the effectiveness of each processor. Three beamformers are represented: the uniform amplitude shaded beamformer, a nonuniformly shaded beamformer and a fully adaptive processor which seeks to optimise array response by minimising the beampower. View full abstract»

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  • Eclipsing effects with high-duty-factor waveforms in long-range radar

    Publication Year: 1985 , Page(s): 598 - 603
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (637 KB)  

    The partial eclipsing of returns in long-range radar with a high-duty-factor waveform is considered, and two eclipsing zones are shown to exist. The effects on clutter levels, by virtue of increased range sidelobes, and on signal/noise ratio, pulsewidth and pulse amplitude are examined. It is shown that the enhancement of range sidelobes caused by eclipsing, and the associated clutter effects, do not extend outside the eclipsing zones. It is further shown that, for a phased array radar, it is feasible to envisage working well within the first eclipsing zone, which extends to the range equivalent of the transmitted pulse length, and that the instrumented range can be usefully extended beyond the range which corresponds to the resumption of transmission. The use of auxiliary compression filters matched to eclipsed returns as a means of restoring low-range sidelobes is considered. View full abstract»

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  • Effect of adjacent channel interference and frequency-selective fading on outage of digital radio

    Publication Year: 1985 , Page(s): 604 - 612
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (923 KB)  

    Digital radio is affected by frequency-selective fading (FSF), which causes intersymbol interference (ISI), and by adjacent channel interference (ACI), which in its turn is also affected by the same FSF. Using a two-ray model for the FSF, the transfer function of the channel is H(f) = a[1 ¿¿ b exp ( ¿¿ j2¿¿¿¿(f ¿¿ f0))]. Outage in digital radio occurs when the bit error probability exceeds a critical value of 10¿¿3, or when an equivalent mean-square error exceeds a critical value ¿¿2¿¿c, which depends on the modulation used. In the paper we compute the critical mean-square error for M-QAM and M-PSK modulation where M = 4, 8, 16, 64 is the number of symbols. In the absence of FSF, the system response for the signal in the main channel is a raised cosine with excess bandwidth ¿¿, and the receiver filter is matched to the transmitter filter. The signal in the adjacent channel has the same modulation as the signal in the main channel, although they differ in carrier frequency, amplitude, phase and symbol timing. We derive an expression for the mean-square error in the presence of FSF and ACI. The outage probability is a product of two terms, one of which is independent of the modulation methods, while the second is proportional to the area under a signature. The signature is a plot of the minimum value of 1 ¿¿ bc as a function of f0, where bc is a critical value of b such that, if b ¿¿ bc, the critical mean-square error is exceeded. We compute the signatures and the area under the signatures for M-QAM and M-PSK (M = 4, 8, 16, 64) with a bit rate of 140 Mbit/s and frequency separation between channels of 40 MHz. We conclude that, for low values of ACI, 4-QAM is the best system, while for large values of ACI, 64-QAM is the best system. 16-QAM is always better than 8-PSK. View full abstract»

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  • Book review: Least-Square Estimation with Applications to Digital Signal Processing

    Publication Year: 1985
    Save to Project icon | PDF file iconPDF (150 KB)  
    Freely Available from IEEE
  • Radar detection prediction in sea clutter using the compound K-distribution model

    Publication Year: 1985 , Page(s): 613 - 620
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (945 KB)  

    In the paper the radar detection of targets in sea clutter modelled by the compound K-distribution is examined from a statistical detection viewpoint. Optimum performance is determined for both fixed threshold and ideal constant false alarm rate (CFAR) receivers for targets modelled by Swerling cases 0, 1 and 2. In particular, the performance of dual threshold binary integrators is assessed. The compound K-distribution sea clutter model is not only a good fit to observed amplitude statistics over a wide range of conditions, but also allows the temporal and spatial correlation characteristics to be accurately modelled. The modelling of pulse-to-pulse correlation characteristics is very important for accurate performance prediction when pulse-to-pulse integration is used. The use of the compound K-distribution model not only gives more accurate results than models based on amplitude distribution alone, but also gives a new insight to the detection characteristics of different radar detection radar detection systems over a wide range of sea conditions. View full abstract»

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  • ESM processor system for high pulse density radar environments

    Publication Year: 1985 , Page(s): 621 - 625
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    A radar ESM system performs two functions: warning of impending threats and surveillance to determine radar activities. Automatic radar ESM systems are passive radar receivers which receive emissions from other platforms, measure the parameters of each pulse received and thus sort the emissions to enable determination of the radar parameters for each emitter. These parameters are then compared with values stored for known radar types, to identify the emitter-type likely threat and platform. The paper concentrates on emitter de-interleaving of pulse data streams of several hundred thousand pulses/second, which is one of the processing steps involved. Emitter de-interleaving involves sorting the received radar pulses into separate trains, each train associated with asingle emitter. The Cutlass automatic radar ESM system, which is widely in service, is used as an example. Emphasis is placed on the advantages of its pipelined architecture for operating in high pulse density environments. View full abstract»

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  • IEE Conference Publication 247 (Advances in Command, Control and Communication Systems: Theory and Applications)

    Publication Year: 1985
    Save to Project icon | PDF file iconPDF (117 KB)  
    Freely Available from IEEE

Aims & Scope

The latest version of this title is Radar, Sonar & Navigation, IET.

Full Aims & Scope