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IEE Proceedings F (Communications, Radar and Signal Processing)

Volume 131, Issue 2, April 1984

Volumes & issues:

Volume 131, Issue 2

April 1984

Mean-square correlation of shift-register sequences
  • Author(s): D.V. Sarwate
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 131, Issue 2, p. 101 –106
  • DOI:  10.1049/ip-f-1.1984.0018
  • Type: Article
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  • p. 101 –106 (6)
    The mean value and the mean-square value of various correlation parameters of linear feedback shift-register sequences are obtained and compared with the corresponding parameters for random sequences. The mean-square correlation parameters for maximal-length shift-register sequences, i.e. pseudonoise or pseudorandom sequences, are considerably better than those for random sequences. The mean-square correlation parameters for Gold sequences are found to be the same as those for random sequences. Thus, performance obtained with shift-register sequences is at least as good as the performance obtained with random coding.
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Serial data transmission over HF radio links
  • Author(s): W. Hodgkiss ; L.F. Turner ; J. Pennington
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 131, Issue 2, p. 107 –116
  • DOI:  10.1049/ip-f-1.1984.0019
  • Type: Article
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  • p. 107 –116 (10)
    The paper reports on an investigation into the use of HF radio links for serial data transmission. A prototype test system was developed and used to study the effectiveness of varios methods of modulation and demodulation, to study ways of varying the data rate, to exmine the performance of serial systems as a function of data rate and to investigate the use of adaptive equalisation as a technique for overcoming multipath interference. Data was transmitted at rates ranging from 0.3 kbit/s to 3.6 kbit/s, and the associated error probabilities were found to be in the range 1.5 × 10−2 to 5.8 × 10−2. The use of equalisation resulted in improved system performance over the entire range of data rates.
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Simplified estimation of ray-path mirroring height for HF radiowaves reflected from the ionospheric F-region
  • Author(s): M. Lockwood
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 131, Issue 2, p. 117 –124
  • DOI:  10.1049/ip-f-1.1984.0020
  • Type: Article
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  • p. 117 –124 (8)
    From Milsom's equations, which describe the geometry of ray-path hops reflected from the ionospheric F-layer, algorithms for the simplified estimation of mirror-reflection height are developed. These allow for hop length and the effects of variations in underlying ionisation (via the ratio of the F2- and E-layer critical frequencies) and F2-layer peak height (via the M(3000)F2-factor). Separate algorithms are presented which are applicable to a range of signal frequencies about the FOT and to propagation at the MUF. The accuracies and complexities of the algorithms are compared with those inherent in the use of a procedure based on an equation developed by Shimazaki.
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Facsimile coding using symbol-matching techniques
Comparison between time-compression multiplexing and frequency-division multiplexing over narrowband radio systems
  • Author(s): R.J. Holbeche  and  R.T. Mannings
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 131, Issue 2, p. 130 –138
  • DOI:  10.1049/ip-f-1.1984.0022
  • Type: Article
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  • p. 130 –138 (9)
    Time-compression multiplexing (TCM) is a spectrally efficient, time-domain multiplexing method, which is an alternative to the conventional and widely used frequency-division multiplexing technique (FDM). The paper demonstrates the significant advantages of TCM over FDM when used over narrowband radio systems which contain inherent nonlinearities. Indeed, these nonlinearities can render FDM unusable for many applications, producing quite unacceptable levels of crosstalk for an adequate signal/noise performance. TCM, however, is shown to overcome this problem without utilising excessive bandwidth, usually associated with time-domain multiplexing systems that employ digital modulation: for example, pulse code modulation. The paper contains details of the design and performance of a fully operational, two-channel TCM prototype, including a simple, yet robust, synchronisation system, which is then compared with an FDM system with an equivalent bandwidth.
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Application of Gram-Schmidt algorithm to optimum radar signal processing
Decision tree design and applications in speech processing
  • Author(s): G.R. Dattatreya  and  V.V.S. Sarma
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 131, Issue 2, p. 146 –152
  • DOI:  10.1049/ip-f-1.1984.0024
  • Type: Article
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  • p. 146 –152 (7)
    The design and operation of the minimum cost classifier, where the total cost is the sum of the measurement cost and the classification cost, is computationally complex. Noting the difficulties associated with this approach, decision tree design directly from a set of labelled samples is proposed in this paper. The feature space is first partitioned to transform the problem to one of discrete features. The resulting problem is solved by a dynamic programming algorithm over an explicitly ordered state space of all outcomes of all feature subsets. The solution procedure is very general and is applicable to any minimum cost pattern classification problem in which each feature has a finite number of outcomes. These techniques are applied to (i) voiced, unvoiced, and silence classification of speech, and (ii) spoken vowel recognition. The resulting decision trees are operationally very efficient and yield attractive classification accuracies.
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Simple cyclic codes for burst errors
An analysis of quasi-synchronous AM mobile radio operation and recommended design parameter values
  • Author(s): R.E. Fudge
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 131, Issue 2, p. 156 –166
  • DOI:  10.1049/ip-f-1.1984.0026
  • Type: Article
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  • p. 156 –166 (11)
    Quasi-synchronous operation of a number of base transmitters is often used to provide extensive area coverage in land mobile radio systems. An analysis is made of the responses of an AM receiver operating in such a system. The effects of automatic level control and the muting action are shown to nullify any predictions made of system performance based on harmonic distortion of sinusoidal modulating tones. A limited analysis of the types of distortion likely to arise from the mismatch of modulation between transmitters is made in order to give a guide to the parameters to be explored in subjective trials. The results of, first laboratory-based and subsequently field-based, trials are presented and from them recommendations are made for the allowable limits which should be used for the design and maintenance of a quasi-synchronous AM system.
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Position, velocity and acceleration estimates from the noisy radar measurements
Autocorrelation function of the multiplexed sequence
M-ary continuous phase frequency shift keying with modulation index 1/M
  • Author(s): N. Ekanayake
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 131, Issue 2, p. 173 –178
  • DOI:  10.1049/ip-f-1.1984.0029
  • Type: Article
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  • p. 173 –178 (6)
    In the paper, two techniques for the detection of multilevel continuous phase frequency shift keyed signals with modulation index equal to the inverse of the number of levels (M-ary CPFSK) are described. The first technique is a noncoherent technique which is similar to the conventional differentially coherent detection method of DPSK and the error rate of this detector is equal to the error-rate in DPSK. The second technique is a coherent technique which utilises a coherent carrier, and the detection method is similar to the coherent detection and differential decoding of differentially encoded PSK. The error rate in this case is equal to the error rate in coherent-detection/differential-decoding of PSK. Finally, expressions are derived for the autocorrelation functions and the power spectral density functions of M-ary CPFSK. By numerical computation, it is shown that M-ary CPFSK have approximately the same autocorrelation function and approximately the same power spectral density function regardless of the number levels when M ≥ 4. The power spectral characteristics of M-ary CPFSK are compared with those of M-ary PSK.
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Detection probability of a partially fluctuating target
  • Author(s): E. Dalle Mese  and  D. Giuli
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 131, Issue 2, p. 179 –182
  • DOI:  10.1049/ip-f-1.1984.0030
  • Type: Article
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  • p. 179 –182 (4)
    In this paper we consider the problem of target detection in the case that the received signal can be considered a mixture of scan-to-scan and pulse-to-pulse fluctuating signals. We analyse in detail a model which is a simple generalisation of the popular Swerling fluctuations models.We study the incoherent receiver which use postdetection integration and derive a closed form expression for PD which depends on the signal/noise ratio, the number of integrated pulses, the false-alarm probability and the ratio between the scan-to-scan to the pulse-to-pulse fluctuating power. Finally, we make some comparisons with results obtained for standard target models.
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Evaluation of hybrid error control systems
Error probability of QASK with rectangular and circular symbol constellations in the presence of intersymbol quadrature channel and adjacent channel interference
  • Author(s): I. Korn
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 131, Issue 2, p. 194 –202
  • DOI:  10.1049/ip-f-1.1984.0032
  • Type: Article
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  • p. 194 –202 (9)
    In the paper we study the effect of intersymbol, quadrature channel and adjacent channel interference (in addition to Gaussian noise) on the error probability of M-ary quadrature amplitude modulation (QAM) with M = 4, 16 symbols and phase shift keying (PSK) with M = 4, 8 and 16 symbols, which are special cases of quadrature amplitude shift keying (QASK) with a rectangular and circular constellation. The transfer function of the system for the main signal is a raised cosine with excess bandwidth β, and the receiver filter is matched to the transmitter filter. The interfering signal is of the same type as the main signal, but its carrier frequency differs from the carrier frequency of the main signal by the frequency fs. In the paper we also present the necessary formulas for the computation of error probability in the presence of frequency selective fading.
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Multiple open-loop interference canceller for a rotating search radar
Pseudobinary Viterbi detector
  • Author(s): A.P. Clark  and  M. Clayden
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 131, Issue 2, p. 208 –218
  • DOI:  10.1049/ip-f-1.1984.0034
  • Type: Article
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  • p. 208 –218 (11)
    Among the detection processes that have recently been described for use in a 9600 bit/s modem are ‘pseudobinary’ processes that are developments of the pseudobinary Viterbi detector. Although no information has been published on the latter, it is of considerable interest both in its own right and in its performance relative to that of other detectors. The aim of the paper is to correct this omission. The pseudobinary Viterbi detector effectively recodes the received multilevel data signal into a binary signal having the same element (symbol) rate as the original signal and implements the conventional Viterbi-algorithm detection process for the corresponding binary signal, thus verygrcatly reducting the complexity of the detector. The paper considers this detector and also a basically different technique, that is a development of a conventional nonlinear qualiser. The two systems may be used with multilevel signals in many different applications and are studied here in an application of digital data transmission at 9600 bit/s over the pulic switched telephone network, where the transmitted signal is a 16-level QAM signal. The particular development of the nonlinear equaliser studied here has not previously been tested under these conditions, and it has furthermore been found to have an interesting relationship with the pseudobinary Viterbi detector. After describing the two detection processes, the paper presents the results of computer-simulation tests over models of two different telephone circuits, comparing the tolerances to additive white Gaussian noise of various arrangements of each process.
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Measurement of signal to quantising-noise ratio in ADPCM systems and its implications for echo cancellation
  • Author(s): P.J. See  and  N.J.A. Forse
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 131, Issue 2, p. 219 –222
  • DOI:  10.1049/ip-f-1.1984.0035
  • Type: Article
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  • p. 219 –222 (4)
    It is questioned whether the standard pulse code modulation (PCM) quantisation distortion test using a narrow band of noise is appropriate to adaptive systems. An investigation of such measurements has been carried out in relation to the use of echo cancellers, where the amount of echo cancellation that can be achieved is a function of the available signal/noise ratio. The recommended performance test for echo cancellers gives results consistent with those obtained from the recommended test on PCM systems, but not with those obtained from the latter test on adaptive systems such as adaptive differential PCM(ADPCM). A wideband test has been adapted from analogue intermodulation distortion measurement practice and realised using a Fourier analyser, both to produce the test signal and to measure the resulting distortion products. The method has given results consistent with the performance of echo cancellers in a software ADPCM environment. An alternative test is also proposed, based on the performance of such echo cancellers, which offers scope for the development of a portable distortion measurement instrument.
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Rapid acquisition techniques in CDMA spread-spectrum systems
  • Author(s): J.W. Mark  and  I.F. Blake
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 131, Issue 2, p. 223 –232
  • DOI:  10.1049/ip-f-1.1984.0036
  • Type: Article
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  • p. 223 –232 (10)
    A rapid acquisition scheme for code division multiple access (CDMA) spread-spectrum systems which utilises partial correlation of maximum length sequences is investigated. The method involves subsequence matched filtering (SMF) to acquire sync. and feedback control to verify sync. acquisition. Expressions of probabilities of sync. acquisition, false alarm, false dismissal and mean acquisition time are derived. Numerical results for a multiuser environment are presented. Acquisition performance for a single-user case is compared with those of the RASE and RARASE methods. The SMF method offers rapid sync. acquisition over a wide range of signal/noise ratios.
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Radar mortar locator development in the UK: the first 30 years
Erratum: Error patterns in correlators with four-level quantisation
Baseband video distortion in memoryless nonlinear bandpass amplifiers

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