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Communications, Radar and Signal Processing, IEE Proceedings F

Issue 2 • Date April 1984

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Displaying Results 1 - 22 of 22
  • Mean-square correlation of shift-register sequences

    Publication Year: 1984 , Page(s): 101 - 106
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (610 KB)  

    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. View full abstract»

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  • Serial data transmission over HF radio links

    Publication Year: 1984 , Page(s): 107 - 116
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1239 KB)  

    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. View full abstract»

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  • Simplified estimation of ray-path mirroring height for HF radiowaves reflected from the ionospheric F-region

    Publication Year: 1984 , Page(s): 117 - 124
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (824 KB)  

    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. View full abstract»

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  • Facsimile coding using symbol-matching techniques

    Publication Year: 1984 , Page(s): 125 - 129
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (691 KB)  

    In this paper, a symbol-matching technique for digital facsimile transmission is described. This technique results in data compression factors typically 2.5 to 3 times that obtained by the standard CCITT codes. New signal-modification techniques are also described. These distort the picture to be transmitted at a microscopic level to increase the correlation between pels. However, the resulting gains in data compression were found to be small. View full abstract»

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  • Comparison between time-compression multiplexing and frequency-division multiplexing over narrowband radio systems

    Publication Year: 1984 , Page(s): 130 - 138
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1029 KB)  

    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. View full abstract»

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  • Application of Gram-Schmidt algorithm to optimum radar signal processing

    Publication Year: 1984 , Page(s): 139 - 145
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (730 KB)  

    The paper deals with the application of Gram-Schmidt decorrelation algorithm to the clutter cancellation and useful signal enhancement in radar signal processing. The proposed system architecture is an adaptive implementation of the well known optimum processor. The performance of the selected approach is evaluated and compared with that of the optimum one. As a general result, the adaptation time is a few tens of range cells and the losses are negligible. Finally, the hardware complexity is briefly considered View full abstract»

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  • Decision tree design and applications in speech processing

    Publication Year: 1984 , Page(s): 146 - 152
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (882 KB)  

    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. View full abstract»

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  • Simple cyclic codes for burst errors

    Publication Year: 1984 , Page(s): 153 - 155
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (334 KB)  

    A subset of recently disclosed burst-error correcting codes are described. The procedure for constructing these codes is very simple. An illustrative example is included. The codes are very efficient for most burst lengths. It is found that the efficiency approached maximum possible for burst-error correcting codes as the burst length increases beyond 10. By virtue of the fact that the codes are cyclic, the circuitry of the codes is very simple. It is shown that the decoder circuitry is similarly simple and suitable for LSI. View full abstract»

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  • An analysis of quasi-synchronous AM mobile radio operation and recommended design parameter values

    Publication Year: 1984 , Page(s): 156 - 166
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1192 KB)  

    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. View full abstract»

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  • Position, velocity and acceleration estimates from the noisy radar measurements

    Publication Year: 1984 , Page(s): 167 - 168
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (223 KB)  

    A two-dimensional Kalman tracking filter is described for obtaining optimum estimates of position, velocity and acceleration of an aircraft whose acceleration is perturbed due to manoeuvres and/or other random factors. In a track-while-scan operation, a two-dimensional radar sensor is assumed to measure the range and bearing of the vehicle at uniform sampling intervals of time T seconds through random noise. The steady-state gain characteristics of the filter have been analytically obtained and the computer results are presented. View full abstract»

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  • Autocorrelation function of the multiplexed sequence

    Publication Year: 1984 , Page(s): 169 - 172
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (426 KB)  

    A multiplexed sequence is one produced in a specific way by two linear feedback shift registers generating PN sequences, in conjunction with a multiplexer. Such a sequence may be a possible candidate for use as a building block in a sequence generator of a stream cipher system. In this paper, we derive some results concerning the autocorrelation function of this sequence. View full abstract»

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  • M-ary continuous phase frequency shift keying with modulation index 1/M

    Publication Year: 1984 , Page(s): 173 - 178
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    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. View full abstract»

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  • Detection probability of a partially fluctuating target

    Publication Year: 1984 , Page(s): 179 - 182
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (477 KB)  

    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. View full abstract»

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  • Evaluation of hybrid error control systems

    Publication Year: 1984 , Page(s): 183 - 193
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1079 KB)  

    In the paper, the performances of hybrid as well as of ARQ and FEC systems are evaluated by simulation generating error statistics corresponding to a case of data transmission over local switched telephone lines. The channel model was based on finite time renewal processes. The criteria for a hybrid system with convolution codes were specially developed. The results show that, for simulated channel, characterised by dense bursts and many random errors in between, hybrid systems based on convolutional codes can improve the reliability considerably. View full abstract»

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  • Error probability of QASK with rectangular and circular symbol constellations in the presence of intersymbol quadrature channel and adjacent channel interference

    Publication Year: 1984 , Page(s): 194 - 202
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (757 KB)  

    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 ¿¿, 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. View full abstract»

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  • Multiple open-loop interference canceller for a rotating search radar

    Publication Year: 1984 , Page(s): 203 - 207
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (634 KB)  

    This paper describes the construction and operation of a triple open-loop interference canceller for a high-PRF high-rotation-rate search radar. Experimental results show that up to 25 dB reduction in jamming power can be achieved when countering the effects of one, two or three jammers present in the sidelobes of the main antenna, without significantly affecting target detection. Results also show substantial benefits even with strong main-beam jamming. View full abstract»

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  • Pseudobinary Viterbi detector

    Publication Year: 1984 , Page(s): 208 - 218
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1540 KB)  

    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. View full abstract»

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  • Measurement of signal to quantising-noise ratio in ADPCM systems and its implications for echo cancellation

    Publication Year: 1984 , Page(s): 219 - 222
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (363 KB)  

    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. View full abstract»

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  • Rapid acquisition techniques in CDMA spread-spectrum systems

    Publication Year: 1984 , Page(s): 223 - 232
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (977 KB)  

    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. View full abstract»

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  • Radar mortar locator development in the UK: the first 30 years

    Publication Year: 1984 , Page(s): 233 - 239
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1188 KB)  

    The advent of centimetric radar techniques in the early 1940's initiated the investigation of some rather novel system applications. One example is that of locating the firing position of hostile artillery. The basic problems in the weapon locating scene are reviewed and the evolutionary progression in UK system developments over a 30 year period is described. View full abstract»

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  • Erratum: Error patterns in correlators with four-level quantisation

    Publication Year: 1984
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  • Baseband video distortion in memoryless nonlinear bandpass amplifiers

    Publication Year: 1984
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (111 KB)  

    An expression is obtained for the spectra of the video baseband distortion resulting from the common amplification of multiple equal-amplitude equally-spaced (in frequency) FM/FDM carriers activated by similar video signals. View full abstract»

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Aims & Scope

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

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