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IEE Proceedings F (Communications, Radar and Signal Processing)

Volume 128, Issue 5, October 1981

Volumes & issues:

Volume 128, Issue 5

October 1981

Improvements in use of congested spectrum for land mobile radio service by adoption of bandsharing spread-spectrum system with TV broadcast channels
  • Author(s): M.S. Shipton  and  R.F. Ormondroyd
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 128, Issue 5, p. 245 –260
  • DOI:  10.1049/ip-f-1.1981.0043
  • Type: Article
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  • p. 245 –260 (16)
    The paper examines the possibility of private mobile radio users sharing the RF spectrum with the television broadcast channels on a mutual noninterference basis, with the aim of accommodating greater spectrum efficiency. A comparison is made between the use of conventional narrowband modulation methods, such as AM, FM and SSB, and the broadband direct-sequence spread-spectrum modulation schemes as contenders for a bandshared system. These comparisons are made using the criteria for establishing imperceptible visual interference on the TV screen for both modulation schemes. The results show that, for a base station sited in Central London with a service area typically that of the Greater London region, 16 MHz of bandwidth may be gained by the use of bandsharing, with either narrowband or spread-spectrum modulation schemes, for guaranteed interference-free TV reception. The paper also shows that, for the same base-station site covering the same area, a further 72 MHz of bandwidth could be opened up by the use of direct-sequence spread-spectrum transmissions, which would otherwise be unavailable for narrowband use. Such a system would also have the advantage that it could be made covert to eavesdroppers using conventional AM or FM receivers with only limited modification to existing transmitters and receivers, It is argued that spread-spectrum techniques can open up significant amounts of bandwidth, by bandsharing, not available to conventional modulation schemes in many urban environments where the normal TV-channel allocations are almost fully utilised, as they appear to be in the Greater London area.
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Virtual polarisation adaptation a method of increasing the detection capability of a radar system through polarisation-vector processing
  • Author(s): A.J. Poelman
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 128, Issue 5, p. 261 –270
  • DOI:  10.1049/ip-f-1.1981.0044
  • Type: Article
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  • p. 261 –270 (10)
    The ratio of the average target-signal power to the average unwanted-signal power at the input of a radar detection receiver can be significantly increased by applying the method of clutter/interference suppression described in the paper. The polarisation state of the emissions, the object-backscatter field, and the interference field are all taken into account in a technique referred to as ‘virtual adaptation’ of the polarisation state of the transmit and receive antennas. This technique can be used to complement filtering techniques in the frequency and space domains. Attention is specifically drawn to the potential advantages of multinotch polarisation suppression filters of the ‘logic-product’ type, which might have applications in cases where there are uncertainties regarding the polarisation state of unwanted signals that are to be suppressed.
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Fast converging stochastic gradient algorithm
Ground-wave propagation. Part 1: Theory for short distances
Ground-wave propagation. Part 2: Theory for medium and long distances and reference propagation curves
Adaptive mean-square-error transversal equaliser
  • Author(s): M.J. Hawksford  and  N. Rezaee
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 128, Issue 5, p. 296 –304
  • DOI:  10.1049/ip-f-1.1981.0048
  • Type: Article
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  • p. 296 –304 (9)
    A new adaptive equaliser for the minimisation of mean-square error has been developed for use over a wide range of transmission channels. The equaliser comprises a transversal filter (with variable tap gains) and a processor. Using the processor, the tap-gain-adjustment information is derived from blocks of samples taken from the channel output. The processor operates independently of the channel speed and can provide variable step size for adjusting the tap gains of the transversal filter and flexibility in the implementation of the equaliser in terms of the channel speed and the equaliser realisation. Analytical and computer-simulation results are presented showing the equaliser performance.
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Sequential radar detection of border penetration
Signal processing for target detection in experimental phased-array radar ELRA
Analysis of response of FM mobile receiver in quasisynchronous field
  • Author(s): M.O. Al-Nuaimi
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 128, Issue 5, p. 317 –322
  • DOI:  10.1049/ip-f-1.1981.0051
  • Type: Article
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  • p. 317 –322 (6)
    Frequency-modulated quasisynchronous (QS) mobile radio systems are of benefit to PMR users already committed to FM in the solution of radio coverage problems. The paper analyses the performance of a conventional FM receiver in the overlap area of two QS transmitters and gives graphs quantifying this performance as a function of system parameters. The paper suggests design criteria for a practical system and shows, on the basis of speech-intelligibility tests, that satisfactory performance of a QS FM system is possible throughout the coverage area, except at those pockets where the two received carriers have approximately equal strength. Here, a receiver modification is proposed which can result in marked improvement in the quality of reception.
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Computer aids for code spectra calculations
  • Author(s): G.S. Poo
  • Source: IEE Proceedings F (Communications, Radar and Signal Processing), Volume 128, Issue 5, p. 323 –330
  • DOI:  10.1049/ip-f-1.1981.0052
  • Type: Article
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  • p. 323 –330 (8)
    A suite of computer programs has been developed to calculate the power spectral density of a wide range of transmission codes. Suitable user interfaces are provided for the automatic construction of the state diagram, the encode function and the codework matrices. The output includes the attractive analytical formula in closed-cosine form, the autocorrelation function and plots, in colour, for Dirac delta and raised-cosine pulses. The paper presents results on the analysis of zero-mean-disparity block codes, general binary/tertiary codes with multiaphabets and an adaptive code based on the Howells-Woodman Miller codes.
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Digital signal processing for target detection FMCW radar
Book review: Digital Signal Processing

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