Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635855
Title: A method of noise cancellation for low frequency radio signals
Author: Ahmad, Z. A.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1983
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Abstract:
This study is concerned with the use of a feature of correlation which provides information on the rate at which a function changes to determine the phase information of a noisy radio signal at very low frequency. The digital correlation process involving multiplying digitised samples of the input waveform with that of the reference waveform is described in detail. Phase information is estimated from the peaks or the minima of the correlation function. Chapter 1 outlines the VLF communication and propagation characteristics with special emphasis on Omega transmissions, and briefly describes the noise factors affecting VLF propagation. Various methods of determining phase information of VLF radio signals are studied and an alternative method using a correlation technique is detailed in Chapter 2. Several methods of noise reduction of signals in the VLF band have been reviewed in Chapter 3, and an alternative method utilising the averaging feature of correlation is described. Chapter 4 looks at the theory on correlation techniques and digital correlation, and points to the principles on which lays the basis of the application in this work. Chapter 5 illustrates the overall system concept, the operational procedures and the typical experimental strategy to execute the correlation process. The reception of ON-OFF Omega signal is enhanced by the preamplifier and the principal filtering circuits. The I.F. signal is sampled and decoded to binary form. The digital data is correlated with the stored reference amplitude. The correlation value per centicycle is accumulated, stored and later displayed numerically using LEDs and graphically using a chart recorder. Chapter 6 discusses the results of several correlation tests performed by the system and subsequently derives the phase informations. This chapter concludes with suggestions for further considerations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.635855  DOI: Not available
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