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Title: Philosophy and realization of SSB receivers for sound broadcasting
Author: Heng, Y-C.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1983
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AM broadcasting, still one of the most important communication media, has suffered from interference, congestion and deteriorating reception quality almost since it first began in the 1920's. The aim of research into broadcast receiver development is to improve this means of communications, so that more people may be better served by the services provided by AM sound broadcasting. Possible remedies have been rained and discussed; among them, a single sideband system of transmission is now the most favoured. It is indeed proposed that SSB should supersede the existing AM system over a 20 year transition period. The success of an SSB broadcast system, however, will rely mainly on a suitable SSB and compatible AM broadcast receiver, which must be easy to operate, reasonably priced and of good quality. The demodulator is a key part in receiver design, and product demodulation is chosen because it enhances reception quality and also has the ability to demodulate SSB signals. It is however necessary to regenerate an exalted carrier component for acceptable product demodulation from the input signal. This matter is discussed at length and preference for a new so-called Feedback Detector circuit is demonstrated. A mathematical model for the modes of operation, which are two-fold, are developed and confirmed by measurement. This detailed knowledge of the system characteristics is applied to practical designs. Using experimental detector circuits, the detector verifies that it is able to regenerate the carrier component form an input signal whose carrier component level is as low as 30dB lower than the side-bands. A regenerated carrier lock-range of 3 kHz is shown to be feasible for a 455 kHz input signal, which is a conventional IF frequency. Flexibility is one of the advantages of the detector's design. With one or two adjustments, an integrated MSI version of the detector can meet a number of customer's design requirements for different input signal levels, carrier suppression levels, and lock range. To complete the requirements of a broadcast receiver, some digital tuning schemes with frequency synthesisers are discussed and described, including the idea of tuning by channel. Finally, on-air evaluation tests are made using (1) a conventional tuned receiver and (2) a digitally-tuned frequency synthesised receiver, in order to demonstrate the ability of the detector to regenerate a carrier accurately and overcome fading distortion. It is believed that mass-produced circuits of this kind will make SSB reception realisable at low cost and assist the adoption of SSB broadcasting schemes. The consequential improvement in quality and convenience will bring information and entertainment to a wider audience.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available