The Application of Spectrum Conserving Modulation Methods to High-Capacity Digital Microwave Radio Relay Systems

The planned introduction of digital switching by the British Post Office has motivated the development of high capacity digital transmission systems. It is intended that the radio relay bands currently carrying FDM-FM analogue transmissions will be re-used for digital systems. The application of spectrum conserving techniques has been found necessary for the realisation of digital radio-relay systems to make efficient use of the spectrum. Various modulation methods have been investigated and this paper illustrates how the application of spectrum conserving modulation methods influences the complexity and required technical standard of the equipment.