Terrestrial transmitters for digital services to the home

The transition to digital transmission will not be easy. In many countries the spectrum is already full and it may be necessary to turn off some of the existing services to provide space for these new transmissions. However the benefits are significant. Digital techniques allow up to four television transmissions to be fitted in the space occupied by one existing transmission, while at the same time providing additional data delivery capability. The paper explores the differences between various digital modulation schemes, comparing them with existing systems for analogue broadcast transmission. For the purposes of this comparison a transmitter is considered as two parts; an exciter where modulation, correction and frequency up-conversion are performed, and an RF amplifier where high power tube or solid state amplifiers are used to produce the required power for transmission, whilst also maximising energy conversion efficiencies.