It depends of what you mean for digital television.
If by digital TV (DTV) you mean the transmission of sound and image by digital signal, replacing the old analog signal it doesn't have a sole inventor. The first digital broadcasts started in the US in November 1998 and in the year 2006 the transition from analog to digital TV began globally.
You can find the information about the transition and the timeline here:
en.wikipedia.org/wiki/Digital_television_transition

If for Digital TV you mean High Definition TV (HDTV) the precursor was the Japanese TV station NHK. In 1968, the NHK engineers started developing the new standards for the HDTV technology that was first presented in the year 1983.In the year 1983 the Japanese TV Networks began broadcasting programs in HD, choosing the NHK's Hi-Vision format as standard.