The first two chapters of this thesis will introduce the background of this project, the research status in domestic country and abroad, and the new technology on VLBI.

The front end in a digital broadcasting receiver means the part of circuit that converting RF analog signal to baseband digital data stream.

Conventional dual up-conversion transmitter usually employs an intermediate frequency (IF) mixer and a radio frequency (RF) mixer to convert baseband user signal to IF and RF in sequence.