Design of High Performance Linear Frequency Modulation Source for Terahertz Imaging

The technology of direct digital synthesis (DDS) has an important role in the modern generation of signal waveform, of which the advantages are output signal frequency high, the high resolution of frequency and the low phase noise. In this paper, the four modes of frequency waveforms of signal source based on the DDS chip are designed and researched based on the field programmable gate array (FPGA), with used for the Terahertz imaging technology. The four modes are single-tone frequency of internal trigger, linear frequency sweeping of internal trigger, single linear frequency sweeping of external trigger and multiple linear frequency sweepings of external trigger.