Review of recent progress on solid-state millimeter-wave and terahertz signal sources

The research and development on solid-state source generators have been making progress on chip, aiming to generate low noise, high output power, and high DC-to-RF energy efficiency in the millimeter-wave (mmW) and terahertz (THz) domains. In particular, their full integration in silicon technologies, such as advanced complementary-metal-oxide-semiconductor processes, has motivated the design of low cost, high performance, and miniature integrated circuits (ICs). This manuscript focuses on providing a general overview of recent progress on solid-state signal source operating beyond 60 GHz till the THz region, from the perspective of operating principle, design metrics, state-of-the-art performance, testing results, and their applications in emerging mmW/THz systems. Finally, with the use of fully integrated source generators, several design arts are highlighted to showcase the recent advances of ICs toward millimeter-wave and THz radiation, imaging, coupled oscillator network (CON), and communication. Potential future research directions enabled by mmW/THz signal sources will be envisioned.