This SPIE Defense & Security paper by Handel investigates 1/f noise and phase noise in AlGaSb/InAs/AlGaSb double-barrier resonant tunneling diode (RTD) oscillators. The research examines low-frequency noise sources in antimonide-based RTD structures and how this noise converts to phase noise in RTD-based terahertz oscillators, analyzing quantum 1/f contributions and providing design strategies for minimizing phase noise in compact solid-state terahertz sources for imaging, spectroscopy, and high-speed wireless communications applications.