Abstract :
The current noise performance in the 100 MHz to 300 GHz range of transistors, paramps, masers, Schottky diode mixers, and superconductor-insulator-superconductor (SIS) mixers will be summarized and compared with the natural limits due to cosmic noise, atmosphere, and quantum effects. Recent advances concerning cooled FET amplifiers, cryogenic coolers, and millimeter wave mixers will be discussed.