primary standard broadband thermal noise

摘要

primary standard broadband thermal noise. coaxial system for a primary pattern employed in tracing sources of thermal noise, comprising a coaxial transmission line (1) and a ring (100), a portion of the coaxial transmission line (1) submerged in liquid nitrogen being and another part of the coaxial transmission line (1) surrounded by a water circuit (3) wherein the ring (100) is comprising said coaxial transmission line (1) an outer conductor (10) and an inner conductor ( 20), both drivers (10, 20) joined by the ring (100) is made of a material that guarantees the thermal conductivity between the outer conductor (10) and the inner conductor (20), the ring (100 comprising) a central section (101) in contact along its length with the inner surface of the outer conductor (10), and that the ratio between the radius of the inner conductor (20) and the outer radius of the ring (100) is such that throughout the length of the ring (100) impedance is the same as the nominal impedance of the coaxial line (1).