Maury Microwave has developed the NBS-Series of primary noise standards for measurement and calibration of extremely low noise figures and noise temperatures. The NBS-Series is based on the primary physical constants of thermal noise and blackbody radiation and is used for noise source calibration, radiometer testing and verification, and low noise amplifier (LNA) measurements. The series is designed as a broadband primary noise standard, eliminating the need for annual single-frequency calibrations.
The system uses a precision waveguide horn with known insertion loss to monitor a blackbody embedded in a cryogenic liquid nitrogen bath. This construction supports lower noise temperature, improved repeatability, and reduced uncertainty associated with temperature gradients, as the horn operates at room temperature while the thermal noise is generated by the liquid nitrogen-cooled absorber. Lower insertion loss also contributes to improved measurement accuracy and reduced reflection loss uncertainty.
The NBS-Series includes a cavity and reservoir with a circulating water bath, with one water bath capable of supporting up to three cavities within a distance of 10 feet (3 meters). The system also directs the boil-off of liquid nitrogen to purge air, moisture vapor, and carbon dioxide from the microwave cavity, removing the need for helium-based equipment.
Maury Microwave provides the NBS-Series across waveguide bands from 18 GHz to 500 GHz. Additional frequency ranges can be supported by replacing the horn, allowing the system to be adapted for different applications. The design also enables integration with switches and room temperature terminations.
The series supports applications including noise temperature calibration, noise source calibration, radiometer reference sources, LNA noise figure measurements, antenna system effective input noise temperature testing, and SATCOM earth station conformance verification. Noise and radiometer calibration systems can also include optional low-loss switches and ambient temperature terminations, which are used as hot noise sources to reduce the impact of reflections on measurement accuracy.
Maury Microwave provides the system with accessories including a wooden horn case, hoses, couplings, and cables. The offering also includes configurable components such as the cavity and dewar assembly, a PC-based controller with circulating water bath, precision thermometer and barometer, interchangeable horns for different frequency bands, and a liquid nitrogen reservoir with an automatic filling system. Optional assemblies include ambient temperature terminations and switch configurations aligned with the selected frequency range.