A Low-Temperature Microwave Noise Standard

Uncertainty of Radiometer Calibration Loads and Its Impact on Radiometric Measurements

“…The physical temperature of an object is the temperature that can be measured at its surface using a thermometer. We call RJ temperature the temperature that is related to the radiation from a blackbody, which results from its physical temperature as (1) where is the Planck constant, is the frequency, and is the Boltzmann constant. Brightness temperature of an object is related to the power spectral density per 0018-9480 © 2014 IEEE.…”

“…The two common methods of creating a CL with liquid nitrogen (LN2) are to submerge a matched load in liquid nitrogen [1] and to view a cooled absorber with an antenna connected to the radiometer [2]- [4].…”

“…Commonly viewed scenes have low emissivities or physical temperatures, leading to low scene brightness temperatures. Therefore, substantial effort has been given to construct cryogenic loads (CLs) [1]- [4]. These loads are either high performance, simple, or inexpensive, but none combine all these features with a detailed uncertainty analysis.…”

Commission 1: Progress in Radio Measurement Methods and Standards

“…For voltage, uncertainties of the order of 0.1% at 0.1 GHz, 1% at 1 GHz, and < 5 % at 10 GHz were obtained, as were 78øK were achieved [Trembath et aI., 1968;Stelzried, 1968]. Problems associated with noise standards and measurements were examined [Miller et al, 1967;$telzreid, 1968], a method of calibration that is independent of the reflection coefficient was devised [Wait and Nemoto, 1968], and an accurate method of calibrating a coaxial noise source in terms of a waveguide standard was concocted [Engen, 1968].…”

Análisis y diseño de un patrón de ruido térmico de 10 MHz a 26,5 GHz en tecnología coaxial

“…De la bibliografía existente sobre patrones de ruido [ACH99], [BUC93], [DAY73], [DAY84], [KES86], [MIL67], [RAN99], [STE68] y [TRE68] se ha utilizado como modelo para el futuro patrón de ruido el presentado en la nota técnica NBS 1074 del NIST [DAY84]. Siguiendo dicha nota técnica se ha definido una estructura de patrón de ruido, como la que se muestra en la figura de esta página, compuesta por una línea coaxial de aire terminada en su parte inferior con una carga adaptada de banda ancha sumergida en nitrógeno líquido y un circuito de agua en su parte superior en contacto con el conductor exterior del coaxial, para forzar una estabilización a la temperatura ambiente.…”