Measurement of 1-40 GHz radiated electric field spurious emissions

Measurement of radiated electric field emissions above 1 GHz is required in the US by FCC and Bellcore. The highest frequency to be investigated can be as high as 40 GHz for equipment which operates below 10 GHz. This paper discusses two common methods, the direct amplification method and the mixer solution, for making radiated emission measurement above 1 GHz; as well as pro-and-cons of each method. Also addressed is a method for verifying the accuracy and sensitivity of the measurement system used. As an example, the HP84125C system is used which employs the direct amplification method. In this study, how to estimate the near- and far-field boundary of a broadband horn antenna, such as double ridged waveguide horn antenna, is also explored. From the study, it concludes that the equivalent aperture size of a broadband horn antenna should be used instead of the maximum physical aperture size in determining the minimum distance of far-field observation.