Impact of measurement system noise figure and gain on emissions measurements above 1 GHz

The ability to make weak signal emissions measurements at frequencies above 1 GHz id directly related to system noise figure, which ultimately sets the system noise floor. Contributing factors to the measurement system noise figure are the front-end coax loss, preamplifier noise figure, preamplifier gain, measurement device (spectrum analyzer or receiver) noise figure and measurement system configuration. Attention to the effects of these factors on EMC measurements is generally not understood. The system noise floor will have a major impact on the ability to detect and measure a weak signal. Impact on other factors, such as the introduction of intermodulation products by the preamplifier is not discussed in this paper.