Experimental determination of the kurtosis of RF noise in microwave low-noise devices

The degree of the Gaussian nature of the white noise present in microwave l ow-noise devices is experimentally investigated. The chosen experimental te chnique consists of simultaneously digitizing four versions of the noise wh ich are amplified by four parallel independent amplifiers. The four indepen dent signals are then used to compute the second, and, to a good approximat ion, the fourth moment of the noise. The ratio of the fourth moment to the square of the second moment is the kurtosis of the noise. Gaussian processe s are characterized by a kurtosis equal to 3. A deviation from this value g ives an indication about the degree of non-Gaussian nature of the noise. By using this technique, the effect of the additive noise introduced by the a mplifiers is strongly reduced. In our experiments, the degree of the Gaussi an nature of the white noise of some microwave devices is measured in the f requency range from 100 to 500 MHz, In all the investigated devices, the ku rtosis is found to be very close to 3. (C) 2000 Elsevier Science Ltd. All r ights reserved.