A complete system to generate electrical noise with arbitrary power spectral density

Reliability and performance of electronic devices are significantly dependent on their noise rejection capability that is usually investigated since their early production stage as well as during the scheduled maintenance. To this aim, white noise sources are mostly available on the market and usually to the purpose, whereas the use of generators capable of producing coloured noise (actually, very uncommon) should be advisable in most of applications. If arbitrary waveform generators (AWGs) are taken into account, either transient signals in single shot generation mode or periodic signals in continuous generation mode can only be produced due to the finite available memory; unfortunately, both modes are not suitable to emulate noise. To overcome the considered limitations, this work presents the design and implementation of a coloured noise generator that offers the possibility of tailoring the noise spectral content to the desired application. As it can be expected, performance of the generator changes according to different hardware selections; with specific regard to the proposed implementation, it performs as good as state of art solutions in terms of both bandwidth and flexibility. It is composed of a digital section implemented on field programmable gate arrays (FPGA) and a digital-to-analogue converter (DAC) mandated to generate the desired analogue output. The bandwidth of the generated noise can be selected up to a maximum of 50 MHz while the evolution of power spectral density versus frequency can be defined with a resolution equal to 0.4% of the bandwidth. Thanks to suitable digital signal processing techniques, spurious components laying outside the selected bandwidth are hardly attenuated.