A digital signal processing instrument for real time phase noise measurements

A digital-signal-processing-based instrument for phase noise measurement on sinusoidal signals is described. It incorporates a special hardware architecture, which is made up of a core digital signal processor that is connected to a data acquisition board, and takes advantage of a new measurement procedure based on a quadrature demodulation scheme, which has been proposed by the authors. Thanks to an optimized implementation of this procedure, the instrument exploits all its hardware resources to achieve high performance and real-time operation. For input frequencies of up to some hundreds of kilohertz, the instrument proves to be capable both of updating phase noise power spectrum while seamlessly capturing the analyzed signal into its memory and of granting frequency resolution as good as a few units of hertz.