The universal application of switching regulators, combined with the powered systems potential for supply noise sensitivity, mandates the need for a reliable noise measurement technique. Actually, switching regulator "noise" isn't really noise at all, but coherent, high frequency residue directly related to the regulators switching. This residue, composed of fundamental switching frequency ripple and wideband harmonic, is the measurand.
Typically, amplitudes of 100µV to 10mV in a 100MHz bandwidth are of interest. This video presents a technique for measuring this "noise", verifies the method to insure meaningful results and concludes with a laboratory demonstration.