Phase-Noise and Amplitude-Noise Measurement of DACs and DDSs

This article proposes a method for the measurement of Phase Noise (PN) and Amplitude Noise (AN) of Digital-to-Analog Converters and Direct Digital Synthesizers. The main virtues of our method are (1) owing to RF amplification of the noise sidebands, the noise specs of the PN analyzer are relaxed by a factor of at least 20 dB, with respect to the noise of the device under test, and (2) the capability to measure AN using a phase noise analyzer, with no need for the analyzer to feature AN measurements. An obvious variant enables the same measurements using only an AN analyzer (i.e., a power-detector diode followed by a FFT analyzer), with no need for PN measurement capability. Exploiting the device-under-test's internal amplitude and phase control, there is no need for external line stretcher and variable attenuators. In one case (AD9144), we observed a flicker PN on 8 decades of frequency, with a discrepancy within ±1 dB with respect to the exact 1/f slope over 7 decades. This summary is an early draft of a larger article that will be submit for the 2019 IFCS Special Issue of the IEEE Transact. on UFFC.