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

This article proposes a method for the measurement of phase noise (PN, or PM noise) and amplitude noise (AN, or AM noise) of digital-to-analog converters (DACs) and direct digital synthesizers (DDSs) based on the modulation-index amplification. The carrier is first reduced by a controlled amount (30...

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Bibliographic Details
Published in:IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2020-02, Vol.67 (2), p.431-439
Main Authors: Calosso, Claudio E., Cardenas Olaya, A. Carolina, Rubiola, Enrico
Format: Article
Language:English
Subjects:
Amplification
Amplitude modulation
Amplitudes
Analog-digital integrated circuits
Attenuators
Background noise
Clocks
Digital to analog conversion
Digital to analog converters
Engineering Sciences
Flicker
Frequency measurement
General Physics
Instrumentation and Detectors
Instruments
integrated circuit noise
Noise
Noise measurement
Other
Phase measurement
Phase noise
Physics
Sidebands
signal synthesis
Synthesizers
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Summary:This article proposes a method for the measurement of phase noise (PN, or PM noise) and amplitude noise (AN, or AM noise) of digital-to-analog converters (DACs) and direct digital synthesizers (DDSs) based on the modulation-index amplification. The carrier is first reduced by a controlled amount (30-40 dB) by adding a reference signal of nearly equal amplitude and opposite in phase. Then, residual carrier and noise sidebands are amplified and sent to a conventional PN analyzer. The main virtues of our method are: 1) the noise specs of the PN analyzer are relaxed by a factor equal to the carrier suppression ratio and 2) the capability to measure the AN using a PN analyzer with no need for the analyzer to feature AN measurement. An obvious variant enables AN and PN measurements using an AN analyzer with no PN measurement capability. Such an instrument is extremely simple and easy to implement with a power-detector diode followed by an FFT analyzer. Unlike the classical bridge (interferometric) method, there is no need for external line stretcher and variable attenuators because phase and amplitude controls are implemented in the device under test. In one case (AD9144), we could measure the noise over 10 decades of frequency. The flicker noise matches the exact 1/f law with a maximum discrepancy of ±1 dB over 7.5 decades. Due to the simplicity, reliability, and low background noise, this method has the potential to become the standard method for the AN and PN measurements of DACs and DDSs.
ISSN:0885-3010
1525-8955
DOI:10.1109/TUFFC.2019.2943390