Flicker Suppressed Direct Digital: Next generation of measurement systems for time and frequency metrology

Published

March 9, 2026

Author(s)

Marco Pomponio, Archita Hati, Craig Nelson

Abstract

In this article, we present a new and innovative technique that reduces the close-to-the-carrier noise floors in direct digital measurement systems. For a 100 MHz carrier, in respect to our previous state-of-the-art direct digital measurement system attempt, we report a noise floor reduction of over 35 dB in the flicker region for both phase and amplitude noise, and greater than a factor of 20 improvement in Allan deviation. Moreover, this technique reduces the impact of analog-to-digital converter's voltage reference noise and aperture jitter on the system noise floor, allowing the construction of multichannel systems for timescales applications while maintaining the same performance levels. We call this new method flicker-suppressed direct digital. At 100 MHz for a single channel, we report single sideband residual phase noise floor of L(1 Hz) = −147 dBc/Hz, with a flicker corner of about 0.03 Hz. The single channel residual Allan deviation noise floor for the same carrier is less than 1.3 × 10−16 at 1 second averaging time (tau) with a 0.5 Hz bandwidth. Further improvement can be achieved with the use of cross-correlation techniques. To our knowledge, this represents the lowest flicker noise and Allan deviation performance ever reported for a digital measurement system.

Citation

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control

Pub Type

Journals

Download Paper

https://doi.org/10.1109/OJUFFC.2026.3672064

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Keywords

Allan Deviation, Amplitude Noise, Analog-to-Digital Converter (ADC), Cross Correlation, Digital Down Conversion, Direct Digital Measurement, Field Programmable Gate Array (FPGA), Flicker Noise, Phase Noise

Citation

Pomponio, M. , Hati, A. and Nelson, C. (2026), Flicker Suppressed Direct Digital: Next generation of measurement systems for time and frequency metrology, IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, [online], https://doi.org/10.1109/OJUFFC.2026.3672064, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=959805 (Accessed May 21, 2026)

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