Abstract

Their article reports on the measurement of phase noise and amplitude noise of direct digital synthesizers (DDS), ultimately intended for precision time and frequency applications. The DDS noise S ϕ (f) tends to scale down as 1/ν 0 2, until the noise hits the limit due to the output stage. The spurs, however disturbing in general, sink power from the white noise. Voltage noise can be more critical in the digital power supply than in the analog supply. Temperature fluctuations are an issue at 10−3 … 1 Hz Fourier frequency. Passive stabilization (thermal mass) proves to be useful. Other paramours affect the phase noise, like the clock frequency and power. The amplitude 1/f noise is of the order of −110 dB(V2/V2)/Hz in some reference (typical) conditions. Owing to the page and file size limitations, only a small part of the available data can be published here. An extended and free version of this article is available on http://rubiola.org and on http://arxiv.org.

Highlights

  • After the original article [1] published more than 40 years ago, the direct digital synthesizers (DDS) is a mature piece of technology

  • The DDS owes its success to the frequency range, to the high resolution, to the fast frequency switching, to the small size and power, and to the suitability to almost-all-digital single-chip implementation

  • The newcomer can refer to a technical tutorial [2] and to two books [3], [4]

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Summary

INTRODUCTION

After the original article [1] published more than 40 years ago, the DDS is a mature piece of technology. The DDS owes its success to the frequency range (dc to GHz and beyond), to the high resolution (μHz), to the fast frequency switching (sub-μs), to the small size and power, and to the suitability to almost-all-digital single-chip implementation. A number of experimental issues of phase noise are not addressed properly in the literature, and amplitude noise is totally absent.

Notation
DDS OPERATION
The Egan model for phase noise
Quantization noise
DAC resolution
Experimental method
Phase noise
Power supply rejection
Thermal effects on the output phase
10 MHz output
APLITUDE NOISE
10 MHz 20 MHz

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