198 research outputs found
Digital electronics based on red pitaya platform for coherent fiber links
No full textRecent improvements and continuous research on accurate clocks and frequency standards require the study of suitable tools and techniques for frequency transfer that minimize the added noise and allow fully exploiting these clocks in metrology applications. Different experiments performed during the last decade validated fiber links as the most performing tool for frequency transfer, reaching a statistical uncertainty of 10^-20 for thousands kilometers links. Recently, digital implementations have been used for metrological applications due to the flexibility, cost effective and compact solutions that can be achieved. In this paper, we propose a digital implementation for the detection and compensation of the phase noise induced by the fiber link. The beat note, representing the fiber length variations, is acquired directly with a fast Analog to Digital Converter (ADC) followed by a Tracking Numerical Controlled Oscillator (NCO). This reduces the component's latency and the communication delay between different blocks, increasing the tracking bandwidth. In addition, we report the characterization of the main components that allows foreseeing which are the limiting aspects and the expected performance of the complete implementation. The proposed system is being implemented on Red Pitaya, an open source platform driven by a Zynq, System on Chip (SoC) of Xilinx that contains a FPGA and an ARM processor embedded on the same chip
On the measurement of frequency and of its sample variance with high-resolution counters
No full text14 pages, 5 figures, 1 table, 18 referencesA frequency counter measures the input frequency averaged over a suitable time , versus the reference clock. High resolution is achieved by interpolating the clock signal. Further increased resolution is obtained by averaging multiple frequency measurements highly overlapped. In the presence of additive white noise or white phase noise, the square uncertainty improves from to . Surprisingly, when a file of contiguous data is fed into the formula of the two-sample (Allan) variance of the fractional frequency fluctuation , the result is the \emph{modified} Allan variance mod . But if a sufficient number of contiguous measures are averaged in order to get a longer and the data are fed into the same formula, the results is the (non-modified) Allan variance. Of course interpretation mistakes are around the corner if the counter internal process is not well understood
Phase noise and frequency stability in oscillators
No full textPresenting a comprehensive account of oscillator phase noise and frequency stability, this practical text is both mathematically rigorous and accessible. An in-depth treatment of the noise mechanism is given, describing the oscillator as a physical system, and showing that simple general laws govern the stability of a large variety of oscillators differing in technology and frequency range. Inevitably, special attention is given to amplifiers, resonators, delay lines, feedback, and flicker (1/f) noise. The reverse engineering of oscillators based on phase-noise spectra is also covered, and end-of-chapter exercises are given. Uniquely, numerous practical examples are presented, including case studies taken from laboratory prototypes and commercial oscillators, which allow the oscillator internal design to be understood by analyzing its phase-noise spectrum. Based on tutorials given by the author at the Jet Propulsion Laboratory, international IEEE meetings, and in industry, this is a useful reference for academic researchers, industry practitioners, and graduate students in RF engineering and communications engineering
Phase Noise and Frequency Stability in Oscillators
No full textPresenting a comprehensive account of oscillator phase noise and frequency stability, this practical text is both mathematically rigorous and accessible. An in-depth treatment of the noise mechanism is given, describing the oscillator as a physical system, and showing that simple general laws govern the stability of a large variety of oscillators differing in technology and frequency range. Inevitably, special attention is given to amplifiers, resonators, delay lines, feedback, and flicker (1/f) noise. The reverse engineering of oscillators based on phase-noise spectra is also covered, and end-of-chapter exercises are given. Uniquely, numerous practical examples are presented, including case studies taken from laboratory prototypes and commercial oscillators, which allow the oscillator internal design to be understood by analyzing its phase-noise spectrum. Based on tutorials given by the author at the Jet Propulsion Laboratory, international IEEE meetings, and in industry, this is a useful reference for academic researchers, industry practitioners, and graduate students in RF engineering and communications engineering.</jats:p
Long term behavior of operational amplifiers
No full textThe voltage and current offsets of two typical precision operational amplifiers with BJT and FET input respectively were continuously measured for two years. The paper presents the experiment, explains the method of data analysis and discusses the results. The long-term stability turns out to be limited mainly by random walk processes
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