Method for Reducing the “Noise Floor” of Digital Phase Fluctuation Analyzers

V. A. Karelin, A. S. Smelchakov

Transactions of IAA RAS, issue 52, 31–35 (2020)

DOI: 10.32876/ApplAstron.52.31-35

Keywords: digital signal processing, spectral power density of phase fluctuations, frequency standart, maximum likelihood method

Abstract

The purpose of the paper is to further develop the previously proposed method of digital signal processing of precision frequency and time standards for measuring phase noise. The solution to a number of problems of creating high-current setting quantum generators is impossible without the use of automated information and measurement systems for precision measurement of the spectral power density of phase fluctuations of signals, since phase noise is probably the most important criterion for frequency stability of generators and synthesizers. The current state of microelectronics allows us to implement optimal methods of measuring the phase shift of radio signals (in particular, orthogonal ones) in digital form when constructing such systems. A special feature of this algorithm is the use of a quantum pulse frequency synthesizer that is synchronized with a reference signal. The method proposed for evaluating metrological parameters of phase and frequency is particularly useful when analyzing the spectrum of phase fluctuations near the carrier frequency of the signal, where high resolution is required. In addition, the method is based on a two-channel phase estimation algorithm, which, in contrast to the known algorithms, significantly reduces the parasitic influence of the phase error of the reference signal. The relatively low computational complexity of the method is achieved by a special selection of the frequency of the quantizing signal. The paper substantiates the main idea of the method proposed and provides a detailed mathematical description of the measurement process. It is shown that the high sensitivity of the method is achieved due to the stroboscopic effect during time quantization of the signal studied. The implementation of the synthesized algorithm is shown by the example of the digital structure of a high-precision estimation of the phase difference based on the orthogonal method. This algorithm is the basis for the development of a precision digital device for evaluating the characteristics of phase and frequency stability.

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