M. Kozioł

Integrated System for Monitoring and Control of the National Time and Frequency Standard

In Poland, the national time and frequency standard (NTFS) is realized by means of three caesium atomic clocks, a system for the generation of the Polish time scale UTC(PL), and measuring systems for comparing directly and indirectly the atomic clocks and time scale. In order to ensure the best realization of NTFS, the Institute of Electrical Metrology at the University of Zielona Góra (IME UZ), in cooperation with the Central Office of Measures (GUM), has developed and built an integrated monitoring and control system. This system significantly increases the functional capabilities of autonomous measuring systems used previously at GUM and adds new features that increase the reliability and safety of the NTFS. Examples of such features are: automatic detection of invalid operating conditions (including breakdowns) of the atomic clocks and remote notification of alarms, as well as a new approach to predicting corrections for UTC(PL) using neural networks (NNs). In this paper, the presentation of hardware and software of the NTFS is limited to their general features. However, the application of NNs for predicting corrections for UTC(PL) and automation in determining the standard radio frequency deviation from its nominal value are presented in more detail.

Characterization of a digitizer for a low value resistor calibration system in the audio-frequency band

The paper characterizes selected properties of a dual-channel digitizer designed for a low value resistor calibration system working in the frequency range from 40 Hz to 10 kHz. There are presented the experimentally determined frequency characteristics of magnitude and phase of the complex voltage ratio, as well as the research results of the digitizer linearity and the phase measurement accuracy.

Reconstruction of Nonlinearly Deformed Periodic Signals Using Inverse Circular Parametric Operators

The original method of the non-linear distortions correction is presented. Aperiodic steady state of the linear periodical time-varying system may be described using a circular parametric operator. Within the domain of discrete time, such an operator takes the form of a constant real entries matrix. This way of system characterization is adopted to describe the steady state of the non-linear system. For reconstructing distorted signals some inverse circular parametric operators are determined using an original identification algorithm based on the set of input and output signals. The non-linear system operation depends on input signal shape and amplitude, thus each operator is determined for the different, so called, basic input signal. The described method is effective in some situations, but it requires further research to improve accuracy.