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• DIGITAL MULTIPLIER-CONVERTING METHOD FOR MEASURING FREQUENCY INSTABILITY USING THE LABVIEW PROGRAMMING ENVIRONMENT

  Jacinto Mba Biye Nsue, V. P. Fedosov , S. V. Kucheryavenko

  2020-10-11

  Abstract ▼

  The article is aimed at measuring the parameters of the harmonic process by the multiplication-
  conversion method. The simulation was carried out through the use of the LabVIEW software
  environment, as applied to the digital multiplier-conversion method, the main points of which are
  presented in the form of a progressive chain: a) development of the first harmonic process; b) the
  multiplication of the indicator of the first harmonic process by four; c) the arrival of to
  the band-pass filter PF1 tuned to the highest frequency, in this case, d) simultaneously, using
  the generator Г2, a second source signal is generated; e) This oscillation is raised to the
  fifth power, f) using the filter PF2 tuned to a frequency of 5 , select the fifth harmonic g) The
  signals received at the outputs of the filters are added and the result of the sum is subjected to nonlinear
  transformation h) Then, from the resulting square of the sum of the signals and using a
  band-pass filter PF3, we extract only the low-frequency harmonic with the frequency i) Then,
  using the Hilbert transform, we extract the total instantaneous phase from the harmonic and it
  becomes the object of the derivative operation, which leads us to obtain the instantaneous frequency
  function, characterized by a fixed dispersion. j) The law of fluctuations of the frequency
  resulting from the use of multiplication-conversion operations is compared with a given frequency,
  and we proceed to determine the mathematical expectation and standard deviation. The conclusion
  about the frequency instability is based on the discrepancies obtained. Applying nonlinear
  transformations of oscillations of oscillators similar in instability and obtaining the oscillations of
  a given frequency in the same way, the measured frequency instability is established. If you apply
  this method many times to the oscillations of highly stable devices, you can develop an oscillation
  with increased instability, and then evaluate it with available measuring equipment. Thus, we bypass
  without high costs by performing this operation. Then, determine the initial instability by the
  formulas given in this article.

• MODEL OF SELF-OSCILLATING CIRCUIT FOR TESTING NUMERICAL METHODS OF TRANSIENT ANALYSIS IN SPICE-SIMULATORS

  А. М. Pilipenko, А. V. Agabekyan

  2022-08-09

  Abstract ▼

  At present time the problem of developing methods for numerical analysis of RF circuits in the
  time domain remains actual because the known Gear and trapezoidal methods used in SPICE simulators
  have a number of significant disadvantages. To evaluate the effectiveness of new numerical methods,
  special test problems are needed to determine the accuracy of methods in various operating modes.
  Numerical analysis of self-oscillating circuits in the time domain offers the most difficulties for circuit
  simulation programs (SPICE-simulators) since models of self-oscillating circuits can be both oscillatory
  and stiff simultaneously. The aim of this work is to create the model of a self-oscillating circuit that allows
  to quantify the accuracy of numerical methods. In accordance with the aim, the following problems
  are solved: the features of the numerical analysis of classical self-oscillators in SPICE-simulators are
  investigated; the generalized mathematical model of self-oscillating circuits is described; the universal
  circuit model of self-oscillating circuits for SPICE-simulators is presented; the quantitative accuracy
  assessment of numerical methods of transient analysis in SPICE-simulators was carried out. The model
  proposed in this paper makes it possible to determine the relative errors of numerical methods in the
  harmonic oscillations mode, in the relaxation oscillations mode, as well as in the «mixed» mode, when
  the circuit response contains both exponential components with different rates of change and quasiharmonic
  components. The obtained results confirm the high accuracy of the trapezoidal method in the
  mode of harmonic oscillations, and the Gear method in the mode of relaxation oscillations. The relative
  errors in determining the amplitude of oscillation using these methods for the corresponding operating
  modes do not exceed 3%. At the same time, in the «mixed» mode, the relative errors in determining the
  amplitude of oscillation for both methods can reach 100%, that confirms the need to use additional
  options or special methods of numerical analysis in SPICE-simulators.