Periodically Variable Two-terminal Impedance Description and Measuring Methods

The subject of this paper is the problem how to describe and measure impedance of a linear periodically time-varying (LPTV) two-terminal. If the two-terminal parameters change synchronously to the supply the two-terminal is able to reach a periodical steady state, but supplied with a sinusoidal source produces a non-sinusoidal voltage or current. The LPTV system in the steady state may be described with a circular parametric operator (CPO). Within the discrete time domain, this operator takes the form of a real entries matrix. The circular parametric operator may be transformed into the spectral circular parametric operator (SCPO) using a two-dimensional DFT. This version of description makes it possible to assess quantitatively the LPTV system coercion and response harmonics aliasing. This paper presents two methods of determination of the impedance CPO of the LPTV two-terminal based on current and voltage signal measurements. The first method is designed for operating in the frequency domain, the second one operates in the discrete time domain and takes advantage of a genuine identification algorithm. Some results of computer simulations are presented.