Spectral analysis usually remains one of the most common analytical approaches to determine diagnostically significant characteristics of electrical activity signals of organs and systems of the body [1, 2]. Regarding the cardiovascular system, the electrocardiogram (ECG) is an integral indicator of the system state and is widely used in diagnostics and research. The paper shows the results of using a polygonal function (PF) as an ECG signal model, which allows simplifying the calculation of the signal spectrum and further revealing the possibilities of correlation analysis.