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1

Analysis of harmonic distortion in analog circuits with the use of Volterra series and Kronecker products

Borys A.

International Journal of Microelectronics and Computer Science

|

2016

|

Vol. 7, nr 1

1--9

EN

This paper was inspired by an article entitled “An approach to model high-frequency distortion in negativefeedback amplifiers” by S. O. Cannizzaro, G. Palumbo, and S. Pennisi. The objective of this presentation is to point out that some results presented therein are not so novel as argued. First, we point out here that an idea of partition of a nonlinear circuit into interconnected smaller basic blocks, used in the above paper under a name of an analytical approach, is not new. For the first time, it has been used in the literature by S. Narayanan, pioneer of the Volterra series usage in calculations of nonlinear distortion in electronic circuits, and afterwards by many others. Second, we show that descriptions of the basic blocks mentioned above follow from their more general representations by the Volterra series, specialized for harmonic inputs. Third, we recall references in which the joint and complementary elements as well as some invariants occurring in modelling of op amp inverting and noninverting configurations for the purpose of nonlinear distortion evaluation have been reported before publication of some similar results by S. O. Cannizzaro, G. Palumbo, and S. Pennisi. Finally, we show that an operator o that was introduced by the above authors in their paper can lead to calculation errors. Alternative approach to this point is presented.

2

Understanding of Meyer and Stephens’s operator o as a multi-operational one

Borys A.

International Journal of Electronics and Telecommunications

|

2016

|

Vol. 62, No. 3

273--277

EN

In this paper, the idea of an extended operator o introduced in the literature on modelling weakly nonlinear circuits by Meyer and Stephens is revisited. The mathematically precise definitions of this operator for the successive Volterra series terms are given. Furthermore, the exhaustive formal and illustrative descriptions of these definitions are also presented. Finally, the possibility of a reverse formulation for the convolution operations occurring in descriptions of weakly nonlinear circuits is reported.

3

Quadrature Mapping, Saleh’s Representation, and Memory Models

Borys A.

International Journal of Electronics and Telecommunications

|

2016

|

Vol. 62, No. 4

389--394

EN

In the literature, Saleh’s description of the AM/AM and AM/PM conversions occurring in communication power amplifiers (PAs) is classified as a representation without memory. We show here that this view must be revised. The need for such revision follows from the fact that the Saleh’s representation is based on the quadrature mapping which, as we show here, can be expanded in a Volterra series different from an usual Taylor series. That is the resulting Volterra series possesses the nonlinear impulse responses in form of sums of ordinary functions and multidimensional Dirac impulses multiplied by coefficients being real numbers. This property can be also expressed, equivalently, by saying that the nonlinear transfer functions associated with the aforementioned Volterra series are complex-valued functions. In conclusion, the above means that the Saleh’s representation incorporates memory effects.

4

Operator o and analysis of harmonic distortion

Borys A.

International Journal of Electronics and Telecommunications

|

2016

|

Vol. 62, No. 3

261--265

EN

It has been shown that the description of mildly nonlinear circuits with the use of an operator o introduced by Meyer and Stephens in their paper published more than forty years ago was flawed. The problem now with their incorrect and imprecise definition is that it is still replicated in one or another form, as, for example, in publications of Palumbo and Pennisi on harmonic distortion calculation in integrated CMOS amplifiers or an article of Shrimali and Chatterjee on nonlinear distortion analysis of a three-terminal MOS-based parametric amplifier. Here, we discuss the versions of o operator presented in the works mentioned above and show points, where mistakes were committed. Also, we derive the correct forms of nonlinear circuit descriptions that should be used.

5

On Modelling AM/AM and AM/PM Conversions via Volterra Series

Borys A., Sieńko W.

International Journal of Electronics and Telecommunications

|

2016

|

Vol. 62, No. 3

267--272

EN

In this paper, we present the expressions, not published up to now, that describe the AM/AM and AM/PM conversions of communication power amplifiers (PAs) via the Volterra series based nonlinear transfer functions. Furthermore, we present a necessary and sufficient condition of occurrence of the nonzero values of AM/PM conversion in PAs. Moreover, it has been shown that Saleh’s approach and related ones, which foresee nonzero level of AM/PM conversion, are not models without memory. It has been also shown that using a polynomial description of a PA does not lead to a nonzero AM/PM conversion. Moreover, a necessary condition of occurrence of an AM/AM conversion in this kind of modelling is existence of at least one nonzero polynomial coefficient associated with its odd terms of degree greater than one.

6

On Definition of Operator o for Weakly Nonlinear Circuits

Borys A.

International Journal of Electronics and Telecommunications

|

2016

|

Vol. 62, No. 3

253--259

EN

For the first time, operator o appeared in the literature on weakly nonlinear circuits in a Narayanan’s paper on modelling transistor nonlinear distortion with the use of Volterra series. Its definition was restricted only to the linear part of a nonlinear circuit description. Obviously, as we show here, Narayanan’s operator o had meaning of a linear convolution integral. The extended version of this operator, which was applied to the whole nonlinear circuit representation by the Volterra series, was introduced by Meyer and Stephens in their paper on modelling nonlinear distortion in variable-capacitance diodes. We show here that its definition as well as another definition communicated to the author of this paper are faulty. We draw here attention to these facts because the faults made by Meyer and Stephens were afterwards replicated in publications of Palumbo and his coworkers on harmonic distortion calculation in integrated CMOS amplifiers, and recently in a paper about distortion analysis of parametric amplifier by H. Shrimali and S. Chatterjee. These faults are also present in some class notes for students, which are available on WWW-pages.

7

Nonlinear system identification with a real-coded genetic algorithm (RCGA)

Cherif I., Fnaiech F.

International Journal of Applied Mathematics and Computer Science

|

2015

|

Vol. 25, no. 4

863--875

EN

This paper is devoted to the blind identification problem of a special class of nonlinear systems, namely, Volterra models, using a real-coded genetic algorithm (RCGA). The model input is assumed to be a stationary Gaussian sequence or an independent identically distributed (i.i.d.) process. The order of the Volterra series is assumed to be known. The fitness function is defined as the difference between the calculated cumulant values and analytical equations in which the kernels and the input variances are considered. Simulation results and a comparative study for the proposed method and some existing techniques are given. They clearly show that the RCGA identification method performs better in terms of precision, time of convergence and simplicity of programming.

8

On minimization of nonlinear distortion in Sallen and Key filter in range of low frequencies

Borys A., Zakrzewski Z.

Zeszyty Naukowe. Telekomunikacja i Elektronika / Uniwersytet Technologiczno-Przyrodniczy w Bydgoszczy

|

2014

|

z. 18

5--10

EN

In this paper, we show that a mildly nonlinear model of an active filter using the Volterra series and any other related one do not give satisfactory results in evaluation of nonlinear distortion in the range of low frequencies, in which the operational amplifier output voltage saturation is a dominating nonlinear phenomenon in this filter. Therefore, minimization of the filter nonlinear distortion cannot be performed by minimization of the gain-sensitivity product (GSP) or the so-called distortion aggravation factor (FDAG) in the aforementioned range of frequencies. This is illustrated, using measured data of filter transfer function distortion, on an example of a low-pass Sallen and Key filter.

PL

W niniejszym artykule pokazano, że słabo nieliniowy model aktywnego filtru wykorzystujący szereg Volterry i inne temu podobne modele, nie daje zadowalających wyników w określaniu zniekształceń nieliniowych filtru w zakresie niskich częstotliwości, w którym napięciowe nasycenie na wyjściu wzmacniacza operacyjnego stanowi podstawowe zjawisko nieliniowe w tym filtrze. Konsekwencją tego jest to, że minimalizacja zniekształceń nieliniowych filtru nie może być wtedy oparta o minimalizację takich miar jak, na przykład, iloczyn wzmocnienia i wrażliwości, czy też odwrotność współczynnika sprzężenia w wyżej wspomnianym zakresie częstotliwości. Zostało to wykazane przy pomocy pomiarowych danych zniekształceń funkcji przenoszenia filtru, na przykładzie dolnoprzepustowego filtru Sallena-Key.

9

Wykorzystanie szeregów Volterry w zadaniu wykrywania uszkodzeń przekładni zębatych

Jasiński M.

Logistyka

|

2014

|

nr 6

4871-4878

PL

Celem prezentowanej pracy było lepsze zrozumienie mechanizmu rozwoju uszkodzeń w dynamicznych układa mechanicznych. Ważne jest, aby dokładnie monitorować, obecne zmiany warunków technicznych elementów systemu przy planowaniu wymogów aktywnej strategii zarządzania ryzykiem. Chociaż układ dynamiczny tradycyjnie jest modelowane rozkładem strukturalnym, w referacie jest modelowane dynamiczne zachowanie systemu przez rozkład zachowań w przepływie zdarzeń i błędów towarzyszących występowaniu awarii. Z tego punktu widzenia nieliniowy model wystąpienia awarii, wykonany z użyciem szeregów Volterry, jest analizowany w celu realizacji długoterminowych korzyści proaktywnej strategii utrzymania. Model opisuje wpływ ewolucji zmiennych procesowych dla każdej hipotezy rozwoju uszkodzenia. W artykule jest również analizowany wpływ nieliniowości poszczególnych elementów na zachowanie całego systemu za pomocą widm wyższego rzędu.

EN

The objectives of the presented paper are to better understand the mechanism of failure development in the dynamic mechanical systems. It is important to consider carefully the present changes in a technical conditions of elements of the system when planning the requirements to a proactive risk managements strategy. While a dynamical system traditionally is modeled by structural decomposition, in the paper the dynamic behavior of system is modeled by decomposition of the behavior flow into events and errors accompanying occurrence of failure. From this point of view the nonlinear model of failure occurrence, made from Volterra Series, is analyzed to realize long term benefits of a proactive maintenance strategy. The models describes the effect on the evolution at the process variables for each hypothesized fault failure. In the paper it is also analyzed the impact of nonlinearity of the sub-section on the behavior of the whole system by using of high-order spectra.

10

Generalization of Linear Rosenstark Method of Feedback Amplifier Analysis to Nonlinear One

Borys A., Zakrzewski Z.

International Journal of Electronics and Telecommunications

|

2014

|

Vol. 60, No. 1

48-60

EN

Generalization of Linear Rosenstark Method of Feedback Amplifier Analysis to Nonlinear One This paper deals with an extension of the Rosenstark’s linear model of an amplifier to a nonlinear one for the purpose of performing nonlinear distortion analysis. Contrary to an approach using phasors, our method uses the Volterra series. Relying upon the linear model mentioned above, we define first a set of the so-called amplifier’s constitutive equations in an operator form. Then, we expand operators using the Volterra series truncated to the first three components. This leads to getting two representations in the time domain, called in-network and input-output type descriptions of an amplifier. Afterwards, both of these representations are transferred into the multi-frequency domains. Their usefulness in calculations of any nonlinear distortion measure as, for example, harmonic, intermodulation, and/or cross-modulation distortion is demonstrated. Moreover, we show that they allow a simple calculation of the so-called nonlinear transfer functions in any topology as, for example, of cascade and feedback structures and their combinations occurring in single-, two-, nd three-stage amplifiers. Examples of such calculations are given. Finally in this paper, we comment on usage of such notions as nonlinear signals, intermodulation nonlinearity, and on identification of transfer function poles and zeros lying on the frequency axis with related real-valued frequencies.

11

Use of Phasors in Nonlinear Analysis

Borys A., Zakrzewski Z

International Journal of Electronics and Telecommunications

|

2013

|

Vol. 59, No. 3

219-228

EN

In this paper, the well-known method of phasor analysis of linear ac circuits is extended in a rigorous mathematical way to nonlinear analysis. This fills the lack of such a theory in the literature. The results derived enable carrying out the needed corrections of some results published recently that regard harmonic distortion analysis of weakly nonlinear circuits.

12

Diagnosis of incipient faults in nonlinear analog circuits

Deng Y., Shi Y., Zhang W.

Metrology and Measurement Systems

|

2012

|

Vol. 19, nr 2

203-218

EN

Considering the problem to diagnose incipient faults in nonlinear analog circuits, a novel approach based on fractional correlation is proposed and the application of the subband Volterra series is used in this paper. Firstly, the subband Volterra series is calculated from the input and output sequences of the circuit under test (CUT). Then the fractional correlation functions between the fault-free case and the incipient faulty cases of the CUT are derived. Using the feature vectors extracted from the fractional correlation functions, the hidden Markov model (HMM) is trained. Finally, the well-trained HMM is used to accomplish the incipient fault diagnosis. The simulations illustrate the proposed method and show its effectiveness in the incipient fault recognition capability.

13

Detecting nonlinear behaviour using the Volterra series to assess damage in beam-like structures

Surace C., Ruotolo R., Storer D.

Journal of Theoretical and Applied Mechanics

|

2011

|

Vol. 49 nr 3

905-926

EN

Using the example of a cracked cantilever beam, this paper illustrates a means of identifying damage in structures using the so-called higher order Frequency Response Function (FRFs) which are based on the Volterra series. It is well known that, when a beam subject to a dynamic excitation vibrates, a transverse “breathing”crack present in the beam can change the state (from open to closed and vice-versa), causing nonlinear dynamic behaviour. A simple model of a cracked cantilever beam vibrating in its first mode is proposed. Across the frequency range which encompasses the first mode of vibration, it is possible to model the response characteristics of a cracked beam using a relatively simple asymmetric bilinear oscillator. As described in this article, it is possible to use these higher order FRFs to characterise the nonlinear behaviour of the cantilever beam and investigate the qualitative relation with the parameters of the fault such as entity and location. In this study, the case of single harmonic excitation has been considered initially. Then, a new characteristic function, again based on the higher order FRFs, is proposed for detecting the crack by exploiting the fact that due to the second-order nonlinear behaviour, two harmonic inputs combine to excite the sum of their frequencies. Comparisons are made between results derived using the simple model described and those obtained from a FE model simulating some experimental tests on the beam.

PL

Na przykładzie belki wspornikowej z karbem, przedstawiono metodę identyfikacji uszkodzenia za pomocą tzw. funkcji częstości odpowiedzi (Frequency Response Function – FRF) wyższego rzędu opartych na szeregu Volterry. Ogólnie wiadomo, że belka z „oddychającym” karbem poddana wymuszeniu dynamicznemu drga w sposób nieliniowy poprzez zmiany stanu (pomiędzy otwarciem i zamknięciem karbu). W pracy omówiono prosty model belki wspornikowej z tego typu uszkodzeniem pozwalający na analizę pierwszej postaci drgań. W zakresie częstości obejmujących pierwszą postać własną belki możliwe jest określenie charakterystyk dynamicznych układu poprzez zamodelowanie go jako względnie prostego oscylatora bi-liniowego. Wykazano, że zastosowanie funkcji FRF wyższego rzędu pozwala na identyfikację nieliniowych zjawisk w uszkodzonej belce oraz jakościową ocenę rodzaju tego uszkodzenia i jego lokalizacji. W pierwszej części pracy scharakteryzowano drgania belki w przypadku wymuszenia harmonicznego. Następnie wprowadzono nową funkcję charakterystyczną – także opartą na FRF – do wykrywania karbu na podstawie nieliniowej odpowiedzi drugiego rzędu, w której dwie składowe harmoniczne wymuszenia nakładają się, pobudzając częstość wynikającą z ich sumy. Przeprowadzono analizę porównawczą pomiędzy wynikami otrzymanymi z zaproponowanego modelu oraz modelu MES symulującego badania eksperymentalne układu.

14

Utilization of NILTs in Simulation of Nonlinear Systems Described by Volterra Series

Brančík L.

Przegląd Elektrotechniczny

|

2010

|

R. 86, nr 1

68-70

EN

The techniques of numerical inverse Laplace transforms (NILTs) are applied to get the time-domain responses of some classes of nonlinear systems. It is enabled by expanding the system response into a Volterra series formulated in multidimensional Laplace domains. For a given system the Volterra kernel transforms are found, and the response Laplace transforms inverted numerically. By this way the use of an association of variables technique is avoided to save CPU time. The NILTs based on FFT/IFFT and q-d algorithms are modified for this purpose.

PL

W pracy pokazano metodę wyznaczania odpowiedzi czasowej układów nieliniowych w oparciu o technikę numeryczną obliczania odwrotnej transformaty Laplace’a. Jest to możliwe przez rozwinięcie odpowiedzi w szereg Volterry wyrażony w postaci wielowymiarowej transformaty Łaplace’a. Dla danego układu wyznaczane są transformaty jądra szeregu Volterry, a następnie numerycznie obliczane odwrotne transformaty Laplace’a. W celu skrócenia czasu obliczeń do obliczania transformaty odwrotnej Laplace’a wykorzystano algorytm FFT/IFFT.

15

On In-Network and Other Types of Amplifier Descriptions for Nonlinear Distortion Analysis

Borys A.

International Journal of Electronics and Telecommunications

|

2010

|

Vol. 56, No. 2

177-184

EN

Basics of modelling analog weakly nonlinear amplifiers at higher frequencies for the purpose of nonlinear distortion analysis are addressed in this paper. First, the constitutive relation for this class of amplifiers, with the use of a Volterra series, is formulated. It is the basis for formulation and derivation of the so-called in-network and input-output type descriptions of an amplifier in the time domain, which are then transferred into the multi-frequency domains. Usefulness of the general models achieved, which were not published up to now in the literature, lies in the fact that they can be used for any topology in which the amplifier is incorporated and for any nonlinear distortion measure assumed. Some examples of calculations are given at the end of the paper for cascade and feedback topologies, and for harmonic distortion measure.

16

On influence of feedback on harmonics in mildly nonlinear analog circuits

Borys A.

Zeszyty Naukowe. Telekomunikacja i Elektronika / Uniwersytet Technologiczno-Przyrodniczy w Bydgoszczy

|

2009

|

z. 12

5-20

EN

First, it is shown that applying the linear feedback increases the order of nonlinearity of the whole mildly nonlinear amplifier in comparison with that characterizing the amplifier without this feedback. Second, the impact of this fact on harmonics, which appear in the feedback amplifier driven by a single complex harmonic signal, is analyzed in detail. Finally, the associated model of the feedback amplifier is derived. It is shown that using this model, and only then, it is possible to interpret correctly the means of harmonic distortion calculations in weakly nonlinear amplifiers proposed by Palumbo and Pennisi in one of their recent papers.

PL

W pracy pokazano, że zastosowanie liniowego sprzężenia zwrotnego w układzie wzmacniacza analogowego pracującego w zakresie tzw. małych nieliniowości powoduje zwiększenie rzędu nieliniowości wykazywanej przez ten wzmacniacz w porównaniu ze wzmacniaczem bez sprzężenia. Przeanalizowano wpływ powyższego zjawiska na składowe harmoniczne wyższych rzędów, powstające przy pobudzeniu wzmacniacza pojedynczym sygnałem harmonicznym. Ponadto wyprowadzono model stowarzyszony wzmacniacza ze sprzężeniem zwrotnym. Pokazano, że wykorzystując ten model, i tylko wtedy, można zinterpretować w sposób prawidłowy metodę obliczeń zniekształceń harmonicznych we wzmacniaczach analogowych pracujących w zakresie tzw. małych nieliniowości, która to została zaproponowana przez Palumbo i Pennisi w jednym z ich ostatnio opublikowanych artykułów.

17

The modified nodal formulation for nonlinear circuits with multiple inputs

Borys A.

Zeszyty Naukowe. Telekomunikacja i Elektronika / Akademia Techniczno-Rolnicza w Bydgoszczy

|

2006

|

z. 9

53-63

EN

The modified nodal formulation (MNF) for nonlinear circuits with multiple inputs is presented in this paper. It is shown that in principle this approach is identical for the nonlinear circuits analyzed apart from that they possess a single or multiple inputs. That is the nonlinear models of basic circuit elements derived for the MNF are identical for both of these two cases as well as is the form of the MNF matrix equations for the corresponding orders of the nonlinear analysis. However, some particular properties are different. For example, the nonlinear transfer functions of a circuit with a single input can be calculated in a simple way by solving the MNF matrix equations for a Dirac impulse excitation. The nonlinear transfer functions are then equal to the corresponding circuit nodal voltages and branch currents for such the excitation. This does not however holds when a nonlinear circuit possesses more inputs. Furthermore, it is shown that solving the MNF matrix equations leads also to the correct results even when the circuit nonlinear impulse responses are the multidimensional Dirac impulses and the input signals at this circuit are the Dirac impulse signals.

PL

W artykule tym przedstawiono sposób, w jaki zmodyfikowana macierz admitancyjna (ZMA) może być wykorzystana w analizie nieliniowych układów elektronicznych z wieloma wejściami. Po-kazano, że podstawowa zasada wykorzystywana w tym podejściu jest taka sama jak w analizie ukła-dów nieliniowych z pojedynczym wejściem. W wyniku zastosowania tej zasady, nieliniowe modele podstawowych elementów składowych ukła-dów, wyprowadzone dla opisu za pomocą ZMA, jak również i postać równań macierzowych opisu-jących układy z wykorzystaniem ZMA (dla poszczególnych rzędów nieliniowości), są takie same - niezależnie od tego, czy dany układ posiada tylko jedno wejście, czy więcej wejść. Pewne szczególne własności są jednakże różne. I tak, przykładowo, nieliniowe transmitancje układu z pojedynczym wejściem mogą być obliczone przy wykorzystaniu ZMA dla poszczególnych rzędów nieliniowości przy pobudzeniu wejścia sygnałem w postaci impulsu Diraca. W tym przypadku nieliniowe transmitancje są równe odpowiednim napięciom węzłowym i prądom gałęziowym w układzie przy powyższym pobudzeniu. Takie relacje nie zachodzą jednakże w układzie, gdy posiada on więcej niż jedno wejście. W pracy pokazano także, że rozwiązując układy równań napisanych z wykorzystaniem ZMA, otrzymuje się poprawne wyniki nawet w takich granicznych przypadkach, jak wtedy, gdy układ posiada nieliniowe odpowiedzi impulsowe w postaci wielowymiarowych impusów Diraca, a sygnały pobudzające jego wejścia mają postać jednowymiarowych impulsów Diraca.

18

Products of dirac impulses in nonlinear analysis with the use of volterra series

Borys A.

Zeszyty Naukowe. Telekomunikacja i Elektronika / Akademia Techniczno-Rolnicza w Bydgoszczy

|

2006

|

z. 9

45-52

EN

It is shown in this paper that the products of Dirac impulses can occur in the nonlinear analysis with the use of Volterra series. Then these products must be however treated as the products of Dirac impulses of different arguments. Moreover, they can be assumed to be multi-dimensional Dirac impulses satisfying similar conditions as those regarding the ordinary one-dimensional Dirac impulse, but now in the corresponding multi-dimensional time or frequency domain. The defining relations for these multi-dimensional Dirac impulses are derived. Also the expressions for their Fourier transforms are given.

PL

W tym artykule pokazano, że iloczyny impulsów Diraca mogą występować w ana-lizie nieliniowej, w której wykorzystuje się szereg Volterry. W takiej analizie te iloczyny muszą być jednakże traktowane jako iloczyny impulsów Diraca różnych argumentów. Pokazano, że mogą one wtedy być rozpatrywane jako wielowymiarowe impulsy Diraca, spełniające podobne warunki do tych, jakie dotyczą zwykłego, jednowymiarowego im-pulsu Diraca, ale teraz we właściwej, wielowymiarowej dziedzinie czasu lub częstotliwo-ści. Wyprowadzono zależności definicyjne dla tych wielowymiarowych impulsów Diraca i podano wyrażenia określające ich transformaty Fouriera.

19

Artificial neural networks as an alternative to the Volterra series in rainfall-runoff modelling

Napiórkowski J.J., Piotrowski A.

Acta Geophysica Polonica

|

2005

|

Vol. 53, nr 4

459-472

EN

Methods of description of the non-linear effects in dynamic rainfall-runoff systems have been surveyed. Particular reference is given to such non-linear methods which do not require detailed topographical survey and determination of rough-ness parameters. To describe rainfall-runoff relation, alternative approaches to non-linear partial differential equations of mass and energy transfer have been discussed, namely conceptual and black-box models. In more details, application of Volterra net, Multi-Layer Perceptron Artificial Neural Network and Radial Basis Function Network is tackled. Illustrative numerical examples of rainfall-runoff simulation and river flow forecast are presented.

20

Bispectral Analysis in Vibroacoustic Diagnostics of Gears

Radkowski S.

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2001

|

vol. 49, nr 2

249-265

EN

The work concerns diagnosis of the origins and development of early stages of defects based on information found in the vibroacoustic signal. At the beginning the necessity of selection of diagnostic parameters dependent upon the amount of dissipated energy and related defect development is proven. Assuming that the basic role in transmission of such diagnostic information is played by the phenomena of amplitude and phase modulation of the vibroacoustic signal and non-linear effect of system, it is points to the significance of the signal non-linear components. For that reason in this work a model of signal in the form of a Volterra series is assumed, which enables examination of the influence that disturbances have upon non-linear components. On the basis of exemplary analysis of the contact condition disturbances, the possibility of generation of a bilinear component is presented. What serves this purpose is the model of non-linear and instantaneous contact. Simultaneously problems of selection of signal analysis methods that enable realisation of assumed aims are presented. Emphasising the fact that defect development does not always lead to a significant growth of the vibroacoustic signal power, the author has shown importance of methods of higher-order spectral analysis like, bispectrum and Wigner's distribution.