Wyniki wyszukiwania - BazTech

1

Modelling of non-ideal signal sampling via averaging operation and spectrum of sampled signal predicted by this model

Borys A.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2022

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Vol. 16 No. 2

274--278

EN

In this paper, a novel model of a non-ideal signal sampling via a local, periodic averaging operation is present-ed. The spectrum of a sampled signal predicted by this model is also analysed as well as compared with a one following from another model.

2

Definition of sampled signal spectrum and shannon’s proof of reconstruction formula

Borys A.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

|

2022

|

Vol. 16 No. 3

473--478

EN

The objective of this paper is to show from another perspective that the definition of the spectrum of a sampled signal, which is used at present by researchers and engineers, is nothing else than an arbitrary choice for what is possibly not uniquely definable. To this end and for illustration, the Shannon’s proof of reconstruction formula is used. As we know, an auxiliary mathematical entity is constructed in this proof by performing periodization of the spectrum of an analog, bandlimited, energy signal. Admittedly, this entity is not called there a spectrum of the sampled signal - there is simply no need for this in the proof – but as such it is used in signal processing. And, it is not clear why just this auxiliary mathematical object has been chosen in signal processing to play a role of a definition of the spectrum of a sampled signal. We show here what are the interpretation inconsistences associated with the above choice. Finally, we propose another, simpler and more useful definition of the spectrum of a sampled signal, for the cases where it can be needed.

3

Simple proof of incorrectness of the formula describing aliasing and folding effects in spectrum of sampled signal in case of Ideal signal sampling

Borys A.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2021

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Vol. 15 No. 4

873--876

EN

A simple proof of the incorrectness of the formula, which is used in the literature nowadays, for description of the aliasing and folding effects in the spectrum of a sampled signal in the case of an ideal signal sampling, is given in this paper. By the way, it is also shown that such the effects cannot occur at all, when the signal sampling is considered to be performed perfectly.

4

Impossibility of perfect recovering cosinusoidal signal of any phase sampled with nyquist rate

Borys A, Korohoda P.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2020

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Vol. 14. no. 3

738--742

EN

In this paper, a problem of a perfect recovering cosinusoidal signal of any phase being sampled critically is considered. It is shown that there is no general solution to this problem. Its detailed analysis presented here shows that recovering both the original cosinusoidal signal amplitude and its phase is not possible at all. Only one of this quantities can be recovered under the assumption that the second one is known. And even then, performing some additional calculations is needed. As a byproduct, it is shown here that a transfer function of the recovering filter that must be used in the case of the critical sampling differs from the one which is used when a cosinusoidal signal is sampled with the use of a sampling frequency greater than the Nyquist rate. All the results achieved in this paper are soundly justified by thorough derivations.

5

Highlighting problems occurring in analysis of critical sampling of cosinusoidal signal

Borys A., Korohoda P.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2020

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Vol. 14. no. 3

729--736

EN

When the sampling of an analog signal uses the sampling rate equal to exactly twice the value of a maximal frequency occurring in the signal spectrum, it is called a critical one. As known from the literature, this kind of sampling can be ambiguous in the sense that the reconstructed signal from the samples obtained by criti-cal sampling is not unique. For example, such is the case of sampling of a cosinusoidal signal of any phase. In this paper, we explain in very detail the reasons of this behavior. Furthermore, it is also shown here that manipulating values of the coefficients of the transfer function of an ideal rectangular reconstruction filter at the transition edges from its zero to non-zero values, and vice versa, does not eliminate the ambiguity mentioned above.

6

Consideration of a general model of stochastic service curve for communication networks

Wasielewska K., Borys A.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2019

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Vol. 13, no. 1

159--164

EN

In this paper, a general framework for modelling stochastic service curves for communication networks is presented. It connects with each other two approaches to the traffic analysis and performance evaluation of communication systems, namely, the one which is called a deterministic network calculus with its stochastic counterpart. Thereby, it enables to treat any communication traffic in a consistent way. Further, as we show here, it enables also achieving new results. Derivation of the above model is presented in details in this paper. Finally, some hints are given how the method presented in this article could be applied in maritime telecommunications area.

7

O wykorzystaniu rahunku sieciowego w analizie ruchu w systemach komunikacji bezprzewodowej

Borys A.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

|

2018

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nr 8-9

730--733, CD

PL

W roku 1991 R. Cruz opublikował dwa artykuły, które dały początek tzw. rachunkowi sieciowemu (ang. network calculus). Rachunek ten został wykorzystany w pracach IETF nad standardami internetowymi usług zintegrowanych (Intserv) i usług zróżnicowanych (Diffserv). Uzupełnia on klasyczną teorię kolejek w zastosowaniach telekomunikacyjnych, a w szczególności w tych przypadkach, w których analizowane sieci znacznie różnią się od stacjonarnych sieci telefonicznych. W literaturze wyróżnia się dwa warianty tego rachunku: deterministyczny i stochastyczny. Rachunek sieciowy można stosować w analizie wydajności, projektowaniu i optymalizacji bezprzewodowych sieci sensorowych, sieci typu ad hoc, a także w rozwiązywaniu problemów występujących w radiu kognitywnym. Głównym celem tego artykułu jest krótkie scharakteryzowanie ww. rachunku właśnie w kontekście możliwości jego wykorzystania w obszarze sieci bezprzewodowych. Ogólne rozważania zilustrowano w artykule przykładem analizy ruchu z uwzględnieniem interferencji pochodzących ze strefy interferencji węzła sąsiadującego w bezprzewodowej sieci typu ad hoc. Uzyskany w przykładzie wynik nie był do tej pory publikowany w literaturze.

EN

In 1991, R. Cruz published two papers, which gave rise to a tool called now a network calculus. This calculus was exploited in works of IETF regarding the Internet standards of integrated (Intserv) and differentiated (Diffserv) services. It complements the classical queueing theory. Two variants of it are called a deterministic calculus and a stochastic one, respectively. The latter is developing recently very intensively and began to be used for wireless sensor and ad hoc type networks, as well as in solving problems occurring in cognitive radio. This paper is about the usage of the network calculus in analyses of wireless systems. The method is illustrated by a one example regarding the problem of taking into account the interference coming from a neighbor node in an ad hoc wireless network - in performance calculations. A solution to this problem, which was not published up to now in the literature, is presented in this paper.

8

Modelowanie stochastycznej odpowiedzi impulsowej w niektórych sieciach bezprzewodowych

Borys A., Mieczyńska M.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2018

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nr 6

246--251, CD

PL

Systemy bezprzewodowe są najczęściej charakteryzowane i analizowane przy wykorzystaniu opisu zgodnego ze schematem: wejście-kanał-wyjście. W tym opisie podstawową rolę odgrywa znajomość charakterystyk kanału (łącza). Najczęściej pod tym określeniem rozumie się znajomość przebiegu odpowiedzi impulsowej kanału, w przypadku gdy można go modelować za pomocą całki splotowej (tj. uważać za system liniowy). W tym artykule pokazano, jak można wykorzystać zależności wyprowadzone dla kanału pomiarowego w przepływach dwufazowych w modelowaniu odpowiedzi impulsowej kanału bezprzewodowego. Pozwoliło to na uzyskanie nowego spojrzenia na omawiane zagadnienie. Otrzymane wyniki zilustrowano na przykładzie modelowania stochastycznej odpowiedzi impulsowej i funkcji gęstości prawdopodobieństwa opóźnień w sieciach ZigBee.

EN

Wireless systems are mostly characterized and analyzed with the use of input-output representations. In this case, the knowledge of channel (link) characteristics plays a fundamental role. This is meant mostly as the knowledge of a channel impulse response, when it can be assumed to behave linearly. In this paper, it has been shown how to exploit relationships derived in literature for a measurement channel in two-phase flows in modelling a wireless channel. This approach has offered a new perspective on the topic discussed here. Outcomes of this paper are illustrated by an example of modelling stochastic impulse response and probability density function of delays in ZigBee networks.

9

Katedra Telekomunikacji Morskiej na Wydziale Elektrycznym Akademii Morskiej w Gdyni

Pałczyńska B., Łuksza A., Borys A.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2018

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nr 1

3--8

PL

Katedra Telekomunikacji Morskiej jest jedną z czterech katedr działających na Wydziale Elektrycznym Akademii Morskiej w Gdyni. Jej działalność dydaktyczna obejmuje prowadzenie wykładów, zajęć laboratoryjnych, projektów oraz prac dyplomowych z różnych obszarów tematycznych szeroko pojętej telekomunikacji, ze szczególnym uwzględnieniem morskich systemów telekomunikacyjnych. Obejmuje ona również przedmioty z zakresu teleinformatyki i informatyki stosowanej. W Katedrze prowadzone są prace naukowe w kilku obszarach badawczych, w zakresie inteligencji obliczeniowej, metod cyfrowego przetwarzania sygnałów w morskich systemach radiokomunikacyjnych, teleinformatycznych i pomiarowych oraz metod i algorytmów dla współczesnych systemów i standardów telekomunikacji bezprzewodowej.

EN

Chair of Marine Telecommunications is one of four chairs at Faculty of Electrical Engineering of Gdynia Maritime University. The Chair’s teaching activities include lectures, laboratory training, projects and supervision of final graduate dissertation in different thematic areas in telecommunications and information technology with particular reference to maritime systems. Several research teams at the Chair are engaged in research in the following areas: computational intelligence, methods of digital signal processing in maritime radio systems, communication and measurement and methods and algorithms for modern systems and telecommunications standards. (Chair of Marine Telecommunications at Faculty of Electrical Engineering of Gdynia Maritime University).

10

When Can a Narrowband Power Amplifier Be Considered to Be Memoryless and when Not?

Borys A.

International Journal of Electronics and Telecommunications

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2018

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Vol. 64, No. 2

229--242

EN

This paper tries to get a response to the following question: When can a narrowband power amplifier (PA) be considered to be memoryless and when can it not be considered memoryless? To this end, a thorough and consistent analysis of the notions and definitions related with the above topic is carried out. In the considerations presented, two models of the narrowband PA are exploited interchangeably: the black box model widely used in the literature and a model developed here, which is based on the Volterra series. These two models complement each other. In this paper, the conditions for a linear or nonlinear narrowband PA to be memoryless or approximately memoryless or possessing memory are derived and illustrated. They are formulated in terms of the signal delay as well as in terms of the amplitude-to-phase (AM/PM) conversion of the amplifier. Furthermore, the two possible interpretations of the amplitude-to-amplitude (AM/AM) and AM/PM conversions are given a mathematical framework. That is these conversions are presented through some operations. One set of these operations allows to treat the AM/AM and AM/PM conversions as distortions of the modulating signals. Or equivalently as distortions of a given signal constellation when it passes through the PA. Finally, it is proved that the Saleh’s and Ghorbani’s models of the AM/AM and AM/PM conversions occurring in the PAs, which were published in the literature, are not memoryless ones.

11

On Correct Understanding and Classification of Saleh’s and Related Models of AM/AM and AM/PM Conversions

Borys A.

International Journal of Electronics and Telecommunications

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2018

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Vol. 64, No. 1

39--44

EN

In this paper, some of the existing classifications of the Saleh’s and related models of the AM/AM and AM/PM conversions occurring in communication power amplifiers (PA) are reviewed. It is shown that these classifications are inconsistent and must be refined. Obviously, carrying out such a refinement properly needs a good knowledge and correct understanding of the mechanisms leading to the AM/AM and AM/PM conversions. This was achieved in this paper by performing a thorough analysis of the PA behavior using an analytical tool, the Volterra series. The main points of this analysis are presented here in great detail. Among others, it is shown that the influence of the PA memory on the AM/PM conversion is two-fold: direct and indirect. The former can be however fully neglected. On the other hand, the indirect influence caused by “the interaction of the carrier with the PA memory” cannot be neglected when the PA has not enough wideband frequency characteristics. The latter effect mentioned causes changes in the carrier phase that are received as the phase changes of the baseband modulating signal.

12

Detailed Consideration of Graphical Calculation of Min-Plus Convolution in Deterministic Network Calculus

Borys A.

International Journal of Electronics and Telecommunications

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2018

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Vol. 64, No. 2

217--222

EN

The convolution operation used in deterministic network calculus differs from its counterpart known from the classic systems theory. A reason for this lies in the fact that the former is defined in terms of the so-called min-plus algebra. Therefore, it is oft difficult to realize how it really works. In these cases, its graphical interpretation can be very helpful. This paper is devoted to a topic of construction of the min-plus convolution curve. This is done here in a systematic way to avoid arriving at non-transparent figures that are presented in publications. Contrary to this, our procedure is very transparent and removes shortcomings of constructions known in the literature. Some examples illustrate its usefulness.

13

Introducing Satellite Remote Sensing to the Curriculum at Maritime University

Borys A., Emery W. J.

Zeszyty Naukowe Akademii Morskiej w Gdyni

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2017

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nr 101

7--21

EN

This paper describes a plan and a procedure to introduce a course on satellite remote sensing to the curriculum of the engineering faculties of Gdynia Maritime University in Gdynia, Poland. This topic is not presently taught at the university and with the move of the Polish Space Agency to Gdańsk, nearby Gdynia, it would be useful to have remote sensing as a topic in the university curriculum for different degree programs. This plan began with the Fulbright Foundation that funded a 5-week visit of a U.S. remote sensing specialist to give orientation lectures to the faculty and students at the university. From this visit a plan was developed on how to present specific topics in remote sensing while the faculty determined how the subject should be introduced into different fields of study.

PL

Polskiej Agencji Kosmicznej w Gdańsku wydaje się, że korzystne byłoby wprowadzenie do oferty dydaktycznej Akademii Morskiej w Gdyni również tematyki telemetrii satelitarnej – na różnych kierunkach i rodzajach studiów (w mniejszym lub większym zakresie). Prace nad przedstawioną tutaj propozycją zaczęły się od wizyty w Akademii Morskiej w Gdyni stypendysty Fundacji im. Fulbrighta z USA, wybitnego specjalisty w zakresie telemetrii satelitarnej. W czasie pięciotygodniowego pobytu w Gdyni wygłosił on szereg wykładów z powyższej tematyki. W tym czasie powstały także zręby omawianej tutaj propozycji, które później zostały uszczegółowione i dopracowane.

14

Operacja splotu w rachunku sieciowym - interpretacja graficzna

Borys A.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2017

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nr 8-9

860--863, CD

PL

Ponieważ rachunek sieciowy wykorzystuje algebrę min-plus w analizie ruchu telekomunikacyjnego, definiowana w nim operacja splotu różni się splotu znanego z klasycznej teorii systemów. Z tego też powodu czasem niełatwo sobie wyobrazić jego działanie. Jednakże pomocna może być w tym interpretacja graficzna. Temu zagadnieniu jest poświęcony ten artykuł. Wykorzystano w nim inny sposób konstrukcji krzywej splotowej niż używany w literaturze. Jest on bardziej przejrzysty i usuwa mankamenty dotychczasowego sposobu prezentacji. Jego użyteczność wykazano na paru przykładach.

EN

As network calculus uses min-plus algebra in the teletraffic analysis, the convolution operation defined in it differs from the convolution used in the classic systems theory. Because of this reason, it is sometimes difficult to imagine its operation. However, graphical interpretation can be helpful in this instance. This paper is devoted to this topic. Another way of constructing the convolution curve than the one used in the literature is used here. It is more transparent and removes drawbacks of the present one. Its usefulness is shown on a couple of examples.

15

Saleh's Model of AM/AM and AM/PM Conversions is not a Model without Memory : Another Proof

Borys A.

International Journal of Electronics and Telecommunications

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2017

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Vol. 63, No. 1

73--77

EN

The so-called Saleh's representation for description of the AM/AM and AM/PM conversions, occurring in communication power amplifiers, consists of two expressions that describe them as functions of a real-valued baseband signal modulating the carrier amplitude. It is a common view that this description forms a model without memory. We show here that the above belief is not correct; just the opposite is true. To prove this, we take into account an equivalent description of the Saleh's model called the quadrature model of bandpass nonlinearities and express it in a form of a nonlinear operator. Afterwards, we check whether this operator possesses a zero memory. To this end, we use an appropriate theorem of the nonlinear systems theory. Finally, as a result of this investigation, we observe that the memory of the above operator is nonzero.

16

Some relationships between effective and leftover service curves

Borys A.

Zeszyty Naukowe Akademii Morskiej w Gdyni

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2016

|

nr 94

5--14

EN

Network service curve plays a fundamental role in the techniques called network calculus. For example, it is very useful in analysis of admission control algorithms and scheduling procedures. Its basic form is assumed to be time-invariant and independent of cross traffic. However, in practice, when cross traffic must be taken into account, another form of this curve has to be used. It is called leftover service curve that depends upon the cross traffic intensity and indicates how much bandwidth is actually left over for through traffic. Outside the field of network calculus, a service curve was also devised that depends upon cross traffic, similarly as the leftover service curve. It was named ∈-effective service curve and proved to be useful for ad hoc networks. In this paper, we discuss the relationships existing between the aforementioned service curves. In particular, we show that under some assumptions the ∈-effective service curve can be viewed as the result of interpolation of the leftover service curve obtained in measurements. The discussions are provided with the relevant derivations.

17

Opis odbioru sygnału z satelity LEO w obecności zniekształceń intermodulacyjnych spowodowanych interakcją satelitarnego sygnału uplink z sygnałami naziemnych systemów komunikacji bezprzewodowej

Borys A.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

|

2016

|

nr 6

401--404, CD

PL

W artykule przedstawiono skorygowany model pozwalający opisać odbiór sygnału z satelity LEO w obecności zniekształceń intermodulacyjnych, spowodowanych interakcją satelitarnego sygnału uplink z sygnałami pochodzącymi z naziemnych systemów komunikacji bezprzewodowej. Model ten wykorzystano do określenia warunków, w których zniekształcenia intermodulacyjne trzeciego i piątego rzędu nie mają praktycznie żadnego wpływu na jakość odbieranego sygnału w odbiorniku stacji naziemnej systemu satelitarnego, w skład którego wchodzi tzw. niskoszumowy wzmacniacz. Wyniki teoretyczne zilustrowano przykładami obliczeń.

EN

In this paper, a corrected description of LEO satellite signal receipt at presence of intermodulation distortion caused by interaction of uplink satellite signals with signals of wireless terrestrial systems is presented. This description is used to determine conditions under which the intermodulation distortions of the third and fifth orders have practically no influence on quality of satellite received signal in receiver containing a low noise amplifier. The theoretical results regarding the model corrected and extended here are illustrated by numerical calculations.

18

O wykorzystaniu oparacji mnożenia impulsów Diraca w teorii systemów radiokomunikacyjnych i mikrofalowych

Borys A.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

|

2016

|

nr 8-9

1112--1118, CD

PL

Sześciotomowa encyklopedia wydawnictwa John Wiley & Sons zatytułowana „Encyclopedia of RF and Microwave Engineering” składa się z ponad 400 artykułów. Jeden z nich pt. „Volterra Modeling in Analog, RF and Microwave Engineering” został poświęcony wykorzystaniu szeregu Volterry do modelowania nieliniowych układów i systemów radiokomunikacyjnych, w tym mikrofalowych. Specyficzna jego postać to taka, w której występują mnożenia tzw. impulsów Diraca. Ta praca uzupełnia wyniki przedstawione w ww. encyklopedii dotyczące powyższej postaci szeregu Volterry.

EN

The John Wiley & Sons encyclopedia entitled „Encyclopedia of RF and Microwave Engineering” consists of six volumes and contains more than 400 articles. One of these articles is devoted to modeling of radiocommunication and microwave systems with the use of the Volterra series. One very specific form of this series comprises Dirac impulse products. This paper completes the results, which were presented in the aforementioned encyclopedia, regarding the above series form.

19

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.

20

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.