Wyniki 1-8 spośród 8 dla zapytania: authorDesc:"Milan CHUPÁČ"

Generalisation of transfer functions of inter-digital transducer and filter on basic of surface acoustic waves

Czytaj za darmo! »

In the report we deal with the generalisation of transfer function which is derived from the three-gate model of the inter-digital transducer. Stated generalisation of transfer function includes the influence of adapter circuits attached to the transducer and allows its application for the description of any model´s functioning. Streszczenie: Analizo przetwornik używany do zasilania i detekcji elementu SAW - z powierzchniową falą akustyczną. W modelu uwzględniono także układ adaptera. (Uogólnienie funkcji transferu przetwornika i filtru bazującego na elemencie z akustyczną fala powierzchniowa SAW) Keywords: inter-digital transducer, surface acoustic waves, complex transfer function, diffusion coefficients, diffusion loss,. Slowa kluzcowe: powierzchniowa fala akustyczna SAW. Introduction Analyzing the activity of inter-digital transducer (IDT) which is used for excitation and detection of surface acoustic waves (SAW) at the moment of realisation of acoustic-electronic components we stem most commonly from the three-gate circuit model (1). Depicted model allows us to state all three-gate transducer transfer functions with the presence of so called secondary features like acoustic reflections created at the edges of electrodes as a consequence of weighted electric load on the surface of the pad (2), (3), which is at the same time often applied to make calculations of delay circuits (DC) or filters with double IDT and various matching circuits. To calculate the transfer functions taking the secondary features into consideration it is convenient to use three-gate matrixes. Calculated transfer functions based on the models of “weak binding" does not include the influence of matching circuits and this method does not allow us to calculate reflection acoustic coefficient of transducer. Reflections from the electrodes of the transducer are often little, eventually they can be strongly choked down by the use of doubled electrodes. [...]

The theory of asymmetrical delay line with the surface acoustic wave for non-electric sensors DOI:10.15199/48.2019.01.45

Czytaj za darmo! »

Among the perspective acoustoelectronic components with the surface acoustic waves (SAW) there are in addition to the bandpass filters also delay lines (DL) and resonators, which are used as selective elements of oscillators with harmonic oscillations. The main advantage is their small size and low weight, high mechanical strength, low sensitivity to vibration as well as the possibility to make the oscillators without the use of inductor. This is what guarantees their manufacturing perspective and wide range of use in measuring of electric and non-electric variables, in radio electronics, telecommunications, and introduces the necessity of elaboration of questions concerning to their theory and manufacturing. In the present paper it is elaborated the theory of an asymmetrical delay line with interdigital transducer (IDT) with diluted electrodes. Synthesis of Asymmetrical Delay Line An asymmetrical delay line has input IDT with a small number of electrodes (i.e. broadband), and output IDT with a large number of electrodes (i.e. narrowband). Module characteristic can be close to the synchronous frequency sufficiently accurately approximated by the function of sinx/x where x = N(f-f0)/f0 When increasing the number of electrodes IDT however, there is a strong signal caused by reflections from the edges of the electrodes, which substantially impairs the delay line properties and at the same time of the whole oscillator [1[. To suppress the signal we partly remove in the narrowband IDT the electrodes (i.e. "diluted" - divided into groups IDT). A similar problem arises in the synthesis of the filter with a narrow and very narrow pass band f3/f0 = 0,1 to 0,5 % (n. On the contrary, the methods of synthesis of filters with SAW are accurate at a relatively wide pass band f3/f0 = 1 to 30 %). Frequency and Time Characteristics of the Individual Groups of Electrodes in IDT with Diluted Electrodes The diluted IDT refers o[...]

Practical applications of thermovision measurements on electric ma DOI:10.15199/48.2019.09.13

Czytaj za darmo! »

Industry is currently based on the widespread use of electrical machinery and equipment without which production would be unthinkable. Requirements for the production growth and in particular on its quality, however, are closely related to reliability requirements of manufacturing equipment. Early diagnostics and monitoring of the technical condition of the equipment also result in an early detection of a malfunction (early stage malfunctions) which could cause relatively large damage during operation (e.g. early replacement of the bearing prevents it from burning or prevents the accident of the electric motor, the ventilator and the like). Of the whole range of fault diagnostics of electrical machinery and equipment, the most advantageous is the method without necessity to dismantle the machine. Technical diagnostics can be defined as a process for detecting the current technical state of objects based on objective evaluation of the symptoms detected by means of the measuring technique. One of the modern methods of investigation that can be used, for example, in developing of an experimental component in research and development work, is the application of industrial thermovision, thus the method of mapping of temperature fields. For sensing of two - dimensional patterns are currently the most preferred decomposition infrared measuring systems operating in real time, these systems are attractive especially when watching fast dynamic phenomena. Theoretical analysis In calculations of temperature rise of connections (e.g. clamp - conductor etc.), on other distributions of electric energy, the following criteria are respected [1]: ● magniture of loading during measurement, ● effect of wind speed on the size of temperature rise. Concerning the heating determination we corne out for a greater approach from the analogy of the solving the dependence between the electrical current, temperatureand time and, in our c[...]

Diagnostics of thermal processes in antenna systems of broadcast stations DOI:10.12915/pe.2014.04.034

Czytaj za darmo! »

Diagnostics is an important element associated with the operation of a radio antenna systems, allowing earlier detection of potential damage. Thermography is one of the diagnostic tools, which allows for non-invasive assessment of technical condition. It brings together both financial savings associated with the removal of the damage and the potential effects caused by it. The article presents an example of using a thermal imaging technique in fault location antenna systems. Streszczenie. Istotnym elementem związanym z eksploatacja radiowych stacji nadawczych jest diagnostyka systemów antenowych, co umożliwia wcześniejsze wykrycie potencjalnych uszkodzeń. Jednym z narzędzi diagnostyki jest termowizja, która pozwala na bezinwazyjną ocenę stanu technicznego. Przynosi to ze sobą oszczędności finansowe związane zarówno z usuwaniem samego uszkodzenia jak I potencjalnymi skutkami przezeń spowodowanymi. W artykule przedstawiono przykład użycia techniki termowizyjnej w lokalizacji uszkodzenia systemów antenowych. (Diagnostyka zjawisk termicznych w systemach antenowych stacji nadawczych). Keywords: antenna, thermography, radio, diagnostics. Słowa kluczowe: anteny, termowizja, radiostacje, diagnostyka. doi:10.12915/pe.2014.04.34 Introduction The main characteristic of radio transmission is the usage of radio waves in order to transmit information. The research area connected with this branch of science is undergoing constant development. It requires many technical innovations as the area of radio telecommunication networks applications is growing steadily and they provide wider and wider range of services. By means of their transmitters radio transmission is realized on a local, regional, national and international scale. Radio waves used are of short, very short and medium wavelengths. Some broadcast stations are able to cover the area of practically the whole world. Exploitation of such broadcast stations equipped with antenna apparatus i[...]

The interdigital transducer and its response in the case of the impact of the inhomogeneous surface acoustic wave DOI:10.12915/pe.2014.06.035

Czytaj za darmo! »

In the paper, the influence of the inhomogeneous surface acoustic wave and the tilt and shift of output interdigital transducer on the transmitted power coefficient and efficiency, is analyzed. Streszczenie: W artykule przedstawiono wpływ nierówności rozchodzenia sie fali akusticznej i obwodu wyjściowego przetwornika na moc transmisyjną oraz sprawność. Wpływ nierówności rozchodzenia sie fali akusticznej i obwodu wyjściowego przetwornika na moc transmisyjną oraz sprawność Keywords: interdigital transducers, surface acoustic wave, power transmission coefficient, the efficiency of shifted and slanted transducer. Slowa kluczowe: przetwornik interdigital, powierzchniowe fale akustyczne, współczynnik transmisji mocy doi:10.12915/pe.2014.06.35 Introduction Normally we assume idealized conditions when designing the surface acoustic wave (SAW) filter. These are: acoustic beam radiated by the input IDT has a constant amplitude and phase across of the beam, the amplitude of SAW drops sharply at the edges of the beam and it has a zero value outside of the beam, the beam width is equal to the aperture of the transducer, the output beam exactly overlaps the beam and the electrodes of the transducer are parallel to the wave front. In reality, these conditions are not always met, because the incident SAW is generally inhomogeneous and inhomogeneity of the waves can be caused by apodization of input transducer or low number of electrodes. Due to design inaccuracies, the output IDT can be shifted and tilted due to the input IDT and the electrodes are not parallel to the wave front. At the same time, diffraction of acoustic beam causes a change in amplitude and phase of SAW across the beam, the beam extends and causes the radiation of energy to the outside of the output IDT. Those phenomena have the effect of additional insertion loss. This article is aimed to contribute to derive the mathematical relations and to present the experimental resu[...]

The delay line with a surface acoustic wave for an oscillator of electric signals in some sensors DOI:10.15199/48.2018.03.38

Czytaj za darmo! »

As selective elements of oscillators of harmonic vibration besides the band-pass filters are also used delay lines (DL) and resonators as a perspective a coustic-electric components based on surface acoustic waves (SAW). From the stability point of view we can classify these oscillators among the ones with volume acoustic waves and LC oscillators. In the article, the DL with SAW for single - mode oscillators. The oscillator with delay line The basic principle of function of oscillator with delay line is represented on the next figure (Fig. 1). The delay line (4) with SAW plugged in the feedback of amplifier (2) is a basic element. Circuits (1, 3) serve to match impedance of the abovementioned to the impedance of the electronic circuitry. Fig.1. Bloc diagram of oscillator. Because the previous signal from the input to the output of DL is delayed, examined oscillators are ones with delayed feedback. The theory of these oscillators is well known in the literature [1]. Different situation is in the case of DL with SAW, where DL themselves have narrow transmission band and their parameters differ fundamentally in this range. Physical distinctiveness of functioning of listed components which are related with phenomena of excitation, extension and reflection of SAW cause that in addition to delay, the DL´s have specific frequency dependencies of input and output admittances. Their replacement with the lumped elements RLC circuit or broad - band DL with outer selective LC is mentioned only very general. The oscillator with mismatched delay line The used delay line with SAW as a selective element of oscillator can be symmetrical or non-symmetrical. Symmetrical DL is characterized by the same input and output IDT while non-symmetrical DL has the input IDT with small number of electrodes (broadband) and output IDT with big number of electrodes (narrowband). In the contribution we will only deal with the symmetrical DL. For simpl[...]

 Strona 1