The origins of the Department
He did not make any particularly high-profile discoveries in Radiophysics. But Fyodor Mikhailovich has no less, perhaps, an important feature for a real scientist: it is the ability to” open “ people devoted to the cause with all their heart.
Fedor Klementyev has been known at the University since 1961, when he came to work here as an associate Professor of the Department of Radiophysics. With the advent of a new, active employee at the faculty of physics revives scientific work. A year later, opened the Department of electronics, it is headed by FM clementyev. Under his leadership, the Department is developing a new scientific direction, which remains relevant to this day: the problem of electromagnetic compatibility.
The faculty talked a lot about the” phenomenon “ of the Department of electronics – its young, but very well-coordinated, efficient team, quickly gained credibility among employees. Here are all carried out their duties in good faith, with the soul, not for fear of micromanagement. On the contrary, everyone knew that he would meet with the head of full confidence, a sincere desire to understand and help. Dostoevsky and the work of trying to allocate among staff, given the propensity and ability of each.
Although F. M. Klementyev was one of the most senior in the Department, he never felt the age difference. Fyodor Mikhailovich was primarily a senior friend, attentive, kind, always collected in the work. Maybe this inner concentration was brought up by Fyodor Mikhailovich in the terrible war years, when he left his most peaceful profession – teachers - became a cadet of infantry school. And after – already as an officer of artillery intelligence-fought for Leningrad, fought on the Baltic front.
A year after the capitulation Of Germany, F. M. clementyev returned to peaceful life, having two orders of the “red Star” and many medals. At the same time, in the forty-sixth, Fyodor became a student of one of the oldest universities in our country – Tomsk state University. University group, which studied former scout, was called “fighting” not only because it consisted of students participating in war, but also because he was the best in school, in Komsomol and party Affairs.
And, perhaps, this internal discipline has been further strengthened after graduation, when Klementyev devoted himself to scientific activities, under the guidance of the famous Professor A. V. Sapozhnikova, the student of one of the founders of Soviet physics, M. A. Bonch-Bruevich. Then, in the early fifties, Fyodor, together with E. by S. Vorobeichikova published the first in our country work on synchronization of microwave oscillators. A year later, F. M. Clementyev was awarded the degree of candidate of physical and mathematical Sciences.
Fyodor Mikhailovich managed not only to adopt the best traits of his teacher, but also to pass them on to his pupils. A lot of students he released in a great science. Among them there are many currently working employees of the Voronezh University and other universities and organizations of Voronezh. Many of his students work in other cities of the country and abroad.
Current research areas
The progress of natural and engineering Sciences led at the turn of XX and XXI centuries to the birth of a new scientific and technical industry, called “nanotechnology”. Over the past two decades, nanotechnology has evolved from a scientific slogan about prospects to an industrial strategic direction that will determine the leaders of global economic growth in the near future. The prospects of this direction are confirmed by billions of funds allocated in the world for nanotechnology today. The uniqueness of this science lies in the direct application of qualitatively new properties of physical, chemical and biological systems, the size of which is less than 100 nm. Thus, nanotechnology is the ability to manipulate individual atoms and molecules to create nano-structured materials and nanoscale objects of interest for technological applications. In the history of science and technology are rarely precedents when one industry combines the interests and prospects of all existing branches of material production. The predicted contribution of nanotechnology to the development of mankind in the first quarter of the XXI century will be comparable with the impact of information technology, advances in cellular and molecular biotechnology. Nanotechnology is designed to provide breakthroughs in areas such as the production of new materials, electronics, medicine, energy, environmental protection, biotechnology, information technology, national security. To date, it is safe to say that nanotechnology will be associated with the onset of a new industrial revolution.
Development and production of various miniature electronic systems is one of the strategic directions of the world scientific and technological progress. Miniaturization leads to revolutionary changes in technology, especially in cases where it is far from obvious that it is possible to develop and use the technology of mass production of the product, which can significantly reduce its price, increase reliability, reduce energy consumption, etc.
Currently, semiconductor heterostructures are the basis of numerous studies of fundamental physical properties, as well as a variety of instrument applications. The main element of the heterostructure is a heterojunction, which is a contact of two chemically different materials, in which the crystal lattice of one material passes into the lattice of another material without breaking the periodicity. The formation of such a transition is only possible for certain pairs of materials (heteropar) with the same type and orientation of the lattices and close values of the periods of the lattice. On the heterojunction there is an abrupt change of material properties: effective mass, band gap and position of zone edges (valence band and conduction band in semiconductors), elastic and phonon characteristics, dielectric and magnetic permeability, magnetization (in magnetic heterostructures), etc.Practically each of these properties is associated with specific instrument applications of heterojunctions and heterostructures.
A heterostructure can contain one or more heterojunctions. According to the recently adopted classification, objects with one or more sizes ranging from 1 to 100 nm belong to nanostructures. A typical example of a nanostructure is two closely spaced heterojunctions. If the energy of the charge carriers (the edge of the corresponding allowed zone) in the space between the heterojunctions is less than outside, then such a heterostructure is a quantum well in which the charge carriers are localized. The scale of 100 nm corresponds to the characteristic wavelength of the electron in semiconductor heterostructures at low temperatures. Therefore, such scales are affected by the wave nature of charge carriers, and their description requires the use of the laws of quantum mechanics. In particular, due to the limitation of the motion of charge carriers (confinement) in the direction of quantum well growth, their energy spectrum is quantized (dimensional quantization). The essentially quantum-mechanical nature of processes and phenomena serves as the basis for the separation of nanostructures into a fundamentally new class of objects, different from macroscopic systems and structures. In real semiconductor heterostructures, the wide-band region near the heterojunction is often doped. In this case, the bulk charge of the ionized impurity creates an electric field that forms a narrow quantum well in the region of the material with a smaller band gap directly near the heterojunction plane. Therefore, even a single such heterojunction is also a nanostructure. To date, the actual task is research and development in the field of various electronic devices, which are based on the properties of heterojunctions. The subject of modern research of the Department of electronics of VSU are field-effect transistors and bipolar transistors with heterojunction.
The most used in practice, the active element is an n-channel field effect transistor with Schottky based on GaAs (MESFET). A field-effect transistor with Schottky gate is created on a semiconductor substrate of GaAs, on which an epitaxial layer of n-type (called a channel) with a thickness of about 200 nm is located, obtained by epitaxial growth. Schottky gate field effect transistors are used in low-noise microwave amplifiers, high-power amplifiers, generators, mixers, modulators, limiters.
A kind of NEMT are devices with reversed structure. In the reversed NEMT, the narrow-band GaAs layer in which the channel is formed is located between the barrier contact and the wide-band AlGaAs heterolayer. This structure has some advantages. In particular, the open surface of GaAs is more stable than AlGaAs. In addition, the “gate dielectric”, which plays the role of the unalloyed GaAs layer, provides higher reproducibility of the threshold voltage. In the last 10 years, the characteristics of NEMT have been significantly improved by the use of new semiconductor compounds A3B5. Very promising were compounds InGaAs, InGaP, InAlAs And INR the introduction of indium into GaAs significantly increases the mobility of electrons. The best characteristics were obtained in pseudomorphic NEMT on an InP substrate (InGaAs/InP structure). studies of p-NEMT On an InP substrate began in the early 80’s. In 1988, instruments with a limiting frequency of fT > 200 GHz (one-third higher than the GaAs substrate) were demonstrated. To the greatest extent, their advantages are manifested in the application to powerful devices, because InP has a higher thermal conductivity than GaAs. In addition, the p-NEMT on the InP substrate provides a high density of deg and high electron velocity limit, which allows to obtain higher current densities.
The bipolar transistor on heterojunction (HBT, Heterojunction Bipolar Transistor) has a number of advantages in comparison with the conventional silicon transistor . The combination of a wide-band emitter and a narrow-band base, a small thickness of the base and high electron mobility cause good high – frequency characteristics.the main application area of these devices is high-power high-frequency (up to 20 GHz) amplifiers and switches.
For the developer of microwave devices it is necessary to know the characteristics of the device and its equivalent circuit. The equivalent circuit may have a different structure. It is important that this model of the transistor as accurately as possible reflects the behavior of the real device in a wide range of frequencies, in conditions of interference of different nature. In addition, it is necessary to select the parameters of the equivalent circuit of the device, which is so necessary at the design stage of the end devices. At the Department of electronics is constantly developing and improving methods of analysis of electronic devices in the traditional Department of scientific direction associated with the tasks of electromagnetic compatibility.
In modern electronics to promising areas include not only nano-size, but also nano-time technology. The latter are based on the use of ultrashort electromagnetic pulses (SKI), namely nanosecond, picosecond and shorter pulses. The use of SCI extends the functionality of existing electronic systems, as well as allows you to create fundamentally new systems designed to solve a wide range of scientific, technical, military and social problems.
The purpose of the planned work in the field of nanosecond technologies is to develop methods and means of ultra-wideband radar and communication, as well as methods and means of electronic suppression based on the use of ultrashort (nanosecond, subnanosecond and picosecond) pulses. Radiolocation of biological objects (including hidden ones), radiolocation flaw detection of building structures and radar methods of underground communications search are considered as priority directions in the field of radar on nano - and sub-temporal signals.
The development of this scientific direction will make it possible to obtain fundamentally new radio-electronic devices:
- radars for search of people during rescue operations in a difficult situation (under blockages of building structures, in mines, under snow avalanches);
- radars for remote monitoring of human life parameters for medical purposes;
- devices of radar flaw detection of building structures;
- radars to search for hidden communications;
- military electronic jamming devices based on SCI.
The problem to be solved by this project is formulated in the program-Research and development in priority areas of development of the scientific and technological complex of Russia for 2007-2012.
The authors proposed project leads the development and research work in the field of nano-time technologies within the research work (FGU “GNIIT EW OESS” MO of the Russian Federation state contract No. 64019/36-06), the research “Study of radio physical processes and fields in a complicated electronic structures” (№ State registration 0120.0408800) and NIR (Ministry of defence of the Russian Federation, state contract No. 54018). The RFBR grant “Development of methods and devices for ultra-wideband radar of biological objects using nanosecond and subnanosecond pulses” №08-02-99012 was supported.
Currently, scientific research in many fields of knowledge is carried out by large teams of scientists, engineers and designers with the help of very complex and expensive equipment.
The high cost of resources for research has made it necessary to improve the efficiency of all work.
The effectiveness of scientific research is largely related to the level of use of computer technology.
The automated system of scientific researches (ASSR)- the software and hardware system on the basis of computer facilities intended for carrying out the automated scientific experiments or complex tests, and also (or) for implementation of modeling of the studied objects, the phenomena and processes which studying by traditional means is difficult or impossible.
Computers in ASSR are used in information retrieval and expert systems, and also solve the following tasks:
- control of the experiment;
- preparation of reports and documentation;
- maintaining a database of experimental data, etc.
As a result of the use of ASSR, the following positive aspects arise:
- several times reduced the time of the study;
- increased accuracy and reliability of results;
- enhanced control over the course of the experiment;
- reduces the number of participants in the experiment;
- improves the quality and informativeness of the experiment by increasing the number of controlled parameters and more thorough data processing;
- the results of the experiments are displayed quickly in the most convenient form — graphical or symbolic (for example, the values of the function of many variables are displayed by means of machine graphics in the form of so-called “mountain ranges”). On the screen of one graphic monitor it is possible to form a whole system of instrument scales (voltmeters, ammeters, etc.), recording the parameters of the experimental object.
At the Department of electronics of VSU in scientific research are widely used the capabilities of modern ASSR and computer-aided design (CAD), as well as developed new ASSR for specific tasks.
The Department has developed an automated measuring system, which is ASSR for the study of the impact of ultrashort pulses of SKI on low-noise field-effect transistors. The developed installation is intended for testing of electronic elements in conditions of influence of ski. The unit has great opportunities for the synthesis and analysis of digital signals, to work with analog devices provides the ability to synthesize and digitize analog signals.
The main idea of the developed research tools is to recreate the operating mode of the tested semiconductor devices and the analysis of failures or changes in the parameters generated by pulse noise, which are either directly supplied by the contact method to the output of the device, or by means of a decoupling device are mixed to a useful signal. Thus, there are three main functions of the measuring unit:
- Reconstruction of the operating mode, i.e. simulation of the environment of the tested device, the conditions of its operation in a real electronic system. These include sources of power, the shaper reference voltages, the generators of input signals and the receivers output.
- Submission to the conclusions of the test device voltage SKI with adjustable parameters (voltage and repetition rate).
- Measurement and monitoring of the functional parameters of the tested device under the conditions of the SKI, including the identification of failures of digital circuits.
To study the effect of ultrashort video pulses on PT and HEMT transistors by contact method on the input circuits, a module was used, the photo of which is shown in the figure.
The test module for studying the effect of ultrashort video pulses on PT and HEMT transistors by contact method on the input circuits allows:
- supply the necessary to ensure the operating modes of static displacement on the terminals of transistors;
- connect to input and output circuits measuring devices for monitoring and measuring both static and microwave voltage at the drain and gate of the transistor;
- apply to the high-frequency input of the transistor ultrashort video pulses by contact method.
The measurement algorithm is controlled, data is entered into the computer and processed using the national Instruments measurement setup with LabView Software. The hardware consists of a chassis, which is a powerful personal computer, equipped with additional slots for connection of PXI modules, and a module containing ADC and DAC.
Ni modular instrument technology is based on the use of compact, high-performance equipment and built-in timing and synchronization systems, providing flexible, accurate and high-performance measurements. The most modern platform for such devices is the PXI platform.
PXI (PCI extensions for Instrumentation) is a computer platform designed to create powerful measurement automation systems. It combines the performance of the PCI bus with advanced clocking and synchronization capabilities. It is based on standard computer technology, which provides greater flexibility and versatility. PXI-architecture is built according to the specifications CompactPCI modular platform (which in turn is based on PCI technology), which ensures full compatibility of PXI and CompactPCI hardware.
The principle of work with the measuring installation of National Instruments is based on the use of the concept of virtual instruments (VP). In fact, a virtual instrument is an application that is created using the LabView graphical programming language of National Instruments, version 8.6. LabVIEW is a highly efficient graphical programming environment where you can create flexible measurement, control, and test applications. A virtual instrument can be the final program and can also act as part of a more complex instrument. The transfer of data between elements within a program determines the order in which they are executed. These elements, virtual devices, process the data coming to their inputs and output the processing results to the outputs. By connecting the inputs and outputs of the respective virtual instruments, the order in which the data is to be processed is determined. Along with traditional programming, LabVIEW uses interactive technology to Express the EP, which includes automatic code generation, the use of assistants when configuring the measurement, application templates, and custom Express vis.
Advantages Of LabVIEW:
- A full-fledged programming language
- Intuitive graphical programming process
- Wide possibilities of data collection, processing and analysis, instrument control, report generation and data exchange via network interfaces
- Driver support for a large number of devices
- The possibility of interactive code generation
- High execution speed of compiled programs
- Compatible operating systems Windows2000/NT/XP, Mac OS X, Linux and Solaris.
The LabView interface consists of two operating window: Block Diagram and Front Panel. Block Diagram contains a diagram of a virtual instrument, Front Panel - its “front (front) panel” with controls and visual data display.
To conduct experimental studies using the LabView programming language, software applications were created: for measuring volt-ampere characteristics, for measuring the flow current and measuring the gain.
The main functions of the created applications are the control of the measurement algorithm, collection, processing and storage of information. This includes setting the operating modes of the PTS, reading the voltage on the drain current sensor, converting it to the value of the drain current, measuring the voltage level at the output of the amplitude logarithmic power detector, processing the received data and displaying the results in graphical form. One of the obvious advantages of the automated measurement method compared to oscillographic methods is the ability to measure large values of relaxation time, which in practice can reach hours. Observation of such long-term processes by oscillographic methods is impossible due to the limitations of the available sets of periods of horizontal scans.
The value measured in the experiment carried out in static mode is the flow current of the transistor. The flow current sensor in the circuit of the analog module is a resistor in the output circuit of the transistor, the voltage at which is converted into the value of the flow current. In the high-frequency mode (in the presence of the input microwave signal), the gain and its changes under the action of the SKI are measured, and the influence of the SKI on the shape of the microwave signal is observed. Figure 8 shows the effect of SKI on the amplitude of the microwave signal. You can see a decrease in the gain under the influence of SKI.
The LabView programming language was used to develop an application for measuring current-voltage and transfer characteristics in the static mode of the transistor. The virtual device shown in Fig., performs the functions of measuring stand control, collection, processing and storage of measured data.
On the front panel, in this case, there are elements that allow you to control the measuring stand by means of the task of the test module operation modes, as well as elements of the data display on the screen.
What is the relationship between ASSR and CAD?
Each of the ASSR and CAD systems, of course, has its own specifics and different goals and methods of achieving them. However, very often between both types of systems found a close relationship, and they have in common not only that they are implemented on the basis of computer technology.
For example, in the design process may require the implementation of a study, and, conversely, in the course of scientific research may be necessary and in the design of a new device and in the design of a scientific experiment.
This relationship leads to the fact that in fact “clean” ASSR and CAD does not happen: in each of them you can find common elements. With the increase of their intelligence they are getting closer. Ultimately, both should be an expert system focused on solving the problems of a particular area.
Education at the Department
The structure of the courses studied at the Department corresponds to its specialization. First of all, students study the basic structures of solid-state electronics and their nonlinear properties, parameters and characteristics underlying the functioning of solid-state devices, including elements of integrated circuits. Much attention is paid to the study of digital and microprocessor systems that form the basis of modern electronics in information processing systems for various purposes.
The methods of computer modeling and their application for the analysis and design of electronic devices are studied. Along with the theoretical foundations of modeling and optimization, the main attention is paid to the study of practical methods, including the use of professional packages of circuit modeling such as DesignLab, Microwave Office, Ansoft Designer, etc.for the analysis of electronic circuits in multi-signal nonlinear modes, the most common in practice, the capabilities of these packages is not enough. For such modes, the original methods of nonlinear modeling are developed, which are studied mainly in the course and diploma works, as well as in the master’s program. Students themselves take part in the development of modeling methods.
One of the modern and fundamental directions in the development of communication systems is the transfer of information through chaotic oscillations. The study of this problem at the Department begins with a course on General issues of stochastic oscillations and continues in the performance of course and diploma works, as well as in the preparation of master’s theses, where specific tasks are solved, for example, related to the stability of communication systems based on chaos in conditions of noise and other distortions in the communication channel.
The educational process at the Department is provided with well-equipped laboratory facilities. Among the educational and scientific laboratories of the Department should be allocated laboratories in the most modern areas of electronics. These are laboratories “Laboratory of ultra-wideband systems”, “Microcontrollers”, “Digital systems”, “Functional electronics”, as well as “satellite TV and video systems”.