An essential issue in power electronics field is the limitation of power losses in the power supply grid. The distortions created by each consumer add up in the main network. The effect seen by customer is distorted mains voltage. The effects observed by the electric energy distribution operator consist in the increase of losses in the network (at the same active power, the supply current of the harmonic polluting consumer is higher than the supply current of the resistive consumer). For an efficient operation, the circuits used to compensate the over polluted grids need ideal reference signals. Starting from the idea of identifying a viable solution to this problem, this paper proposes a designing method and testing of a quadrature oscillator (QVCO) to provide the compensation circuit with the ideal necessary signal. The proposed circuit was designed and tested. The experimental results obtained during the QVCO testing show that the designed QVCO circuit provides a perfect reference sinusoidal signal, synchronous with the fundamental voltage of power supply network/grid.

The objective of the work is to present some aspects related to the use of negative resistances in selective electronic circuits, i.e., based on capacitors and inductors (RLC circuits). The results of the computer-based experiments, with ideal and real models of the electronic components, are presented and compared, also from stability point of view. Next, the results of the physical experiments with real operational amplifiers are discussed. All these aspects promote and prepare a better understanding and wider use of the electronic circuits with negative resistances in various applications, as e.g., pass-band filters, adjustable active loads, and harmonic oscillators.

It is easy to optimize a voltage stabilizer which works in switching mode, when it is used in a power supply circuit for a specified load that operates in permanent mode. A good example is an embedded system with microcontroller. It has many working modes, but in this paper two of them are considered: active (wake) and sleep. The paper is a study of the influence of the coil quality factor under efficiency for the aforementioned modes. It was used a dc-dc converter MC34063 in a domestic automation circuit. In its operation there are shorts intervals of activity interleaved between long standby time intervals (sleep mode). In terms of power consumption, different optimization criteria are formulated for each of the two states. Theoretically, the efficiency is a weighted sum of the efficiency for each state. If the activity time is negligible, the optimization criteria are: the safety of the wake-up and sleep transitions and the energy consumption in sleep mode.

The design of active filters (e.g. Sallen-Key filter, voltage-controlled voltage-source (VCVS) topology or multiple feedbacks filter) is well known, but the resulted filter parameters: corner frequency, damping coefficient, gain, etc., depend on 4 or 5 component parametric dispersion. This paper presents a case study: the tuning method of a 4th order Butterworth band pass filter build with two VCVS active filters. This filter is used in the measuring chain of the signal conditioner of the linear inductive position sensor (LIPS).

The analog part of the lock-in amplifier consists in three units: the measuring channel, the synchronization channel and one or two PSD (phase sensitive detector) circuits. For low frequency applications, the PSD circuit can be build with ordinary operational amplifiers and CMOS multiplexers. The paper presents a study of the proposed PSD circuit and two examples: a conditioner for the LVDT (linear variable differential transformer) sensor, and an device which together with a laboratory DDT (direct digital synthesis) signal generator can measure the gain-frequency and phase-frequency diagrams (Bode diagrams) of an electric circuit.

In almost all linear applications the internally compensated operational amplifiers have no stability problems. But, some particular circuits as “the capacitive load amplifier” or “the composite amplifier” may have ringing step response. The paper proposes a new technique by which the integrated circuit user can estimate the open-loop Bode diagrams of the amplifier configured with a negative feedback loop. The method has three advantages. First, the phase measurements are executed directly on the op-amp application circuit. Second, the application designer can calculate the open-loop transfer function dynamic model, and the amplifier phase margin. Third, if there are stability issues, the circuit designer has information necessary to calculate the op-amp frequency compensation network.

The research carried on in the field of dielectric nanomaterials requires a large amount of fast and accurate measurements, such as the current/voltage characteristics, which produce currents under the 1nA range. The size of the available devices forces them to be placed outside the measurement setup, allowing a large influence of the electric noise. Supplementary, they are unable to measure during the transient phenomena and expensive (“sourcemeters” available from different producers). This paper presents a more convenient solution (under 500 euros) for fast automatically measuring the characteristics in the range of 10pA to 1000nA. A major advantage of this device is its size (10×6×10cm), allowing it to fit into the shielding enclosure, together with the probe, needle manipulator and microscope. It allows the experimenter to specify the voltage range and the number of measuring points and it automatically provides the resulting data file, without raising neither the uncertainty level (under 10pA), nor the measuring time (down to 0.1 seconds per measuring point). The error is kept low through active guarding, mains synchronization, careful shielding and the use of extremely low bias amplifiers (3fA). The device communicates with the host computer via the galvanic isolated USB interface and does not require separate power supply (USB powered).

In power electronics area, the PLL (Phase Lock Loop) circuit is needed to reconstruct the sinusoidal reference signal used on the APF (active power filters) or grid-tied inverters, starting from the distorted grid voltage. Research area of the APF focuses more on the current of voltage control loops and less on the sinusoidal reference signal, usually considered available by default. Implementing in practice such a circuit poses difficulties since the available PLL integrated circuits are designed for digital telecommunication area, where signals are digital and a small phase error is acceptable. This paper presents a phase lock loop model with harmonic output and zero phase error during normal use.

The paper describes a fully automated system for measurement of the ultrasonic signals generated by ultrasonic transducers, designed for operating in air for a frequency range from 40 to 300 kHz. Study of new material's properties and sensitivity patterns for bio-mimetic ultrasonic transducers will be made. Measurements to estimate other important parameters of transducers will be possible as well. The system is designed as a computer controlled four axis system, where one element (usually transmitter) can be positioned in XYZ space and the other element (receiver) can be rotated around its axis. The relative position between transmitter and receiver is controlled by specialized software running on a personal computer. The system is flexible, in the sense that it supports any kind of materials and environment media for testing and can be driven from distance via internet.

The paper presents some transceivers for ultrasonic transducers based on Emfit Ferro-Electret Film (EMFi). The proposed and discussed transceivers use the wide bandwidth of EMFi material-from audio up to hundreds of kHz, for in-air biomimetic sonar applications, allowing thus to develop new algorithms for object detection, recognition and navigation based on frequency modulation algorithms. Technological process of building new ultrasonic transducers, starting from blank EMFi foil, is presented as well as electronic circuits used for transmitter and receiver. Three transmitter circuits were designed and presented, all of them being capable to drive a capacitive load of about 30pF with 300Vpp sinusoidal signal, up to 300 kHz.

Some of recent technological advances in electronics need very compact magnetic materials. The paper presents the morphology and the magnetic properties of very dense polycrystalline magnetic materials obtained from co-precipitated manganese ferrite nanoparticles. The ferrite nanoparticles, with average diameter in the range of 13–25nm, were obtained through an original low-cost co-precipitation route from aqueous solution of Mn2+ and Fe3+ ions generated by redox reactions between stoichiometric amounts of MnO2 (piroluzite) and FeSO4·7H2O raw materials. Very dense homogeneous polycrystalline magnetic materials with high square hysteresis loop (Br/Bs=0.91) and low intrinsic coercivity were obtained using the co-precipitated un-doped manganese ferrite nanoparticles.

In autonomous vehicles, e.g. mobile robots, the sonar is frequently used for navigation. There are some drawbacks of the system, generated mainly from the small bandwidth of the ultrasonic transducers and from high absorption of ultrasounds in air. Currently, there are two research directions under development: (a) the use of sensors based on new materials as EMFi, with wide frequency range; (b) the use of arrays of sensors, in order to design the beam width and to build sonar images instead of single or multiple echoes processing. The present work presents some results from the first directions and the preparations for the second approach, i.e. array of sensors, from electronics point of view. The work is part of the ADBIOSONAR research project.

This paper first introduces a unified representation of both real-coded genes and binary-coded genes, in order to efficiently analyse the convergence of a genetic algorithm. In the literature, the syntagm "the entire population premature convergence" is used with the meaning of closing the evolution before reaching the optimal point. It can be emphasised only on a test function with known landscape. If the function landscape is unknown, one can only notice the population convergence. This paper aims to answer to the question: "how can we influence the control parameters of the genetic algorithm so that the exploration period of the parameter space be longer and the risk of the premature convergence be reduced?" The answer to the above question implies the selection of a crossover operator with good performance in the landscape exploration and the use of two indicators for the detection of the population convergence. In order to choose the appropriate control parameters of the genetic algorithm, the fitness function landscape must be taken into consideration.

In the literature, the term premature convergence of the entire population is used with the meaning of closing the evolution before reaching the optimal point. It can be emphasized only on a test function with known landscape. If the function landscape is unknown, one can notice the population convergence only. This paper aims to answer to the question: "how can we influence the control parameters of the genetic algorithm so that the exploration time of the parameter space be longer and the risk of premature convergence be reduced?". The answer to the above question implies choosing a crossover operator with good performances in the landscape exploration and the use of two performance indicators for the detection of the population convergence. In choosing the control parameters of the genetic algorithm, the fitness function landscape must be taken into consideration.

This paper deals with the model identification of the biosynthesis process of the alpha-amylase and bacterial protease with the microorganism Bacillus Subtilis. The authors suggest the use of the multi-objective optimization based on genetic algorithms for the computing of the process parameters. The process identification was done based on the experimental data given by Food Industry Institute from Bucharest.

In a parametric optimization problem the genes code the real parameters of the fitness function. There are two coding techniques known under the names of: binary coded genes and real coded genes. The comparison between these two is a controversial subject since the first papers about parametric optimization have appeared. An objective analysis regarding the advantages and disadvantages of the two coding techniques is difficult to be done while different format information is compared. The present paper suggests a gene coding technique that uses the same format for both binary coded genes and for the real coded genes. After unifying the real parameters representation, the next criterion is going to be applied: the differences between the two techniques are statistically measured by the effect of the genetic operators over some random generated fellows.

The genetic algorithms are developing in three directions: the genetic algorithms theory, the genetic algorithms programming and the study of the problems that can be solved with genetic algorithms. In this paper it is presented a study on the identification of the parameters of a JFET (Junction Field Effect Transistor). The problem is very exciting because the JFET has two mathematical models: an empirical one, and an analytic one, both of the models being nonlinear in parameters. In a parametric identification problem, it is minimized the distance between an experimental data set and an analytical function, which represent the mathematical model of the studied phenomenon. Basically, a genetic algorithm can maximize a fitness function, which is a positive defined function whose maximum is searched. However, genetic algorithms can also solve minimum problems, on condition that to the minimum problem can be applied an algebraic transform or a rank based transform in a maximum problem.