Jiri Petrzela

Simple Chaotic Flow with Circle and Square Equilibrium

Simple systems of third-order autonomous nonlinear differential equations can exhibit chaotic behavior. In this paper, we present a new class of chaotic flow with a square-shaped equilibrium. This unique property has apparently not yet been described. Such a system belongs to a newly introduced category of chaotic systems with hidden attractors that are interesting and important in engineering applications. The mathematical model is accompanied by an electrical circuit implementation, demonstrating structural stability of the strange attractor. The circuit is simulated with PSpice, constructed, and analyzed (measured).

Fundamental oscillators based on diamond transistors

This paper brings complete list of the simplest network structures capable to generate harmonic signals. The core elements used are modern analog building blocks known as the diamond transistors. Utilized design procedure is based on the prescribed state space representation of the second-order oscillators such that the final circuits contain minimum amount of the components and its basic frequency can be electronically adjusted. Each oscillator has been analyzed numerically, verified by the Pspice simulations as well as validated experimentally. The selected results of some importance are included. Since the nonlinear higher-order complex motions have been recognized during the measurement this behavior is briefly discussed.

High frequency chaos converters

The aim of this paper is to prove an interesting feature of some simple second-order dynamical systems with an external AC force called chaos-based signal conversion. To do this, algebraically simplest case of mathematical model has been selected and corresponding spectrum of the Lja-punov exponents (LE) has been calculated. Finally an electronic circuit suitable to model such behavior is derived and its correct function is experimentally verified.

Current mode tunable KHN filter based on controlled MO-CFTAs

This paper deals with application of novel active block called multiple-output current follower transconductance amplifier (MO-CFTA) in multiple-loop structure of current mode active filter. The well-known transconductance amplifier (OTA) is modified in such a way that single-input multiple-output active block is obtained. Using this device in the suggested network structure allows us to achieve low pass (LP), high pass (HP), band pass (BP) and band reject (BR) filter. The effects of the parasitic properties of the active devices as well as biquad sensitivities are briefly discussed. The possibility of electronic tuning of the main parameters of the individual filter configuration is verified.

Comparison of Two Solutions of Quadrature Oscillators With Linear Control of Frequency of Oscillation Employing Modern Commercially Available Devices

This paper proposes two circuits of frequency-controlled oscillators, whose structures are based only on simple commercially available active elements with minimum number of terminals, in particular, the differential voltage buffer, controllable voltage amplifier and electronically controllable current conveyor. Two methods for achieving linear control (tuning) of frequency of oscillations (FO) are discussed. The first method employs a simple structure. However, the generated signal level (amplitude) depends on the tuning process. This is a drawback of this method. The second method solves this drawback completely, and the generated signals have constant amplitudes during the tuning of FO. The expected behavior is confirmed by laboratory experiments utilizing commercially available high-speed active elements (current- and voltage-mode multipliers, video difference amplifier). Operational range was tested from frequencies of hundreds of kHz up to frequencies of tens of MHz.

Bilinear reconfigurable filters derived by using matrix method of unknown nodal voltages

This paper brings a systematic procedure towards analog fully reconfigurable first-order filters. Such property can be understood as a chance to continuously move transfer zero and pole independently on each other leading to the possibility of changing type of frequency response of filter. It is demonstrated that active element known as a differential voltage current conveyor (DVCC) is an ideal candidate for circuit synthesis of the linear circuits, in particular bilinear filters.

Matrix-pencil approach to design super-immittances

This summary paper introduces several circuitry implementations of the super-immittances, i.e. super-inductors and super-capacitors. The proposed circuits are ready neither for immediate design nor practical applications; further analysis is required here to answer stability questions or quantify other limitations. These networks are derived by using systematic procedure based on the matrix method of the unknown nodal voltages with prescribed form of input immittance. Doing this the realizations can be without inductors, electronically tunable via trans-admittance of the operational trans-admittance amplifiers. Proper functions of derived individual two-terminal elements are preliminary verified by Orcad Pspice circuit simulator. The non-ideal and parasitic properties of the used active elements are studied only briefly leaving the place for future research.

Arbitrary phase shifters with decreasing phase

This paper describes a new class of the versatile network elements for analog signal processing; two-ports with frequency dependent phase shift which starts with arbitrary value and tends towards different but still arbitrary value. Speaking in terms of the complex frequency response plotted in polar coordinates the characteristics can connect any two lines in any segment. The idea behind this concept is in utilization of coupled two-terminal devices which are able to keep constant phase shift between driving force and response signal from dc up to infinite frequency; the so-called constant phase elements. The passive realizations of these constant phase elements as well as the proposed network structures based on positive second generation current conveyors are verified by Orcad Pspice circuit simulator as well as experimental measurement.

Simple approach for synthesis of fractional-order grounded immittances based on OTAs

This paper briefly introduces an approach towards a simple synthesis of the grounded fractional-order immittances. Proposed method is based on multiplication of partial grounded immittance emulators with mutually independent electronic control of zero and pole location. General structure is based on the operational transconductance amplifiers (OTAs) while practical realization implements the so-called diamond transistors OPA860. Workability of the proposed concepts in the frequency domain was verified in Orcad PSpice simulations.

Analog continuous-time filtering extended to fractional-order network elements

This paper brings a note on the possibility to utilize the fractional-order two-port circuit element in different filtering applications. The proposed network structures are based on decomposition of final voltage transfer function into fundamental integer-order cells and single two-port described by K(s)=β·sα where αϵ(0, 1) is fractional-order constant with arbitrary step. Some simulation results are provided in the form of Orcad Pspice optimizer, frequency responses and Monte-Carlo analysis.