Unconventional Signals Oscillators

Dizertační práce se zabývá elektronicky nastavitelnými oscilátory, studiem nelineárních vlastností spojených s použitými aktivními prvky a posouzením možnosti vzniku chaotického signálu v harmonických oscilátorech. Jednotlivé příklady vzniku podivných atraktorů jsou detailně diskutovány. V doktorské práci je dále prezentováno modelování reálných fyzikálních a biologických systémů vykazujících chaotické chování pomocí analogových elektronických obvodů a moderních aktivních prvků (OTA, MO-OTA, CCII ±, DVCC ±, atd.), včetně experimentálního ověření navržených struktur. Další část práce se zabývá možnostmi v oblasti analogově – digitální syntézy nelineárních dynamických systémů, studiem změny matematických modelů a odpovídajícím řešením. Na závěr je uvedena analýza vlivu a dopadu parazitních vlastností aktivních prvků z hlediska kvalitativních změn v globálním dynamickém chování jednotlivých systémů s možností zániku chaosu v důsledku parazitních vlastností použitých aktivních prvků.The doctoral thesis deals with electronically adjustable oscillators suitable for signal generation, study of the nonlinear properties associated with the active elements used and, considering these, its capability to convert harmonic signal into chaotic waveform. Individual platforms for evolution of the strange attractors are discussed in detail. In the doctoral thesis, modeling of the real physical and biological systems exhibiting chaotic behavior by using analog electronic building blocks and modern functional devices (OTA, MO-OTA, CCII±, DVCC±, etc.) with experimental verification of proposed structures is presented. One part of theses deals with possibilities in the area of analog–digital synthesis of the nonlinear dynamical systems, the study of changes in the mathematical models and corresponding solutions. At the end is presented detailed analysis of the impact and influences of active elements parasitics in terms of qualitative changes in the global dynamic behavior of the individual systems and possibility of chaos destruction via parasitic properties of the used active devices.

Biquadratic Filter Applications Using a Fully-Differential Active-Only Integrator

A new class of active filters, real active-only filters is described and possible implementation issues of these filters are discussed. To remedy these issues, a fully-differential active-only integrator block built around current controlled current conveyors is presented. The integration frequency of the proposed circuit is adjustable over a wide frequency range. As an application, a real active-only filter based on the classical two-integrator loop topology is presented and designed. The feasibility of this filter in a 0.35µm CMOS process is verified through SPECTRE simulation program in the CADENCE design tool

Nonlinear Resistor with Polynomial AV Characteristics and Its Application in Chaotic Oscillator

This paper shows the realization of two terminal devices with an arbitrary polynomial nonlinearity up to the fifth order. The proposed design procedure is completely systematic using minimum of components. The very heart of our conception is four-channel four-quadrant analog multiplier MLT04. The implementation of synthesized nonlinear resistor as a general nonlinearity in chaotic oscillator is also presented and experimentally verified

Current-Controlled Current-Mode Universal Biquad Employing Multi-Output Transconductors

This paper deals with RC active biquad working in the so-called current mode (CM). The design approach uses only three transconductors (OTA) with the minimum necessary number of outputs and with only three passive grounded elements. The proposed filter has simple circuit configuration providing all standard transfer functions such as high-pass (HP), band-pass (BP), low-pass (LP), band-reject (BR) and all-pass (AP). Electronic tuning and independent adjusting of the quality factor and bandwidth of BP filter is possible. The presented circuits are verified by PSpice simulations utilizing OTAs on transistor level of abstraction. The linear parasitic effects of the real active elements in each suggested circuit are briefly discussed. Experimental verification is also given. Designed networks can be used in many applications such as antialiasing filters, in high-speed data telecommunication systems, for signal processing in the cable modems, in regulation and measurement techniques etc

Study of chaotic behavior in automatic tuning loops for continuous–time filters

Continuous–time filters (CTFs) with automatic tuning loops are nonlinear feedback systems with potential instability. Thus, their appropriate linear dynamic modeling should be obtained to assure stability in case an improved design of the loop controllers is to be carried out. A systematic approach using a small signal model would allow obtaining these controllers. However, bifurcations and nonlinear phenomena may appear which cannot be predicted by this analysis. This leads to potential instability, semiperiodic or chaotic behavior and, thus, circuit malfunction. The aim of this paper is to show by means of simulations and experimental results that nonlinear phenomena, which cannot be predicted by the common small signal analysis, may appear in this kind of circuits when circuit parameters are varied.Postprint (published version

Reconnection–less Reconfigurable Fractional–Order Current–Mode Integrator Design with Simple Control

A design of a fractional-order (FO) integrator is introduced for operation of resulting solution in the current mode (CM). The solution of the integrator is based on the utilization of RC structures, but in comparison to other RC structure based FO designs, the proposed integrator offers the electronic control of the order. Moreover, the control of the proposed integrator does not require multiple specific and accurate values of the control voltages/currents in comparison to the topologies based on the approximation of the FO Laplacian operator. The electronic control of a gain level (gain adjustment) of the proposed integrator is available. The paper offers the results of Cadence IC6 (spectre) simulations and more importantly experimental measurements to support the presented design. The proposed integrator can be used to build various FO circuits as demonstrated by the utilization of the integrator into a structure of a frequency filter in order to provide FO characteristics