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In modern communication systems advanced techniques such as digital predistortion (DPD) are required to satisfy stringent demands on transmitter linearity and efficiency. DPD, however, increases the hardware and computational complexity of transmitters. In this article we show that the computational complexity of DPD adaptation can be drastically reduced if a low number of samples is properly selected for DPD adaptation. For this purpose we propose methods of sample selection for DPD adaptation. Among the proposed methods, the highest computational complexity reduction is achieved by a method based on the histogram of signal magnitudes, optimised with respect to characteristics of the radio frequency power amplifier and of the transmitted signal. Simulations indicate that this proposed method can reduce the computational complexity of DPD adaptation by a factor of up to 400 while the linearisation performance of conventional methods is preserved. Besides simulations for three models of distinct power amplifiers, measurements on a real power amplifier further verify the linearisation capabilities of the proposed methods.

This contribution deals with the main parts of the textile-integrated transmitting unit, a transmitter and an antenna, operating in the ISM 5.8 GHz band. The transmitter is based on commercially available WLAN UART Serial Port OWS451 and it is controlled via the UART interface by microprocessor ATmega328. The antenna is based on the circular ring-slot concept and it is able to provide monopolar radiation pattern to ensure maximum coverage of the unit. The unit will be integrated in a seat cover and it will transmit the telemetry of sensors integrated in the seat (temperature, pressure…).

Millimeter waves will play an important role in communication systems in the near future. On the one hand, the bandwidths available at millimeter-wave frequencies allow for elevated data rates, but on the other hand, the wide bandwidth accentuates the effects of wireless front-end impairments on transmitted waveforms and makes their compensation more difficult. Research into front-end impairment compensation in millimeter-wave frequency bands is currently being carried out, mainly using expensive laboratory setups consisting of universal signal generators, spectral analyzers and high-speed oscilloscopes. This paper presents a detailed description of an in-house built MATLAB-controlled 60 GHz measurement test-bed developed using relatively inexpensive hardware components that are available on the market and equipped with digital compensation for the most critical front-end impairments, including the digital predistortion of the power amplifier. It also demonstrates the potential of digital predistortion linearization on two distinct 60 GHz power amplifiers: one integrated in a direct-conversion transceiver and an external one with 24 dBm output power.

Interference between users in adjacent channels negatively affects throughput of mobile networks. In this paper we aim at cancellation of interference caused by a nonlinear power amplifier in a generalized orthogonal frequency division system. We propose an interference cancellation method to subtract these out-of-band emissions from the received signal. In contrast to state-of-the-art methods, our proposed method employs over-the-air estimation of power amplifier model parameters together with a particular frequency domain filtering method that allows to generate the required training data. The proposed interference cancellation method is also verified by an experiment on a software defined radio test bench.

Graphical abstract, Memristor is a non-linear circuit element in which voltage-current relationship is determined by the previous values of the voltage and current, generally the history of the circuit. The nonlinearity in this component can be considered as a fractional-order form, which yields a fractional memristor (fracmemristor). In this paper, a fractional-order memristor in a chaotic oscillator is applied, while the other electronic elements are of integer order. The fractional-order range is determined in a way that the circuit has chaotic solutions. Also, the statistical and dynamical features of this circuit are analyzed. Tools like Lyapunov exponents and bifurcation diagram show the existence of multistability and antimonotonicity, two less common properties in chaotic circuits.

High performance amplifiers are always a demanding component in the world of wireless communication. The amplifier is the heart that drives each radio system. We have designed and developed a high performance one-stage class-B GaN power amplifier for drone applications in the S-band (at 1,6 GHz) with maximum output power 6 W. This paper compares fixed settings of the bias point option and optimized bias point for the best efficiency within the entire output power range. Applying the proposed method, that is particularly advantageous for low power performance to improve efficiency by more than 15 %.

Hybrid evolutionary passive analog circuits syn- thesis method based on modified Univariate Marginal Dis- tribution Algorithm (UMDA) and a local search algorithm is proposed in the paper. The modification of the UMDA algorithm which allows to specify the maximum number of the nodes and the maximum number of the components of the synthesized circuit is proposed. The proposed hybrid ap- proach efficiently reduces the number of the objective func- tion evaluations. The modified UMDA algorithm is used for synthesis of the topology and the local search algorithm is used for determination of the parameters of the components of the designed circuit. As an example the proposed method is applied to a problem of synthesis of the fractional capaci- tor circuit.

This paper provides an innovative practical realization of a memristor based chaotic circuit. The first part discusses the mathematical analysis of the proposed system, including calculation of an eigenvalues, bifurcation diagram and largest Lyapunov exponents. Another parts deal with circuitry realization and the influence of parasitic properties of active elements. The circuit simulations obtained by PSpice environment and the practical measurement results on a breadboard are presented in the last part of this paper. The main aim of this work is an innovative realization of the memristor based chaotic circuit with one type of energy-storage element (linear passive capacitor) and with simpler construction in comparison to other circuits. The next contribution consists in verification of designed circuit with respect to influence of parasitic properties of active elements to chaos destruction. Tento článek poskytuje inovativní realizaci chaotického systému na základě vlastností memristoru. První část pojednává o matematické analýze navrhovaného systému, včetně výpočtu vlastních čísel, bifurkačního diagramu a největších Ljapunových exponentů. Další části se zabývají obvodovou realizací a vlivem parazitních vlastností aktivních prvků. Simulace obvodů získaná v simulačním systému PSpice a výsledky praktického měření jsou uvedeny v poslední části. Hlavním přínosem této práce je inovativní realizace chaotického systému s jedním akumulačním prvkem (lineární pasivní kondenzátor) a jednoduchá konstrukce ve srovnání s dosud publikovanými zapojeními. Další přínos spočívá v ověření funkčnosti navrženého zapojení s uvažováním kritických hodnot parazitních vlastností použitých aktivních prvků.

In this paper the discrete step functions are used in order to generate m×n scroll chaotic hypercube attractors. The design and realization of multi-scroll attractors depends on synthesizing the nonlinearity with an electrical circuit. The essence of the novel approach is in designing the transfer function with analog to digital converters connected directly without any microcomputer, instead of using standard comparator or hysteresis methods. Therefore there is no special need for synthesizing the nonlinearity towards m × n scroll chaotic attractors. The approach is verified with PSpice16.0 circuit simulator and experimentally measured. K e y w o r d s: multi grid scrolls, chaos, dynamical systems, integrator synthesis, digital converters

This review paper describes different lumped circuitry realizations of the chaotic dynamical systems having equilibrium degeneration into a plane object with topological dimension of the equilibrium structure equals one. This property has limited amount (but still increasing, especially recently) of third-order autonomous deterministic dynamical systems. Mathematical models are generalized into classes to design analog networks as universal as possible, capable of modeling the rich scale of associated dynamics including the so-called chaos. Reference state trajectories for the chaotic attractors are generated via numerical analysis. Since used active devices can be precisely approximated by using third-level frequency dependent model, it is believed that computer simulations are close enough to capture real behavior. These simulations are included to demonstrate the existence of chaotic motion.

This contribution brings a deep and detailed study of the dynamical behavior associated with nonlinear oscillator described by a single third-order differential equation with scalar jump nonlinearity. The relative primitive geometry of the vector field allows making an exhaustive numerical analysis of its possible solutions, visualizations of the invariant manifolds and basins of attraction as well as proving the existence of chaotic motion by using the concept of both Shilnikov theorems. The aim of this paper is also to complete, carry out and link the previous works on simple Newtonian dynamics and answer the question how individual types of the phenomenon evolve with time via understandable notes. Tento příspěvek přináší podrobnou studii dynamického chování spojené s nelineárním oscilátorem popsaným systémem třetího řádu se skokovou skalární nelinearitou.

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).

This short paper describes the experimental measurement setup for extraction of dynamical parameters of the encapsulated bond wires. Based on the proposed method a current carrying capability as well as fatigue process can be quantified and statistically evaluated. The integrated circuits with bonding wires and Kelvin probes were fabricated by ON Semiconductor Company in Belgium.

This paper brings a new mathematical model of the third-order autonomous deterministic dynamical system with associated chaotic motion. Its unique property lies in the existence of circular equilibrium which was not, by referring to the best knowledge of the authors, so far reported. Both mathematical analysis and circuitry implementation of the corresponding differential equations are presented. It is shown that discovered system provides a structurally stable strange attractor which fulfills fractal dimensionality and geometrical density and is bounded into a finite state space volume. Článek přináší nový matematický model nelineárního autonomního systému s cirkulárním ekvilibriem. Celý systém je matematicky analyzován, poté je prezentováno obvodové zapojení jako důkaz strukturální stability včetně měření.

The FP7 project nanoCOPS derives new methods for simulation during development of designs of integrated products. It covers advanced simulation techniques for electromagnetics with feedback couplings to electronic circuits, heat and stress. It is inspired by interest from semiconductor industry and by a simulation tool vendor in electronic design automation. The project is on-going and the paper presents the outcomes achieved after the first half of the project duration.

In this paper, electrothermal field phenomena in electronic components are considered. This coupling is tackled by multiphysical field simulations using the Finite Integration Technique (FIT). In particular, the design of bonding wires with respect to thermal degradation is investigated. Instead of resolving the wires by the computational grid, lumped element representations are introduced as point-to-point connections in the spatially distributed model. Fabrication tolerances lead to uncertainties of the wires' parameters and influence the operation and reliability of the final product. Based on geometric measurements, the resulting variability of the wire temperatures is determined using the stochastic electrothermal field-circuit model., Comment: submitted to DATE, available at http://ieeexplore.ieee.org/document/7459510/