Nonideal Circuits Research Articles

Investigation of a nonlinear piezoelectric energy harvester with advanced electric circuits with the finite element method

In this contribution, a system simulation method based on the finite element method (FEM) is applied to simulate a strongly coupled bimorph piezoelectric vibration-based energy harvester (PVEH) with various nonlinear, non-ideal and active circuits: The standard circuit, the synchronized switch harvesting on inductor circuit and the synchronized electric charge extraction circuit are considered. Furthermore, nonlinear elastic behavior of the piezoelectric material is taken into account and harmonic base excitations of different magnitudes at a fixed frequency are applied. The holistic FEM-based system simulation approach solves the complete set of piezoelectric equations together with the equation of the electric circuit such that all electromechanical coupling phenomena are taken into account. This fully coupled numerical analysis enables the detailed evaluation of the influences of the electric circuits on the vibrational behavior and the harvested energy of the PVEH with respect to the magnitude of base excitation. Results from literature on the efficiency of electric circuits are confirmed and interactions between mechanical and electrical nonlinearities of PVEHs are revealed.Article highlightsSystem simulations of a mechanically and electrically nonlinear piezoelectric energy harvester are performed using only one software tool.The infuence of electric circuits on the vibration behavior and the effciency of an energy harvester are investigated in detail.Interactions between mechanical and electrical nonlinearities of an energy harvester are revealed.

Energy-Efficient Transmission of Hybrid Array With Non-Ideal Power Amplifiers and Circuitry

This paper presents a new approach to efficiently maximizing the energy efficiency (EE) of hybrid arrays under a practical setting of non-ideal power amplifiers (PAs) and non-negligible circuit power, where coherent and non-coherent beamforming are considered. As a key contribution, we reveal that a bursty transmission mode can be energy-efficient to achieve steady transmissions of a data stream under the practical setting. This is distinctively different from existing studies under ideal circuits and PAs, where continuous transmissions are the most energy-efficient. Another important contribution is that the optimal transmit duration and powers are identified to balance energy consumptions in the non-ideal circuits and PAs, and maximize the EE. This is achieved by establishing the most energy-efficient structure of transmit powers, given a transmit duration, and correspondingly partitioning the non-convex feasible region of the transmit duration into segments with self-contained convexity or concavity. Evident from simulations, significant EE gains of the proposed approach are demonstrated through comparisons with the state of the art, and the superiority of the bursty transmission mode is confirmed especially under low data rate demands.

A corrected microwave multisine waveform generator

This paper proposes a solution for one of the major difficulties associated with arbitrary waveform generation at microwave frequencies: the nonideal RF circuits used for signal generation. It presents a practical implementation of a RF multisine signal generator that corrects for the linear and nonlinear impairments identified with its output RF circuitry. The integration of an adaptive predistortion algorithm with a previously presented methodology for multisine synthesis with prescribed higher-order statistics, proved the feasibility of a simple microwave arbitrary waveform generator that meets the aims of previously developed signal synthesis theory

Development of efficient switched network and mixed-mode simulators

The philosophy, theory and numerical techniques required in the development of a contemporary suite of simulators for switched network and mixed-mode analysis are described in detail. The evolution of a general simulator, SCNAP4, from earlier software is outlined, and comprehensive sensitivity analysis of switched capacitor (SC) and switched current (SI) networks is shown, together with full noise analysis for large SC and SI networks. An extension into semi-symbolic analysis of non-ideal SC and SI circuits is shown to be feasible, with good accuracy being maintained for large networks. The highly efficient techniques are then utilised for large signal distortion analysis and implemented in the SCNAPDIS simulator. The natural progression of the software development subsequently leads to SCNAP5, which interfaces with the commercial logic simulator Verilog to produce a most effective mixed-mode simulator capable of delivering very detailed analysis of mixed-mode SC and SI circuits. In the development of this latest suite of SCNAP software much effort has been directed towards producing highly efficient algorithms, very versatile packages and a uniform structure with a simple user interface. All the software is written in C. A variety of examples are given to illustrate the wide range of application of the software.

1 Gbit/s zero-IF DPSK coherent optical system using a single photodetector

We have demonstrated zero-IF DPSK coherent optical detection at 1Gbit/s without the use of multiple receivers and special optical couplers. To achieve this, we have added a 1GHz sinusoidal phase switching signal to the NRZ phase modulator drive. The measured sensitivity of −37.5dBm, compared with a theoretical estimate of −54.8dBm, is impaired mainly by nonideal electronic circuits.

Compact formulation for exact analysis of nonideal SC circuits

A systematic analysis procedure to obtain closed-form expressions for the z-domain transfer functions of SC circuits with finite GB product op-amps is presented. This method allows exact frequential analysis of a general class of SC circuits, without imposing any restriction in the ratio between GB and clock frequencies.

Performance Limitations of a Practical PCM Terminal

This paper discusses the performance of a practical PCM terminal for time-division speech transmission. Limitations which make performance different from more conventional frequency-division systems are considered. Particular emphasis is placed on limitations resulting from nonideal circuits and signal conditions. Both analytical and experimental results are presented with comparisons given where appropriate.