Optimal Matching Conditions Research Articles

Asymmetrical Sequential Load Modulated Balanced Amplifier With Composited Impedance Inverter and Reciprocal Mode for Broadband Applications

In this paper, the design of a broadband asymmetrical sequential load modulation balanced amplifier (ASLMBA) is presented. The composited impedance inverters, which contain the intrinsic elements and the output matching networks (OMNs) of the balanced power amplifier (BPA) transistors, are inserted before the output coupler of the BPA pair. In this way, optimal matching condition of the BPA transistors can be maintained over a wide bandwidth. In addition, to ensure an optimal load modulation trajectory of the control amplifier (CA) without over-saturation, a reciprocal mode is applied to the BPA pair by elaborately changing the turn-on sequence of the sub-amplifiers, which is affected by the composited impedance inverter and the OMN of the control amplifier. It is illustrated that the proposed ASLMBA can effectively maintain high efficiency over an extended dynamic range and a wide bandwidth. As a proof of concept, a broadband ASLMBA working over 1.35-2.55 GHz is designed and measured in this work. Experimental results show that the designed ASLMBA achieves a saturation output power of 43.2-45.1 dBm with a saturation gain of 6.5-10.5 dB and a saturation drain efficiency (DE) of 57.8-77.7%. Meanwhile, the 6 dB and 10 dB back-off DEs of the designed ASLMBA are 51.3-66.6% and 47.7-68.9%, respectively.

Nonreciprocal coupling modulated difference-sideband generation in a double-cavity optomechanical system.

We theoretically study the difference-sideband generation in a double-cavity optomechanical system with nonreciprocal coupling. Beyond the conventional linearized description of optomechanical interactions, we derive analytical expressions for the efficiency of difference-sideband generation by using a perturbation method. Here we investigate bistable behaviors of the system and show the difference-sideband generation modulated by the nonreciprocal coupling strength between the two cavities. We find that the nonreciprocal coupling strength can not only affect the bistability of the system but also lead to different efficiencies of difference-sideband generation at low power. To achieve high efficiency of difference-sideband generation, we give the optimal matching conditions under different parameter mechanisms. Especially as the power increases, we find new matching conditions with remarkable difference-sideband generation emerging, which is attribute to the strong coherence between the cavity field and the mechanical oscillator. Furthermore, a feasible scheme to obtain difference-sideband generation by employing multiple adjustable variables is proposed. Our results may find applications in nonreciprocal optical frequency combs and communications, and provide a potential method for precision measurements and on-chip manipulation of light transmission.

Type-2 fuzzy-logic based control of photovoltaic-hydrogen production systems

Green hydrogen will play an important role for sustainable development, it can be considered as a promising solution for energy transition. In this paper, direct and indirect-coupled configuration of hydrogen production system consisted of Photovoltaic (PV) source and electrolyzer stack are investigated. A study on power loss and efficiency in PV-electrolyzer system is conducted for both cases. Optimal matching conditions in directly coupled hydrogen system can be achieved by modifying the configuration of series/parallel cells in electrolyzer stack or PV generator. However, the energy transfer can be improved by incorporating a buck converter between PV string and electrolyzer stack. In this article, the type-2 fuzzy inference system is proposed to control the operating point of PV string by adjusting the duty cycle of control signal of buck converter. A comparison with classical MPPT methods is carried out in order to verify the efficiency of suggested technique. It has been found that the indirect-coupled hydrogen system can achieve higher energy transfer rate by ensuring continuous extracting of maximum power of PV source under various operating conditions. The obtained results, under Matlab/Simulink environment, demonstrated a satisfactory performance of type-2 fuzzy logic controller in both transient and permanent regimes. We obtain a minimal power loss value (less than 8.1%) in directly-coupled hydrogen production system, in addition a satisfactory value of efficiency (more than 93%) has been obtained.

Increased Spurious-Free Dynamic Range in Frequency Sweeping Interferometry by Suppression of Parasitic Amplitude Modulation

We propose an envelope detrending method to correct parasitic amplitude modulation (AM) in frequency sweeping interferometry (FSI). Parasitic AM arises from effects such as device spectral response and residual AM of laser. The periodic component in parasitic AM introduces spurious harmonics, which degrade the spurious-free dynamic range (SFDR) and interfere with information analysis. The proposed method employs a Hilbert transform to obtain a time-varying amplitude fluctuation curve from an auxiliary interferometer. This curve is then employed to detrend the parasitic AM in the main interferometric signal, thus restoring the point spread function and improving the SFDR. An optimal SFDR can be obtained when the optical path differences (OPDs) of the two interferometers are equal, while mismatched OPDs lead to a rapid degradation of the SFDR correction. Experimental results demonstrate the effectiveness of the proposed method and the optimal matching condition. A maximum SFDR of 90.2dB can be achieved when the OPD matching condition is satisfied. By applying the method to an optical frequency domain polarimeter, we realized a measured 81.1dB polarization extinction ratio. We believe that the proposed method can also help to improve the SFDR in other FSI systems.

Hydrodynamic characteristic investigations of a collaborative spoiled rudder under open water conditions

This study presents the hydrodynamic performance estimation of a collaborative spoiled rudder (CSR) - a new concept of ship rudder under open water conditions. The grid sensitivity study is carried out and the numerical method used in this work is validated by comparing with experimental data. The hydrodynamic performances of different CSR configurations at various rudder angles are simulated. The result shows that the existence of the spoiler has positive effect on the rudder lift and the effect gets more obvious with the increase of spoiler open angle. The spoiler can be controlled easily owing to the small spoiler stock torque. The optimal matching results show that, under the optimal matching conditions, the lift to drag ratios of the CSR are generally higher than those of the CR for the same target lift, and the improvement of the CSR in the rudder effectiveness gets more obvious with the increase of target lift. Furthermore, the CSR having the optimal matching rudder angle and spoiler open angle is much easier to steer compared with the CR with the same lift being generated. Overall, properly adjusting the rudder angle and the spoiler open angle of the CSR can significantly improve the rudder effectiveness.

Beam loading assisted matching scheme for high quality plasma acceleration in linear regime

We propose and we numerically design a working point for beam driven plasma wakefield acceleration that allows us to preserve the witness quality. This working point is a new scheme where a low density driver generates a wakefield in linear regime and the witness transverse evolution is dominated by the beam loading effect. We derived optimal matching conditions to prevent the phase space degradation by means of a transverse envelope equation.

Generation and enhancement of sum sideband in a parity-time-symmetric optomechanical system

This paper studies sum sideband generation in a parity-time ()-symmetric optomechanical system, where an active cavity is coupled to the passive cavity of a general optomechanical system. We find that the upper and lower sum sideband generation efficiencies can be greatly enhanced by the introduction of the gain cavity. Furthermore, when the coupling coefficient and gain–loss ratio are near the exceptional point, the upper sum sideband amplitude is larger than that of the probe fields. This paper also investigates the optimal matching conditions for upper and lower sum sideband generation in the -symmetric phase, the broken -symmetric phase and at the exceptional point, respectively. As a result, new matching conditions are discovered and the appearance of these new matching conditions is ascribed to eigenfrequency splitting. The enhanced sum sideband can be applied to coherent light manipulation, quantum information processing and sensitive quantum metrology.

Alkaline Sustained-Release Material Based on In Situ Manganese Removal Technique of Groundwater

To improve the pH of groundwater for in situ manganese removal, we prepared high-performance and long-life alkali sustained-release materials (ASRMs) from calcium oxide (CaO) and cement (CEM) by a physical mixing method. The ASRMs were tested by alkali-releasing experiments under dynamic conditions and filtration experiments. Surface microstructures were characterized using scanning electron microscopy and energy-dispersive spectrometry. ASRMs exhibited high alkali-releasing performance and effective pH controllability. The optimal matching conditions were flow rate of 5.0 ml/min, solid–liquid ratio of 13.5 g/l, and CaO:CEM weight ratio of 1:20. Under the influence of flow velocity, initial dosage and raw material ratio, the Elovich equation well fitted alkali release with correlation coefficients above 0.982476. The release kinetic equation of ASRMs was determined on MATLAB. In these conditions, the ASRMs could release well and maintain the aqueous pH over 9.5, with a long releasing life of 10 days. This study can be referred to for practical application of this technology into groundwater restoration.

Analysis of Wireless Power Transfer for Adjustable Power Distribution among Multiple Receivers

In a multiple-receiver wireless power transfer system, most of the power tends to be transferred to a receiver close to a transmitter. Therefore, it is highly desirable to find a way of providing the required amount of power to each receiver, as well as to improve the overall power transfer efficiency. In this letter, we investigate an impedance matching method of providing adjustable power distribution among receivers while preserving a high overall power transfer efficiency using coupled mode theory and circuit model. We also derive an optimal matching condition and the upper bound of the overall power transfer efficiency, in order to assess the performance of the proposed method. Finally, we perform circuit-level simulations to validate the accuracy of our analysis and the effectiveness of the proposed method.

The parametric optimum analysis of a proton exchange membrane (PEM) fuel cell and its load matching

Based on the irreversible model of a PEM fuel cell working at steady state, expressions for the power output, efficiency and entropy production rate of the PEM fuel cell are analytically derived by using the theory of electrochemistry and non-equilibrium thermodynamics. The effects of multi-irreversibilities resulting from electrochemical reaction, heat transfer and electrical resistance on the key parameters of the PEM fuel cell are analyzed. The curves of the power output, efficiency and entropy production rate of the PEM fuel cell varying with the electric current density are represented through numerical calculation. The general performance characteristics of the PEM fuel cell are revealed and the optimum criteria of the main performance parameters are determined. Moreover, the optimal matching condition of the load resistance is obtained from the relations between the load resistance and the power output and efficiency. The effects of the leakage resistance on the performance of the PEM fuel cell are expounded and the optimally operating states of the PEM fuel cell are further discussed.

A unified approach to optimal conditions of power harvesting using electromagnetic andpiezoelectric transducers

Power harvesting systems generate electric power from mechanical vibration usingelectromechanical transducers. To assess the practical performance of these systems, it isimportant to be able to estimate the maximum power that could be harvested from aspecific structure and to derive the optimal conditions for the harvesting. Weintroduce a two-port network model which can fully describe the electromechanicalcoupled dynamics of the transducer, including the interaction between the structureand the electrical load in a unified manner. Electromagnetic and piezoelectrictransducers are then considered as special cases of this general treatment. Thepower harvested by both types of transducer on a simply supported beam isderived and the optimal matching conditions and the maximum harvested powerare obtained theoretically. In this numerical example, a piezoelectric transducerwould have higher potential than an electromagnetic device of equal mass forthe harvesting, but only when the transducer parameters are tuned optimally.

Optimal Antenna Matching and Mutual Coupling Effect of Antenna Array in MIMO Receiver

Antenna array is essential factor for multiple- input multiple-output (MIMO) wireless systems. Since the antenna array is composed of closely spaced elements, the mutual coupling among the elements cannot be ignored for the best performance of the array. Mutual coupling affects the MIMO channel, so the performance of a MIMO system, including channel capacity and diversity, varies with the degree of mutual coupling. The effect of mutual coupling is a function of the antenna load impedance. Therefore, designing an optimal element-matched array for a MIMO system requires consideration of the optimal matching condition for the array elements, the one that maximizes the channel capacity. We evaluated the effects of mutual coupling with various matching conditions in dipole arrays, and investigated their effects on the path correlation and channel capacity of MIMO systems. Simulation showed that the conventional conjugate matching of each element is still suitable for closely spaced elements except when the separation is about less than 0.1λ. Theoretical consideration of the received power of a closely-spaced-element array is also provided to show the effects of mutual coupling.

The maximum work output of an electric battery in a given time

A new model of an electric battery is established, based on the simplest battery model and Denno's battery model with an internal dissipation. The model is used to investigate the fundamental problem of how to maximize the work output of an electric battery in a given time. The important relation of the voltage across the battery terminals varying with the discharging time is derived by using variational calculus. The maximum work output of the battery is calculated. The optimal matching condition of the load resistance is determined. The reasonable range of the discharging time is given. The other characteristics of the battery at the maximum work output are discussed further. The results obtained here have some theoretical applications not only for raising the utilization of the electric energy stored in batteries, but also for improving the performance of some electric circuits.

The influence of Thomson effect on the maximum power output and maximum efficiency of a thermoelectric generator

Considering a thermoelectric generator as a heat engine cycle, the general differential equations of the temperature field inside thermoelectric elements are established by means of nonequilibrium thermodynamics. These equations are used to study the influence of heat leak, Joule’s heat, and Thomson heat on the performance of the thermoelectric generator. New expressions are derived for the power output and the efficiency of the thermoelectric generator. The maximum power output is calculated and the optimal matching condition of load is determined. The maximum efficiency is discussed by a representative numerical example. The aim of this research is to provide some novel conclusions and redress some errors existing in a related investigation.

Coupling an injection laser to a single-mode optical fiberguide with the aid of a microlens in a matching-module system

The present paper is devoted to theoretical and experimental investigations of the optimal matching conditions when an elliptic-geometry laser beam is fed into an SFG with hemispherical input end. A rigid fiber-optics module that ensures effective and stable coupling of a laser with an SFG has been constructed on the basis of the investigated matching method, using a heterolaser with slightly elongated elliptic beam geometry cross section.

The Scattering Matrix: Normalized to Complex n-Port Load Networks

The scattering matrix is normalized to complex n-port loads, and some of the elementary properties of this generalized scattering matrix are discussed. The normalized scattering matrix is obtained in a straightforward manner from both the current-basis and voltage-basis scattering matrices. These matrices are presented from the intuitively attractive viewpoint of measures of the deviation of actual circuit behavior from optimal circuit behavior. The optimal matching condition employed is the specialization to the timeinvariant case of that obtained for complex, time-varying n-port networks excited by arbitrary waveforms.