Phase Shift Research Articles

Optically controlled fine-tuning phase shift cell based on thin-film Ge2Sb2Te5 for light beam phase modulation

Optically controlled fine-tuning phase shift cell based on thin-film Ge2Sb2Te5 for light beam phase modulation

1-Bit Reconfigurable Transmitarray Antenna with Out-of-Band RCS Reduction

Stealth reconfigurable transmitarray antennas (RTAs) are essential components in wireless communication and radar detection systems. Therefore, in this study, we propose a 1-bit RTA with out-of-band radar cross-section (RCS) reduction. The antenna consists of an absorptive frequency selective transmission (AFST) layer and RTA layer separated by air. Specifically, the AFST layer achieves out-of-band RCS reduction and in-band transmission utilizing the first three resonant modes of a bent metallic strip with a centrally loaded resistor. Meanwhile, the RTA layer adopts a receiver–transmitter structure with an active receiving dipole and a passive orthogonal transmitting dipole. 1-bit phase shift is achieved by alternating two pin diodes integrated on the active dipole to reverse its current direction. To evaluate the proposed design, a 16 × 16-element prototype was designed, fabricated, and measured. For scattering, the bandwidth of 10 dB RCS reduction was about 52.5% and 43.8%, respectively. For radiation, the measured gain was 20.1 dBi at 7.5 GHz, corresponding to an aperture efficiency of 12.7%. The gain loss of beam scans to ±60° was about 5 dB in both two principal planes.

On Large Amplitude Vibrations of the Softening Duffing Oscillator at Low Excitation Frequencies—Some Fundamental Considerations

The Duffing equation containing a cubic nonlinearity is probably the most popular example of a nonlinear oscillator. For its harmonically excited, slightly damped, and softening version, stationary large amplitude solutions at subcritical excitation frequencies are obtained when standard semi-analytical methods like Harmonic Balance or Perturbation Analysis are applied. These solutions have the shape of a nose in the amplitude-frequency diagram. In prior work, it has been observed that these solutions may contain large errors and that high ansatz orders may be necessary when applying the Harmonic Balance or other semi-analytical methods to make them converge. Some of these solutions are observed to be asymptotically stable, while in most cases, they are unstable. The current paper aims to give a descriptive explanation for this behavior of the nose solutions, which is mainly related to the exact solution of the free undamped vibrations. Based on this, approximations of the nose solutions are calculated with a procedure combining properties of Perturbation Analysis and Harmonic Balance. Therein, the exact solution of the free undamped vibrations is taken as the zeroth approximation, while higher-order solution parts are calculated by balancing the harmonics, and the phase shift of the zeroth approximation is calculated by a residuum minimization. This method just requires the solution of a system of linear algebraic equations, while systems of nonlinear algebraic equations have to be solved in the case of directly applying Harmonic Balance.

A Novel Six-Dimensional Chimp Optimization Algorithm—Deep Reinforcement Learning-Based Optimization Scheme for Reconfigurable Intelligent Surface-Assisted Energy Harvesting in Batteryless IoT Networks

The rapid advancement of Internet of Things (IoT) networks has revolutionized modern connectivity by integrating many low-power devices into various applications. As IoT networks expand, the demand for energy-efficient, batteryless devices becomes increasingly critical for sustainable future networks. These devices play a pivotal role in next-generation IoT applications by reducing the dependence on conventional batteries and enabling continuous operation through energy harvesting capabilities. However, several challenges hinder the widespread adoption of batteryless IoT devices, including the limited transmission range, constrained energy resources, and low spectral efficiency in IoT receivers. To address these limitations, reconfigurable intelligent surfaces (RISs) offer a promising solution by dynamically manipulating the wireless propagation environment to enhance signal strength and improve energy harvesting capabilities. In this paper, we propose a novel deep reinforcement learning (DRL) algorithm that optimizes the phase shifts of RISs to maximize the network’s achievable rate while satisfying IoT devices’ energy harvesting constraints. Our DRL framework leverages a novel six-dimensional chimp optimization algorithm (6DChOA) to fine-tune the hyper-parameters, ensuring efficient and adaptive learning. The proposed 6DChOA-DRL algorithm optimizes RIS phase shifts to enhance the received power of IoT devices while mitigating interference from direct and RIS-cascaded links. The simulation results demonstrate that our optimized RIS design significantly improves energy harvesting and achievable data rates under various system configurations. Compared to benchmark algorithms, our approach achieves higher gains in harvested power, an improvement in the data rate at a transmit power of 20 dBm, and a significantly lower root mean square error (RMSE) of 0.13 compared to 3.34 for standard RL and 6.91 for the DNN, indicating more precise optimization of RIS phase shifts.

Fiber Bragg Grating-Based Tunable Wavelength Orbital Angular Momentum Beam Generation with

This paper introduces and theoretically analyze the generation of orbital angular momentum (OAM) modes with different polarization in a few-mode optical fiber using short-period gratings (Bragg gratings) at telecommunication wavelengths. The modal characteristics of the supported modes have been studied using a full-vector true-mode analysis. Additionally, a appropriately designed raised-cosine apodized grating is employed to couple the HE11 core mode to the counter-propagating cladding mode. In contrast to the long-period grating based OAM mode generation, the present scheme is free from periodic back-coupling of optical power into the fundamental core mode which drastically enhances the OAM mode purity. The ±1-order OAM beam has been generated by combining the first higher order core modes with a π/2 phase shift between them. This paper also shows that by combining different higher order modes, it is possible to obtain a linearly polarised OAM mode or a circularly polarised OAM mode. Finally, I also report that in fibers with larger core radius, the higher order OAM mode of topological charge ±2 or higher can also be generated using similar approach of using short-period gratings. The topological charge of the OAM mode is verified by observing both the coaxial and off axial interference fringes.

Theoretical Analysis and Optimization Strategies of Wavefront Errors and Chromatic Aberrations Induced by Optical Coatings

This research addresses the frequently overlooked wavefront errors and chromatic aberrations in optical coatings. It identifies intrinsic phase shifts within the coating system as the primary cause of these aberrations, rather than errors in surface form accuracy. This study investigates the impact of group delay (GD) on wavefront errors in optical coatings. The results reveal that GD contributes significantly to wavefront errors in two cases: when coatings exhibit thickness non-uniformity and when they operate over a wide range of incident angles. At a single incident angle, wavefront errors are only induced when both GD and thickness non-uniformity exist. In the case of a wide range of incident angles, even in the absence of thickness non-uniformity, GD still introduces wavefront errors. This study introduces novel optimization strategies for thin-film components through theoretical derivation, aiming to minimize wavefront errors by optimizing GD.

Interaction Between Gravitational Waves and Trapped Bose–Einstein Condensates

Inspired by recent proposals for detecting gravitational waves by using Bose–Einstein condensates (BECs), we investigated the interplay between these two phenomena. A gravitational wave induces a phase shift in the fidelity amplitude of the many-body quantum state. We investigated the enhancement of the phase shift in the case of Bose condensates confined by an anisotropic harmonic potential, considering both ideal and interacting BECs.

Enhanced Surface Plasmon Resonance Sensing via Kramers-Kronig Phase Extraction.

This study introduces a novel approach to enhance surface plasmon resonance (SPR) sensing using Kramers-Kronig (K-K) relations for phase extraction from reflection spectra. By applying the K-K relations, a phase shift sensitivity of 3400°/RIU is achieved improving SPR detection limits to 9 × 10-6 RIU, which is four times more sensitive than conventional methods for determining SPR peak shifts. This advancement enables more precise detection of refractive index changes in aqueous solutions, making it valuable for biosensing and environmental monitoring with spectrometers.

Asymptotic analysis of resonance behaviors for the (2+1)-dimensional generalized fifth-order KdV equation via Hirota's bi-linear method

Abstract The generalized fifth-order Korteweg–de Vries (KdV) equation, encompasses certain characteristics of the original KdV equation and is capable of describing more complex wave phenomena. The Miles resonance conditions are achieved for Y-shaped solitons by rendering the phase shift induced by the elastic interaction among N-solitons. Our investigation not only conducts a thorough analysis of the low-order resonant solutions but also presents general resonant conditions that enable the degeneration of N-solitons solutions into resonant solutions.

On elastic deformations of cylindrical bodies under the influence of the gravitational field

Background Elastic deformations of gravitating cylindrical bodies are relevant for state-of-the-art photonic experiments, as they affect the physical properties of materials under consideration, impacting wave propagation. This is of key importance for a recently planned experiment to explore the influence of the gravitational field on entangled photons propagating in waveguides. The purpose of this work is to determine these elastic deformations as functions of temperature, pressure, and of the gravitational field. We thus determine the deformations of the body due to changes of the gravitational field, and obtain stringent bounds on the control of temperature and pressure so that the effects of the associated elastic deformations on the photons propagating in a waveguide are smaller than the phase shifts associated with the change of the gravitational field. Methods We use the methods of linear elasticity, including thermoelasticity, to determine the stresses and strains of the medium. For this, the symmetry of the cylinder allows us to solve the problem by using Mitchell’s solutions of the equations satisfied by the Airy functions. The boundary conditions are implemented by an approximation of the Hertz contact method. Results We calculate the displacements, the stresses and strains for several classes of boundary conditions, and give explicit solutions for a number of physically motivated configurations. The influence of the resulting deformations on the planned GRAVITES experiment is determined. Conclusions The results are relevant for fiber interferometry experiments sensitive to the effects of the gravitational field on photon propagation. Our calculations give stringent bounds on the environmental variables, which need to be controlled in such experiments.

Susceptibility to Low-Frequency Breakdown in Full-Wave Models of Liquid Crystal-Coaxially-Filled Noise-Shielded Analog Phase Shifters

Building on the fully encapsulated architecture of liquid crystal (LC) coaxial phase shifters, which leverages noise-shielding advantages for millimeter-wave wideband reconfigurable applications, this study addresses the less-explored issue of low-frequency breakdown (LFB) susceptibility in modern full-wave solvers. Specifically, it identifies the vulnerability nexus between the tuning states (driven by low-frequency bias voltages) and the constitutive elements of LC-filled coaxial phase shifters—namely, the core line, housing grounding, and radially sandwiched tunable dielectrics—operating at millimeter-wave frequencies (60 GHz WiGig), microwave (1 GHz), and far lower frequency regimes (down to 1 MHz, 1 kHz, and 1 Hz) for long-wavelength or quasi-static conditions, with specialized applications in submarine communications and geophysical exploration. For completeness, the study also investigates the device state prior to LC injection, when the cavity is air-filled. Key computational metrics, such as effective permittivity and characteristic impedance, are analyzed. The results show that at 1 kHz, deviations in effective permittivity exceed four orders of magnitude compared to 1 GHz, while characteristic impedance exhibits deviations of three orders of magnitude. More critically, in the LFB regime, theoretical benchmarks from 1 MHz to 1 kHz and 1 Hz demonstrate an exponential increase in prediction error for both effective permittivity, rising from 16.8% to 1.5 × 104% and 1.5 × 107%, and for characteristic impedance, escalating from 8.1% to 1.15 × 103% and 3.9 × 104%, respectively. Consequently, the prediction error of the differential phase shift, minimal at 60 GHz (0.16%), becomes noticeable at 1 MHz (4.39%), increases sharply to 743.88% at 1 kHz, and escalates dramatically to 2.18 × 1010% at 1 Hz. The findings reveal a pronounced frequency asymmetry in LFB susceptibility for the LC coaxial phase shifter biased at extremely low frequencies.

Design and FPGA Implementation of Relative Dynamics Measurement Techniques for Satellite Communication Systems

Performance of a satellite communication receiver is greatly affected by the relative dynamics scenario. Relative dynamics is related to the variable motion between communication source and destination systems. It encompasses relative acceleration and relative jerk. The paper presents the phase error-based measurement techniques for relative dynamics. Binary Phase Shift Keying (BPSK) demodulator is considered for development and verification of the techniques. Paper describes the requirement and design of 3rd order BPSK demodulator for measurement and handling relative jerk. System level simulation is carried out for different scenario. Design is coded in VHDL and realized on the Xilinx platform. Application of developed system in adaptive signal processing based BPSK demodulator is also dealt in detail.

Development of a Wollaston phase grating polarized interferometer for simultaneous generation of interferograms

Wollaston phase-grating interferometer is introduced to measure of the optical phase across various samples. The system employs a Wollaston prism to create two angularly separated beams and with orthogonal linear polarizations. Working as a quasi-common-path interferometer, one of these beams serves as a reference while the other acts as the sample. Circular polarization states are induced in each beam using a quarter-wave plate. Both beams are directed onto a 4-f imaging system, within which a 2D phase grating is positioned at the Fourier plane. This 2D grating enables the superposition of the two beams, generating a polarized interferogram. The characteristics of the diffractive elements cause the grating to produce replicas of interference patterns, which are centered around the diffraction orders of the 2D phase grating itself. Due to the presence of interference patterns with inherent π phase shifts, this configuration reduces the number of polarizers needed to implement phase shifting methods. It is shown that by using two polarizers it is possible to generate four phase shifts. A polarizer oriented at 0° covers two of the replicas and another polarizer oriented at π/4 covers the remaining interferograms. This configuration introduces phase shifts of ξ1 = 0, ξ2 = π/2, ξ3 = π and ξ4 = 3π/2. Results obtained for static and dynamic samples are presented, as well as the corresponding statistics on the repeatability of the configuration.

Low-Power Design of Fully Digital BPSK Modulator and Demodulator Utilizing Nanoscale FinFET for Smart Implants

This study aims to create a high-speed, low-power data transmission solution for implantable medical devices based on cutting-edge FinFET technology. The work examines the application of Binary Phase Shift Keying (BPSK) modulation through a transmission gate design, which provides an optimal blend of low resistance, high-speed performance, and minimal power consumption. Additionally, the work includes the design of a sine-to-square wave converter and a modulating signal generator. FinFET is employed owing to its high switching speed, low power consumption, low leakage current, and excellent tolerance of short channel effects. The design exhibits a steady electric field at the source end, a high electrostatic potential, and an improved ON current at low work function values using Sentaurus TCAD simulations of a 20nm FinFET, allowing high-speed data modulation in smart implants. A nonoverlapping phase generator, a low-power, current-starved gated ring oscillator, a frequency divider utilizing a True Single Phase Clock D-Flip-flop, and an XOR gate serving as a pulse counter are all featured in the design of the BPSK demodulator. This work is significant for its ability to drastically reduce power consumption to 1.75μW while retaining high data transmission speeds, making it perfect for next-generation implantable medical devices. With a 0.9 V power supply, this FinFET-based BPSK modulator and demodulator achieve a far lower power consumption than conventional CMOS-based designs, which increases device longevity and efficiency in settings with limited resources.

Precise beam control in optical phased arrays using the four steps rotating element electric field vector method

The integrated optical phase arrays (OPAs) possess the capability for rapid modulation and precise control of output beam deflection, making it widely applicable in fields such as three-dimensional terrain reconstruction, autonomous driving, and holographic imaging. However, the unknown initial phase introduced during the manufacturing and packaging processes of current OPAs results in low beam alignment quality and random output beam phases, significantly limiting the development and application of OPAs. To address these challenges, this paper proposes a precise control technology for OPA output beams, utilizing a beam calibration method we have developed, known as the Four Steps Rotating Element Electric Field Vector Method. This method enables rapid and accurate calibration, achieving precise phase control for each antenna on the OPA chip by calibrating the phase shift and controlling the voltage relationship. It overcomes the challenges of unknown phase distributions common in passive calibration methods, aligning the calibrated phase distribution more closely with theoretical expectations. The proposed method further enhances control over the OPA output beam. Based on this technology, we constructed an experimental platform to achieve a main lobe with a PSLR of 15.98 dB and successfully generated vortex beams using a 4×4 OPA. This innovation not only addresses the initial phase issues caused by manufacturing errors but also significantly enhances the precise control of OPA phases, expanding its applications in LiDAR systems.

Novel multi-modular power conditioning system and decoupling control strategy for SMES with coupled superconducting coil

The high-temperature superconducting magnetic energy storage system (HTS-SMES) utilizes a superconducting coil (SC) to store electric energy in a magnetic field. It has several advantages such as high efficiency, fast response, and infinite charge–discharge cycles. Coupling two SCs made of different HTS materials, known as coupled SC (CSC), can enhance the utilization rate of HTS tapes, reduce manufacturing costs, increase the energy storage density of the SC, and lower magnetic leakage. However, the presence of a coupled magnetic field in CSC makes precise power and current regulation of the individual SC challenging. Additionally, the self-inductances of the individual SCs, composed of different materials, typically differ from each other. Consequently, the current variation induces electromotive force in each SC that differs from the others, necessitating the design of power converters with different voltage ratings connected to each SC. To address the difficulties associated with SMES implementation using CSC, this paper proposes novel modular power conditioning system (MPCS) and decoupling control strategy for SMES. The MPCS enables the flexible design of individual SC power ratings by selecting the appropriate number of power modules. The decoupling control ensures precise current control of each individual SC, which significantly reduces the current ripple of the SCs. Moreover, by employing carrier phase shift modulation, the total harmonic distortion (THD) of the PCS output current is as low as 0.79%. Furthermore, the feedforward power control is proposed to reduce the power control overshoot, and the current sharing control is presented to ensure precise current sharing between each SC. Simulation results verify the efficacy of the proposed approaches.

Time-restricted feeding reinforces gut rhythmicity by restoring rhythms in intestinal metabolism in a jetlag mouse model.

Circadian disturbances result in adverse health effects, including gastrointestinal symptoms. We investigated which physiological pathways in jejunal mucosa were disrupted during chronic jetlag and prevented during time-restricted feeding (TRF). Enteroids from Bmal1+/+ and Bmal1-/- mice were used to replicate the processes that were affected by chronic jetlag and rescued by TRF. C57BL/6J male mice were subjected to chronic jetlag or night-TRF for 4 weeks. An around-the-clock bulk-RNA sequencing study was performed on the jejunal mucosa. Bmal1+/+ and Bmal1-/- mouse enteroids were generated to study the jejunal epithelial clock dependency of rhythmic jejunal processes. Chronic jetlag disrupted the rhythmicity of jejunal clock genes and the jejunal transcriptome which was partially rescued by TRF. Genes whose rhythm was altered by chronic jetlag but prevented by TRF were primarily associated with nutrient transport, lipid metabolism, ketogenesis and cellular organization. In vivo, chronic jetlag caused a phase shift in the rhythmic accumulation of neutral lipids and induced a diurnal rhythm in the number of crypt epithelial cells, both of which were prevented by TRF. In vitro, enteroids replicated the in vivo rhythmic accumulation of neutral lipids in a clock-dependent manner, while the rhythm of S phase proliferation was ultradian in both genotypes of enteroids. This pioneering transcriptomic study demonstrates that TRF acts as a robust entrainer during chronic jetlag, realigning disturbances in the circadian clock and the transcriptome involved in metabolic functions in the jejunal mucosa. Enteroids can replicate the rhythmic accumulation of neutral lipids dependent on the jejunal epithelial clock, enabling these functions to be studied in vitro.

An intelligent transformer enabled medium voltage AC network for loss minimization and node voltage improvement

Abstract The research work presented here discusses about design and integration of intelligent transformer (IT) to the 15 kV/0.4 kV overloaded distribution feeder in Wolaita Sodo Town. The feeder contains 113 distribution transformers with different capacities ranging from 50 kVA to 1250 kVA. The proposed intelligent transformer is a three-stage modular type using phase shift multicarrier modulations for MMC front end converter. Its middle stage is dual active bridge having input series output parallel (DAB-ISOP) configuration using a phase shift modulation. The smart transformer’s back end uses an MMC inverter using interleaved phase shift modulation. The distribution feeder is modeled in MATLAB/Simulink and the designed intelligent transformer is allocated to it using voltage stability index (VSI). The peak load data, feeder data and transformer data of the distribution system under study are obtained from the utility office. The existing distribution feeder’s performance was evaluated by using backward-forward sweep load flow simulation for peak loading condition. The line flows and voltage profile at all nodes were observed and candidate nodes for enhancement were identified. Placement of modular intelligent transformer by using voltage stability index (VSI) was conducted to improve the voltage profiles, minimize reactive power flows and losses. Based on the simulation results for base case scenario, total power loss of 936.5 kW is obtained. The minimum node voltage of 0.81PU and maximum reactive power flow of 10.9MVAr were observed for the base case simulation. Placement of intelligent transformer at weak node 67 and node 111 improves the node voltages to have a minimum value 0.965 PU and maximum value of 1.05PU. The total power loss is reduced to 511.5 kW (54.5% improvement) after integration of intelligent transformer

Advanced control and optimization strategies for a 2-phase interleaved boost converter

Renowned for their adeptness in smoothing current flow and maintaining balanced operation, 2-phase interleaved boost converters (IBC) demonstrate remarkable efficiency, especially when confronted with demanding loads. This makes them a preferred choice for high-power applications such as renewable energy systems, high-power supplies, and electric vehicle power trains. In contrast, standard boost converters are typically favored in low-power, low-demand scenarios. The control of a 2-phase IBC involves running two boost converters in parallel but with a phase shift to reduce ripple currents, improve efficiency, and increase power handling capabilities. To ensure stability and optimal performance, the control strategies for these converters focus on achieving balanced operation between the phases. Hence, the control of 2-phase IBC presents a significant challenge due to their non-minimum phase behavior. The core focus of this article is the implementation of a composite model predictive control (MPC) technique to regulate a 2-phase interleaved boost converter. It introduces a novel approach, model predictive sliding mode control (MPSMC), which leverages the strengths of both MPC and sliding mode control (SMC). The benefits of this hybrid method, termed MPSMC, are thoroughly developed and simulated using MATLAB/Simulink. The results, as discussed in the respective section, provide an in-depth understanding of its effectiveness in practical applications.

Предварительный анализ годовой составляющей движения полюса на 180-летнем интервале данных

The paper presents preliminary results of studying variations in the annual component in the Earth’s polar motion. For this purpose, a signal with an annual period was extracted, firstly, from the series of pole coordinates of the International Earth Rotation and Reference Systems Service (IERS), and secondly, from the combined series of Pulkovo latitude variations for 1840–2017. For this purpose, one-dimensional and multidimensional singular spectrum analysis was used. The Hilbert transform was used to calculate the change in the amplitude and phase of the annual oscillation over time. As a result, it turned out that over an interval of about 180 years, an almost monotonic increase in the amplitude of the annual oscillation from ≈60 mas to ≈90 mas and an almost monotonic phase shift of ≈45◦ are observed. A correlation was also found between the amplitude of the annual component and the difference in average temperatures from November to March in the northern and southern hemispheres.