Signal Processing Devices Research Articles

Fault detection in a power transformer based on reverberation time

The power transformer is one of the vital elements of electric power systems. The reliability of power transformer operation is directly related to its condition. Detection of winding deformations is possible by means of sweep frequency response analysis. Interpretation of SFRA results is usually performed by visualization of images generated using specialized devices and comparison of transfer functions obtained from successive tests. This diagnostic method is known as a fingerprint and its disadvantage is the subjectivity and relying on engineer’s experience. This paper presents an experimental approach for detection of internal transformer short-circuit faults. Existing mathematical indicators based on frequency response analysis are often unable to unambiguously indicate the degree of fault and their determination requires high-cost measurement and signal processing equipment. A new indicator based on the reverberation time, commonly employed in acoustics, is proposed instead. The proposed parameter is based on time-domain calculation and enables reliable detection of transformer inter-turn short circuits and accurate estimation of their degree. A significant advantage of the proposed approach is its low dependence on the frequency range of the measured signal, which allows employment of low-cost measuring and signal processing devices.

Visualization of acoustic power flow in suspended thin-film lithium niobate phononic devices

We report direct visualization of gigahertz-frequency acoustic waves in lithium niobate phononic circuits. Primary propagation parameters, such as the power flow angle and propagation loss, are measured by transmission-mode microwave impedance microscopy. Using a fast Fourier transform, we can separately analyze forward and backward propagating waves and quantitatively evaluate the propagation loss. Our work provides insightful information on the propagation, diffraction, and attenuation in piezoelectric thin films, which is highly desirable for designing and optimizing phononic devices for microwave signal processing.

Phonon-induced anomalous gauge potential for photonic isolation in frequency space

Photonic gauge potentials are crucial for manipulating charge-neutral photons like their counterpart electrons in the electromagnetic field, allowing the analogous Aharonov–Bohm effect in photonics and paving the way for critical applications such as photonic isolation. Normally, a gauge potential exhibits phase inversion along two opposite propagation paths. Here we experimentally demonstrate phonon-induced anomalous gauge potentials with noninverted gauge phases in a spatial-frequency space, where near-phase-matched nonlinear Brillouin scatterings enable such unique direction-dependent gauge phases. Based on this scheme, we construct photonic isolators in the frequency domain permitting nonreciprocal propagation of light along the frequency axis, where coherent phase control in the photonic isolator allows switching completely the directionality through an Aharonov–Bohm interferometer. Moreover, similar coherent controlled unidirectional frequency conversions are also illustrated. These results may offer a unique platform for a compact, integrated solution to implement synthetic-dimension devices for on-chip optical signal processing.

Direct Visualization of Gigahertz Acoustic Wave Propagation in Suspended Phononic Circuits

We report direct visualization of gigahertz-frequency Lamb waves propagation in aluminum nitride phononic circuits by transmission-mode microwave impedance microscopy (TMIM). Consistent with the finite-element modeling, the acoustic eigenmodes in both a horn-shaped coupler and a sub-wavelength waveguide are revealed in the TMIM images. Using fast Fourier transform filtering, we quantitatively analyze the acoustic loss of individual Lamb modes along the waveguide and the power coupling coefficient between the waveguide and the parabolic couplers. Our work provides insightful information on the propagation, mode conversion, and attenuation of acoustic waves in piezoelectric nanostructures, which is highly desirable for designing and optimizing phononic devices for microwave signal processing and quantum information transduction.

Angular-Adaptive Reconfigurable Spin-Locked Metasurface Retroreflector.

Metasurface retroreflectors, which scatter the incident electromagnetic wave back to incoming direction, have received significant attention due to their compelling advantages of low profile and light weight compared with conventional bulky retroreflection devices. However, the current metasurface retroreflectors still have limitations in wide‐angle and omnidirectional operations. This work proposes a high‐efficiency, wide‐angle, reconfigurable, and omnidirectional retroreflector composed of spin‐locked phase gradient metasurface with a thickness of only 5.2 mm or 0.07 operating wavelength. The reflection phase of constituent meta‐atoms can be controlled dynamically and continuously by altering their orientation states through individually addressing each mechanically rotational meta‐atom, whereas the reflection handedness is kept the same as incidence. Therefore, adaptive and arbitrary momentum can be imparted to the incident wave, providing high‐efficiency retroreflection over a wide continuous range from −47° to 47°. Moreover, such high‐performance retroreflection is extended to omnidirectional level, enabling great degrees of freedom that are unavailable by previous researches. As a proof of concept, a retroreflective metasurface is fabricated and experimentally demonstrated at microwave frequencies. The proposed thin thickness, high efficiency, and reconfigurable metasurface retroreflector can be extended to other frequencies that may offer an untapped platform toward reconfigurable spin‐based retroreflection devices for electromagnetic signal processing.

Solidly Mounted Longitudinally Excited Shear Wave Resonator (YBAR) Based on Lithium Niobate Thin-Film.

This paper proposed a solid-mounted (SM) longitudinally excited shear wave resonator (i.e., YBAR). By adopting a 200 nm x-cut LiNbO3 film, top (aluminum) and bottom (platinum) electrodes in 50 nm thickness and 500 nm width, this resonator simultaneously achieves an operating frequency over 5 GHz with an electromechanical coupling coefficient exceeding 50%. Compared with previously proposed YBAR with suspended structure, the proposed SM-YBAR can effectively suppress unwanted spurious modes with only a slight loss of the electromechanical coupling coefficient. The SM-YABR also provides better device stability, possible low-temperature drift coefficient, and a more convenient and mature device processing. It has the potential to meet the multiple requirements for the next generation signal processing devices in terms of high frequency, large bandwidth, stability, and low cost, etc.

A phased approach for the adaptation of telemedicine in arrythmia management.

Cardiovascular disease is the world's leading cause of death. People at higher risk of heart disease need early detection to prevent or delay serious disease complications. In this paper, we present a new design of a wireless portable ECG (electrocardiogram). The ECG signal was preprocessed by analog filters and amplifiers before it was converted into digital data via an Arduino board, a highly available device for real-time signal processing. In order to allow communication between Arduino and Android phone, we use a Bluetooth module. The proposed mobile telemedicine technique allows immediate and rapid detection of heart defects followed by an alarm message from the patient to the doctor.

State of the art in development of molecularly imprinted biosensors

AbstractBiosensors are a class of smart devices fabricated for target analyte detection. A biosensor is commonly made of three basic components: a specific bioreceptor, a physicochemical transducer, and a signal processing device. The bioreceptor part features one of the more crucial technologies of a biosensor to perform specific detection of analytes. They commonly make use of various molecular recognition elements, such as enzymes, natural receptors, antibodies, nucleic acid aptamers, and even synthetic receptors. Then, the molecular recognition events of these bioreceptors can be translated into readable signals in various forms like electrochemical, optical, piezo/pyro electric, etc. Finally, these signals are mathematically processed for quantitative analysis. Nowadays, the great advances in biomimetic materials, in particular the synthetic receptors based on molecularly imprinted polymers (MIPs), promote tremendous development of biosensors. Integration of this field with artificial intelligence enables emerging design of advanced biosensors, which has moved from concept to implementation, meanwhile facing new opportunities and challenges. With no doubt, bioreceptor innovation based on molecular imprinting is an emerging driving force for biosensors development. In this review paper, we provide an overview of MIP‐based biosensors, and also their challenges and opportunities moving forward toward wearable devices are discussed.

Lumps and rogue waves on the periodic backgrounds for a (2 + 1)-dimensional nonlinear Schrödinger equation in a Heisenberg ferromagnetic spin chain

Spin excitations for the magnetic materials are used in the nonlinear signal processing devices and microwave communication systems. Under consideration in this paper is a [Formula: see text]-dimensional nonlinear Schrödinger (NLS) equation which describes the spin dynamics for a Heisenberg ferromagnetic spin chain. Through a reduced transformation, we convert such an equation into the [Formula: see text]-dimensional focusing NLS equation. Via the rogue-periodic solutions associated with two types of the Lie symmetry transformations of the NLS equation, we present the lump- and rogue-periodic solutions. Besides, the lump and mixed lump-soliton solutions are deduced. We graphically investigate the lump- and rogue-periodic waves and find that the amplitudes of the lumps and rogue waves are negatively related to [Formula: see text] and [Formula: see text]; the distances between two valleys of the lumps and widths of the rogue waves are affected by [Formula: see text] and [Formula: see text], where [Formula: see text] is the uniaxial crystal field anisotropy parameter, [Formula: see text] and [Formula: see text] are related to the bilinear exchange interaction, [Formula: see text] is the lattice parameter.

Enhancing the impedance matched bandwidth of bottle microresonator signal processing devices.

Light pulses entering an elongated bottle microresonator (BMR) from a transversely oriented input-output waveguide (microfiber) slowly propagate along the BMR length and bounce between turning points at its constricting edges. To avoid insertion losses and processing errors, a pulse should completely transfer from the waveguide into the BMR and, after being processed, completely return back into the waveguide. For this purpose, the waveguide and BMR should be impedance matched along the pulse bandwidth. Here we show how to enhance the impedance matched bandwidth by optimization of the BMR effective radius variation in a small vicinity of the input-output waveguide.

Gain without population inversion and superluminal propagation in the metal nanoparticles-graphene nanodisks-quantum dots hybrid systems

Nanoplasmonic hybrid systems are novel materials due to their optical properties that can be manipulated by sub-wavelength structures of these materials paving the way for interesting optical phenomena such as superluminal propagation. We study the optical properties of metal nanoparticle-graphene nanodisks-quantum dots hybrid system using density matrix approach. The quantum dot is modeled as a three level lambda type configuration interacting with a weak probe field and strong control field. We realize that due to the surface plasmon effects, we can control the optical properties of the quantum dot including absorption, dispersion and group index by the geometrical features of these components in addition to the parameters of the interacting fields. A controllable switching between subliminal and superluminal propagation is observed at certain parametric conditions leading to interesting potential applications such as signal processing and optoelectronic devices.

Formation of Efficient Microfilm Converters with Reproducible Parameters

The use of microfilm converters provides information in the field of processing, storage, transmission and presentation of information, especially in the process of control and measurement of physical quantities, as well as in the technology of manufacturing high technology products. Microfilm transducers form an equivalent output signal, which is a function of the measured quantity; their design and manufacturing technology are interrelated and highly correlated. Microfilm transducers are manufactured using microelectronic technology, in which group methods are used in the formation of a structure, which increases the reproducibility of parameters, are characterized by high sensitivity, low inertia, low power consumption, high reliability, and are combined with measuring signal processing devices. When creating microfilm converters, a structure is determined that most closely meets the requirements, design parameters, modes of manufacturing operations, the effect of operating conditions on characteristics, and optimal modes of operation. Structurally, a microfilm transducer consists of a base, an insulated structure, heat-generating and temperature-sensitive elements that provide the transmission of electrical signals, film conductors and contact pads, which provide a specified function of converting the measured value into an output signal. In microfilm converters, film thermocouples are used as thermosensitive elements, and adhesive sublayers are used in their manufacturing technology. The use of technological methods of microelectronics when creating microfilm converters can significantly improve their operational parameters.

All‐fibre phase shifter based on tapered fibre coated with MoWS 2 ‐rGO

In this work, an all-fibre phase shifter using tapered fibre coated with molybdenum tungsten disulfide - reduced graphene oxide (MoWS2-rGO) is demonstrated. The large evanescent field of tapered fibre allows MoWS2-rGO to absorb injected light from a 1400-nm pump. It subsequently modifies the refractive index of both an MoWS2-rGO solution and tapered fibre because of the thermo-optic effect. A maximum wavelength shift of 2.489 nm is observed and the equivalent phase shift is 0.91π. The efficiency of the phase shifter is calculated at 0.0175 nm/mW. The proposed phase shifter is beneficial for a variety of applications, specifically for future optical beam-forming networks and all optical signal processing devices.

Design of Vedic multiplierbased FIR filter for signal processing applications

Digital Signal Processing (DSP) devices are becoming increasingly important with the introduction of multiple signal processing techniques. Vedic Multiplier is one of the most common applications for high-speed DSP deployment. This paper constitutes a significant development in the design of the FIR filter architecture based on the modified Nikhalam Sutra Vedic multiplier. In addition, the Kongestone adder is used to increase speed performance. Using Xilinx FPGA Spartan 6 with Xilinx ISE, the modified architecture of FIR filter has been simulated and synthesized for achieving optimized results. The simulation results of the proposed FIR filter architecture illustrate that it operates at least 20 percent faster than traditional multiplier-based FIR filters

Efficiency stability of HPGe detectors under distinct count rates

In this work the reproducibility of the efficiency of different HPGe detectors was analyzed under a series of different conditions. The detectors studied were plugged either to a regular analogical amplifier or to a digital signal processing (DSP) device, in order to evaluate the possible differences between either setup. Detectors were inspected by performing a long series of sequential measurements with standard calibration sources, and comparing the standard deviation of the number of counts per second in each series to the uncertainty of the individual measurements. Detectors were also subjected to distinct count rates, in order to verify the possible experimental issues associated with this parameter. The results allow a discussion on the stability of the detectors’ efficiencies over a few days, the possible dependence with the count rate, and the estimation of the uncertainty related to the efficiency variation.

Multimode unidirectional spin-wave coupling in an array of non-identical magnonic crystals near band gap frequencies

Using Brillouin light spectroscopy and micromagnetic simulation methods, we show how the intermodal coupling between two magnonic crystals (MCs) affects signals spatial selection with frequency separation during spin-wave transport. We have experimentally demonstrated control of the intermodal coupling of spin waves (SWs) propagating in non-identical magnonic-crystal microwaveguides near the band gap frequency. We show that the spin-wave propagation direction within the MCs of different width can be controlled by the lateral coupling between SWs. Our findings provide an alternative method for signal filtering and separation within magnonic networks for the implementation of magnonic demultiplexers, power dividers, couplers and microwave signal processing devices. based on the lateral array of non-identical MCs.

A density functional theory (DFT) study of the doping effect on 4-[2-(2-N, N-dihydroxy amino thiophene) vinyl] benzenamine

In the present work, density functional theory was used at the B3LYP, CAM-B3LYP and B3PW91 levels with the 6–311 + + G (d, p) basis set, in other to study the structural, optoelectronic, nonlinear optical, piezoelectric and thermodynamic properties of 4-[2-(2-N, N-dihydroxy amino thiophene) vinyl] benzenamine (DATVB) molecule doped with chlorine and fluorine respectively. The results obtained show that doping significantly improves the properties of this material. The materials obtained after doping 4-[2-(2-(5-(bis (chlorooxy) amino) thiophene) vinyl] benzenamine (BCATVB) and 4-[2-(2-(5-(bis (fluorooxy) amino) thiophene) vinyl] benzenamine (BFATVB) are good semiconductors because their gap energy is range between 1 and 1.5 eV which is less than 3 ev. Their first order hyperpolarizabilities ({beta }_{mol}) are very high compared to para-nitroaniline (p-NA) known as reference molecule for nonlinear optical properties. The obtained results predisposes them as good nonlinear optical materials with applications in photonics, optical signal processing devices, dynamic imaging, data storage and computer devices. The piezoelectric and pyroelectric coefficients of the fluorinated molecule are higher than those of the reference organic molecule polyvinylidene fluoride. This led us to the conclusion that, these molecules can also be used for applications in piezoelectricity.

Dynamic Hybrid Metasurfaces

Efficient hybrid plasmonic-photonic metasurfaces that simultaneously take advantage of the potential of both pure metallic and all-dielectric nanoantennas are identified as an emerging technology in flat optics. Nevertheless, postfabrication tunable hybrid metasurfaces are still elusive. Here, we present a reconfigurable hybrid metasurface platform by incorporating the phase-change material Ge2Sb2Te5 (GST) into metal-dielectric meta-atoms for active and nonvolatile tuning of properties of light. We systematically design a reduced-dimension meta-atom, which selectively controls the hybrid plasmonic-photonic resonances of the metasurface via the dynamic change of optical constants of GST without compromising the scattering efficiency. As a proof-of-concept, we experimentally demonstrate two tunable metasurfaces that control the amplitude (with relative modulation depth as high as ≈80%) or phase (with tunability >230°) of incident light promising for high-contrast optical switching and efficient anomalous to specular beam deflection, respectively. Our findings further substantiate dynamic hybrid metasurfaces as compelling candidates for next-generation reprogrammable meta-optics.

Improved design debugging architecture using low power serial communication protocols for signal processing applications

Now-a-days FPGA designers are facing the problem of unprecedented challenges in debugging their designs. In the past, designers debugged their FPGAs by plugging them onto a board and then analyzing them with probes and logic analyzers. But right now the vendors of FPGA are offering tools that make it somewhat easier to probe internal design signals inside the FPGA, Once unexpected behavior is observed, on-chip debug is notoriously difficult; typically a design is instrumented with on-chip trace buffers that record the run-time behavior for later interrogation. Based on the demand for verification leads to an increase in FPGA-based tools that improves the performance of the architecture. The low power communication protocols can run at much higher operating frequencies with less area.FPGAs provide a promising implementation option for many DSP applications particularly in speech signal processing devices such as data converters, digital filters, etc. This work improves the performance of current debugging techniques and makes them more reliable. This work proposes a novel design debugging architecture based on implementation of reconfigurable insertion technique with the help of low power communication protocols used in the FIR filter to debug the entire architecture with less area. If there is any possibility of bug occurs in the UART protocol then the data is transferred through SPI protocol. SPI protocol worked in the operating frequency of 330.12 MHz. According to the power consumption, the UART protocol consumes 0.0135W which is far better than other protocols like SPI, I2C etc. Moreover, the area overhead is reduced. This is achieved by implementing the extra instrumentation. The design debugging architecture is developed using Verilog HDL and implemented on FPGA with the help of Xilinx ISE tool.

Subwavelength confinement of propagating surface acoustic waves

The ability to confine light to subwavelength scales has led to exciting developments in fields ranging from sensing to single molecule chemistry. In this paper, we demonstrate how arrays of annular hole resonators can be used to confine surface acoustic waves (SAWs) to regions of the propagating surface that are much smaller than the wavelength of the SAWs. These microscopic elastic waves are used in devices for signal processing and sensing and, increasingly, in areas such as quantum information and microfluidics. This work potentially transforms the ability to enhance interactions with SAWs and could pave the way for advances that mirror those in nano-photonics.