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Bistability, a universal phenomenon found in diverse fields such as biology, chemistry, and physics, describes a scenario in which a system has two stable equilibrium states and resets to one of the two states. The ability to switch between these two states is the basis for a wide range of applications, particularly in memory and logic operations. Here, we present a universal approach to achieve bistable switching in magnonics, the field processing data using spin waves. A pronounced bistable window is observed in a 1 μm wide magnonic conduit under an external rf drive. The system is characterized by two magnonic stable states defined as low and high spin-wave amplitude states. The switching between these two states is realized by another propagating spin wave sent into the rf driven region. This magnonic bistable switching is used to design a magnonic repeater, which receives the original decayed and distorted spin wave and regenerates a new spin wave with amplified amplitude and normalized phase. Our magnonic repeater can be installed at the inputs of each magnonic logic gate to overcome the spin-wave amplitude degradation and phase distortion during previous propagation and achieve integrated magnonic circuits or magnonic neuromorphic networks. A repeater takes an input signal and retransmits is, and a vital component for extending the range of signals. Here, Wang et al. demonstrate a magnon repeater, based on the bistable switching between low and high amplitude spin-waves. [ABSTRACT FROM AUTHOR]

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A Negative Group Delay (NGD) prototype filter design, based on the ratio of two Chebyshev filter transfer functions, is presented. The two transfer functions are of the same order, but with different in-band ripple amplitudes and different 3 dB-bandwidths. The overall transfer function exhibits both an in-band ripple and an out-of-band steep-slope magnitude transition characteristic of a Chebyshev filter, while also exhibiting an in-band NGD. For high-order designs and in the upper asymptotic limit, the NGD-bandwidth product of the filter is shown to be a linear function of out-of-band gain in decibels. A resonator-based methodology is used to show how frequency upshifted filter designs can be implemented in a Sallen-Key topology or in an all-passive ladder topology. An in-band combined magnitude/phase distortion metric is evaluated for examples of the NGD filter. It is shown that the distortion metric is proportional to the design order, the in-band ripple amplitude, and the out-of-band gain. For a prescribed distortion metric value, it is demonstrated that the proposed design can achieve a higher NGD-bandwidth product than an equivalent Butterworth design, which has a flat in-band magnitude characteristic. Additionally, input waveforms with bandwidths extending to the entire frequency range where the group delay is negative (typically larger than the 3 dB-bandwidth) should not be applied to this filter design as it results in strong levels of distortion. [ABSTRACT FROM AUTHOR]

Due to resilience to background noise, avoidance of linear phase distortion, and stability of redundant representation, various simply symmetric frame scaling functions and derived framelets are becoming widely-used tools in data processing and transmission systems. In this study, we will reveal topological features (range, diameter, origin behavior, etc.) of spectral domain of fully symmetric frame scaling functions in the higher-dimensional space. Moreover, we present sufficient and necessary conditions for fully symmetric frame scaling functions with cube-shaped, sphere-shaped and ellipsoid-shape spectral domains. At the same time, we give the construction of fully symmetric frame scaling function and derived framelets with fully symmetry. [ABSTRACT FROM AUTHOR]

A Negative Group Delay (NGD) prototype filter design based on the reciprocal transfer function of a low-pass Butterworth filter of a given order, is presented. The out-of-band gain of the prototype transfer function is capped at a finite constant value via multiplication by a transfer function of a low-pass Butterworth filter with 3 dB bandwidth that is wider than the reciprocal function bandwidth. Such synthesized transfer function exhibits maximal magnitude characteristic flatness within the 3 dB bandwidth (Butterworth-like property), while it also exhibits NGD and satisfies Kramers-Kronig relations (causal transfer function). The prototype design achieves an NGD-bandwidth product that in the upper asymptotic limit as the design order increases, is a linear function of out-of-band gain in decibels. This is an improvement compared with previously reported cascaded first-order and second-order designs, which have NGDbandwidth functional dependency of out-of-band gain in decibels to the power of 1/2 and 3/4, respectively. It is shown that the transfer function of the corresponding design transformed to a non-zero center frequency can be exactly implemented with a Sallen-Key topology employing parallel resonators, or approximately implemented with an all-passive ladder topology. An in-band magnitude/phase distortion metric is applied to the prototype designs, evaluated for Gaussian and sinc pulse input waveforms, and compared with values obtained for a well-known commonly used medium. It is also shown that when the specified bandwidth corresponds to the entire bandwidth over which the group delay characteristic is negative, the magnitude characteristic variation approximately equals half the out-of-band gain value in decibels. Therefore, for any NGD design with large out-of-band gain (typically higher than 6 dB), using the entire bandwidth where group delay is negative can result in strong levels of distortion and should be checked for applied waveforms. [ABSTRACT FROM AUTHOR]

• Fringe superposition is an essential challenge for the deflectometric measurement of transparent elements. • A general-purpose fringe separation strategy is proposed by the empirical curvelet based frequency domain filtering. • Over-separated patterns are recombined based on the weighted permutation entropy method to avoid phase distortion. In the deflectometric measurement of transparent elements, it is critical to separate the superposed fringes reflected from the front and rear surfaces to establish the pixel correspondences between the camera and screen pixels. But it is a challenging task due to the low reflectivity and uneven background of transparent elements. A reliable fringe separation method is proposed based on the empirical curvelet transform. The captured fringe images are decomposed into different modes according to their directions, periods, curvatures or modulation coefficients, and then a weighted-permutation-entropy-based fusing algorithm is developed to automatically aggregate those over-separated patterns. By employing the proposed method, the measurement accuracy is significantly improved, the number of demanded images is effectively reduced, and high-precision, automatic, and rapid measurement is thereby achieved. The measurement accuracy of spherical and cylindrical lenses can achieve 73 nm and 332 nm Root-of-Mean-Squares-Error, respectively. [ABSTRACT FROM AUTHOR]

This paper develops a new method for the design of a recursive allpass phase-compensating system (PCS) with an arbitrarily prescribed stability margin (SM). The design methodology comes from the generalised stability-triangle (GST) that defines a closed stability region for the second-order system, and the closed stability region is described by a pair of parameterised inequalities. Since the GST is developed for the second-order recursive system, to design a high-order PCS, we first construct a high-order PCS using the cascade of a set of second-order systems (sections), and then apply the GST to each of the second-order sections. The two coefficients of each second-order section are first transformed into two new variables by employing a coefficient-transformation technique, and then all the new variables are optimised in such a way that a given phase specification is best approximated. Thanks to both the coefficient transformations and the general stability condition from the GST, the resulting high-order PCS is not only stable, but also satisfies a prescribed SM design specification. This paper includes two examples to illustrate the usefulness of the GST-based PCS design. [ABSTRACT FROM AUTHOR]

The interfacial Dzyaloshinskii–Moriya interaction (DMI) is an essential ingredient for stabilizing chiral spin configurations in spintronic applications. Here, via first-principles calculations, we reveal the influence of lattice strain on DMI in Co/Pt interface. We observed a considerable enhancement for a certain lattice strain. Furthermore, a direct correlation is established between the DMI and interlayer distances dominated by the strain, which is attributed to a hybridization of electronic orbitals. This hybridization has also been presented as the microscopic origin of the interfacial DMI. We anticipate that our predictions provide new insights into the control of interfacial DMI for skyrmion-based spintronic devices. [ABSTRACT FROM AUTHOR]

Phase-frequency characteristics of approximate sinusoidal geomagnetic signals can be used for projectile roll positioning and other high-precision trajectory correction applications. The sinusoidal geomagnetic signal deforms in the exposed and magnetically contaminated environment. In order to preciously recognize the roll information and effectively separate the noise component from the original geomagnetic sequence, based on the error source analysis, we propose a moving horizon based wavelet de-noising method for the dual-observed geomagnetic signal filtering where the captured rough roll frequency value provides reasonable wavelet decomposition and reconstruction level selection basis for sampled sequence; a moving horizon window guarantees real-time performance and non-cumulative calculation amount. The complete geomagnetic data in full ballistic range and three intercepted paragraphs are used for performance assessment. The positioning performance of the moving horizon wavelet de-noising method is compared with the band-pass filter. The results show that both noise reduction techniques improve the positioning accuracy while the wavelet de-noising method is always better than the band-pass filter. These results suggest that the proposed moving horizon based wavelet de-noising method of the dual-observed geomagnetic signal is more applicable for various launch conditions with better positioning performance. [ABSTRACT FROM AUTHOR]

We have used the Josephson arbitrary waveform synthesizer (JAWS) to provide traceability for the phase of the harmonics, relative to their fundamental frequency, of a distorted waveform. For distorted waveforms with rms values from 0.154 to 0.2 V and harmonic magnitudes from 5% to 40% of the fundamental, our system can generate odd harmonics up to the 39th with best phase uncertainties from 0.001° to 0.010° ($k = 2.0$), depending on the harmonic number and harmonic magnitude. We anticipate that the ability of the JAWS to generate distorted waveforms with the lowest possible uncertainty in the magnitude, and phase spectra will make it a unique tool for low-frequency spectrum analysis. [ABSTRACT FROM AUTHOR]

Abstract Although there is an urgent need, it is still a significant challenge to establish high-speed laser communication links between satellites to ground stations owing to the influence of atmospheric turbulence. Adaptive optics (AO) is a considerable scheme to solve the problem. In this paper, the primary experiment of satellite-to-ground laser communication with the data rate of 5Gbps and BPSK modulation is carried out through a 500 m horizontal channel with relatively strong turbulence. A 137-element AO unit is used for correcting the phase distortion brought by the turbulence. When the AO unit is working, both the received optical power and bit error rate (BER) (All the eight experimental results of BER at different time are below 10−6.) are improved significantly. The primary results demonstrate that the ground station with AO technology has the capability to establish the satellite-to-ground laser communication links and provide a reference for the design of satellite terminals. [ABSTRACT FROM AUTHOR]

This letter proposes a new architecture of a simple and sub-1μs fast-response voltage-mode buck converter using adaptive on-time and frequency-locked controlled techniques. The adaptive on-time-controller with frequency-locked loop is employed to keep the switching frequency (fsw) constant at 1 MHz to achieve fixed frequency. Therefore, the switching losses, and frequency variations can be reduced to improve the converter efficiency. In addition, the proposed buck converter does not include slope compensation circuit, which will simplify the system design and shorten the transient response of the converter without adding extra acceleration circuits. Moreover, the transient response of the converter can be accelerated by choosing the appropriate equivalent-series-resistance (ESR) value for the load capacitance. The chip is fabricated in TSMC 0.35 μm 2P4M process. The experimental results show that the maximum efficiency is 90.04% when the load current is 140 mA and output voltage is 1.8 V. The load transient response time is about 0.96 and 0.94 μs when the load current changes from 100 to 500 mA and from 500 to 100 mA, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Technisches Messen is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High-power solid state lasers of the mid-IR spectral range are extremely interesting for both basic research and technological applications and they are actively developing at present. However, the implementation of projects with the use of such lasers is hampered by the absence of Faraday isolators (FIs) for the radiation with the corresponding characteristics. The need for such devices is growing with laser power enhancement. They reduce the risk of self-excitation of the damage of amplifiers and optical elements and are a handy tool for organizing multipass schemes. Magneto-active crystals based on Eu2+ ions are promising media for the development of FIs for high-power lasers of the mid-IR spectral range because of the unique combination of their spectral and magneto-optical properties. Thermo-optical characteristics are also of principal importance when operating with high-power laser radiation. This letter presents the results of investigation of thermo-optical constants Q and P of the EuF2.11 solid solution crystal which determines the values of polarization and phase distortions of passing laser radiation. The measured values can be considered as the corresponding values for the EuF2 crystal, which is of greatest interest for the development of FIs for high-power mid-IR lasers. The obtained results can be used to determine the characteristics of FIs based on EuF2 crystals in various implementations of their optical schemes for various parameters of laser radiation. According to the estimates, for the radiation wavelength of 2 μm, the maximum permissible laser power of the Faraday isolator based on one magneto-optical element with [001] orientation will be more than 200 W. [ABSTRACT FROM AUTHOR]

A handy formula is presented to evaluate the effects of random surface errors on average power pattern for distorted reflector antennas. Based on the previous work of Rahmat-Samii on average power pattern degradation for random surface errors, the surface distortion-induced phase error is expanded into a second-order Taylor series expansion in radiation integral. With the probabilistic distribution of phase errors, the closed-form expressions of average power pattern and variance on boresight gain and sidelobe levels are demonstrated by this handy formula. To show the effectiveness of this formula, its applicability region is derived. The derivation clearly shows that when the root-mean-square amplitude of surface distortion is below $\lambda $ /30, the handy formula presents a good agreement with the exact one in boresight gain within a 0.1 dB computational accuracy. Comparing with the previous work, this formula can estimate the boresight gain loss by hand quickly without the exponential calculation, which will benefit the antenna design. [ABSTRACT FROM AUTHOR]

We extend the lifetime of Flash memory in embedded processors by exploiting the fact that data from sensors is inherently analog. Prior work in the computer architecture community has assumed that all data is digital and has overlooked the opportunities available when working with analog data, such as the data recorded by sensors. In this paper, we introduce redundancy into the quantization of sensor data in order to provide several alternative representations. Notably, we tradeoff distortion—the difference between the sensed analog value and the digital quantization of that value—to improve lifetime. Our simulations show that when combining rate, distortion, and lifetime tradeoffs we can extend Flash lifetime at a far smaller capacity cost compared to prior work. More specifically the simulated system shows that it is possible to achieve up to $2.75 \times$ less capacity cost compared to redundant Flash memory and $1.29 \times$ less capacity cost compared to the state of the art coding schemes. [ABSTRACT FROM AUTHOR]

This paper presents the design of a multibeam phased array of microstrip patch antennas at 38 GHz with a parallel‐plate beam‐forming network (BFN). This antenna set, including the antenna elements and BFN, is equivalently triple‐folded into two stacked printed circuit board substrates for a compact design of nearly 60% size reduction in comparison to conventional implementation on a single planar dielectric substrate. In particular, the BFN employs a shaped metal reflecting boundary in the bottom substrate to transform the cylindrical waves of feed excitations into planar ones for a relatively linear phase variation to feed the column subarrays on the top substrate. A slot feeding transition structure is designed to couple the energy from the BFN to feed the microstrip patch antenna ports. These two mechanisms are then used to compensate the phase distortions due to BFN cavity disturbance and mutual coupling from subarrays of antennas at millimeter wave frequencies. Numerical techniques to optimize both the metal reflecting boundary and slot feeding transition structure are introduced to minimize phase distortions. Numerical and experimental results are presented to demonstrate the radiation characteristics of the integrated antenna set. Key Points: An antenna design methodology is proposed for mobile communication of 5GA multi‐beam antenna is designed with SIW PCB‐based beam‐forming network for compact sizeA planar phased array of antenna is implemented at millimeter wave frequencies [ABSTRACT FROM AUTHOR]

Based on the generalized Huygens Fresnel principle, the propagation equation of fundamental Gaussian vortex beam with phase distortion is derived. To quantitatively analyze the influence of random phase distortion on the quality of vortex beam, the variance of light intensity relative deviation is proposed as the evaluation parameter. The influences of some key factors on the quality of a vortex beam are emphatically discussed. The results show that with the increasing of distortion strength the beam quality becomes worse. On the contrary, with the increasing of the topological charge, the beam quality improves gradually. [ABSTRACT FROM AUTHOR]

The angle resolved velocity distributions of excited (4F7/2) and ground state (4F9/2) Rh atoms ejected from the Rh {100} surface due to keV Ar+ ion bombardment are described with a model that takes into account the local electronic environment. The lifetime of the excitation probability for each excited Rh atom is assumed to depend on the local embedded-atom method (EAM) density. It is thus possible to distinguish between ejected atoms that experience very little difference in their electronic environments. Although most excited atoms that survive with significantly high excitation probabilities originate from the surface layer, it is not uncommon for an atom beneath the surface to eject from a disrupted environment and end up with a high excitation probability. This model improves upon a previous one, where the lifetime was assumed to vary with the height above the original surface. [ABSTRACT FROM AUTHOR]

A tunable noise suppressor at gigahertz frequency using sub-micrometer patterned Permalloy (Py) loaded coplanar waveguide transmission line is presented. The transmission line consists of 100 nm thick Py patterns on top of 0.9 μm thick gold lines. Measured results show that the stop band frequency of the noise suppressor is changed from 4.8GHz to 6GHz depending on the aspect ratios of Py patterns. Variation of the gap in between Py patterns changed the stop band frequency from 4 GHz to 6 GHz. Furthermore, a novel way of tuning the stop band frequency of the noise suppressor by using an external direct current is reported. By applying 150mA direct current along the transmission line, the frequency is changed from 6 GHz to 4.3GHz. The measured results of 1.5% pass band loss, 2° transmitted signal phase distortion, and 3 dB extra return loss of the designed noise suppressor are demonstrated. Noise suppression frequency and the magnitude of signal attenuation can be further improved by increasing the thickness of Py or using multi-layer Py. [ABSTRACT FROM AUTHOR]

Analytical solution to the scattered field and near-surface field of a multilayered chiral sphere illuminated by a high-order Bessel vortex beam (HOBVB) are investigated. Using the vector wave theory, the expansion coefficients of a HOBVB in terms of spherical vector wave functions (SVWFs) are derived. Based on the fields expansion in each region and continuous boundary condition at each interface, the expansion coefficients of the sphere are solved by constructing the iterative form of the coefficients equations. Influences of the topological charge, half-cone angle and chirality on the scattering pattern of far region and near-surface field are analyzed in detail. In addition, the intensity and phase distributions at the transverse plane after interaction are presented for on- and off-axis incidences. Comparisons of orbital angular momentum (OAM) spectrum indicate that off-axis incidence results in topological charge shift from the incident case, and the farther from the axis and the more complex the particles, the more serious the phase distortion. The results provide insights into the scattering and light-matter interactions and may find important applications in optical propagation and multicasting optical communication. [ABSTRACT FROM AUTHOR]

Antenna frequency response can be characterized in terms of effective aperture and gain. Antennas can also be characterized as a two-port network to ascertain the antenna transfer function ($S_{\mathbf {21}}$). This characterization is important in point-to-point (P2P) communication, as the frequency response can vary due to changes in the radiation pattern in the physical channel. This paper presents a process to investigate the frequency response of a wideband antenna in order to identify the best orientation of the antenna for P2P communication. The process predicts the antenna’s effective aperture and gain for each orientation. An equivalent circuit for the wideband antenna is also derived to obtain the total radiated power. The frequency-variant radiation pattern is ascertained from the $S_{\mathbf {21}}$ phase obtained from the equivalent circuit. For each orientation, the $S_{\mathbf {21}}$ phase is analyzed based on the linear, minimum, and all-pass phase components, which enables the derivation of an equivalent circuit. The variation of group delay for each orientation is also obtained and compared. The measurements between two identical antennas at the two orientations with a free-space channel were then modeled for simulation in a digital system. This simulation predicts the antenna effects for the two orientations used. Finally, this process was validated by using a nonminimum-phase monopole ultra-wideband antenna. [ABSTRACT FROM AUTHOR]

Electronic distortions, which are inherent in the oxide fluoride anions [MOF5]2− (M = Nb and Ta), provide an origin of polar molecular arrangements for the development of new polar second‐harmonic‐generating, piezo‐, pyro‐ and ferroelectric materials. It is still a challenge to expand this approach to the realm of metal–organic polymers, while insufficient control over the environment of the [MOF5]2− units results in their orientational disorder and loss of polarity. The structures of catena‐poly[[tris(3,4,5‐trimethyl‐1H‐pyrazole‐κN2)copper(II)]‐μ‐oxido‐[tetrafluoridoniobium(V)]‐μ‐fluorido], [CuNbF5O(C6H10N2)3]n, (I), and its isostructural pentafluoridooxidotantalate(V) analogue, catena‐poly[[tris(3,4,5‐trimethyl‐1H‐pyrazole‐κN2)copper(II)]‐μ‐oxido‐[tetrafluoridotantalum(V)]‐μ‐fluorido], [CuTaF5O(C6H10N2)3]n, (II), are the first examples of the strict orientational order of [MOF5]2− (M = Nb and Ta) in one‐dimensional coordination chains. A primary factor for the exact discrimination of one orientation of the anion over the other is strong and shape‐selective multiple interactions of [MOF5]2− with the inherently acentric CuL32+ platform, with a set of two coordination and three N—H…F hydrogen bonds. In (I) and (II), the Cu2+ ions exhibit distorted square‐pyramidal fivefold coordination formed by three pyrazole N atoms and the oxide O atom, defining the equatorial plane, and the anionic bridging F atom (which is trans with respect to the M—O bond) residing in the apical position. The inorganic bridges connect CuL32+ moieties into polar zigzag chains; the bulk polarity of the structure is eliminated by an antiparallel alignment of the individual chains. These chains are further connected through C—H…F hydrogen bonding and very weak C—H…π interactions of the organic ligands. [ABSTRACT FROM AUTHOR]

Recently, a filamentation instability was observed when a laser-generated pair cloud interacted with an ambient plasma. The magnetic field it drove was strong enough to magnetize and accelerate the ambient electrons. It is of interest to determine if and how pair cloud-driven instabilities can accelerate ions in the laboratory or in astrophysical plasma. For this purpose, the expansion of a localized pair cloud with the temperature 400 keV into a cooler ambient electron-proton plasma is studied by means of one-dimensional particle-in-cell simulations. The cloud's expansion triggers the formation of electron phase space holes that accelerate some protons to MeV energies. Forthcoming lasers might provide the energy needed to create a cloud that can accelerate protons. [ABSTRACT FROM AUTHOR]

A real-time photonic sampling structure with effective nonlinearity suppression and excellent signal-to-noise ratio (SNR) performance is proposed. The key points of this scheme are the polarization-dependent modulators (P-DMZMs) and the sagnac loop structure. Thanks to the polarization sensitive characteristic of P-DMZMs, the differences between transfer functions of the fundamental signal and the distortion become visible. Meanwhile, the selection of specific biases in P-DMZMs is helpful to achieve a preferable linearized performance with a low noise level for real-time photonic sampling. Compared with the quadrature-biased scheme, the proposed scheme is capable of valid nonlinearity suppression and is able to provide a better SNR performance even in a large frequency range. The proposed scheme is proved to be effective and easily implemented for real time photonic applications. [ABSTRACT FROM AUTHOR]

The just noticeable distortion (JND) has been considered a suitable solution for controlling the watermark strength and generating robust watermarking schemes with distortions that are below the sensitivity threshold. However, JND assumes the same attention level for all image regions, which does not reflect the behavior of an observer. Recently, several models have utilized the modulatory effect of visual attention over JND to improve the efficiency of watermarking schemes. However, most of them have focused on still images. In this paper, we propose a saliency-modulated JND profile for improving video watermarking schemes. Our method aims to adapt the watermark strength to obtain the most robust possible scheme with an imperceptible watermark. Moreover, it has the advantage of fully exploiting the spatiotemporal properties of video to minimize its perceptual redundancies and achieve low computational complexity. Experimental results show the effectiveness of our proposed method and its contributions to video watermarking process. [ABSTRACT FROM AUTHOR]

This paper analyzes the influence of phase noise and distortion on the performance of oscillator-based sensor data acquisition systems. Circuit noise inherent to the oscillator circuit manifests as phase noise and limits the SNR. Moreover, oscillator nonlinearity generates distortion for large input signals. Phase noise analysis of oscillators is well known in the literature, but the relationship between phase noise and the SNR of an oscillator-based sensor is not straightforward. This paper proposes a model to estimate the influence of phase noise in the performance of an oscillator-based system by reflecting the phase noise to the oscillator input. The proposed model is based on periodic steady-state analysis tools to predict the SNR of the oscillator. The accuracy of this model has been validated by both simulation and experiment in a 130 nm CMOS prototype. We also propose a method to estimate the SNDR and the dynamic range of an oscillator-based readout circuit that improves by more than one order of magnitude the simulation time compared to standard time domain simulations. This speed up enables the optimization and verification of this kind of systems with iterative algorithms. [ABSTRACT FROM AUTHOR]

Recent investigations show that high-rate telemetry systems, based on the CCSDS 131.2-B-1 standard and employed in Earth observation missions, do not fully exploit the available capacity. Thus, we propose and discuss possible ways to improve the data return of these systems that can be considered for a revision of the current standard. Some of them are represented by a revision and/or an extension of the currently adopted modulation and coding formats. The remaining techniques are related to an enhancement of the transceiver architecture. Different bandwidth allocation strategies are also considered. The benefits of the proposed techniques are assessed by means of computer simulations with reference to a realistic scenario where a real non-linear amplifier, real filters, and real impairments are considered. [ABSTRACT FROM PUBLISHER]

We describe an improved method to estimate the Total Electron Content (TEC) of the Mars ionosphere from the echoes recorded by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) ( Picardi et al., 2005; Orosei et al., 2015 ) onboard Mars Express in its subsurface sounding mode. In particular, we demonstrate that this method solves the issue of the former algorithm described at ( Cartacci et al., 2013 ), which produced an overestimation of TEC estimates on the day side. The MARSIS signal is affected by a phase distortion introduced by the Mars ionosphere that produces a variation of the signal shape and a delay in its travel time. The new TEC estimation is achieved correlating the parameters obtained through the correction of the aforementioned effects. In detail, the knowledge of the quadratic term of the phase distortion estimated by the Contrast Method ( Cartacci et al., 2013 ), together with the linear term (i.e. the extra time delay), estimated through a radar signal simulator, allows to develop a new algorithm particularly well suited to estimate the TEC for solar zenith angles (SZA) lower than 95° The new algorithm for the dayside has been validated with independent data from MARSIS in its Active Ionospheric Sounding (AIS) operational mode, with comparisons with other previous algorithms based on MARSIS subsurface data, with modeling and with modeling ionospheric distortion TEC reconstruction. [ABSTRACT FROM AUTHOR]

In optical interferometry, noise and distortions in the recovered wrapped phase are very common, and their nature is inherent to the quality and visibility of the fringe patterns that modulate the phase. Filtering these phase imperfections from the wrapped phase is not straightforward since we cannot directly apply filters without damaging their information, that is, its modulus 2π phase jumps. However, having a way to filter noise and distortions from the wrapped phase is desirable and very important because, at the end, the filtered phase is closer to the expected, errors are reduced, and the unwrapping task can be less complex. We propose a modulus 2π filtering method to remove noise and distortions directly from the wrapped phase without damaging its information. The presented method is a global filtering process, but we use the local frequencies from the wrapped phase in such a way that each pixel is tuned to its instant frequency. [ABSTRACT FROM AUTHOR]

A generalization and subsequent development of experimental techniques, including methods of studying the phase-frequency relations between the measured components of admittance and instantaneous power are considered. The conditions of electric loading where electric currents, voltages, or instantaneous powers of constant amplitude in the piezoresonators are specified are numerically modeled. It is particularly established that the advanced Mason circuit with additional switch allows acquiring much more data on the forced vibrations of piezoceramic transducers than the classical circuit. The measured (at an arbitrary frequency) voltage drop across the piezoelement, its pull-up resistor, and at the input of the measuring circuit allow determining, with high accuracy, the current, conductivity, impedance, instantaneous power, and phase shifts when the amplitudes of electric current and voltage are given. [ABSTRACT FROM AUTHOR]

Anelastic attenuation often causes amplitude decrease and phase distortion in seismic data. Seismic migration of such attenuated data often yields poor images of subsurface structures, especially under high-attenuation areas. Previous studies have been focusing on the compensation of attenuation to obtain higher resolution images. However, it is still challenging to achieve a good ray-based Q-compensated migration for seismic data. In this paper, we firstly introduce the multiscale Gabor transform to obtain a local time-frequency data for Q-dependent compensation, where the local lengths of filtering windows varied from frequencies are computed automatically. Then, we propose an efficient Q-compensated beam migration based on the multiscale Gabor transform. The attenuation of seismic wave is compensated based on Q-dependent traveltimes before imaging loop, and the Q-dependent traveltimes are purchased using the spatial variant Q models within imaging loop. The proposed Q-compensated migration has similar computational cost as the traditional beam migrations, because the frequency integral loop in the imaging process is solved in our implementation scheme. Both synthetic and real data examples show the effectiveness and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

To solve the phase distortion and high error rate in optical signal transmission, an equalized technique is proposed, which aims to improve the constant modulus algorithm (CMA). In order to correct phase rotating and reduce the error rate with 64 quadrature amplitude modulation (QAM), the method takes the mean square error as the judgment and utilizes the time-varying step size. Simulation results demonstrate that the proposed algorithm can improve the convergence speed of constellation points, make the eye opening larger, and the signal noise ratio (SNR) can be increased by 4 dB under the same bit error rate (BER), which is efficient for the recovery of information in high-speed transmission. [ABSTRACT FROM AUTHOR]

Layered LiNi0.6Mn0.2Co0.2O2 (LNMC) cathode has attracted enormous attentions for Li-ion batteries thanks to its appealing combination of large capacity and desirable thermal stability. But it still suffers from repugnant phase distortion and serious capacity degradation upon cycling particularly with high cut-off voltages and elevated working temperatures. Herein, an efficient sur-/interface engineering strategy to finely fabricate hierarchical LNMC@LiCoPO4@graphene (LNMC@LCP@G) architectures is purposefully devised. Physicochemical characterizations comprehensively reveal that a uniform LCP nanoshell adheres tightly to the surface of bulk LNMC, and G sheets intersperse among LNMC@LCP microparticles as electron 'bridge.' By virtue of synergetic sur-/interface contributions from the multicomponents, the LNMC@LCP@G cathodes exhibit encouraging Li-storage behaviors including larger capacities, higher capacity retention, and better cycling performance with high upper cut-off voltage of 4.6 V both at 25 and 55 °C, and enhanced thermal stability in the delithiated state. More significantly, it is strongly believed that the electrode design concept here holds huge promise for smart synthesis of other advanced Ni-based cathodes for next-generation rechargeable lithium power batteries. [ABSTRACT FROM AUTHOR]

We demonstrate the influence on output coupling mode with introducing typical intracavity disturbation and results of aberrated mode compensation in a folded-type optical resonator used in high-energy lasers. The eigenmode profiles and relevant Zernike aberration with intracavity reflector misalignment are achieved by numerical calculation. Experimental result about the function of the reflector maladjustment and the mode features are described in terms of model reconstruction combined with Zernike annular polynomials. Results show that phase disturbation has significant influence on out-coupling beam property, and the uniform and symmetry of the mode are rapidly disrupted by a slight misalignment of the resonator reflectors. The influence on PSF profile in the far-field will be obviously different even if equivalent disturbation is inputted into the same cavity. The device of real-time controlling of the cavity reflector for compensating intracavity phase distortion is successfully constructed. In addition, Zernike defocus aberration is effectively controlled by precisely adjusting the resonator length. A high beam quality in the output coupling mode is realized, which is in good agreement with the analytical predictions. [ABSTRACT FROM AUTHOR]

Karhunen–Loeve functions for the case of non-Kolmogorov turbulence are calculated. The calculations are performed using the covariance matrix of Zernike coefficients which is derived in analytical form. It is shown that the Karhunen–Loeve expansion is more efficient than the Zernike one for simulations of high-order, turbulence-induced phase distortions. [ABSTRACT FROM PUBLISHER]

A computational solution to the inverse sinusoidal input describing function (SIDF) for a broad class of static nonlinearities is presented. The proposed numerical solution uses the SIDF gain and phase distortions to identify the nonlinearity. This solution, unlike existing methods in the literature, does not require a priori knowledge of the nonlinearity structure in the estimation process and is applicable to both single- and double-valued nonlinearities. The output from the algorithm is a nonparametric model of the nonlinearity from which a parametric model can be recovered by least-square estimation (LSE) method. Three examples are presented to validate the proposed algorithm. [ABSTRACT FROM AUTHOR]

A method for determination of antenna far-fields, based on a measurement at Fresnel distances, is presented. The method is applicable to highly directive antennas, measured in anechoic chambers, which size is not large enough to satisfy the far-field condition for the antenna under test (AUT). The method is based on an approximation of the accurate diffraction integral at Fresnel distances by a Fourier integral. According to the method, a quasi far-field radiation pattern of the AUT is measured at a Fresnel distance R, the measured pattern is used for a reconstruction of a distorted, due to the short range, aperture excitation, and the distorted aperture excitation is corrected magnitudewise and phasewise in accordance with R and, then, forward propagated to the far-field. An advantage of the method is that it allows an accurate treatment of the distorted phase and the magnitude of the Green kernel in the diffraction integral, with respect to the ideal far-field, in contrast to the usual quadratic approximation of the phase and expansion in an infinite row of the exponential phase term. The method offers computational precision advantages over existing methods in shorter measurement distances R and low levels of sidelobes. The accuracy of the method improves as the directivity of the AUT gets higher. The measurement distance R must not be too short to smear too much the measured Fresnel pattern and to compromise the validity of the mentioned Fourier approximation of the diffraction integral. [ABSTRACT FROM PUBLISHER]

A photorefractive composite based on a triphenyldiamine (TPD) derivative was used to restore a severely phase-aberrated laser beam to a nearly aberration-free state. Here, a forward degenerate four-wave mixing geometry was employed for the elimination of phase distortions and its practical applicability in the transmission of optically encoded data is demonstrated. In addition, it is demonstrated that the experimental geometry is able to effectively restore dynamically updating images. Conventional two-beam coupling and degenerate four-wave mixing experiments were used to characterize the composite subject to the current experimental setup. The two-beam coupling net gain coefficient was 100 cm with an applied external electric field of 70 V/µm. Internal and external diffraction efficiencies of 10 and 6%, respectively, were observed with a similar external electric field. Due to its superior charge-carrier mobility, the TPD-based composite exhibited a response time of 0.28 s, approximately five times faster than traditional PVK-based composites. [ABSTRACT FROM AUTHOR]

Results of testing of algorithm for estimation of phase-frequency characteristics of vibration protection systems for existence of significant non-linear distortions are presented. Estimations of maximal error are obtained for phase shift changes from 0.2 to 0.0001 angle degree in dependency on ADS capacity and amount of sampling. The algorithm is realized as m -files of MatLab software. [ABSTRACT FROM AUTHOR]

High linearity and low noise are important conditions for high-resolution imaging in wideband linear frequency modulation (LFM) radar systems, where stretch processing is commonly adopted. However, in practice, hardware may introduce amplitude and phase distortions to radar signals. The distortions will increase the range sidelobes (RSLs) of the dechirped returns and cause the decline of imaging quality. Traditional time-domain RSL correction methods are greatly influenced by time delay and can only be used in a small range window. To solve the problem, we propose a novel frequency-domain RSL correction (FDRC) method in this paper. For FDRC, we first multiply the extracted distortion and the stretched return by a baseband LFM signal and then perform the correction in the frequency domain. Both theoretical and simulation results show that the proposed method provides equivalent performances in RSLs compared to other existing distortion correction methods in a large range window. Besides, the proposed method can be much easily implemented in practical radar systems. [ABSTRACT FROM AUTHOR]

The goal of the current study was to characterize the normative features of wideband acoustic immittance in children for describing the functional maturation of the middle ear in 5 to 12-year-old children. Absorbance and group delay were measured in adults and three groups of children, 5–6, 7–9 and 10–12-year-olds, in a cross-sectional design. Absorbance showed significant effects of the age group in four out of ten center frequencies of one-half-octave bins from 211 to 6000 Hz, while there was no significant effect for group delay at any frequency. Older children (10–12 years) showed absorbance similar to adults. Test-retest reliability was high for absorbance for all age groups. However, group delay was modestly reliable only for adults. We conclude that the middle ear transmission follows a protracted period of maturation for high frequencies and reaches adult-like feature by 10–12 years of age. [ABSTRACT FROM AUTHOR]

One of the biggest power consuming devices in wireless communications system is the Power Amplifier (PA) which amplifies signals non-linearly when operating in real-world systems. The negative effects of PA non-linearity are energy inefficiency, amplitude and phase distortion. The increases in transmission speed in present day communication technology introduces Memory Effects, where signal spreading happens at the PA output, thus causing overhead in signal processing at the receiver side. PA Linearization is therefore required to counter the non-linearity and Memory Effects. Digital Pre-distortion (DPD) is one of the outstanding PA Linearization methods in terms of its strengths in implementation simplicity, bandwidth, efficiency, flexibility and cost. DPD pre-distorts the input signal, using an inversed model function of the PA. Modelling of the PA is therefore vital in DPD, where the Memory Polynomial Method (MP) is used to model the PA with memory effects. In this paper, the MP method is improved in Memory Polynomial using Binomial Reduction method (MPB-imag-2k). The method is simulated using a modelled ZVE-8G Power Amplifier and sampled 4G (LTE) signals. It was found MPB-imag-2k is capable of achieving comparable anti-scattering/anti-distortion in MP for non-linearity order of 3, memory depth of 3 and pre-amplifier gain of 2. [ABSTRACT FROM AUTHOR]

The filter bank multicarrier (FBMC) with offset quadrature amplitude modulation (OQAM) is one of the alternative modulation schemes to orthogonal frequency division multiplexing for next generation broadband wireless access systems. The non-linearity of high-power amplifiers (HPA) has a crucial effect on the performance of FBMC systems. In this study, the impacts of non-linear distortion effects are considered in a FBMC-OQAM system when the signal is passed through a HPA for medium- and high-power signals which are modelled as amplitude and phase distortions. Specifically, memory-less HPA non-linear distortion models such as solid-state power amplifier (SSPA), soft-envelope limiter (SEL), travelling wave tube amplifier are proposed for FBMC systems. A closed-form expression for bit error rate expression is derived and analysed for SSPA and SEL models for FBMC/OQAM system with non-linear HPA in frequency-selective Rayleigh channel by varying constellation size in OQAM modulation and input back-off. The performance is compared for the models with 64 sub-channels and input back-off for 6 and 8 dB. In lieu of validating the obtained simulation results, theoretical results are being compared. [ABSTRACT FROM AUTHOR]

Polyimide (PI) based composites filled by modified-TiO 2 particles were fabricated by in-situ dispersive polymerization. The results show that there are lots of interface regions between organic-inorganic. With TiO 2 content increasing, the dielectric constant of the composites firstly varies from 3.35 to 3.16 (0–3 wt%), then increases to 3.46 (3–7 wt%) at 0.1 Hz. The restricted orientation and electronic distortion polarizabilities in the interface are responsible for the reduced dielectric constant. The restricted effect along with the enhanced interfacial polarization determines the variation of dielectric constant of PI/TiO 2 composites. The present work provides a promising route to the design and fabrication of low- K polymer composites. [ABSTRACT FROM AUTHOR]

A novel Doherty power amplifier (PA) design method enabling high efficiency and high linearity simultaneously is proposed. The output combiner network is treated as a black box, and its parameters, together with the input phase delay, are solved based on given transistor characteristics and design requirements. This opens for new PA solutions with nonconventional Doherty behavior. The increased design space enables new tradeoffs in Doherty PA designs, including solutions with both high efficiency and high linearity simultaneously. A method utilizing the new design space is developed. For verification, a 20-W 2.14-GHz symmetrical gallium nitride high electron mobility transistors Doherty PA is fabricated and measured. The PA obtains an average power added efficiency of 40% and an adjacent power leakage ratio of −41 dBc without any linearization for an 8.6-dB peak to average power ratio 10-MHz-long term evolution signal, at an average output power of 35.5 dBm. [ABSTRACT FROM PUBLISHER]