Amplitude Shift Research Articles

A novel method for UWB weak signal detection based on stochastic resonance and wavelet transform

Pulse ultra-wideband (UWB) signal is a transient pulse in time domain with very low power spectral density; In the long-distance communication, it is difficult to detect the low signal to noise ratio (SNR) pulse UWB signal submerged in strong noise. To solve the above problems, a novel adaptive stochastic resonance fusion wavelet transform method for UWB weak signal detection is proposed. Firstly, the adaptive optimization method which is based on the improved stochastic resonance potential well model is used to match the optimal parameters of the stochastic resonance (SR) system for the noisy signal, so that the noise energy can be transferred to the UWB signal and the signal amplification can be realized; Secondly, in view of the problem that SR method is insensitive to phase transient information and amplitude shift, wavelet transform is used to extract mutation information, so as to realize the accurate detection of UWB weak signal. The simulation results show that the proposed method can solve the problem that it is difficult to distinguish the change of signal state by using stochastic resonance method alone. Finally, two groups of actual signals with bandwidth of 10 MHz and 20 MHz are collected by the experimental system to test the effectiveness of the method.

Adaptive Noise-Resistant Low-Power ASK Demodulator Design in UHF RFID Chips

This paper presents a new signal demodulator for ultra-high frequency (UHF) radio frequency identification (RFID) tag chips. The demodulator is used to demodulate amplitude shift keying (ASK) modulated signals with the advantages of high noise immunity, large input range and low power consumption. The demodulator consists of a charge pump, an envelope detector, and a comparator. In particular, the demodulator provides a hysteresis input signal to the comparator through two envelope detectors, resulting in better noise immunity. The demodulator is based on a standard 0.13 µm CMOS process. The demodulator is suitable for demodulating high frequency signals at 900 MHz with a data rate of 128 Kbps and can operate up to 78 °C. The input signal has a peak of 1.2 V and consumes as little as 113.6 nW. The demodulator also has a noise immunity threshold of approximately 3.729 V.

Relay interlayer synchronisation: invariance and stability conditions

In this paper, the existence (invariance) and stability (locally and globally) of relay interlayer synchronisation (RIS) are investigated in a chain of multiplex networks. The local dynamics of the nodes in the symmetric positions layers on both sides of the non-identical middlemost layer(s) are identical. The local and global stability conditions for this synchronisation state are analytically derived based on the master stability function approach and by constructing a suitable Lyapunov function, respectively. We propose an appropriate demultiplexing process for the existence of the RIS state. Then the variational equation transverse to the RIS manifold for demultiplexed networks is derived. In numerical simulations, the impact of interlayer and intralayer coupling strengths, variations of the system parameter in the relay layers and demultiplexing on the emergence of RIS in triplex and pentaplex networks are explored. Interestingly, in this multiplex network, enhancement of RIS is observed when a type of impurity via parameter mismatch in the local dynamics of the nodes is introduced in the middlemost layer. A common time-lag with small amplitude shift between the symmetric positions and central layers plays an important role for the enhancing of relay interlayer synchrony. This analysis improves our understanding of synchronisation states in multiplex networks with nonidentical layers.

Reconfigurable Mach–Zehnder interferometer for dynamic modulations of spoof surface plasmon polaritons

Abstract We propose an ultrathin reconfigurable Mach–Zehnder interferometer (MZI) for realizing dynamic frequency and amplitude modulations of spoof surface plasmon (SSP) signal. Active varactor diodes are integrated in the SSP unit cells on one of the MZI arms to introduce asymmetry to the MZI structure, which can control the interference patterns by varying bias voltages applied on the varactor diodes. We show that the spectral positions of multiple sharp interference dips are very sensitive to the change of diode capacitance, thereby allowing for good frequency modulation. We also demonstrate continuous amplitude modulation by tuning the varactor diodes at multiple selected frequencies. To verify the reconfigurable feature of the proposed SSP MZI, the frequency shift keying (FSK) and amplitude modulations have been experimentally demonstrated on the same structure. The modulation depth of the amplitude modulation can be further improved by designing geometrical parameters of the SSP structure, reaching a significant amplitude change from 0.88 to 0.05 in experiments.

Dirty Paper Coding Based on Polar Codes and Probabilistic Shaping

A precoding technique based on polar codes and probabilistic shaping is introduced for dirty paper coding. Two variants of the precoding use multi-level shaping and sign-bit shaping in one dimension. The decoder uses multi-stage successive-cancellation list decoding with list-passing across the bit levels. The approach achieves approximately the same frame error rates as polar codes with multi-level shaping over standard additive white Gaussian noise channels at a block length of 256 symbols and with different amplitude shift keying (ASK) constellations.

Theoretical study on the sensitivity of dynamic acoustic force measurement through monomodal and bimodal excitations of rectangular micro-cantilever

We present a detailed analysis on measurement sensitivity of dynamic acoustic forces via numerical simulation of the micro-cantilever responses. The rectangular micro-cantilever is regarded as a point mass in the dynamic model of forced and damped harmonic oscillator. We use single- and bimodal-frequency excitation schemes for actuation of the micro-cantilever in the presence of dynamic acoustic forces. In bimodal-frequency excitation scheme, the micro-cantilever is excited at its first two eigenmode frequencies simultaneously as opposed to single-frequency excitation. First, we numerically obtain micro-cantilever deflections by solving the equations of Motions (EOMs) constructed for the first two eigenmodes. Then, we determine oscillation amplitude and phase shift as a function of acoustic force strength within different frequency regions. Moreover, we relate amplitude and phase shift to virial and energy dissipation in order to explore the interaction between flexural modes in multifrequency excitation. The simulation results point out that bimodal-frequency excitation improves the measurement sensitivity of dynamic acoustic forces at particular frequencies. Herein, simultaneous application of driving forces enables higher sensitivities of observables and energy quantities as acoustic force frequencies become around the eigenmode frequencies. For our case, we obtain the highest phase shift (∼178°) for the acoustic force strength of 100 pN at the frequency of around 307.2 kHz. Therefore, this method can be easily adapted to improve measurement sensitivity of dynamic acoustic forces in a wider frequency window.

Construction of a test system for smart meter dynamic error using TASK algorithm

This exploration aims to improve the measurement accuracy of the electric energy meter under dynamic load conditions, and try to minimize the dynamic error. With the popularization of energy-saving and environmental protection concepts, exploring the dynamic power error of electric meters in the electric field becomes the basis for the reliable, economical, and efficient operation of smart grids. According to the actual dynamic load working mode in the electric power field, a Ternary Amplitude Shift Keying (TASK) dynamic test current and dynamic test power model are designed. Then, a test system for smart meter dynamic error is constructed based on the TASK algorithm and the model designed above. Furthermore, different sample meters are used to simulate and analyze the dynamic power error test performance of the error test system. The unidirectional dynamic power error of each sample meter is analyzed. Results demonstrate that the unidirectional power error of the foreign factory's sample meter is less than 0.2% when the test current is 2.5A. The bi-directional power analysis suggests that only the dynamic error of the foreign factory's sample meter is within the error range of 0.2%. The construction scheme of the dynamic error test system for electric energy meters is achieved to solve the dynamic error test problem under the bidirectional power test model oriented to time process. This system provides the basis for the development of the power field.

Frequency response analysis for MSMPR crystallizer with modulated feed flow rate: A method for studying secondary nucleation mechanism

In industrial crystallization, understanding the effect of individual secondary nucleation mechanisms is difficult. This paper presents frequency response of a mixed suspension mixed product removal (MSMPR) crystallizer to a periodic modulation in feed rate. This will help in roughly understanding the effect of magma density or thick solute layer adsorbed on crystals, on the formation of secondary nucleation, which are otherwise practically impossible to understand through stirrer speed modulation (V. Bal and B. Peters, Cryst. Groth Des., 21 (2021) 227–234). Feed rate modulation drives the oscillation in magma density, which in turn drives the supersaturation. Combined effect of magma density and supersaturation controls the oscillation in nucleation rate and hence, damped oscillation in number density. In the intermediate frequency limit, strong oscillation in either amplitude or phase shift can be exploited to study the different secondary nucleation mechanisms. There is a narrow range of frequency and amplitude of feed rate modulation over which the crystallizer should be operated for detectable response.

Secret key rate of multi-ring M-APSK continuous variable quantum key distribution.

Discrete modulation continuous variable quantum key distribution (DM-CV-QKD) is highly considered in real implementations to avoid the complexity of Gaussian modulation (GM), which is optimum in terms of the key rate. DM-CV-QKD systems usually consider M-symbol phase shift keying (M-PSK) constellations. However, this type of constellation cannot reach transmission distances and key rates as high as GM, limiting the practical implementation of CV-QKD systems. Here, by considering M-symbol amplitude and phase shift keying (M-APSK) constellations, we can approximate GM. Indeed, considering finite-size effects, 4 ring 64-APSK can reach 52.0 km, only 7.2 km less than GM and 282% the maximum achievable transmission distance for 8-PSK.

Brain signaling dynamics after vagus nerve stimulation

The vagus nerve projects to a well-defined neural circuit via the nucleus tractus solitarii (NTS) and its stimulation elicits a wide range of metabolic, neuromodulatory, and behavioral effects. Transcutaneous vagus nerve stimulation (tVNS) has been established as a promising technique to non-invasively alter brain function. However, the precise dynamics elicited by tVNS in humans are still largely unknown. Here, we performed fMRI with concurrent right-sided tVNS (vs. sham) following a randomized cross-over design (N = 40). First, to unravel the temporal profile of tVNS-induced changes in the NTS, we compared fMRI time series to canonical profiles for stimulation ON and OFF cycles. Model comparisons indicated that NTS time series were best fit by block-wise shifts in signal amplitude with stimulation ON and OFF estimates being highly correlated. Therefore, we compared stimulation (ON + OFF) versus baseline phases and found that tVNS increased fMRI BOLD activation in the NTS, but this effect was dependent on sufficient temporal signal-to-noise ratio (tSNR) in the mask. Second, to identify the spatiotemporal evolution of tVNS-induced changes in the brain, we examined lagged co-activation patterns and phase coherence. In contrast to our hypothesis, tVNS did not alter dynamic functional connectivity after correction for multiple comparisons. Third, to establish a positive control for future research, we measured changes in gastric myoelectrical frequency via an electrogastrogram. Again, in contrast to our hypothesis, tVNS induced no changes in gastric frequency. Collectively, our study provides evidence that tVNS can perturb brain signaling in the NTS, but these effects are dependent on tSNR and require precise localization. In light of an absence of acute tVNS-induced effects on dynamic functional connectivity and gastric motility, we discuss which steps are necessary to advance future research on afferent and efferent effects of tVNS.

Mapping active strain using terahertz metamaterial laminates

The ability to image strain fields in composite materials is an indispensable necessity for structural health monitoring. Embedded electromagnetic metamaterials sensitive to applied stresses and operating in the terahertz regime have been proposed as a solution, but they have traditionally relied on slight amplitude or frequency shifts of their terahertz spectral resonance relative to a presumably unchanging, unstrained reference spectral map. Here, we demonstrate a facile, reference-free imaging technique to map the currently active local strain throughout a composite structure using a reversible passive terahertz metamaterial laminate with a tailored polarimetric signature. Only two orthogonal polarizations and a few frequencies are required to measure this strong terahertz response, from which the local strain environment may be rapidly and quantitatively mapped over large areas.

Performance Analysis of Typical Telemetry Modulation Methods Under Downlink Integrated Channel of Hypersonic Vehicles

Due to the severe impact of dynamic plasma sheath on electromagnetic (EM) waves, the communication quality of hypersonic vehicles deteriorates, even resulting in communication blackouts during the reentry process. In this article, the hypersonic vehicle downlink integrated channels that cascade the plasma sheath channel and Rice fading channel, i.e., the downlink telemetry channels, are first established, and then the demodulation method and performance of typical telemetry modulations including the M-ary phase shift keying (MPSK), M-ary amplitude shift keying (MASK), and M-ary frequency shift keying (MFSK) are studied. Considering the high dynamics of the plasma sheath, the pilot signals are used to detect the signal correctly for MPSK, and the non-coherent demodulation is adopted for MASK and MFSK. Especially, an adaptive maximum likelihood (ML) receiver for ASK is proposed based on a reduced reversible jump Markov chain Monte Carlo (RRJ-MCMC) algorithm to estimate the probability density function (pdf) of the received signal. The simulation results show that the communication performance of PSK and ASK is improved with the modulation order $M$ decreasing; the performance of non-coherent FSK is improved with the modulation order $M$ increasing. Meanwhile, the performance follows the order of NC-MFSK (M ≥ 8) > BPSK > NC-4FSK > NC-2FSK > 2ASK. For NC-8FSK, when the electron density peak value ${Ne}_{\mathrm {peak}}$ = {2, 4, 6, 8, 10} $\times 10^{18}\,\,\text{m}^{-3}$ , the signal to noise ratio (SNR) required to reduce the bit error rate (BER) to 10−6 are 17, 18, 19, 21, and 34 dB, respectively.

Study on piezo-electric flapping wing mechanism for bio-inspired micro aerial vehicles

The Micro Aerial Vehicle (MAV) with a flapping wing configuration is much more efficient and capable of generating substantial lift at low flight speeds and has excellent maneuverability. Different motor-driven mechanisms have been developed to mimic this flapping motion, but these mechanisms introduced mechanical complexity and heavy weight to the system. Piezo-electric based mechanisms have been used to solve these problems, but provide very small flapping amplitudes within the size limitation of MAVs. So some kind of amplification mechanism is needed. In this paper, a flexible wing is created by attaching a polymer skin to a pair of carbon fiber reinforced plastic spars. This wing is connected by means of an elastic-element (EE) to a pair of piezoelectric unimorphs (piezofan). The motion from the piezofan to the wing is transferred through this EE. Simulation has been done by applying sinusoidal voltages of varying frequency to this piezofan and observations have been made for the flapping amplitude of the wing for different stiffness of the EE. It is observed that the amplitude of the peak flapping amplitude initially increases, attains a maximum value, then decreases again with an increase in the stiffness of the EE. It is also observed that as the EE stiffness increases, the corresponding peak of the flapping amplitude shifts towards higher frequency.

An ASK Data Demodulator Circuit for Implantable Medical Devices Supporting a Minimum Modulation Depth of 0.034.

Amplitude shift keying (ASK) data demodulation method has been widely used for simultaneous wireless data and power transfer in implantable medical devices (IMDs). Small amplitude modulation depth (MD) is usually preferred as it helps promote energy harvesting efficiency. This paper presents an ASK data demodulator that has good immunity to disturbances and can demodulate ultra-low MD ASK signal. A three-stage amplifying structure (3SAS) is proposed, in which the common-mode level of each amplifier is set between the high and low levels of its input signal envelope to prevent amplifier gain saturation and maximize the amplification of the envelope difference. Two envelope detectors (EDs) are used before and after the 3SAS respectively. The first one is to obtain a coarse envelope for 3SAS input and the second one is to further suppress the residual carrier interference and get a fine envelope. The proposed demodulator is implemented in 0.18-μm high-voltage Bipolar-CMOS-DMOS (BCD) technology. The detectable MD is measured as low as 0.034%, showing that the proposed demodulator can work smoothly and robustly in some extreme cases of simultaneous data and power transferring.Clinical Relevance- The ASK data demodulator proposed in this paper supports ultra-low modulation depth. This reduces the bit error rate of the data link and keeps a highly power conversion efficiency for wireless power and data transfer in implantable medical devices.

Development of a tracking error prediction system for the CyberKnife Synchrony Respiratory Tracking System with use of support vector regression.

The accuracy of the CyberKnife Synchrony Respiratory Tracking System is dependent on the breathing pattern of a patient. Therefore, the tracking error in each patient must be determined. Support vector regression (SVR) can be used to easily identify the tracking error in each patient. This study aimed to develop a system with SVR that can predict tracking error according to a patient's respiratory waveform. Datasets of the respiratory waveforms of 93 patients were obtained. The feature variables were variation in respiration amplitude, tumor velocity, and phase shift between tumor and the chest wall, and the target variable was tracking error. A learning model was evaluated with tenfold cross-validation. We documented the difference between the predicted and actual tracking errors and assessed the correlation coefficient and coefficient of determination. The average difference and maximum difference between the actual and predicted tracking errors were 0.57 ± 0.63 mm and 2.1 mm, respectively. The correlation coefficient and coefficient of determination were 0.86 and 0.74, respectively. We developed a system for obtaining tracking error by using SVR. The accuracy of such a system is clinically useful. Moreover, the system can easily evaluate tracking error. We developed a system that can be used to predict the tracking error of SRTS in the CyberKnife Robotic Radiosurgery System using machine learning. The feature variables were the breathing parameters, and the target variable was the tracking error. We used support vector regression algorithm.

A 2.0-GHz compact ESR spectrometer for monitoring automobile lubrication oil degradation

This article reports a simple, compact, and cost-effective electron spin resonance (ESR) spectrometer for monitoring automobile lubrication oil degradation. Lubrication oil degradation strongly correlates with the concentration of stable free radicals caused by hydrocarbon chain decomposition due to heating. For the prototype spectrometer, the amplitude shift in a marginal oscillator output detects ESR absorption in a sample. The spectrometer’s spin sensitivity of 2.3 × 1014 spins for a used oil sample was achieved using the marginal oscillator with a loop-gap resonator. For the prototype spectrometer, the oscillation frequency was 2.09 GHz. The volume of the prototype spectrometer was 1.3 L, including a permanent magnet, microwave circuits, and digital communication circuitry on printed circuit boards. The weight of the spectrometer setup was 1.45 kg. This prototype spectrometer successfully detected the ESR signal from a 50 μL oil sample (spin concentration 8.3 x1019 spins/L) with a signal-to-noise ratio of 37 and an acquisition time of 30 s.

Do food images as action outcomes evoke a reward positivity?

Favourable compared to unfavourable action outcomes typically evoke a positive-going amplitude shift at frontomedial electrodes in the scalp-recorded electroencephalogram. Since prior studies on this Reward Positivity (RewP) have heavily relied on monetary outcomes, it is still debated whether the RewP is also elicited by other kinds of reward. We addressed this issue by focussing on food as another major category of daily reward. Twenty-eight healthy participants completed a decision task, in which they received images of personally liked, neutral or disliked food as outcome stimuli. Importantly, single trial outcomes were of relevance for a prolonged task goal (i.e., obtaining the liked foods and avoiding the disliked foods). The observed amplitude pattern did not correspond to the typical RewP effect observed for monetary outcomes. In particular, disliked foods evoked a similar positive-going amplitude shift as liked foods when compared to neutral foods. Exploratory analyses indicated that this pattern may result from a spatiotemporal overlap between a potential RewP response and other, emotion-related ERP components (i.e., the Early Posterior Negativity and the Late Positive Potential). We discuss our findings with regard to theoretical and methodological implications for the usage of the RewP in the study of reward processing.

Mice heterozygous for the Serpinb6a null mutation show deficits in central auditory function after acoustic trauma.

Complete deficiency of the serine protease inhibitor gene, SERPINB6, is responsible for autosomal-recessive, nonsyndromic sensorineural hearing loss in humans. A mouse model of this deafness gene identifies Serpinb6a expression in the neurosensory epithelium and fibrocytes of the cochlea. Homozygous Serpinb6a mutant mice display an exaggerated hearing loss after exposure to moderate acoustic trauma. It is unknown if and how heterozygous Serpinb6a mice show increased vulnerability to acoustic trauma. We exposed Serpinb6a+/- and Serpinb6a+/+ mice to acoustic trauma and measured their hearing function prior to, 3 and 14 days postexposure, analysing shifts in hearing threshold and amplitudes of Wave I and II of the auditory brainstem-evoked response (ABR) to 4, 8, 16 and 32 kHz tones. Shifts in hearing threshold and Wave I amplitude of Serpinb6a+/- mice were not significantly different from Serpinb6a+/+ mice at both time points and all frequencies tested (P > 0.05, Mann-Whitney test). However, Wave II amplitudes at 16 and 32 kHz tones, were more severely diminished in Serpinb6a+/- mice (P < 0.05). To exclude any effects of ageing on auditory function in Serpinb6a+/- mice, hearing function of unexposed Serpinb6a+/- mice was measured at start and end of the experimental period. The shift in Wave II amplitude of exposed Serpinb6a+/- mice was significantly lower than unexposed Serpinb6a+/- mice only at 16 and 32 kHz (P < 0.01), confirming acoustic trauma as the main cause of hearing deficits in Serpinb6a+/- mice. These results suggest that heterozygous Serpinb6a humans may be vulnerable to noise.

Low power ASK modulator based on direct injection‐locked current reuse VCO in 130‐nm CMOS technology for high data rate RFID applications

AbstractA low power consumption Amplitude Shift Keying (ASK) modulator employing current reuse cross‐coupled (CRC) LC‐VCO topology and direct injection locking (IL) technique at 10.5‐GHz frequency is presented in this paper. The modulator consumes 864 μW with a DC supply of 1.2 V drawing an average current of 720 μA. The differential VCO is composed of a PMOS‐NMOS pair in stacked series cross‐coupled connection enabling current reuse which results in reduction of the average current drawn from the power source. For comparison, the ASK modulator is also realized with conventional cross‐coupled (CC) topology using NMOS pair. Both circuit approaches are carried out in GF 130‐nm CMOS technology and the post‐layout simulation results of 0.5 × 0.5 mm2 integrated circuits (ICs) show that the CRC topology consumes less power and half of the average current compared to CC topology. Owing to low power requirements, the CRC ASK modulator can be used in self‐powered active Radio Frequency Identification (RFID) tag transmitters for higher data rates.

Open Science Practices for Studies of Event-Related Potentials (ERPs): Reporting ERP Reliability and Data Quality in the Spirit of Transparency

Hydrological frequency analysis (HFA) is commonly used for the assessment of the risk associated to hydrological events. HFA is generally based on the assumptions of homogeneity, independence and stationarity of the hydrological data. Hydrological events are often described through a number of dependent characteristics, such as peak, volume and duration for floods. Unfortunately, in this multivariate setting, the verification of the above assumptions is often neglected. When a shift occurs in a data series, it can affect the stationarity and the homogeneity of the data. The objective of this paper is to study tests for shift detection in multivariate hydrological data. The considered shift tests are mainly based on the notion of depth function, except for one test that is considered for comparison purposes. A simulation study is performed to evaluate and compare the power of all these tests with hydrological constraints. A flood analysis application is also carried out to show the practical aspects of the considered tests. The power of the considered tests is influenced by a number of factors, including the sample size, the shift amplitude, the magnitude of the series and the location of the shift in the series.