Signal Processing Scheme Research Articles

Strain resolution enhancement in Rayleigh-OTDR based DSS system using LWT-MPSO scheme

This paper presents a scheme for performance improvement of a Rayleigh-optical time domain reflectometry (OTDR) based distributed strain sensing (DSS) system using the combined effect of lifting wavelet transform (LWT) and modified particle swarm optimization (MPSO) method. In our proposed scheme, MPSO evolutionary algorithm produces an optimum threshold and helps in minimizing the noisy lifting wavelet coefficients effectively. This allows an order-of-magnitude increase in strain resolution of the proposed system. The proposed sensing system is capable of measurement up to 50 km using a 10 mW of input laser source power. We have applied 30 με strain at 30 km position of the fiber under test. The proposed signal processing scheme offers better performance over a conventional system. The system achieved a strain resolution of ∼ 1.8 με. Relevant numerical simulations are presented using MATLAB 15.0.

Artificial Shape Perception Retina Network Based on Tunable Memristive Neurons

Retina shows an extremely high signal processing efficiency because of its specific signal processing strategy which called computing in sensor. In retina, photoreceptor cells encode light signals into spikes and ganglion cells finish the shape perception process. In order to realize the neuromorphic vision sensor, the one-transistor-one-memristor (1T1M) structure which formed by one memristor and one MOSFET in serial is used to construct photoreceptor cell and ganglion cell. The voltage changes between two terminals of memristor and MOSFET can mimic the changes of membrane potential caused by spikes and illumination respectively. In this paper, the tunable memristive neurons with 1T1M structures are built. According to the concept of receptive field of ganglion cells (GCs) in the retina, the artificial shape perception retina network is constructed with these memristive neurons. The final results show that the artificial retina can extract shape information from the image and transfer it into spike frequency realizing the function of computing in sensor.

Effects for emphasis, enhancement, expression, and exaggeration

Sound recordings built through multitrack production face a competitive soundscape. Signal processing strategies have evolved with the production goal of increasing the audibility of specific signal traits — making the subtle more apparent, the performance more compelling, the recorded art more successful.

A novel ultrasonic array signal processing scheme for wind measurement

This article presents a novel ultrasonic array signal processing scheme for wind speed and wind direction measurement. Two ultrasonic array structures are illustrated and the corresponding array signal processing method is proposed. The statistical performance of proposed scheme, such as estimation variance and Cramer Rao Bound (CRB), is derived. The ambiguity problem for traditional uniform line array (ULA) structure is theoretically discussed. The hardware experiment results verify the feasibility of the proposed wind measurement method.

A New Model Based Signal Processing Scheme for Detecting Delay and Doppler in Bistatic Radars

In this paper, a new method is presented for joint estimation of delay and Doppler in bistatic radars by using model-based signal processing framework. In the proposed method, the time history of each cell in ambiguity function is modeled as a stochastic process consisting of a stationary component caused by clutter and noise as well as a possible transient component which is caused by a target. Then some cells are indicated as candidates for being targeted based on estimating the higher order statistics of the above stochastic processes. Finally, the spatial processing scheme is performed to prune false candidates. To evaluate the proposed method, its performance is simulated under two different scenarios (i.e., slow and fast moving targets) which have been inspirited from real conditions. Comparison of the results obtained from the proposed method with its alternatives, shows its better performance in such a way that it detects fast targets at least 8% better than the best among all examined methods. Furthermore, the proposed method detects slow targets at least 4.3% better than the best among all examined methods. Both of the above superiorities are obtained in those conditions while the false alarm of the proposed method does not show the meaningful difference against other examined algorithms.

Side lobe free medical ultrasonic imaging with application to assessing side lobe suppression filter.

When focusing using an ultrasonic transducer array, a main lobe is formed in the focal region of an ultrasound field, but side lobes also arise around the focal region due to the leakage. Since the side lobes cannot be completely eliminated in the focusing process, they are responsible for subsequent ultrasound image quality degradation. To improve ultrasound image quality, a signal processing strategy to reduce side lobes is definitely in demand. To this end, quantitative determination of main and side lobes is necessary. We propose a theoretically and actually error-free method of exactly discriminating and separately computing the main lobe and side lobe parts in ultrasound image by computer simulation. We refer to images constructed using the main and side lobe signals as the main and side lobe images, respectively. Since the main and side lobe images exactly represent their main and side lobe components, respectively, they can be used to evaluate ultrasound image quality. Defining the average brightness of the main and side lobe images, the conventional to side lobe image ratio, and the main to side lobe image ratio as image quality metrics, we can evaluate image characteristics in speckle images. The proposed method is also applied in assessing the performance of side lobe suppression filtering. We show that the proposed method may greatly aid in the evaluation of medical ultrasonic images using computer simulations, albeit lacking the use of actual experimental data.

Experimental Demonstration of Flexible Hybrid Modulation Formats for Future Adaptive Optical Transmission Systems

The exponentially growing demand for high-speed data transmission is one of the main reasons for the ongoing evolution from fixed and static to link-adaptive systems in fiber-optic communications. The need to maximize the flexibility as well as the capacity of the system, while keeping the optical network infrastructure unchanged, leads to modifications of the system terminals, resulting in so-called flexible transceivers. A highly desired property of such a transceiver is a fine data rate granularity, which allows us to match the transmission capacity to the link budget. In this paper, we experimentally analyze flexible quadrature-division hybrid modulation formats, namely Flex-PAM, as a promising candidate for flexible transceivers. This method works at every integer number of bits-per-symbol, and, compared with other candidates proposed in the literature, requires a very simple digital signal processing scheme. We focus in particular on the effects of the effective number of bits in state-of-the-art digital/analog and analog/digital converters and fiber nonlinearities on the performance of Flex-PAM transmission. We analyze the capabilities of flexible modulation in a $ \text{5} \times \text{32}$ GBd wavelength division multiplexing coherent transmission on a dense $ \text{37.5}$ GHz grid and support the results by thorough numerical simulations. We successfully demonstrate the capability of Flex-PAM modulation to handle a wide range of bit-rates ( $ \text{5}\times \text{128}$ to $ \text{5}\times \text{320}$ Gbit/s), a maximum spectral efficiency of 6.8(b/s)/Hz, and propose a simple and adaptive digital signal processing scheme to compensate for the major linear and nonlinear impairments of the system.

Characterizing Seismo-stratigraphic and Structural Framework of Late Cretaceous-Recent succession of offshore Indus Pakistan

Abstract Regional seismic reflection profiles and deep exploratory wells have been used to characterize the subsurface structural trends and seismo-stratigraphic architecture of the sedimentary successions in offshore Indus Pakistan. To improve the data quality, we have reprocessed the seismic data by applying signal processing scheme to enhance the reflection continuity for obtaining better results. Synthetic seismograms have been used to identify and tie the seismic reflections to the well data. The seismic data revealed tectonically controlled, distinct episodes of normal faulting representing rifting during Mesozoic and transpression at Late Eocene time. A SW-NE oriented anticlinal type push up structure is observed resulted from the basement reactivation and recent transpression along Indian Plate margin. The structural growth of this particular pushup geometry was computed. Six mappable seismic sequences have been identified on seismic records. In general, geological formations are at shallow depths towards northwest due to basement blocks uplift. A paleoshelf is also identified on seismic records overlain by Cretaceous sediments, which is indicative of Indian-African Plates rifting at Jurassic time. The seismic interpretation reveals that the structural styles and stratigraphy of the region were significantly affected by the northward drift of the Indian Plate, post-rifting, and sedimentation along its western margin during Middle Cenozoic. A considerable structural growth along the push up geometry indicates present day transpression in the margin sediments. The present comprehensive interpretation can help in understanding the complex structures in passive continental margins worldwide that display similar characteristics but are considered to be dominated by rifting and drifting tectonics.

Validation of an inertial measurement unit for the quantification of rearfoot kinematics during running

BackgroundThe popular protocol used to study running motion suffers from problems that lead to a limited ability to generalize the obtained results. Inertial measurement units (IMU) appear to be promising in increasing ecological validity of the collected data. However, quantifying running kinematics utilizing IMU signals is complex and potentially affected by several well-established and less well-known errors. Research questionThe purpose of this study was to examine the validity of kinematic variables obtained from a single, shoe-mounted IMU using an opto-electronic motion analysis reference system. Methods51 recreational runners were analyzed, performing a single continuous run at three different speeds (10, 12, 15 km/h) on a treadmill. Descriptive statistics (Bland & Altman analysis, box plots, scatter plots) were employed to analyze the agreement between the two instruments. ResultsThe findings of this study revealed considerable systematic and large random disagreement, which, in turn, is characterized by substantial inter-individual differences in the error distribution. These discrepancies may partly be explained by differences in foot strike behavior, resulting in varying degrees of vibration impact acting on the IMU. SignificanceAdvances in IMU technology, as well as exploring new application approaches and signal processing strategies, might enhance the usability of IMUs in analyzing running kinematics.

Comparative study of two geometrical acoustic simulation models

Simulations based on the concepts of geometrical acoustics are today well-established tools for acousticians, being widely used for evaluation of sound quality in rooms and urban spaces. However, although a lot of different models are available and have been evaluated in the past, it is still very important to guarantee the validity and quality of simulated data and reproduced sound. This work presents a comparison between the signal processing strategies in two acoustic simulators based on geometrical models. Obvious expectation was that both simulators would produce the same results when fed by exactly the same input data. However, issues related to model assumptions, propagation methods characteristics and signal processing techniques adopted by each simulator introduce differences which alter the final results, i.e., the simulated acoustic impulse responses. This papers aims to present such deviation and helps to understand the influence of each component over the results. Firstly, both simulators are described in detail, presenting their acoustic models and the signal processing approaches. In addition, an extensive analysis of early reflections is performed, considering pressure levels, reflection order, their arrival time and directional characteristics. Next, simulated energy decay curves, monaural room acoustic parameters and spectra are objectively compared to measured data of a reverberant chamber, in two different conditions. The differences are then pointed out and minimized by unifying the signal processing of both simulators. The results of this comparison reveal that signal processing and inherit method characteristics still have strong influence over the simulated impulse responses, mainly for the late part. Some consequences are energy misbalance between early and late parts of impulse response, leading to differences over the room acoustic parameters, mainly clarity and definition.

Factors Affecting Speech Reception in Background Noise with a Vocoder Implementation of the FAST Algorithm.

Speech segregation in background noise remains a difficult task for individuals with hearing loss. Several signal processing strategies have been developed to improve the efficacy of hearing assistive technologies in complex listening environments. The present study measured speech reception thresholds in normal-hearing listeners attending to a vocoder based on the Fundamental Asynchronous Stimulus Timing algorithm (FAST: Smith et al. 2014), which triggers pulses based on the amplitudes of channel magnitudes in order to preserve envelope timing cues, with two different reconstruction bandwidths (narrowband and broadband) to control the degree of spectrotemporal resolution. Five types of background noise were used including same male talker, female talker, time-reversed male talker, time-reversed female talker, and speech-shaped noise to probe the contributions of different types of speech segregation cues and to elucidate how degradation affects speech reception across these conditions. Maskers were spatialized using head-related transfer functions in order to create co-located and spatially separated conditions. Results indicate that benefits arising from voicing and spatial cues can be preserved using the FAST algorithm but are reduced with a reduction in spectral resolution.

Frequency Comb-Based WDM Transmission Systems Enabling Joint Signal Processing

We review the use of optical frequency combs in wavelength-division multiplexed (WDM) fiber optic communication systems. In particular, we focus on the unique possibilities that are opened up by the stability of the comb-line spacing and the phase coherence between the lines. We give an overview of different techniques for the generation of optical frequency combs and review their use in WDM systems. We discuss the benefits of the stable line spacing of frequency combs for creating densely-packed optical superchannels with high spectral efficiency. Additionally, we discuss practical considerations when implementing frequency-comb-based transmitters. Furthermore, we describe several techniques for comb-based superchannel receivers that enables the phase coherence between the lines to be used to simplify or increase the performance of the digital carrier recovery. The first set of receiver techniques is based on comb-regeneration from optical pilot tones, enabling low-overhead self-homodyne detection. The second set of techniques takes advantage of the phase coherence by sharing phase information between the channels through joint digital signal processing (DSP) schemes. This enables a lower DSP complexity or a higher phase-noise tolerance.

Energy efficiency state identification in milling processes based on information reasoning and Hidden Markov Model

Abstract Energy efficiency state identification of milling process plays an important role in energy saving efforts for manufacturing systems. However, it is very difficult to track energy efficiency state in machining processes based on traditional signal processing strategies due to the fact that energy state is usually coupled with a lot of factors like machine tool states, tool conditions, and cutting conditions. An identification method of information reasoning and Hidden Markov model for energy efficiency state is proposed in this paper. Utilizing cutting conditions, empirical models of the energy efficiency, experimental data and signal features, an expert system is established for initial probability optimization and the state is further identified by Hidden Markov model. The experiments show that energy efficiency state can be identified with this method.

Baseline Correction of Digital Accelerograms from Field Testing of a Seismically Isolated Building

A three-story reinforced-concrete building in Augusta, Sicily, isolated at the base and designed according to the provisions of the latest Italian seismic regulations, was subjected to a series of push and sudden release tests in March 2013. During the tests, the displacements at the isolation level were measured along with the accelerations at each floor. The obtained records were then treated for the removal of low-frequency noise using a simple baseline-fitting scheme. The developed signal-processing scheme consists of defining the duration of the main event, removing the background noise, and using polynomial curves for the adjustment of the distorted baseline. The method does not require significant computational effort and accounts for initial and end conditions provided that these are known. Implementation of the method provides the adjusted response in terms of absolute and relative floor accelerations, velocities, and displacements, as well as interstory drifts.

Discovering acoustic structure of novel sounds.

Natural sounds have substantial acoustic structure (predictability, nonrandomness) in their spectral and temporal compositions. Listeners are expected to exploit this structure to distinguish simultaneous sound sources; however, previous studies confounded acoustic structure and listening experience. Here, sensitivity to acoustic structure in novel sounds was measured in discrimination and identification tasks. Complementary signal-processing strategies independently varied relative acoustic entropy (the inverse of acoustic structure) across frequency or time. In one condition, instantaneous frequency of low-pass-filtered 300-ms random noise was rescaled to 5 kHz bandwidth and resynthesized. In another condition, the instantaneous frequency of a short gated 5-kHz noise was resampled up to 300 ms. In both cases, entropy relative to full bandwidth or full duration was a fraction of that in 300-ms noise sampled at 10 kHz. Discrimination of sounds improved with less relative entropy. Listeners identified a probe sound as a target sound (1%, 3.2%, or 10% relative entropy) that repeated amidst distractor sounds (1%, 10%, or 100% relative entropy) at 0 dB SNR. Performance depended on differences in relative entropy between targets and background. Lower-relative-entropy targets were better identified against higher-relative-entropy distractors than lower-relative-entropy distractors; higher-relative-entropy targets were better identified amidst lower-relative-entropy distractors. Results were consistent across signal-processing strategies.

Characterization and optimization of an optical and electronic architecture for photon counting

This work shows a time-domain method for the discrimination and digitization of pulses coming from optical detectors, considering the presence of electronic noise and afterpulsing. The developed signal processing scheme is based on a time-to-digital converter (TDC) and a voltage discriminator. After setting appropriate parameters for taking spectra, acquisition data was corrected by wavelength, intensity response function, and noise suppression. The performance of this scheme is discussed by its characterization as well as the comparison of its spectra to those obtained by an Ocean Optics HR4000 commercial reference.

Graph‐based iterative measurement‐denoising and radio‐map generation for semi‐supervised indoor localisation

This study considers the problem of indoor localisation in which the authors try to generate the radio map of the environment based on both labelled and unlabelled measurements (i.e. measurements with and without information about the location that they have been collected). In such problems, the method that has been used for radio-map generation as well as the quality of the measurements (the received signal strength from different environment's WiFi Access Points) are very critical in the overall accuracy of the generated radio map. In this study, they apply two of the well-known graph-based signal processing schemes (namely iterative least square reconstruction and graph-based label propagation) for polishing the input data, determining the outliers and radio-map generation. Experimental results show the superior performance of the proposed method compared to previous schemes.

Design and performance analysis of all-optical cascaded adder using SOA-based MZI

With the performance enhancements in all-optical signal processing and switching schemes in terms of data rate and processing speed, various devices enabled with all-optical operation are becoming primary requirements for current and future telecommunications and data networks. All-optical logic gates represent the best solution to realize both combinational as well as sequential devices in the optical domain, representing the basic building blocks for optical computing circuits. We propose herein an all-optical cascaded adder whose elementary blocks are a half-adder and full-adder, designed using semiconductor optical amplifier (SOA)-based Mach–Zehnder interferometer (MZI) gate configurations. They have high thermal stability and require low power. The nonlinear effects in the SOA device are used to implement different logic operations. The proposed cascaded adder was simulated in OptiSystem. The optical signal-to-noise ratio, bit error rate (BER), and Q-factor values were evaluated for different data rates. The design showed good performance up to 60 Gbps. The proposed design could find application in implementation of multistage arithmetic logic units.

An enhanced morphology gradient product filter for bearing fault detection

Abstract This paper presents a signal processing scheme, namely enhanced morphology gradient product filter (EMGPF), for rolling element bearing fault detection. In this scheme, a morphology gradient product operation (MGPO) is firstly proposed to extract impulsive features of a raw signal according to a comprehensive investigation of the working mechanism of the reported morphological operations. Then, a higher-order spectrum analysis method, the third-order cumulant slice spectrum, is used to improve the performance of the MGPO based morphology filter for the purpose of highlighting fault features further. Experimental vibration signals were employed to evaluate the effectiveness of the proposed EMGPF. Results show that the proposed method has a superior performance in extracting fault features of defective rolling element bearing over four reported morphology filters.

Highly localized distributed Brillouin scattering response in a photonic integrated circuit

The interaction of optical and acoustic waves via stimulated Brillouin scattering (SBS) has recently reached on-chip platforms, which has opened new fields of applications ranging from integrated microwave photonics and on-chip narrow-linewidth lasers, to phonon-based optical delay and signal processing schemes. Since SBS is an effect that scales exponentially with interaction length, on-chip implementation on a short length scale is challenging, requiring carefully designed waveguides with optimized opto-acoustic overlap. In this work, we use the principle of Brillouin optical correlation domain analysis to locally measure the SBS spectrum with high spatial resolution of 800 μm and perform a distributed measurement of the Brillouin spectrum along a spiral waveguide in a photonic integrated circuit. This approach gives access to local opto-acoustic properties of the waveguides, including the Brillouin frequency shift and linewidth, essential information for the further development of high quality photonic-phononic waveguides for SBS applications.