Envelope Cross-correlation Research Articles

Instantaneous Velocity Estimation Based on Envelope Cross Correlation and Joint Frequency-Phase Estimation for Wideband LFM Radar

Instantaneous Velocity Estimation Based on Envelope Cross Correlation and Joint Frequency-Phase Estimation for Wideband LFM Radar

Fault localization on power cables using time delay estimation of partial discharge signals

Precise localization of partial discharge (PD) sources on power cables is vital to prevent power line failures that can lead to significant economic losses for electrical suppliers. This study proposes four methods to estimate the time delay of PD signals under electromagnetic interference, including white Gaussian noise (WGN) and discrete sinusoidal interference (DSI), using denoised PD signals with signal-to-noise ratios ranging from 10.6 to -7.02 dB. The maximum peak detection (MPD) and cross-correlation (CC) approaches, as well as two new techniques, interpolation cross-correlation (ICC) and envelope cross-correlation (ECC), are evaluated for their effectiveness in PD source localization. The researchers employ the time difference of arrival (TDoA) algorithm to compute PD location using the double-end PD location algorithm, where the PD location precision serves as an indicator of the accuracy of the time delay estimation methods. The study concludes that CC and ICC are the most suitable methods for estimating the time delay of PD signals in the PD location algorithm, as they exhibit the lowest error rates. These results suggest that CC and ICC can be used effectively for precise PD source localization under electromagnetic interference on power cables.

Comment on “Sources of Long-Range Anthropogenic Noise in Southern California and Implications for Tectonic Tremor Detection” by Asaf Inbal, Tudor Cristea-Platon, Jean-Paul Ampuero, Gregor Hillers, Duncan Agnew, and Susan E. Hough

Article Commentary| May 17, 2023 Comment on “Sources of Long‐Range Anthropogenic Noise in Southern California and Implications for Tectonic Tremor Detection” by Asaf Inbal, Tudor Cristea‐Platon, Jean‐Paul Ampuero, Gregor Hillers, Duncan Agnew, and Susan E. Hough Allie Hutchison; Allie Hutchison 1University of California, Riverside, Riverside, California, U.S.A. https://orcid.org/0000-0001-9350-7975 Search for other works by this author on: GSW Google Scholar Yijian Zhou; Yijian Zhou 1University of California, Riverside, Riverside, California, U.S.A. https://orcid.org/0000-0002-7205-1769 Search for other works by this author on: GSW Google Scholar Abhijit Ghosh Abhijit Ghosh * 1University of California, Riverside, Riverside, California, U.S.A. *Corresponding author: aghosh.earth@gmail.com https://orcid.org/0000-0002-0557-2839 Search for other works by this author on: GSW Google Scholar Author and Article Information Allie Hutchison https://orcid.org/0000-0001-9350-7975 1University of California, Riverside, Riverside, California, U.S.A. Yijian Zhou https://orcid.org/0000-0002-7205-1769 1University of California, Riverside, Riverside, California, U.S.A. Abhijit Ghosh https://orcid.org/0000-0002-0557-2839 * 1University of California, Riverside, Riverside, California, U.S.A. *Corresponding author: aghosh.earth@gmail.com Publisher: Seismological Society of America First Online: 17 May 2023 Online ISSN: 1943-3573 Print ISSN: 0037-1106 © Seismological Society of America Bulletin of the Seismological Society of America (2023) https://doi.org/10.1785/0120190171 Article history First Online: 17 May 2023 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation Allie Hutchison, Yijian Zhou, Abhijit Ghosh; Comment on “Sources of Long‐Range Anthropogenic Noise in Southern California and Implications for Tectonic Tremor Detection” by Asaf Inbal, Tudor Cristea‐Platon, Jean‐Paul Ampuero, Gregor Hillers, Duncan Agnew, and Susan E. Hough. Bulletin of the Seismological Society of America 2023; doi: https://doi.org/10.1785/0120190171 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search Inbal et al. (2018; hereafter, I18) dismissed all the tremor events found in Hutchison and Ghosh (2017; hereafter, HG17) as noise or earthquakes. Despite these assertions, and given all of the evidence put forth at this point, we stand by the findings that these signals are tremor. Unless further evidence can be provided to definitively substantiate alternative sources, tremor is the best explanation. In HG17, we use five independent sets of evidence across multiple datasets and independent techniques including (1) multibeam backprojection (Ghosh et al., 2009, 2012), (2) envelope cross correlation (Wech and... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Simulation of the Security Assessment Information Leakage Channel Method Based on the Speech Signal Envelope

A method of information leakage channel security estimating based on the test speech signal envelope cross-correlation analysis is proposed and its includes: test signal generating and extracting its envelope, emitting and measuring in a leakage channel, extracting the resulting signal envelope, calculating the correlation coefficient between the original and received envelopes, and comparing with a threshold value. A metod for extracting a low-frequency signal envelope using the Hilbert transform is shown. A description of the cross-correlation analysis based on the Pearson correlation coefficient is given. The leakage channel simulation modeling, formation and measurement of the test signals was performed in the MatLab. The obtained results confirm the greater efficiency of using the envelope compared to the original signal, and demonstrate the speech signals advantage over harmonic signals as test signals for assessing the information leakage channel security.

Continuous Tremor Activity With Stable Polarization Direction Following the 2014 Large Slow Slip Event in the Hikurangi Subduction Margin Offshore New Zealand

AbstractMany types of slow earthquakes have been discovered at subduction zones around the world. However, the physical process of these slow earthquakes is not well understood. To monitor offshore slow earthquakes, a marine seismic and geodetic experiment was conducted at the Hikurangi subduction margin from May 2014 to June 2015. During this experiment, a large slow slip event (Mw 6.8) occurred directly beneath the ocean bottom seismometer (OBS) network. In this study, S‐wave splitting and polarization analysis methods, which have been previously used on onshore data to investigate tremor and anisotropy, are applied to continuous OBS waveform data to identify tremors that are too small to detect by the envelope cross correlation method. Continuous tremor activity with stable polarization directions is detected at the end of the 2014 slow slip event and continued for about 2 weeks. The tremors are generated around a southwest bend in the slow slip contours and at the landward edge of a subducted seamount. Our findings corroborate a previous interpretation, based on burst‐type repeating earthquakes and intermittent tremor, that localized slow slip and tremor around the seamount was triggered by fluid migration following the large plate boundary slow slip event and indicate tremor occurred continuously rather than as isolated and sporadic individual events.

An Efficient Analytical Evaluation of the Electromagnetic Cross Correlation Green’s Function in MIMO Systems

In this paper, we completely eliminate all numerical integrations needed to compute the far-field envelope cross-correlation (ECC) in multiple-input-multiple-output (MIMO) systems by deriving accurate and efficient analytical expressions for the frequency-domain cross-correlation Green's functions (CGF), the most fundamental electromagnetic kernel needed for understanding and estimating spatial correlation metrics in multiple-antenna configurations. The analytical CGF is derived for the most general three-dimensional case, which can be used for fast CGF-based correlation matrix calculations in MIMO systems valid for arbitrary locations and relative polarizations of the constituent elements.

An Algorithm to Obtain Boat Engine RPM from Passive Sonar Signals Based on DEMON Processing and Wavelets Packets Transform

The detection of the engine rotational speed in revolutions per minute (RPM) is of great importance to estimate the speed of boats. This value can be obtained from the fundamental frequency component of acquired sonar signals. However, detection can often be seriously affected by noise and distortion introduced by the underwater environment. Several methods have been proposed for fundamental component detection, but they do not specifically take advantage of the passive sonar signal characteristics to improve the performance of the process. In this context, the proposed algorithm uses DEMON processing applied to wavelets packets subbands to exploit the characterization of the sonar signal in the time and frequency domains. The algorithm involves signal segmentation, wavelet packet decomposition, subband envelope cross-correlation and fundamental component detection from the power spectrum. The method was applied in passive sonar signals acquired in navigation and also obtained by simulation. The performance of the proposed algorithm was evaluated with signals of different SNR values that were also corrupted by a simulated multipath underwater channel. The signals were evaluated by both the experienced sonar operators and the proposed algorithm. The results obtained were very satisfactory for RPM detection and are detailed at the end of this document.

Development of a modified envelope correlation method based on maximum-likelihood method and application to detecting and locating deep tectonic tremors in western Japan

We develop a modified envelope correlation method for locating deep tectonic tremors and apply it to construct a tremor catalog for western Japan. We redefine the envelope cross-correlation method as a maximum-likelihood method by using the cross-correlation functions as objective functions and then weighting components of the data by the inverse of the error variances. This method is also capable of detecting multiple sources that occur almost simultaneously because they appear as local maxima in our analysis. We employ a nonlinear function, the average of the weighted cross-correlation functions (ACC), to locate the deep tectonic tremor hypocenters. Our optimization method is performed in two steps. We first fix the source depth and use a grid search to find the local ACC maxima, which are the potential event locations. We then use each potential event location as an initial value and apply the gradient method to determine its hypocentral location. Several source locations are sometimes determined in a 5-min time window. We also perform a numerical test using synthetic waveforms to validate our tremor hypocenter estimations. We apply our proposed method to continuous seismograms in western Japan for 12.5-year period, with our new approach detecting 35% more tremors than the envelope correlation method with the outlier control owing to the detection of multiple tremors in a single time window and to the improved tremor hypocenter accuracy yielded by the appropriate weighting scheme. We estimate the spatial resolution, which is defined as the epicentral distance between sources that can be distinguished by the location method, to be ~ 100 km.

Real-time envelope cross-correlation detector: application to induced seismicity in the Insheim and Landau deep geothermal reservoirs

We develop and test a real-time envelope cross-correlation detector for use in seismic response plans to mitigate hazard of induced seismicity. The incoming seismological data are cross-correlated in real-time with a set of previously recorded master events. For robustness against small changes in the earthquake source locations or in the focal mechanisms we cross-correlate the envelopes of the seismograms rather than the seismograms themselves. Two sequenced detection conditions are implemented: After passing a single trace cross-correlation condition, a network cross-correlation is calculated taking amplitude ratios between stations into account. Besides detecting the earthquake and assigning it to the respective reservoir, real-time magnitudes are important for seismic response plans. We estimate the magnitudes of induced microseismicity using the relative amplitudes between master event and detected event. The real-time detector is implemented as a SeisComP3 module. We carry out offline and online performance tests using seismic monitoring data of the Insheim and Landau geothermal power plants (Upper Rhine Graben, Germany), also including blasts from a nearby quarry. The comparison of the automatic real-time catalogue with a manually processed catalogue shows, that with the implemented parameters events are always correctly assigned to the respective reservoir (4 km distance between reservoirs) or the quarry (8 km and 10 km distance, respectively, from the reservoirs). The real-time catalogue achieves a magnitude of completeness around 0.0. Four per cent of the events assigned to the Insheim reservoir and zero per cent of the Landau events are misdetections. All wrong detections are local tectonic events, whereas none are caused by seismic noise.

A novel technique for automatic seismic data processing using both integral and local feature of seismograms

A novel technique for automatic seismic data processing using both integral and local feature of seismograms was presented in this paper. Here, the term integral feature of seismograms refers to feature which may depict the shape of the whole seismograms. However, unlike some previous efforts which completely abandon the DIAL approach, i.e., signal detection, phase identification, association, and event localization, and seek to use envelope cross-correlation to detect seismic events directly, our technique keeps following the DIAL approach, but in addition to detect signals corresponding to individual seismic phases, it also detects continuous wave-trains and explores their feature for phase-type identification and signal association. More concrete ideas about how to define wave-trains and combine them with various detections, as well as how to measure and utilize their feature in the seismic data processing were expatiated in the paper. This approach has been applied to the routine data processing by us for years, and test results for a 16 days’ period using data from the Xinjiang seismic station network were presented. The automatic processing results have fairly low false and missed event rate simultaneously, showing that the new technique has good application prospects for improvement of the automatic seismic data processing.

Semiautomated tremor detection using a combined cross-correlation and neural network approach

[1] Despite observations of tectonic tremor in many locations around the globe, the emergent phase arrivals, low-amplitude waveforms, and variable event durations make automatic detection a nontrivial task. In this study, we employ a new method to identify tremor in large data sets using a semiautomated technique. The method first reduces the data volume with an envelope cross-correlation technique, followed by a Self-Organizing Map (SOM) algorithm to identify and classify event types. The method detects tremor in an automated fashion after calibrating for a specific data set, hence we refer to it as being “semiautomated”. We apply the semiautomated detection algorithm to a newly acquired data set of waveforms from a temporary deployment of 13 seismometers near Cholame, California, from May 2010 to July 2011. We manually identify tremor events in a 3 week long test data set and compare to the SOM output and find a detection accuracy of 79.5%. Detection accuracy improves with increasing signal-to-noise ratios and number of available stations. We find detection completeness of 96% for tremor events with signal-to-noise ratios above 3 and optimal results when data from at least 10 stations are available. We compare the SOM algorithm to the envelope correlation method of Wech and Creager and find the SOM performs significantly better, at least for the data set examined here. Using the SOM algorithm, we detect 2606 tremor events with a cumulative signal duration of nearly 55 h during the 13 month deployment. Overall, the SOM algorithm is shown to be a flexible new method that utilizes characteristics of the waveforms to identify tremor from noise or other seismic signals.

Robust Strain-Estimation Algorithm Using Combined Radiofrequency and Envelope Cross-Correlation with Diffusion Filtering

In ultrasound elastography, the strain in compressed tissue due to external deformation is estimated and is smaller in harder than softer tissue. With increased stress, the nonaxial motions of tissue elements increase and result in noisier strain images. At high strain, the envelope of the rf signal exhibits robustness to signal decorrelation. However, the precision of strain estimates using envelope signals is much worse compared to that using the rf signals. In this paper, we propose a novel approach for robust strain estimation by combining weighted rf cross-correlation and envelope cross-correlation functions. An applied strain-dependent piecewise-linear-weight is used for this purpose. In addition, we introduce nonlinear diffusion filtering to further enhance the resulting strain image. The results of our algorithm are demonstrated for up to 10% applied strain using a finite-element modelling (FEM) simulation phantom. It reveals that the elastographic signal-to-noise ratio (SNRe) and the elastographic contrast-to-noise ratio (CNRe) of the strain images can be improved more significantly than with other algorithms used in this paper. In addition, comparative results in terms of the mean structural similarity (MSSIM) using in vivo breast data show that the strain image quality can be improved noticeably by the proposed method than with the techniques employed in this work.

Enhanced detection capability of non-volcanic tremor using a 3-level vertical seismic array network, VA-net, in southwest Japan

[1] This study evaluates a method that enhances detection of non-volcanic low frequency tremor (NVT) using VA-net, a 3-level vertical seismic array network that was recently constructed in southwest Japan. The method employs semblance analysis for continuous vertical array records and calculates semblance coefficients as a function of time and apparent vertical velocity. The sign of the best apparent velocity provides information about propagation direction, either upward or downward, allowing easy discrimination between seismic signals of natural origin and unwanted noise such as man-made vibrations. We applied the method to a NVT episode that occurred beneath the Kii Peninsula during November 2008, to demonstrate that NVT signals can be detected using only the 3-level array. Furthermore, we demonstrate that the method enables us to detect minor NVT activity which is not detected by a conventional envelope cross-correlation method, resulting in a dramatic improvement in detection capability.

Predicted effects of sensorineural hearing loss on across-fiber envelope coding in the auditory nerve

Cross-channel envelope correlations are hypothesized to influence speech intelligibility, particularly in adverse conditions. Acoustic analyses suggest speech envelope correlations differ for syllabic and phonemic ranges of modulation frequency. The influence of cochlear filtering was examined here by predicting cross-channel envelope correlations in different speech modulation ranges for normal and impaired auditory-nerve (AN) responses. Neural cross-correlation coefficients quantified across-fiber envelope coding in syllabic (0-5 Hz), phonemic (5-64 Hz), and periodicity (64-300 Hz) modulation ranges. Spike trains were generated from a physiologically based AN model. Correlations were also computed using the model with selective hair-cell damage. Neural predictions revealed that envelope cross-correlation decreased with increased characteristic-frequency separation for all modulation ranges (with greater syllabic-envelope correlation than phonemic or periodicity). Syllabic envelope was highly correlated across many spectral channels, whereas phonemic and periodicity envelopes were correlated mainly between adjacent channels. Outer-hair-cell impairment increased the degree of cross-channel correlation for phonemic and periodicity ranges for speech in quiet and in noise, thereby reducing the number of independent neural information channels for envelope coding. In contrast, outer-hair-cell impairment was predicted to decrease cross-channel correlation for syllabic envelopes in noise, which may partially account for the reduced ability of hearing-impaired listeners to segregate speech in complex backgrounds.

Dual-feed PIFA diversity antenna for wireless applications

A novel dual-feed planar inverted-F antenna (PIFA) suitable for wireless diversity/MIMO applications is presented. By exploiting the pattern diversity, successful provision of two isolated feeding ports using one common radiating plate has been achieved. The main technique introduced is to etch the ground plane under the radiating plate to reduce the mutual coupling between the two ports. It is found that the envelope cross-correlation is less than 0.02 and the ratio of the mean effective gain between the two ports is close to unity. Thus, this new PIFA antenna can provide a better solution than two separate antennas for diversity and MIMO applications by saving space and cost. Simulated and measured results verify the conclusion.

Compact Antenna Array With Port Decoupling for LTE-Standardized Mobile Phones

A compact dual-element antenna has been designed at 710 MHz for newly emerging long-term evolution (LTE) personal wireless communication standard applications. The proposed antenna consists of two printed meander-line monopoles with edge-to-edge separation of nearly ?/45. The antenna elements are printed on FR-4 substrate and are located at the top edge of the ground plane measuring 50 × 87 mm2. An LC-components-based branchline hybrid coupler is used to decouple the antenna elements. The prototype antenna has been evaluated through the scattering parameters, radiation patterns, envelope cross correlation, and the channel capacity measurements. Isolation between the ports is better than 35 dB with matched ports at 710 MHz. The antenna offers reasonable multiple-input-multiple-output (MIMO) performances that make it suitable for LTE-standardized mobile phones.

Low profile diversity antenna for MIMO applications

A low profile diversity antenna for MIMO application is introduced. The design is based on a double folded dipole antenna filled with a slab of ceramic of ɛr=6. Two diversity antennas operating at 5.2 GHz are designed and implemented on a handset for IEEE.11a wireless systems. The isolation is found to be better than 20 dB in both measurement and simulation and measured bandwidth is about 250 MHz at −10 dB. Simulated and measured radiation patterns are close to each other. The envelope cross-correlation is calculated to be much less than 0.1 and the ratio of the mean effective gain between the antennas is close to unity.

Integrated diversity antenna for laptop and PDA terminal in a MIMO system

The paper introduces an integrated diversity antenna for MIMO application specifically in a laptop and in a PDA terminal. The design is based on a double-folded dipole antenna filled with a slab of dielectric material. With the insertion of the dielectric slab, the size is reduced significantly while still maintaining good bandwidth and gain. One of the important features of the design is that the antennas can be spatially placed close to each other (less than λ/2), while implementing polarisation diversity. This is important especially in a PDA terminal where the size of the device is relatively small compared to a laptop. The antennas are designed on a laptop and PDA with frequency of operation at 5.2 GHz for the IEEE802.11a wireless systems. For the laptop design, two different orientations of the dielectric loaded doubled-folded dipole were considered. The isolation is better than 20 dB and measured bandwidth at −10 dB is up to 400 MHz for a laptop design and up to 200 MHz for a PDA design. Experimental verifications are reported for S-parameters and radiation patterns, while the envelope cross-correlation is calculated to be much less than 0.1 and the ratio of the mean effective gain (MEG) between the antennas is close to unity for the laptops and PDA.

Generation of correlated Rayleigh fading envelopes

A previous technique for generating correlated Rayleigh envelopes is generalized and physically interpreted to model specified propagation delay spread and frequency separation. Two accurate closed-form expressions that give explicitly the squared magnitude of the complex Gaussian cross-correlation coefficient in terms of the real envelope cross-correlation coefficient are derived to improve the efficiency and facility of the technique.

Correlated amplitude fluctuations of spontaneous otoacoustic emissions in six lizard species

Spontaneous otoacoustic emissions were recorded from 17 lizard ears (six species: Gerrhosaurus major, Iguana iguana, Basiliscus vittatus, Tupinambis teguixin, Varanus exanthematicus, and Cordylus tropidosternum). The spectrum of each recording contained multiple spectral peaks. For each peak, the envelope cross-correlation R(τ) with all other peaks from the same ear was computed. Of the total of 346 emission peak pairs, 58 (17%) showed a significant correlation. Thus like in humans, multiple emission peaks in lizards frequently interact. In the lizards, the cross-correlation was positive in 30 cases, and negative in 28 cases. The cross-correlation function peaked at either a positive (τpeak>0) or a negative (τpeak<0) delay time. Peak delays ranged from −3.7 ms to 6.2 ms with an average 0.2 ms (s.d. 1.8 ms). The range of observed peak delay values differs from that in human [average τpeak=11.0 ms (s.d. 22.1 ms)].