The movement of an objective in a stratified medium such as oceans, generates internal waves that propagate with the specific directions. The frequency of the internal waves is very low (0.01-0.008 Hz) and they can sp...
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The movement of an objective in a stratified medium such as oceans, generates internal waves that propagate with the specific directions. The frequency of the internal waves is very low (0.01-0.008 Hz) and they can spread over long distance (similar to 50 km). Also, direction-of-arrival (DOA) estimation refers to the process of retrieving the direction information of several electromagnetic waves/sources from the outputs of a number of receiving antennas that form a sensor array. In this theoretical-experimental study using DOA conception, the propagation direction of internal waves induced by a moving objective in a stratified medium is estimated. It can lead to detect moving targets inside of stratified mediums in a passive way with various applications. As a case study, a fluctuating cylinder in the stratified water is utilized to generate internal waves and as well as five fast response salinity sensors are used in a uniform linear array (ULA) arrangement to mine data. In current work, six wellknown algorithms Bartlet, MUSIC, WMUSIC, DML, SML and WSF are used to DOA estimation of the generated internal wave. The comparative results show the proper performance of DOA estimation (for the direction of wave propagation) so that estimation errors are insignificant.
This paper investigates array processing methods for the analysis of experimental sructural acoustic data to understand wave propagation on fluid-loaded, elstic, cylindrical shells in the mid-frequency range, 2<ka&...
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This paper investigates array processing methods for the analysis of experimental sructural acoustic data to understand wave propagation on fluid-loaded, elstic, cylindrical shells in the mid-frequency range, 2array for three shells: A finite, air-filled, empty shell, a duplicate shell stiffened with unequally spaced ring-stiffeners and a duplicate ribbed shell augmented by resiliently mounted, wave-bearing, internal structural elements. array and signal processing techniques, including source deconvolution, array weighting, conventional focusing and the removal of the geometrically scattered contribution, are used to transform the collected data to a more easily interpreted representation. The resulting waveforms show that part of the transient, dynamic, structural response of the shell surface which is caapble pf radiating to the far field. Compressional membrane waves are directly obseryable in this representation, and evidence of flexural membranewaves is present. Comparisons between the shells show energy compartmentalized by he ring stiffeners and coupled into the wave-bering internals. Energy calculations show a decay rate of 30 dB/ms due to radiation for the empty shell but only 10 dB/ms for the other shells. The Radon transform is used to estimate the refl
We introduce a novel method of array processing for measuring arrival times and relative amplitudes of teleseismic body waves recorded on large aperture seismic arrays. The algorithm uses a robust stacking algorithm w...
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We introduce a novel method of array processing for measuring arrival times and relative amplitudes of teleseismic body waves recorded on large aperture seismic arrays. The algorithm uses a robust stacking algorithm with three features: (1) an initial 'reference' signal is required for initial alignment by crosscorrelation;(2) a robust stacking method is used that penalizes signals that are not well matched to the stack;and (3) an iterative procedure alternates between cross-correlation with the current stack and the robust stacking algorithm. This procedure always converges in a few iterations making it well suited for interactive processing. We describe concepts behind a graphical interface developed to utilize this algorithm for processing body waves. We found it was important to compute several data quality metrics and allow the analyst to sort on these metrics. This is combined with a 'pick cutoff' function that simplifies data editing. Application of the algorithm to data from the USarray show four features of this method. (1) The program can produce superior results to that produced by a skilled analyst in approximately 1/5 of the time required for conventional interactive picking. (2) We show an illustrative example comparing residuals from S and SS for an event from northern Chile. The SS data show a remarkable +/- 10 s residual pattern across the USarray that we argue is caused by propagation approximately parallel to the subduction zones in Central and South America. (3) Quality metrics were found to be useful in identifying data problems. (4) We analyzed 50 events from the Tonga-Fiji region to compare residuals produced by this new algorithm with those measured by interactive picking. Both sets of residuals are approximately normally distributed, but corrupted by about 5% outliers. The scatter of the data estimated by waveform correlation was found to be approximately 1/2 that of the hand picked data. The outlier populations of both data sets are likely
Combined spatial and time-frequency signatures of signal arrivals at a multisensor array are used for nonstationary interference suppression in direct-sequence spread-spectrum (DS/SS) communications. With random PN sp...
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Combined spatial and time-frequency signatures of signal arrivals at a multisensor array are used for nonstationary interference suppression in direct-sequence spread-spectrum (DS/SS) communications. With random PN spreading code and deterministic nonstationary interferers, the use of antenna arrays offers increased DS/SS signal dimensionality relative to the interferers. Interference mitigation through a spatio-temporal subspace projection technique leads to reduced DS/SS signal distortion and improved performance over the case of a single antenna receiver. The angular separation between the interference and desired signals is shown to play a fundamental role in trading off the contribution of the spatial and time-frequency signatures to the interference mitigation process. The expressions of the receiver signal-to-interference-noise ratio (SINR) implementing subspace projections are derived, and numerical results are provided.
In this paper, we investigate how to send space-time codes with full diversity and low decoding complexity for interference channels using precoders. We assume that we have two transmitters and two receivers. Each tra...
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In this paper, we investigate how to send space-time codes with full diversity and low decoding complexity for interference channels using precoders. We assume that we have two transmitters and two receivers. Each transmitter sends codewords to respective receiver at the same time. We propose an orthogonal transmission scheme that combines space-time codes and array processing to achieve low-complexity decoding and full diversity for transmitted signals. To our best knowledge, this is the first scheme which can achieve low-complexity decoding and full diversity for any transmitted codeword in interference channel when all the users transmit at the same time. Simulation results validate our theoretical analysis.
In recent years more and more multi-array logging tools, such as the array induction and the array lateralog, are applied in place of conventional logging tools resulting in increased resolution, better radial and ver...
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In recent years more and more multi-array logging tools, such as the array induction and the array lateralog, are applied in place of conventional logging tools resulting in increased resolution, better radial and vertical sounding capability and other features. Multi-array logging tools acquire several times more individual measurements than conventional logging tools. In addition to new information contained in these data, there is a certain redundancy among the measurements. The sum of the measurements actually composes a large matrix. Providing the measurements are error-free, the elements of this matrix show certain consistencies. Taking advantage of these consistencies, an innovative method is developed to detect and correct errors in the array resistivity logging tool raw measurements, and evaluate the quality of the data. The method can be described in several steps. First, data consistency patterns are identified based on the physics of the measurements. Second, the measurements are compared against the consistency patterns for error and bad data detection. Third, the erroneous data are eliminated and the measurements are re-constructed according to the consistency patterns. Finally, the data quality is evaluated by comparing the raw measurements with the re-constructed measurements. The method can be applied to all array type logging tools, such as array induction tool and array resistivity tool. This paper describes the method and illustrates its application with the High Definition Lateral Log （HDLL, Baker Atlas） instrument. To demonstrate the efficiency of the method, several field examples are shown and discussed.
Techniques often used in the area of adaptive array signal processing are applied to the multiuser defection problem, The results of this effort include a robust detector, suitable for use in the presence of modeling ...
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Techniques often used in the area of adaptive array signal processing are applied to the multiuser defection problem, The results of this effort include a robust detector, suitable for use in the presence of modeling errors, and a reduced-rank detector with improved transient behavior relative to full-rank detectors, Algorithm performance is presented in the form of bit-error-rate (BER) curves and least mean square (LMS)-like learning curves.
In this paper we derive the generalized likelihood ratio test (GLRT) for time reversal detection. We consider a multi-static array configuration with two antenna arrays, one for transmitting and one for receiving. We ...
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ISBN:
(纸本)9781424404681
In this paper we derive the generalized likelihood ratio test (GLRT) for time reversal detection. We consider a multi-static array configuration with two antenna arrays, one for transmitting and one for receiving. We examine the time reversal GLRT performance with experimental measurements in the electromagnetic domain in a highly cluttered laboratory environment. The experiments show that time reversal provides significant performance gain over the conventional energy detector.
An efficient, general purpose modelling algorithm known as fast orthogonal search (FOS) is applied to the problem of estimating the angles of arrival of multiple plane waves incident on an array of sensors and to the ...
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An efficient, general purpose modelling algorithm known as fast orthogonal search (FOS) is applied to the problem of estimating the angles of arrival of multiple plane waves incident on an array of sensors and to the related problem of estimating the temporal frequencies of narrow-band signals in noise. An iterative version of the algorithm (IFOS), which approaches a minimum in the mean squared error between observed and modelled data, is introduced. A modification to the array steering vector model which is beneficial when the incident signals are coherent is described. FOS and IFOS are compared with MUSIC and root MUSIC in computer simulations.
This paper discusses about unambiguous positioning with signals with multi-peak correlation functions when an array of antennas is featured by the GNSS receiver. In particular, the unambiguous positioning problem is t...
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ISBN:
(纸本)0936406232
This paper discusses about unambiguous positioning with signals with multi-peak correlation functions when an array of antennas is featured by the GNSS receiver. In particular, the unambiguous positioning problem is treated as a multiple-input multiple-output (MIMO) estimation problem in which the available transmission and reception spatial diversities are jointly exploited. The simulation results show that an improved ambiguity resolution is achieved by exploiting all the available spatial diversities in the position domain, instead of tackling the ambiguity problem at single-satellite level. Therefore, the solution discussed is considered a promising approach for enabling the exploitation of the so-called high-order BOC signals and meta-signals in the presence of deep fading and strong multipath.
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