Abstract ：

A Ka-band power divider/combiner with dual magnetic coupling semicircular ring probes is proposed in this paper. Firstly, a broadband microstrip-to-waveguide transition with semicircular ring probe is designed based on the side-inserted structure of magnetic field excitation in a rectangular waveguide. The insertion loss of the proposed transition is less than 0.7 dB in Ka-band assisted by the dual symmetrical broadband probes and rectangular waveguide. Then, the divider/combiner is proposed using the new transition with magnetic coupling from narrow wall into the rectangular waveguide. The bandwidth of the divider/combiner is more than 9 GHz (from 27 to 36.7 GHz), and the insertion loss of the single divider/combiner is less than 3.3 dB. Finally, the performance of the proposed divider/combiner is validated through simulations and measurements. The proposed design has potential applications in microstrip circuits. © 2020 Wiley Periodicals, Inc.

Keyword ：

Insertion losses Magnetic couplings Magnetism Probes Rectangular waveguides Voltage dividers

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Abstract ：

In this article, a high-efficient approach is presented for obtaining S-parameters from coupling matrix of a microwave filter whether it is lossless or lossy (assuming all the resonators with the same unloaded Q). Computing time is usually large because inversion matrix needs to be carried out once at each frequency in traditional method. By making the application of matrix inversion Lemma and eigenvalue decomposition theory, the matrix inversion operation is replaced by one-time matrix eigenvalue decomposition in the whole process, no matter how many frequency we need to concern. After reorganizing the equations of the S-parameters, the time complexity is decreased from O(N3) to O(N). An example of 14th cavity cross-coupled filter is reported for illustrating the capabilities of the new proposed approach. Compared with the general method, the time spending on computing was shortened by 70% with our new approach. Therefore, the proposed approach will be very popular and suitable in the industry. © 2018 Wiley Periodicals, Inc.

Keyword ：

Computing time Coupling matrix Cross-coupled filters Eigenvalue decomposition High efficient Matrix inversions New approaches Time complexity

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In this paper, the modeling of the random noise in prestack seismic data is discussed. The statistic character of the local wavelet power spectrum of the random noise is studied by qualitative analysis and Monte Carlo simulation using physical wavelet. A conclusion is drawn that the distribution of the local wavelet power spectrum of the noise is ?22 . On the basis of the conclusion, a method of confirming the space of the useful signal energy distribution in wavelet domain is given and the noise can be restrained by reconstruction of the signal from the space. The validity of the method is proved by model and field seismic data. © 1996-2018 Society of Exploration Geophysicists. All rights reserved.

Keyword ：

Denoising methods Pre-stack seismic data Qualitative analysis Random noise Seismic datas Signal energy Wavelet domain Wavelet power spectra

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In this paper, the ambient noise in VSP is explored. The correlation between ambient noise and real data after the first seismic arrivals is calculated and the result shows that in some traces the correlation is small enough to apply the wavelet shrinkage, and in the other traces the correlation is too large to use waveShrink. Besides estimation of the correlation, the ambient noise provides a reference in estimating the threshold of wavelet shrinkage. Two methods of wavelet shrinkage are presented in this paper. Their performance is compared by synthetic data and real data . © 1996-2018 Society of Exploration Geophysicists. All rights reserved.

Keyword ：

Ambient noise Stochastic noise Synthetic data Wavelet shrinkage Waveshrink

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Abstract ：

Using a tensor product of a local exponential frame vector as the time-frequency atom (a drumbeat) and a local cosine basis function as the space-wavenumber atom (a beamlet), we construct a localized (t − ω , x − ξ ) atom (a drumbeat-beamlet). The imaging condition in the local t − ω domain is introduced and the propagator matrix in the local (t − ω , x − ξ ) domain is derived. The compression of seismic data using the new decomposition is tested and simple numerical tests on the propagator matrix are performed. The sparseness in both data and propagator decompositions is demonstrated through these examples. The method has potential application in efficient representation of seismic data and wave-theory based seismic imaging using compressed data. Copyright © (2008) by the Society of Exploration Geophysicists All rights reserved.

Keyword ：

Atoms Decomposition Geophysical prospecting Matrix algebra Seismic response Seismic waves Vector spaces Wave propagation

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Abstract ：

Using a tensor product of a local exponential frame vector as the time-frequency atom (a drumbeat) and a local cosine basis function as the space-wavenumber atom (a beamlet), we construct a localized (t − ω , x − ξ ) atom (a drumbeat-beamlet). The imaging condition in the local t − ω domain is introduced and the propagator matrix in the local (t − ω , x − ξ ) domain is derived. The compression of seismic data using the new decomposition is tested and simple numerical tests on the propagator matrix are performed. The sparseness in both data and propagator decompositions is demonstrated through these examples. The method has potential application in efficient representation of seismic data and wave-theory based seismic imaging using compressed data. Copyright © (2008) by the Society of Exploration Geophysicists All rights reserved.

Keyword ：

Compressed datum Imaging conditions Local cosine basis Numerical tests Propagator matrix Seismic imaging Tensor products Time-frequency atoms

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A cognitive modelling based new inversion method, the successive differential evolution (DE-S) algorithm, is proposed to estimate the Q factor and velocity from the zero-offset vertical seismic profile (VSP) record for oil-gas reservoir exploration. The DE algorithm seeks optimal solutions by simulating the natural species evolution processes and makes the individuals become optimal. This algorithm is suitable for the high-dimensional nonseparable model space where the inversion leads to recognition and prediction of hydrocarbon reservoirs. The viscoelastic medium is split into layers whose thicknesses equal to the space between two successive VSP geophones, and the estimated parameters of each layer span the related subspace. All estimated parameters span to a high dimensional nonseparable model space. We develop bottom-up workflow, in which the Q factor and the velocity are estimated using the DE algorithm layer by layer. In order to improve the inversion precision, the crossover strategy is discarded and we derive the weighted mutation strategy. Additionally, two kinds of stopping criteria for effective iteration are proposed to speed up the computation. The new method has fast speed, good convergence and is no longer dependent on the initial values of model parameters. Experimental results on both synthetic and real zero-offset VSP data indicate that this method is noise robust and has great potential to derive reliable seismic attenuation and velocity, which is an important diagnostic tool for reservoir characterization. © 2018 Elsevier B.V.

Keyword ：

Differential Evolution Differential evolution algorithms High dimensional data Hydrocarbon reservoir Reservoir characterization Vertical seismic profiles Visco-elastic mediums VSP data

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Because the seismic wave propagates through the subsurface, part of the elastic energy eventually ends up as heat energy. This phenomenon is known as absorption (or anelastic attenuation). The factors causing anelastic attenuation include fluid movement and grain boundary friction. The seismic quality factor (Q) quantifies the anelastic attenuation and is commonly used in assisting reservoir characterization. However, current Q-estimation approaches are mainly implemented on a poststack seismic volume. The Q-estimation approaches applied to poststack seismic data assume that the seismic data are normal incident reflections, and they do not consider the effect of the travel path on seismic attenuation. In theory, the attenuation degree of the low-frequency component should differ from the attenuation degree of the high-frequency component for large-offset seismic data. We have developed a method to qualitatively estimate seismic attenuation in the prestack seismic domain. A continuous wavelet transform is used to extract the low-and high-frequency components for the common-reflection point gathers. The difference between the amplitude of the low-frequency component and the amplitude of the high-frequency component is used to measure the seismic attenuation factor. We have determined the effectiveness of our method by applying it to synthetic and real seismic data.

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