In this paper, an interference detection and angle estimation algorithm for two-dimensional monopulse antenna is proposed to solve the problem that the interference in the main lobe is difficult to be detected. Only t...
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In this paper, an interference detection and angle estimation algorithm for two-dimensional monopulse antenna is proposed to solve the problem that the interference in the main lobe is difficult to be detected. Only the sum signal, difference signal and noise variance are required in this algorithm. We use the generalized likelihood ratio criterion (GLRT) to obtain a detection statistic, compare this statistic with the set threshold, and then realize the detection of interference according to the comparison result. The angle estimation formula is further derived. Simulation results show that the performance of interference detection and angle estimation is well achieved.
The traditional q-derivative method has the advantage of fast convergence, it also has a wide optimization space for various beamforming algorithms. In this paper, based on the generalized sidelobe canceller (GSC) bea...
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The traditional q-derivative method has the advantage of fast convergence, it also has a wide optimization space for various beamforming algorithms. In this paper, based on the generalized sidelobe canceller (GSC) beamforming algorithm, the q-derivative method is optimized by mode transformation, which further improves the convergence speed of the algorithm. Meanwhile, the stability of the algorithm is guaranteed. Therefore, the algorithm can greatly reduce the computation amount by reducing the number of iterations, which provides the possibility for application in practice. The simulation results show that the algorithm has excellent convergence speed and good stability.
Through tubing cement evaluation (TTCE) in a multistring well has been considered a cost-effective way for well integrity evaluation without removing the production tubing. Conventional acoustic cement bond logging me...
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Through tubing cement evaluation (TTCE) in a multistring well has been considered a cost-effective way for well integrity evaluation without removing the production tubing. Conventional acoustic cement bond logging methods are not able to operate accurately with the multistring structure due to an extremely low sensitivity and signal-to-noise ratio (SNR). Therefore, it is important to develop novel technology and an apparatus that can accurately and efficiently monitor the cement condition in the multiple pipe cased well. Applications would include use in production, injection, and storage well configurations as well as for plug and abandonment planning. To this end, a novel TTGE technology based on a selective non-harmonic resonance (SNHR) is proposed. Unlike the traditional acoustic wave propagation method (WPM), the new tool emits continuous energy to excite the SNHR of the multistring structure, considered to be a multiple degree of the freedom Duffing system. This includes coupling of the hydraulic pressure in fluid and elastic stress-strain of solid materials. The continuous sinusoidal excitation from the SNHR tool drives the structure in a long burst mode and measures the resonance power loss due to the energy leaking through the cement layer, to represent the casing cement bond, as well as the cement formation bond condition. The SNHR tool, therefore, has overcome the main challenge, which is the acoustic energy reflections and dissipation through multiple interfaces for existing WPMs. The SNHR tool was validated theoretically and experimentally. Results showed that the SNHR tool can reach high sensitivity (> 10%) and SNR (> 10 dB) for variable combinations of pipe sizes up to 14". This implies that the SNHR is a promising technique for evaluating cement bond integrity in the annulus of an outermost pipe string when multiple inner pipes and their associated annuli are liquid filled. In addition, the SNHR tool does not require direct coupling to the first pip
The small satellite SAR has received increasing attention due to its flexibility and low cost. But limited by the data transmission technology, real-time transmission of a large amount of raw data generated by the spa...
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ISBN:
(数字)9781728163741
ISBN:
(纸本)9781728163758
The small satellite SAR has received increasing attention due to its flexibility and low cost. But limited by the data transmission technology, real-time transmission of a large amount of raw data generated by the spaceborne spotlight SAR can hardly be achieved. Meanwhile, the azimuth bandwidth of the spotlight mode is larger than the PRF, resulting in aliasing of the azimuth spectrum. Based on these, this paper proposes a real-time scheme for small satellite SAR with spotlight mode. The method can solve the problem of data transmission and eliminate spectrum overlap in Doppler domain by means of sub-aperture processing. The modified range migration algorithm (RMA) is used to perform range compression and range cell migration compensation (RCMC) on sub-aperture data. Then dechirp in the azimuth time domain is applied to obtain the low-resolution complex image focused in the range time-azimuth frequency domain. Finally, all theected onto a grid image with azimuth interval matching the azimuth full-resolution to complete image fusion.
The application of Wireless Sensor Networks (WSNs) is hindered by the limited energy budget available for the member nodes. Energy aware solutions have been proposed for all tasks involved in WSNs, such as processing,...
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