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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - High Resolution Measurements and Characterization of Urban, Suburban and Country Clutter at X-Band and Related Radar Calibration
摘要： At Tor Vergata University we are working on measurements and phenomenological characterization of urban, suburban and country radar clutter at X-band (3 cm wavelength, range resolution 8 to 10 m, azimuth resolution @ 1 km about 23.5 m) and on the related radar calibration problems. Measurements are 'high resolution' when compared to most surveillance radars, and the related applications are in the frame of clutter maps for cognitive radar, drones detection, radar ornithology, and more. After calibration, done using opportunity targets with known radar cross section and a clutter fence, we carry on an analysis and a comparison of land clutter, considering different weather conditions: dry and wet soil, as well as the rare event of snow. Using fixed opportunity targets, such as lamppost and/or a large cylindrical steel tanker, we describe the attenuation effects due to the natural clutter fence (in this case due to cane thicket near to the target position) and its mitigation when the natural fence is gradually removed. Finally, but importantly, we analyze the multipath phenomenon due to reflection/scattering on ground, and propose a procedure to estimate the multipath factor and to correct for it.
关键词： urban clutter,radar calibration,high resolution radar,multipath,X-band
更新于2025-09-23 15:23:52
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[IEEE 2017 9th IEEE-GCC Conference and Exhibition (GCCCE) - Manama, Bahrain (2017.5.8-2017.5.11)] 2017 9th IEEE-GCC Conference and Exhibition (GCCCE) - OFDM Based Robust Digital Image Watermarking Resistant to Multipath Spatial Shifts
摘要： A digital watermark is a visible or invisible pattern embedded in a digital image which can be used for copyright protection, authentication, broadcast monitoring, telemedicine and many more. This paper describes how an efficient CDMA based spread spectrum technique can be combined with the most prominent spectrum efficient OFDM technology to formulate a robust watermarking algorithm which is suitable for image distortions due to time delays and spatial shift that may occur during the transmission of watermarked images. A detailed simulation of embedding and decoding algorithm was performed. Simulation results reveal that the algorithm is computationally efficient, robust and is well suited for wireless multipath fading channel. The algorithm was tested against a number of the possible noises in the wireless channels and various geometric and signal processing operations. The proposed algorithm is proved to be robust enough to extract a good quality watermark compared to well-known techniques.
关键词： Watermarking,OFDM,multipath,robust,distortion
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Radar (RADAR) - Brisbane, Australia (2018.8.27-2018.8.31)] 2018 International Conference on Radar (RADAR) - Real Aperture Imaging Using Sparse Optimisation with Application to Low-Angle Tracking
摘要： Estimating the angle of arrival of a low-altitude target over the sea surface is made difficult due to the coherent multipath interference caused by the target image. A real aperture imaging technique for estimating azimuth and elevation of targets using a phased array multichannel radar, as described by Berry et al [1], is applied to this classical problem of suppressing low-angle multipath signals received by a naval radar from a low-flying target. The degree of spatial resolution which can be usefully attained is explored; this depends on many factors and the nonlinear problem formulation is not easily amenable to analysis. It is found that the technique is feasible for resolving the direct target signal, its specular reflection and multiple diffuse reflections even when the signals would be combined by a conventional beamformer to form a multipath null.
关键词： radar signal processing,low-angle tracking,sparse optimisation,multipath propagation,phased array multichannel radar
更新于2025-09-23 15:22:29
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Measurements of Beamswitching Gains and Fade Dynamics for 28 GHz Indoor Static Links in the Presence of Pedestrian Traffic
摘要： We measured channel dynamics for fixed wireless indoor channels at 28 GHz. We characterize pedestrian-induced fades in open indoor spaces and the effectiveness of beamswitching to mitigate them. We find that fades of the dominant propagation path may be as deep as 9 dB at the 90th percentile and that alternative signal paths are typically not strong enough to provide significant beamswitching gains.
关键词： Millimeter wave propagation,Rician channels,Channel models,Multipath channels,Fading channels
更新于2025-09-23 15:22:29
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Experimental Evaluation of Multipath Mitigation in TDOA-Based Indoor Passive Localization System Using A Beam Steering Broadband Circular Polarization Antenna
摘要： An experimental evaluation of multipath mitigation using a beam steering broadband circular polarization antenna (BSBCPA) in indoor passive localization system based on time differences of arrival (TDOA) is presented in this paper. The BSBCPA consists of a beam switch network, four identical hexagon patch elements and their respective feeding networks. By controlling the states of a radio frequency (RF) switch in the beam switch network, four steering circular polarization beams can be excited separately for azimuth omnidirectional coverage. Combining the spatial selectivity of steering beams and circular polarization in the BSBCPA, the positioning inaccuracy from indoor multipath propagation can be mitigated. In two different indoor environments with line of sight (LOS), complex multipath, when transmitting a 20 MHz bandwidth signal in WLAN, the 2D positioning mean error obtained is 0.7 m and 0.82 m, respectively. Compared with conventional omnidirectional linear polarization antenna (OLPA), the BSBCPA can at least improve positioning accuracy by 51%. The experimental results show that the proposed BSBCPA can significantly mitigate multipath propagation for TDOA-based indoor passive localization.
关键词： multipath mitigation,beam steering antenna,indoor passive localization,circular polarization,TDOA
更新于2025-09-23 15:22:29
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A Domain Decomposition Finite Element Method for Modeling Electromagnetic Scattering from Rough Sea Surfaces with Emphasis on Near-Forward Scattering
摘要： A high fidelity full-wave simulator is presented to perform numerical experiments for rough sea scattering problem by considering different polarizations, frequencies, grazing angles, wind speeds and sea surface spectra. The simulator is based on a novel Finite Element Domain Decomposition (FEDD) method for solving the problem of two dimensional electromagnetic scattering over one-dimensional sea surface. This non-iterative method partitions the computational domain into a number of overlapping subdomains and solves each domain individually by employing the Locally-Conformal Perfectly Matched Layer (LC-PML) at the truncation boundaries. LC-PML has a unique feature such that it can be applied to irregular domains on the contrary to standard PML methods, and hence inspired the birth of FEDD. The FEDD method is used at each Monte Carlo realization corresponding to a sample from random rough surfaces, and decreases the computational load especially for electrically-large problems. The accuracy and computational efficiency of the method is investigated through several simulations. Using the FEDD method, the statistical behavior of the bistatic Radar Cross Section (RCS) is obtained for both horizontal and vertical polarizations. A special emphasis is given to forward-scattered RCS and the mean reflection coefficient for sea surface especially at low grazing angles, and it is shown that the simulator produces results in agreement with the Ament and Miller-Brown approximations, and experimental data, proving the reliability of the simulation approach. The results are also compared with the standard finite element method and method of moments. Rough sea surfaces are created by using both Pierson-Moskowitz and Elfouhaily spectra.
关键词： Locally-Conformal Perfectly Matched Layer (PML),forward scattering,sea surface,Domain decomposition,Monte Carlo,rough surface scattering,Finite Element Method (FEM),propagation,reflection coefficient,bistatic Radar Cross Section (RCS),multipath
更新于2025-09-23 15:21:21
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Programmable Photonics: An Opportunity for an Accessible Large-Volume PIC Ecosystem
摘要： Underwater acoustic (UWA) channels are characterized by a severe spread in time and frequency, and are usually labeled as “doubly spread channels.” In this paper, we propose Doppler-resilient orthogonal signal-division multiplexing (D–OSDM), to provide a highly reliable communication environment in doubly spread channels for UWA communication. D–OSDM multiplexes several data vectors in addition to a pilot vector, and preserves orthogonality among them even after propagation through doubly spread channels, under the assumption that the channel can be modeled by a basis expansion model (BEM). We describe the signal processing steps at the transmitter and the receiver for D–OSDM, and evaluate its performance by both simulations and experiments. To generate a doubly spread channel, a test tank with a wave generator is employed. The obtained results suggest that D–OSDM can provide low-power and high-quality UWA communications in channels with large delay and Doppler spreads; for example, D–OSDM succeeds to achieve a block error rate (BLER) of 10 while BEM-based orthogonal frequency-division multiplexing (OFDM) has a BLER ?oor of in the experiments. Equivalently, D–OSDM can reduce the 10 signal power required for communications to achieve the same BER signi?cantly. Overall, it was found that D–OSDM can become a powerful communication tool for underwater operations.
关键词： multipath channels,Doppler,underwater acoustic (UWA) communication
更新于2025-09-23 15:21:01
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[IEEE 2018 IEEE 5G World Forum (5GWF) - Silicon Valley, CA, USA (2018.7.9-2018.7.11)] 2018 IEEE 5G World Forum (5GWF) - Multipath Propagation Analysis of 5G Systems at Higher Frequencies in Courtyard (Small Cell) Environment
摘要： The main target of this paper is to study the propagation characteristics of an outdoor and indoor user utilizing 5G system at higher frequency in a courtyard surrounded by building walls i.e. small cell environment. This research work is carried out by doing 3D ray tracing simulations utilizing “sAGA” – a 3D ray tracing tool. Unlike the conventional cellular network frequencies, the considered frequencies in the scope of this work are 15 GHz, 28 GHz and 60 GHz. For simulation routes, the results are provided in the form of received signal strength. For static points, the results are presented in the form of power angular spectrum and power delay profile. The achieved simulation results show that an adequate outdoor and indoor service can be provisioned at the considered frequencies. However, it is challenging to provide services to indoor user at 60 GHz using an outdoor base station even in such a small cell environment.
关键词： 3D ray tracing,multipath propagation,small cell,system performance,millimeter wave frequencies,5G
更新于2025-09-23 15:21:01
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[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - High-Enthalpy Flow Investigations by UV Laser-Induced Fluorescence
摘要： With the advance of software receiver, multipath estimation becomes a key issue for high accuracy positioning systems. It is crucial for eliminating the multipath error and improving the positioning accuracy to estimate multipath parameters. The accessible multipath estimation algorithms are usually designed for Gaussian noise, and their performances degrade dramatically in non-Gaussian noise, since the mean square error criterion is adopted. To tackle the problem, a new filter based on centered error entropy criterion (CEEC) is proposed for multipath estimation. In the proposed filter, the CEEC is considered as a performance index, which is not limited to the assumption of Gaussian and linearity. According to a stochastic information gradient method, an optimal filer gain matrix is obtained by maximizing the performance function of centered error entropy. Meanwhile, a convergence analysis of the proposed filter is offered. Furthermore, a recursive estimation method based on modified Parzen windowing technique is proposed for practical implementation. The simulation results indicate that the proposed filter outperforms the filter based on minimum error entropy criterion for multipath estimation.
关键词： stochastic information gradient (SIG),minimum error entropy criterion (MEEC),centered error entropy criterion (CEEC),Multipath estimation
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE International Electron Devices Meeting (IEDM) - San Francisco, CA, USA (2019.12.7-2019.12.11)] 2019 IEEE International Electron Devices Meeting (IEDM) - Integrated DFB Laser Diode and High-efficiency Mach-Zehnder Modulator using Membrane III-V Semiconductors on Si Photonics Platform
摘要： This paper presents a 3-D statistical channel impulse response (IR) model for urban line of sight (LOS) and non-LOS channels developed from 28- and 73-GHz ultrawide-band propagation measurements in New York City, useful in the design of 5G wireless systems that will operate in both the ultra-high frequency/microwave and millimeter-wave (mmWave) spectrum to increase channel capacities. A 3GPP-like stochastic IR channel model is developed from measured power delay profiles, angle of departure, and angle of arrival power spectra. The extracted statistics are used to implement a channel model and simulator capable of generating 3-D mmWave temporal and spatial channel parameters for arbitrary mmWave carrier frequency, signal bandwidth, and antenna beamwidth. The model presented here faithfully reproduces realistic IRs of measured urban channels, supporting air interface design of mmWave transceivers, filters, and multi-element antenna arrays.
关键词： 28 GHz,multipath,time cluster spatial lobe (TCSL),spatial lobe (SL),statistical simulator,5G,spatial channel model (SCM),73 GHz,Channel model,millimeter-wave (mmWave) propagation,3-D ray-tracing,time cluster (TC),impulse response (IR)
更新于2025-09-23 15:19:57