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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Statistics of Rain Attenuation in Prague, Empirical Data and Numerical Predictions
摘要： Attenuation of electromagnetic waves in microwave bands is determined experimentally via measurement of received signal variations on terrestrial radio links operating in three frequency bands around 58, 94 and 122 GHz. The measured time series of attenuation are processed to obtain long-term cumulative distributions of attenuation due to hydrometeors. The obtained empirical distributions are compared with the ones predicted using the model of the Recommendation ITU-R P.530. For a given time percentages, the predicted attenuation levels exceeded are apparently lower than the levels of empirical distributions. A power-law relationship between attenuation and rain intensity is obtained by a least square approximation of measured simultaneous rain intensity and rain attenuation. The results are discussed and compared with the numerical predictions.
关键词： electromagnetic wave propagation,atmospheric hydrometeors,rain attenuation
更新于2025-09-04 15:30:14
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Effects of anisotropic oceanic turbulence on the propagation of the OAM mode of a partially coherent modified Bessel correlated vortex beam
摘要： We have studied the impacts of anisotropic turbulence on the orbital angular momentum (OAM) mode of a partially coherent modified Bessel correlated vortex beam propagation in an oceanic channel. In the weak turbulence paraxial channel, a new model of the probability density of OAM modes has been established. Effects of specific parameters of the oceanic turbulence on it have been studied, it is shown that there is an optimizing receiving aperture diameter in the specific interval of the ratio of temperature and salinity (cid:2) , which can reduce the effect of (cid:2) on the normalized energy weight of OAM modes and the reception of fluctuation signal. The effect of oceanic turbulence with higher anisotropy on the OAM signal is weaker than the turbulence possessing lower anisotropy. We can choose the mode carrying lower OAM quantum number to transfer information more efficiently, and we can utilize the OAM mode with large energy level difference between modes and so on to reduce mode interference and enhance the information capacity of optical communication links.
关键词： optical communication,partially coherent modified Bessel correlated vortex beam,propagation,OAM mode,anisotropic oceanic turbulence
更新于2025-09-04 15:30:14
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An Efficient ISAR Imaging Method for Non-uniformly Rotating Targets Based on Multiple Geometry-Aided Parameters Estimation
摘要： The inverse synthetic aperture radar (ISAR) imaging for non-uniformly rotating target plays an important role in many applications. However, it always faces a serious challenge, i.e., the time-varying Doppler frequency induced by the target complex motions will degrade the quality of ISAR image seriously. Several algorithms based on motion parameter estimation have been proposed in recent years. However, most of them always suffer from the heavy computational burden and considerable propagation errors, which deteriorates the performances of algorithms and limits their practical applications. To tackle this problem, an efficient ISAR imaging algorithm is proposed for non-uniformly rotating targets based on geometry-aided the motion parameters estimation in this paper. After compensation, the ISAR echoes are modeled as the quadratic frequency modulated (QFM) signal first, then is transformed into time-chirp distribution (TCD) plane and the least square Radon transform based on TCD (LSRT-TCD) to estimate the derivative of chirp rate efficiently is proposed. To improve the estimation performance and robustness, the pre-processing and the weighted least square Radon transform (WLSRT-TCD) method are both developed. Similarly, the weighted least square Radon transform based on time-frequency distribution (WLSRT-TFD) is also proposed to estimate the chirp rate. The proposed multiple geometry-aided method can eliminate the effect of propagation error and reduce the computational complexity simultaneously. The simulated data and real-measured data results are both presented to validate the proposed method.
关键词： propagation error,time-frequency distribution (TFD),Radon transform (RT),Parameter estimation,time-chirp distribution (TCD)
更新于2025-09-04 15:30:14
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[IEEE 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC) - Xuzhou (2018.7.21-2018.7.24)] 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC) - Study of Propagation of Airy Array Vortex Beams in Turbulent Atmosphere
摘要： A circular phased-locked Airy beam array carrying orbital angular momentum (OAM) propagating through turbulent atmosphere is investigated in detail. The results testify that the OAM modes generated by the array are closely associated with the number of beamlets, requiring the number of beamlets at least twice more than the values of the OAM signal precisely. Furthermore, through multiple-phase-screen simulations, it is shown that the anti-jamming performance of an Airy beam array is significantly enhanced.
关键词： Atmospheric optics,Atmospheric propagation,Airy array vortex beam
更新于2025-09-04 15:30:14
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Input-to-Output Instantaneous Polarization Characterization
摘要： This paper proposes a method to represent and predict received signal instantaneous polarization states as a function of arbitrary transmit polarization states for time-dispersive channels. The model incorporates frequency-dependent characterizations to represent the polarization dispersion behavior of a received signal across its bandwidth in a multipath channel. The representation takes advantage of signal dispersion features typical of depolarized signals, and employs subbanded characterizations to achieve polarization representations exhibiting high degrees of polarization in each subband. Experiments are conducted that demonstrate the utility of the modeling approach to predict polarization dispersion responses for arbitrary transmit polarizations based on measurements from two orthogonal transmit polarizations.
关键词： radiowave propagation,Stokes parameters,polarization estimation,dispersion
更新于2025-09-04 15:30:14
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Normalized power propagation on 1x6 fiber coupler
摘要： The simulation of normalized power propagation on interaction region of 1x6 monolithic fiber coupler is reported. Power distribution on fiber couplers is much affected by arrangement of fibers. The theoretical model has been used to calculate power coupling propagation on linear and pentagonal arrangement of 1x6 fiber coupler. The calculation is based on a matrix transfer which is the solution of coupled-mode theory. The six parallel fiber is in linear array and pentagonal placement. By launching input power to single input of 1x6 monolithic fiber couplers for both configurations, power distribution shows how the initial power is distributed to the others. It is found that linear configuration cannot initiate its power to the initial fiber, and maximum peak is not periodically such as power propagation on 1x2 and 1x3 fiber coupler. By changing the arrangement to be a pentagonal and one fiber as in the center where input power is launched, the input power will be distributed identically from the center to five surrounding fibers. At certain coupling length, about 4.7 mm and 6.3 mm, six fibers with pentagonal configuration will have identical output power for wavelength input 1550 and 1310 nm respectively. Based on this distribution, 1x6 monolithic fiber couplers are applicable as a power divider.
关键词： linear and pentagonal configurations,1x6 monolithic fiber couplers,power propagation
更新于2025-09-04 15:30:14
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Improving Interferometry Instrumentation by Mixing Stereoscopy for 2π Ambiguity Solving
摘要： Phase measurements obtained by high-coherence interferometry are restricted by the 2π ambiguity to height differences smaller than λ/2. A further restriction considers linear and nonlinear aberrations evolving in most interferometric systems due to the CCD-type array detectors. The authors present a new method to overcome the 2π ambiguity in interferometry when using a stereoscopic approach. In this method, a reconstructed wavefront reflected from an object was propagated into two different angles to obtain two different images of the object. These two different images were subsequently processed by stereo algorithms to resolve the 2π ambiguity. Such a method of wavefront propagation may enable several applications such as focusing and resolving the 2π ambiguity, as described in the article.
关键词： Wavefront Propagation,Stereoscopy,2π Ambiguity,Coupling Techniques,Interferometric Measurements
更新于2025-09-04 15:30:14