scholarly journals A Range Resolution Enhancement Algorithm for Active Millimeter Wave Based on Phase Unwrapping Mechanism

Electronics ◽  
2021 ◽  
Vol 10 (14) ◽  
pp. 1689
Author(s):  
He Zhang ◽  
Hua Zong ◽  
Jinghui Qiu
Keyword(s):  
Millimeter Wave ◽  
Phase Distribution ◽  
Resolution Enhancement ◽  
Continuous Phase ◽  
Target Object ◽  
Phase Unwrapping ◽  
Practical Applications ◽  
Range Resolution ◽  
Security Inspection ◽  
Security Check

Traditional security check technology is mainly based on metal detection by manual inspection. This method is simple and convenient, can detect a few different kinds of contrabands, and also takes into account the safety of inspectors. Because of its strong penetration characteristics, millimeter waves make up for the deficiency of existing security check technologies. Therefore, it is urgent to research and develop millimeter wave holographic imaging technology for human security inspection. In traditional imaging methods, the azimuthal resolution can be improved through various methods of image processing, but the traditional way to improve the range direction resolution is to increase the system bandwidth. However, improvements of the system bandwidth will greatly increase the cost. The bandwidth improvement space is also limited, so it cannot be expanded indefinitely in practical applications. In this study, the interferometric synthetic aperture theory was used to improve the range direction resolution of 3D millimeter wave holographic images without improving the system bandwidth. Phase unwrapping was used to reconstruct the phase information of complex images and restore the continuous phase distribution of the target object so as to achieve improvement of the range direction resolution without increasing the system bandwidth. This work has theoretical guiding significance to improve the range resolution of millimeter wave imaging.

scholarly journals A FOD Detection Approach on Millimeter-Wave Radar Sensors Based on Optimal VMD and SVDD

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 997
Author(s):  
Jun Zhong ◽  
Xin Gou ◽  
Qin Shu ◽  
Xing Liu ◽  
Qi Zeng
Keyword(s):  
Millimeter Wave ◽  
Detection Methods ◽  
Economic Losses ◽  
Support Vector ◽  
Support Vector Data Description ◽  
Range Resolution ◽  
Radar Sensors ◽  
Detection Approach ◽  
Wave Radar ◽  
Whale Optimization

Foreign object debris (FOD) on airport runways can cause serious accidents and huge economic losses. FOD detection systems based on millimeter-wave (MMW) radar sensors have the advantages of higher range resolution and lower power consumption. However, it is difficult for traditional FOD detection methods to detect and distinguish weak signals of targets from strong ground clutter. To solve this problem, this paper proposes a new FOD detection approach based on optimized variational mode decomposition (VMD) and support vector data description (SVDD). This approach utilizes SVDD as a classifier to distinguish FOD signals from clutter signals. More importantly, the VMD optimized by whale optimization algorithm (WOA) is used to improve the accuracy and stability of the classifier. The results from both the simulation and field case show the excellent FOD detection performance of the proposed VMD-SVDD method.

Percolation phase transition of static and growing networks under a weighted function

2016 ◽  
Vol 27 (07) ◽  
pp. 1650082 ◽  
Author(s):  
Xiao Jia ◽  
Jin-Song Hong ◽  
Ya-Chun Gao ◽  
Hong-Chun Yang ◽  
Chun Yang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Continuous Phase ◽  
Weighted Function ◽  
Percolation Process ◽  
Practical Applications ◽  
Network Intervention ◽  
Growing Networks ◽  
Discontinuous Phase ◽  
And Control ◽  
Growing Network

We investigate the percolation phase transitions in both the static and growing networks where the nodes are sampled according to a weighted function with a tunable parameter [Formula: see text]. For the static network, i.e. the number of nodes is constant during the percolation process, the percolation phase transition can evolve from continuous to discontinuous as the value of [Formula: see text] is tuned. Based on the properties of the weighted function, three typical values of [Formula: see text] are analyzed. The model becomes the classical Erdös–Rényi (ER) network model at [Formula: see text]. When [Formula: see text], it is shown that the percolation process generates a weakly discontinuous phase transition where the order parameter exhibits an extremely abrupt transition with a significant jump in large but finite system. For [Formula: see text], the cluster size distribution at the lower pseudo-transition point does not obey the power-law behavior, indicating a strongly discontinuous phase transition. In the case of growing network, in which the collection of nodes is increasing, a smoother continuous phase transition emerges at [Formula: see text], in contrast to the weakly discontinuous phase transition of the static network. At [Formula: see text], on the other hand, probability modulation effect shows that the nature of strongly discontinuous phase transition remains the same with the static network despite the node arrival even in the thermodynamic limit. These percolation properties of the growing networks could provide useful reference for network intervention and control in practical applications in consideration of the increasing size of most actual networks.

scholarly journals Theoretical and Experimental Study on Echo Fluctuation Suppression of a Cirrus Cloud by Millimeter Wave MIMO Radar

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Jinhu Wang ◽  
Junxiang Ge ◽  
Ming Wei ◽  
Hongbin Chen ◽  
Zexin Yang ◽  
...  
Keyword(s):  
Millimeter Wave ◽  
Mimo Radar ◽  
Physical Parameters ◽  
Cirrus Cloud ◽  
Nonspherical Particles ◽  
Range Resolution ◽  
Rayleigh Approximation ◽  
Ice Particles ◽  
Wave Radar ◽  
Classical Vector

The scattering properties of nonspherical particles can be approximately computed by equivalent spherical theory. The scattering properties of ice particles were approximately computed by Rayleigh approximation because the sizes of the ice particles are smaller than the wavelength of millimeter wave radar. Based on the above assumption, the echo fluctuation of moving particles was analyzed by computing the total backscattering field of a cirrus cloud using the classical vector potential technique. The simulation results showed that echo fluctuation influences the accuracy of retrieving the physical parameters of a cloud. To suppress the echo fluctuation of moving ice particles, a video integrator of a millimeter wave cloud radar would be used. However, video integrators lose the rapidly changing information of ice particles and reduce radar range resolution; thus, we propose the pace-diversity technique of MIMO radar to reduce the echo fluctuation, which could be validated by theoretical computation and experimental measurements.

Subarray‐based coherent pulsed‐LFM frequency diverse array for range resolution enhancement

2020 ◽  
Vol 14 (4) ◽  
pp. 251-258
Author(s):  
Huake Wang ◽  
Guisheng Liao ◽  
Jingwei Xu ◽  
Shengqi Zhu
Keyword(s):  
Resolution Enhancement ◽  
Range Resolution ◽  
Frequency Diverse Array

Phase-distribution mechanisms in turbulent low-quality two-phase flow in a circular pipe

1982 ◽  
Vol 117 ◽  
pp. 91-106 ◽  
Author(s):  
D. A. Drew ◽  
R. T. Lahey
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Phase Distribution ◽  
Outer Region ◽  
Continuous Phase ◽  
Circular Pipe ◽  
Phase Flow ◽  
Two Phase ◽  
Centre Line ◽  
Mixing Length Theory

The radial distribution of the volumetric vapour (or void) fraction in steady, fully developed turbulent two-phase flow is described for vertical low-quality bubbly flows in a circular pipe. The analysis is based on the phasic equations of conservation of momentum in the axial and radial directions. Mixing-length theory is used to model the turbulent stresses in the continuous phase. The predicted flow structure shows three distinct regions. The ‘outer’ region, that is, the region away from the wall and the centre-line, has a uniform void distribution. For upflow, a bubble layer is predicted near the wall, while for downflow, vapour coring is predicted, with a peak in void fraction at the centre-line. These predictions are in agreement with observed void profiles.

scholarly journals Millimeter-wave InSAR phase unwrapping and DEM reconstruction based on three-baseline

2013 ◽  
Vol 32 (5) ◽  
pp. 474
Author(s):  
Zhou-Hao PAN ◽  
Bo LIU ◽  
Qing-Juan ZHANG ◽  
Dao-Jing LI
Keyword(s):  
Millimeter Wave ◽  
Phase Unwrapping

Speedup of minimum discontinuity phase unwrapping algorithm with a reference phase distribution

2018 ◽  
Vol 417 ◽  
pp. 97-102 ◽  
Author(s):  
Yihang Liu ◽  
Yu Han ◽  
Fengjiao Li ◽  
Qican Zhang
Keyword(s):  
Phase Distribution ◽  
Phase Unwrapping ◽  
Reference Phase

Observation of Single Magnetic-Flux Quanta Using Electron Holography

1990 ◽  
Vol 48 (1) ◽  
pp. 210-211
Author(s):  
T. Matsuda ◽  
S. Hasegawa ◽  
J. Endo ◽  
N. Osakabe ◽  
A. Tonomura ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Tungsten Wire ◽  
Thin Filament ◽  
Phase Distribution ◽  
Electron Holography ◽  
Practical Applications ◽  
Magnetic Flux Quantum ◽  
Lead Film ◽  
The Magnetic Field

A Magnetic flux quantum (fluxon) penetrating a superconductor plays an important role in both fundamental and practical applications of superconductivity. However, the fluxon has evaded direct observation, because it is shaped like an extremely thin filament in addition to its small flux value, h/2e (=2x10−15Wb). Several methods have already been developed to indirectly observe each filament of flux. One method is Bitter's [1], in which magnetic powder is sprinkled on the superconductor surface. The powder accumulates at the fluxons, and the image is observed by electron microscopy.We have observed the magnetic field of a single fluxon using holographic electron interferometry [2], in which the phase distribution of an electron beam can be measured to a precision of 2Π/50. The schematic diagram of the experiment is shown in Fig. 1. A weak magnetic field is applied perpendicularly to a superconducting lead film. Fiuxons penetrating the film are observed as phase contour fringes through the electron holography process. The sample is prepared by evaporating lead on one side of a thin tungsten wire, which is shown in Fig. 2.

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