scholarly journals Study on Characteristics of Coupling Field from Super-low Altitude Target under Diverse Terrestrial Environments in Semi-active Radar System

2018 ◽  
Vol 173 ◽  
pp. 02034
Author(s):  
Gao Xiang Zou ◽  
Chuang Ming Tong ◽  
Qian Gao ◽  
Tong Wang ◽  
Peng Peng ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Radiation Pattern ◽  
Hybrid Method ◽  
Electromagnetic Scattering ◽  
Radar System ◽  
Physical Optics ◽  
Coupling Field ◽  
Terrestrial Environments ◽  
Simulation Results ◽  
Low Altitude

A novel electromagnetic scattering model is presented for studying coupling field of super-low altitude target under diverse terrestrial environments in semi-active radar system. The PO+MEC hybrid method is applied to obtain the electromagnetic scattering of target. The Physical Optics (PO) is introduced to calculate the scattering from facets of target. The Method of Equivalent Currents (MEC) is introduced to calculate the scattering from edges of target. Antenna radiation pattern of seeker is introduced to modify traditional Four Path Method (FPM) in semi-active radar system. Based on the modified FPM, the characteristics of coupling field from super-low altitude target under diverse terrestrial environments in semi-active radar system are studied. Simulation results can use for reference in the fields of remote sensing and detection for super-low altitude target.

scholarly journals A Novel Deceptive Jamming Approach for Hiding Actual Target and Generating False Targets

2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Shahid Mehmood ◽  
Aqdas Naveed Malik ◽  
Ijaz Manssor Qureshi ◽  
Muhammad Zafar Ullah Khan ◽  
Fawad Zaman
Keyword(s):  
Mathematical Model ◽  
Radiation Pattern ◽  
Radar System ◽  
The Novel ◽  
Novel Approach ◽  
Electronic Countermeasure ◽  
Deceptive Jamming ◽  
Frequency Diverse Array ◽  
Simulation Results ◽  
Actual Target

Deceptive jamming is a popular electronic countermeasure (ECM) technique that generates false targets to confuse opponent surveillance radars. This work presents a novel approach for hiding the actual target while producing multiple false targets at the same time against frequency diverse array (FDA) radar. For this purpose, the modified FDA radar is assumed to be mounted on the actual aircraft. It intercepts the opponent’s radar signals and transmits back to place nulls in the radiation pattern at the desired range and direction to exploit FDA radar’s range-dependent pattern nulling capability. The proposed deceptive jammer produces delayed versions of the intercepted signals to create false targets with multiple ranges to confuse the opponent’s radar system. The novel mathematical model is proposed whose effectiveness is verified through several simulation results for different numbers of ranges, directions, and antenna elements.

Design and Development of wide beam width Antenna for Ionosphere Wireless Remote Sensing Applications

2020 ◽  
Vol 10 ◽  
Author(s):  
M. Durga Rao ◽  
I. Srinivasa Rao
Keyword(s):  
Remote Sensing ◽  
Reflection Coefficient ◽  
Radiation Pattern ◽  
Beam Width ◽  
New Approach ◽  
Wide Beam ◽  
Sensing Applications ◽  
Remote Sensing Applications ◽  
Simulation Results ◽  
Ionospheric Radar

Background: The Yagi-Uda antenna is a highly directive antenna used widely in many applications including pulsed Doppler radars to study the dynamics of the atmosphere. Yagi antennas configured in planar array configurations in phased array radars to achieve high peak powers to probe the atmosphere from troposphere. In this paper, a twoelement Yagi-Uda antenna design is presented to investigate the ionospheric irregularities from the Gadanki Ionospheric Radar Interferometer. A new approach devised for the first time to design the two element, wide beam width tilted Yagi antenna, where folded dipole acts as active driver element and reflector as parasitic element. Methods: Several design techniques have been studied and new approach has been employed in designing the antenna and simulations have been carriedout and optimized the performance at 30 MHz with 14o tilt towards geometric north from vertical (zenith) direction for the maximum back scattered echo gain. Based on the design antenna has been fabricated and the system performance has been evaluated. Detailed validation methods have been listed to validate the parameters like reflection coefficient, gain, bandwidth and front-to-back ratio. Results: The antenna is designed and simulated results with 4NEC2 provided the optimized parameters before fabrication. The measured results indicate that the antenna has a gain of 5.65dBi and a reflection coefficient of -30 dB and these results are in close agreement with the simulation results. The band width obtained is about 2MHz is very good for the ionospheric remote sensing applications. The peak power handling capability upto 1kW shows the reliable system design for continuous and long term use of the system. Conclusion: Two element wide beam width 14o tilted Yagi-Uda antenna at 30MHz has been designed, simulated and optimized. Realized system performance validated to use for ionospheric radar remote sensing application. Details of the test methodologies are explained and the same have been executed to characterize the performance of the fabricated antenna with simulation results by measuring reflection coefficient, gain, radiation pattern. All the measured results have very close agreement with the simulation results and satisfy the design requirements to fit into 30 MHz radar antenna array for dedicated ionospheric probing. In future, we intended to carry out the radiation pattern simulation of the 20x8 phased array antennas to describe the overall radiation pattern.

FEATURES OF CONSTRUCTION OF ON-BOARD HELICOPTER RADAR ICE EXPLORATION ON BASIS OF CIRCULAR GROUND SURFACE WITH SYNTHESIS OF APERTURE ROTATING ANTENNA

2019 ◽  
pp. 31-37
Author(s):  
I. G. Antсev ◽  
A. P. Aleshkin ◽  
V. V. Vladimirov ◽  
E. O. Kudrina ◽  
O. L. Polonchik ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Ground Surface ◽  
Rotor Blades ◽  
Navigation Systems ◽  
Propeller Blade ◽  
Antenna Aperture ◽  
Sensing System ◽  
Radar Systems ◽  
Simulation Results ◽  
Circular Antenna Array

The results of modeling the processes of receiving and processing the signals of remote sensing of the Earth’s surface using helicopter radar and synthesizing the antenna aperture due to its placement on the rotating rotor blades are presented. The mathematical correctness of the application of the developed algorithms for processing probing signals, as well as the uniqueness of the measurements, was confirmed. At the same time, the dimensions of the synthesized aperture due to the rotation of the radiator placed at the end of the propeller blade are equivalent to a circular antenna array with a diameter of tens of meters. The functionality of the remote sensing system based on this radar meets the requirements for ice observation and navigation systems for seagoing ships off the coast. The simulation results confirm the promise of further research in this direction and can be used in the development of radar systems with synthesized antenna aperture mounted on rotating rotor blades.

scholarly journals Monitoring Hybrid Rice Phenology at Initial Heading Stage Based on Low-Altitude Remote Sensing Data

2020 ◽  
Vol 13 (1) ◽  
pp. 86
Author(s):  
Yi Ma ◽  
Qi Jiang ◽  
Xianting Wu ◽  
Renshan Zhu ◽  
Yan Gong ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Air Temperature ◽  
Hybrid Rice ◽  
Remote Sensing Data ◽  
Rice Cultivars ◽  
Sensing Data ◽  
Gauss Function ◽  
Low Altitude ◽  
Rice Phenology ◽  
Heading Stage

Accurate monitoring of hybrid rice phenology (RP) is crucial for breeding rice cultivars and controlling fertilizing amount. The aim of this study is to monitor the exact date of hybrid rice initial heading stage (IHSDAS) based on low-altitude remote sensing data and analyze the influence factors of RP. In this study, six field experiments were conducted in Ezhou city and Lingshui city from 2016 to 2019, which involved different rice cultivars and nitrogen rates. Three low-altitude remote sensing platforms were used to collect rice canopy reflectance. Firstly, we compared the performance of normalized difference vegetation index (NDVI) and red edge chlorophyll index (CIred edge) for monitoring RP. Secondly, double logistic function (DLF), asymmetric gauss function (AGF), and symmetric gauss function (SGF) were used to fit time-series CIred edge for acquiring phenological curves (PC), the feature: maximum curvature (MC) of PC was extracted to monitor IHSDAS. Finally, we analyzed the influence of rice cultivars, N rates, and air temperature on RP. The results indicated that CIred edge was more appropriate than NDVI for monitoring RP without saturation problem. Compared with DLF and AGF, SGF could fit CIred edge without over fitting problem. MC of SGF_CIred edge from all three platforms showed good performance in monitoring IHSDAS with good robustness, R2 varied between 0.82 and 0.95, RMSE ranged from 2.31 to 3.81. In addition, the results demonstrated that high air temperature might cause a decrease of IHSDAS, and the growth process of rice was delayed when more nitrogen fertilizer was applied before IHSDAS. This study illustrated that low-altitude remote sensing technology could be used for monitoring field-scale hybrid rice IHSDAS accurately.

scholarly journals Over/Undervoltage and Undervoltage Shift of Hybrid Islanding Detection Method of Distributed Generation

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Manop Yingram ◽  
Suttichai Premrudeepreechacharn
Keyword(s):  
Control System ◽  
Distributed Generation ◽  
Hybrid Method ◽  
Detection Method ◽  
System Simulation ◽  
Detection Methods ◽  
Islanding Detection ◽  
Active Method ◽  
Passive Method ◽  
Simulation Results

The mainly used local islanding detection methods may be classified as active and passive methods. Passive methods do not perturb the system but they have larger nondetection zones, whereas active methods have smaller nondetection zones but they perturb the system. In this paper, a new hybrid method is proposed to solve this problem. An over/undervoltage (passive method) has been used to initiate an undervoltage shift (active method), which changes the undervoltage shift of inverter, when the passive method cannot have a clear discrimination between islanding and other events in the system. Simulation results on MATLAB/SIMULINK show that over/undervoltage and undervoltage shifts of hybrid islanding detection method are very effective because they can determine anti-islanding condition very fast.ΔP/P>38.41% could determine anti-islanding condition within 0.04 s;ΔP/P<-24.39% could determine anti-islanding condition within 0.04 s;-24.39%≤ΔP/P≤ 38.41% could determine anti-islanding condition within 0.08 s. This method perturbed the system, only in the case of-24.39% ≤ΔP/P ≤38.41% at which the control system of inverter injected a signal of undervoltage shift as necessary to check if the occurrence condition was an islanding condition or not.

Improved MoM-PO-Based Technique for Wideband Analysis of Antennas around Large Platforms

2012 ◽  
Vol 629 ◽  
pp. 646-648
Author(s):  
Ji Ma ◽  
Shu Xi Gong ◽  
Qian Wang
Keyword(s):  
Frequency Response ◽  
Method Of Moments ◽  
Hybrid Method ◽  
Wide Band ◽  
Numerical Results ◽  
Physical Optics ◽  
Impedance Matrix ◽  
Mutual Impedance ◽  
Interpolation Technique ◽  
Matrix Interpolation

An improved wide-band analysis which combines the hybrid method of moments-physical optics (MoM-PO) formula with impedance matrix interpolation technique for antennas around large platforms is presented. The algorithm proposed in this paper interpolated the mutual impedance matrix between MoM and PO regions rather than the MoM self-matrix. This practice can result in more accurate frequency response than the conventional approach. Sample numerical results demonstrate the capability of the algorithm.

A Hybrid Method for Multi-sensor Remote Sensing Image Registration Based on Salience Region

2014 ◽  
Vol 33 (7) ◽  
pp. 2293-2317 ◽  
Author(s):  
Jichao Jiao ◽  
Zhongliang Deng ◽  
Baojun Zhao ◽  
John Femiani ◽  
Xin Wang
Keyword(s):  
Remote Sensing ◽  
Image Registration ◽  
Hybrid Method ◽  
Remote Sensing Image
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