scholarly journals The Scattering Coefficient for Shore-to-Air Bistatic High Frequency (HF) Radar Configurations as Applied to Ocean Observations

2019 ◽  
Vol 11 (24) ◽  
pp. 2978 ◽  
Author(s):  
Zezong Chen ◽  
Jian Li ◽  
Chen Zhao ◽  
Fan Ding ◽  
Xi Chen
Keyword(s):  
Electromagnetic Scattering ◽  
High Frequency ◽  
Doppler Frequency ◽  
Second Order ◽  
Hf Radar ◽  
Scattering Coefficient ◽  
Sea State ◽  
Scattering Coefficients ◽  
Wind Speeds ◽  
Ocean Observations

To extend the scope of high frequency (HF) radio oceanography, a new HF radar model, named shore-to-air bistatic HF radar, has been proposed for ocean observations. To explore this model, the first-order scattering coefficient and the second-order electromagnetic scattering coefficient for shore-to-air bistatic HF radar are derived using the perturbation method. In conjunction with the contribution of the hydrodynamic component, the second-order scattering coefficient is derived. Based on the derived scattering coefficients, we analyzed the simulated echo Doppler spectra for various scattering angles and azimuthal angles, operation frequencies, wind speeds, and directions of wind, which may provide the guideline on the extraction of sea state information for shore-to-air bistatic HF radar. The singularities in the simulated echo Doppler spectra are discussed using the normalized constant Doppler frequency contours. In addition, the scattering coefficients of shore-to-air bistatic HF radar are compared with that of monostatic HF radar and land-based bistatic HF radar. The results verify the correctness of the proposed scattering coefficients. The model of shore-to-air bistatic HF radar is effective for ocean observations.

scholarly journals A Quality Control Method for Broad-Beam HF Radar Current Velocity Measurements

2019 ◽  
Vol 7 (4) ◽  
pp. 112 ◽  
Author(s):  
Lipa ◽  
Barrick ◽  
Whelan
Keyword(s):  
Quality Control ◽  
High Frequency ◽  
Control Method ◽  
Doppler Frequency ◽  
Hf Radar ◽  
Velocity Measurements ◽  
Poor Agreement ◽  
Broad Beam ◽  
Radar Echo ◽  
Basic Equations

This paper describes a method to provide quality control for radial velocity maps derived from radar echo voltage cross spectra measured by broad-beam high frequency radars. The method involves the comparison of voltage cross spectra measured at Doppler frequencies in the Bragg region with values predicted from basic equations defining the complex voltage cross spectra in terms of the measured antenna patterns and the radar cross section. Poor agreement at a given Doppler frequency indicates contamination of the spectra, usually due to interference; velocity results from that Doppler frequency are then eliminated. Examples are given of its application to broad-beam radars operating at four sites.

High-frequency scattering of electromagnetic waves

1957 ◽  
Vol 240 (1221) ◽  
pp. 206-213 ◽  
Keyword(s):  
Circular Cylinder ◽  
Electromagnetic Scattering ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Convex Bodies ◽  
Sound Waves ◽  
Shadow Boundary ◽  
High Frequencies ◽  
Scattering Coefficients ◽  
Solid Of Revolution

The assumption that the illuminated region and the penumbra of a body scatter independently at high frequencies is used to obtain scattering coefficients for perfectly reflecting convex bodies in plane electromagnetic and sound waves. The formulae involve only the scattering coefficients of the circular cylinder and the geometry of the shadow boundary. One general result is that the electromagnetic scattering coefficient of a solid of revolution, when the direction of propagation of the incident wave is along the axis of revolution, is the average of the sound-hard and sound-soft scattering coefficients.

scholarly journals Dependence of 25-MHz HF Radar Working Range on Near-Surface Conductivity, Sea State, and Tides

2017 ◽  
Vol 34 (2) ◽  
pp. 447-462 ◽  
Author(s):  
Mark Halverson ◽  
Rich Pawlowicz ◽  
Cédric Chavanne
Keyword(s):  
Time Series ◽  
Surface Conductivity ◽  
Hf Radar ◽  
Sea State ◽  
Near Surface ◽  
High Frequency Radar ◽  
Wind Speeds ◽  
Spatially Resolved ◽  
Coastal River ◽  
Range Variation

AbstractA 1.6-yr time series of radial current velocity from a 25-MHz high-frequency radar system located near a coastal river plume is analyzed to determine how the working range varies in response to changing near-surface conductivity, sea state, and tides. Working range is defined as the distance to the farthest radial velocity solution along a fixed bearing. A comparison to spatially resolved near-surface conductivity measurements from an instrumented ferry shows that fluctuations in conductivity had the largest impact of the three factors considered. The working range increases nearly linearly with increasing conductivity, almost doubling from 19.4 km at 0.9 S m−1 to 37.4 km at 3.5 S m−1, which yields a slope of 7.0 km per S m−1. The next largest factor was sea state, which was investigated using measured winds. The working range increases linearly at a rate of 1 km per m s−1 of wind speed over the range of 0.5–6.5 m s−1, but it decreases weakly for wind speeds higher than 7.5 m s−1. Finally, a power spectrum of the working range time series reveals variability at tidal frequencies. Tides cause about 3 km of range variation; however, the mechanism(s) underlying this are not known explicitly. Evidence for both sea level height and the interaction of tidal currents with sea state are presented.

Research on the electromagnetic scattering from foam sea based on SMCG

Frequenz ◽  
2021 ◽  
Vol 75 (7-8) ◽  
pp. 251-258
Author(s):  
Weifan Huang
Keyword(s):  
Wind Speed ◽  
Marine Environment ◽  
Electromagnetic Scattering ◽  
Incident Angle ◽  
Grazing Angle ◽  
Surface Current ◽  
Dielectric Constants ◽  
Scattering Coefficients ◽  
Wind Speeds ◽  
Calculation Results

Abstract The electromagnetic scattering characteristics of foam in Marine environment are studied in this paper. The Elfouhaily sea spectrum model is established, and the dielectric constants of seawater/ocean foam are calculated based on the double Debye dielectric constant model, furthermore, the formula relation between them is given. As an important factor affecting ocean electromagnetic scattering, the thickness of foam is proportional to the wind speed above the sea surface. In this paper, the SMCG method based on the surface current equation is mainly used to calculate the electromagnetic scattering coefficient of the environment, and the correctness of the SMCG algorithm is verified by comparing the calculated results with the actual measured data. Based on the computer simulation, the influence of the existence of ocean foam on the environmental scattering is discussed, and the Marine electromagnetic scattering coefficients under different wind speeds, different scrape angles and different radar bands are calculated. Through the analysis of the calculation results, the influences of wind speed, grazing angle and frequency on the electromagnetic scattering characteristics of the Marine environment containing foam are studied, and the general variation rule is obtained: the intensity of electromagnetic scattering increases with the increase of wind speed, the decrease of incident Angle and the increase of frequency. The results of this paper can be used to guide ocean navigation and fishery, and have reference significance in the military field.

scholarly journals An Analytical Method for Dynamic Wave-Related Errors of Interferometric SAR Ocean Altimetry under Multiple Sea States

2021 ◽  
Vol 13 (5) ◽  
pp. 986
Author(s):  
Yao Chen ◽  
Mo Huang ◽  
Yuanyuan Zhang ◽  
Changyuan Wang ◽  
Tao Duan
Keyword(s):  
Electromagnetic Scattering ◽  
Analytical Method ◽  
Wave Spectrum ◽  
High Accuracy ◽  
Sea State ◽  
Error Budget ◽  
Ocean Topography ◽  
Mean Square Errors ◽  
Dynamic Wave ◽  
Wide Swath

The spaceborne interferometric synthetic aperture radar (InSAR) is expected to measure the sea surface height (SSH) with high accuracy over a wide swath. Since centimeter-level accuracy is required to monitor the ocean sub-mesoscale dynamics, the high accuracy implies that the altimetric errors should be totally understood and strictly controlled. However, for the dynamic waves, they move randomly all the time, and this will lead to significant altimetric errors. This study proposes an analytical method for the dynamic wave-related errors of InSAR SSH measurement based on the wave spectrum and electromagnetic scattering model. Additionally, the mechanisms of the dynamic wave-related errors of InSAR altimetry are analyzed, and the detailed numerical model is derived. The proposed analytical method is validated with NASA’s Surface Water and Ocean Topography (SWOT) project error budget, and the Root-Mean-Square Errors (RMSEs) are in good agreement (0.2486 and 0.2470 cm on a 0.5 km2 grid, respectively). Instead of analysis for a typical project, the proposed method can be applied to different radar parameters under multiple sea states. The RMSEs of Ka-band under low sea state, moderate sea state, and high sea state are 0.2670, 1.3154, and 6.6361 cm, respectively. Moreover, the RMSEs of X-band and Ku-band are also simulated and presented. The experimental results demonstrate that the dynamic wave-related errors of InSAR altimetry are not sensitive to the frequencies but are sensitive to the sea states. The error compensation method is necessary for moderate and higher sea states for centimetric accuracy requirements. This can provide feasible suggestions on system design and error budget for the future interferometric wide-swath altimeter.

scholarly journals How Good Is the STW Sensor? An Account from a Larger Shipping Company

2021 ◽  
Vol 9 (5) ◽  
pp. 465
Author(s):  
Angelos Ikonomakis ◽  
Ulrik Dam Nielsen ◽  
Klaus Kähler Holst ◽  
Jesper Dietz ◽  
Roberto Galeazzi
Keyword(s):  
High Frequency ◽  
Additional Data ◽  
Empirical Method ◽  
Influential Factor ◽  
Sensor Data ◽  
Sea State ◽  
Shipping Company ◽  
Frequency Sensor ◽  
Semi Empirical

This paper examines the statistical properties and the quality of the speed through water (STW) measurement based on data extracted from almost 200 container ships of Maersk Line’s fleet for 3 years of operation. The analysis uses high-frequency sensor data along with additional data sources derived from external providers. The interest of the study has its background in the accuracy of STW measurement as the most important parameter in the assessment of a ship’s performance analysis. The paper contains a thorough analysis of the measurements assumed to be related with the STW error, along with a descriptive decomposition of the main variables by sea region including sea state, vessel class, vessel IMO number and manufacturer of the speed-log installed in each ship. The paper suggests a semi-empirical method using a threshold to identify potential error in a ship’s STW measurement. The study revealed that the sea region is the most influential factor for the STW accuracy and that 26% of the ships of the dataset’s fleet warrant further investigation.

Backtracking drifting objects using surface currents from high-frequency (HF) radar technology

2012 ◽  
Vol 62 (7) ◽  
pp. 1073-1089 ◽  
Author(s):  
Ana Julia Abascal ◽  
Sonia Castanedo ◽  
Vicente Fernández ◽  
Raúl Medina
Keyword(s):  
High Frequency ◽  
Hf Radar ◽  
Surface Currents

Design and Construction of a Small Reverberation Chamber Applied to Absorption and Scattering Acoustic Measurements

2014 ◽  
Vol 1077 ◽  
pp. 197-202
Author(s):  
D. Hernandez ◽  
E.J. Liu ◽  
J.H. Huang ◽  
Y.C. Liu
Keyword(s):  
High Frequency ◽  
Integration Method ◽  
Sound Field ◽  
Acoustic Measurements ◽  
Acoustic Characteristics ◽  
Reverberation Chamber ◽  
Scattering Coefficients ◽  
Reverberation Chambers ◽  
The Cost ◽  
Design And Construction

Reverberation chambers are used to create a diffuse incidence sound field, where multiple types of acoustic measurements can be performed. The chambers tend to have a large volume in order to extent the reverberation time. However, this requirement may be conditioned by the cost and the infrastructure limitations. This paper presents the design and construction of a small-scaled reverberation chamber of 3 m3 for middle-high frequency acoustic measurements. On the design, the acoustic characteristics of chamber are confirmed via finite element computer simulation. As case studies, absorption and scattering coefficients of several materials and diffusors are measured. The reverberation times needed for the measurements were obtained by the impulse response integration method. The small reverberation chamber demonstrated to be a reliable tool for middle and high frequency acoustic measurements.

Near Field Electromagnetic Scattering Model Studying for Coarse Sea Surface

2013 ◽  
Vol 756-759 ◽  
pp. 4586-4590
Author(s):  
Jun Gu ◽  
Kun Cai ◽  
Zi Chang Liang
Keyword(s):  
Electromagnetic Scattering ◽  
Near Field ◽  
Horn Antenna ◽  
Measured Data ◽  
Sea Surface ◽  
Scattering Coefficient ◽  
Distributed Model ◽  
Echo Signal ◽  
Scattering Model ◽  
Rough Sea

The simulated PM-spectrum fractal sea surfaces and the 3-D near-field distributed model of horn antenna are built, the near-field formulas of KA method are deduced. The near-field scattering coefficient and the Doppler echo signal of rough sea surfaces are calculated, the agreement with measured data proved the correctness and validity of the near-field scattering model.

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