Validation of Sensing Ocean Surface Currents Using Multi-Frequency HF Radar Based on a Circular Receiving Array

Abstract

Abstract:To reduce the floor space of receiving antenna arrays, the Radio Ocean Remote SEnsing (RORSE) laboratory of Wuhan University developed a circular receiving array for a multi-frequency high frequency (MHF) radar system in 2014, consisting of seven uniformly spaced antenna elements positioned on a circle with a diameter of 5 m. The new system, which is abbreviated MHF-C radar, adopts frequency modulated interrupted continuous wave (FMICW) chirps and is capable of simultaneously operating at a maximum of four frequencies in the band of 7.5-25 MHz, and providing current, wave and wind maps every ten minutes. The phase direction-finding method is utilized to estimate the directions of the current signals, and array phase uncertainties are also taken into consideration in the signal model. This paper introduces the system in detail and investigates the performance of current measurements using MHF-C radars installed at Shengshan and Zhujiajian along the coast of the East China Sea. Radial current measurements derived from 8.27 MHz and 19.20 MHz at the same range are compared. Observations and comparisons between MHF-C radars and acoustic Doppler current profilers (ADCPs) are also presented in this paper. The results preliminarily demonstrate that the MHF-C radar system is capable of maintaining the same performance for current measurements whenever it steers to any other azimuth in the coverage and has a good ability to measure currents.

The Traveling Wave Loop Antenna: A Terminated Wire Loop Aerial for Directional High-Frequency Ocean RADAR Transmission

“…Depending on the operating frequency, this measurement is representative of the top 0.5-2.5 m layer of the ocean [8]. Multifrequency HFR systems, such as for instance [9][10][11][12], therefore allow for the vertical resolution of the velocity profile within a water column. Two or more HFRs overlooking the same patch of ocean from different locations are required to resolve the two-dimensional current field in the area of common overlap.…”

Validation and Evaluation of a Ship Echo-Based Array Phase Manifold Calibration Method for HF Surface Wave Radar DOA Estimation and Current Measurement

“…The capability of obtaining ocean parameters with a relatively high temporal resolution and a fairly extensive coverage makes HF radars suitable for oceanography research [7], hazard forecasting [8], coastal engineering [9], and maritime security [10,11]. Many types of HF radars are in operation worldwide [12][13][14]. Estimating the range and bearing from the backscattering patch to the receiving antennas is a necessary step for a HF radar to map ocean surface currents [15].…”