Channeling phenomenon in electromagnetic forward scattering at low grazing

Abstract

Channeling phenomenon is a type of forward scattering and multipath that occasionally occurs when a well-formed sea wave briefly reflects or focuses the out-of-plane energy toward the receiver, yielding a higher than expected, broadband power gain. A series of X-band, forward-scattering measurements in a large wave tank observed multiple channeling events at low grazing angles. The wave tank simulated a one-dimensional, 1/10th-scale Pierson-Moskowitz surface at sea states 0, 3, and 5. During the measurements, channeling events were observed under crosswind wave conditions when a properly constructed wave trough, coinciding with the radar's line of sight, channeled or focused the out-of-plane, forward-scattered energy toward the receiver. Presented is a summary of the channeling events observed and a physical model of the channeling phenomenon based on experimental observations and numerical simulations.Index Terms-Electromagnetic scattering by rough surfaces, physical optics (PO), sea surface electromagnetic scattering.

Exact Analysis of the Main Bistatic Scattering Area on Sea Surface

“…Assume the transmitter antenna's pitch axial is zero, the point that the antenna beam low fringe reachs the sea is 1 M ,as the same, assume the receiver antenna's pitch axial is zero, the point that the antenna beam low fringe reachs the sea is 2 M . The lapping area is the main scattering area between 1 M and 2 M . Divides it to two cases.…”

“…In the calculation of sea electromagnetic wave, we should consider the transmitted beam and received beam, both of them should shot sea, and they should have overlap region in the irradiated region on sea, then the scattering electromagnetic waves of the transmitter can be detected by the receiver. Define scattering intensity reference value 0dBreFS [1], it's refers to scattering signal strength on sea surface in certain direction which ensures the scattering enagy can be received by the receiver's antenna. Definition of main scattering area: Refer to receiver, transmitter radiating electromagnetic wave, it is scattered by sea surface, when signal strength per unit acreage that is can be received by receiver antenna is exceeded a certain value, all the points satisfying condition compose an area, it is namely main scattering area.…”

Simultaneous data collection of small maritime targets using multistatic radar and forward scatter radar

“…Previous work [9][10][11] has investigated the channelling phenomena happening over the sea surface in forward scattering configuration at low grazing angles, with the aid of numerical simulations and of a series of X-band measurements in a controlled environment (large water tank to simulate different sea states). This allowed characterising the effect of the propagation channel on radar waveforms for different polarisations and different sea states, enabling a better understanding of the conditions of this scattering regime, and of how this can affect the detection of targets in these configurations.…”

Accurate Calculation Receiving Power of the Electromagnetic Wave Scattering between Two Stations on Sea Surface

“…The electromagnetic wave scattering on sea surface of double station is very important for electronic reconnaissance receiver, electronic warfare jamming and bistatic radar etc., the key to solve this conundrum is calculation of the receiving power of the receiver [1].The power received by the receiver of scattering electromagnetic wave lies on transmitting power, beam direction, antenna beam shape, sea surface scattering coefficient, frequency of electromagnetic wave, radiator transmitting direction, relative position, antennae beams alignment relation, etc. [2][3][4][5][6][7]. When the transmitting and receiving equipments are in different positions, the receiving area of transmitter is not exactly the same as the area that transmitting the sea, especially when the beams of receiver and transmitter both are strongly directional as like Fig.…”