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In AUV operations high resolution 3D-Sonars shall provide acoustical information utilized for the detection and classification of anomalies. Therefore, we present the concept of a high resolution 3D imaging sonar system, where the antenna concept is based on a mills cross antenna configuration. The provided beam signals are input of the proposed 3D...
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Citations
... To achieve ABFM, the source needs to employ a GSD array rather than a single GSD because the beam of a single GSD is diffused in a spherical style and cannot be manually intervened, which is called the symmetric beamforming method (SBFM) in this paper. As for the antenna array, many scholars have conducted research in many fields, such as aerospace [8,9]; multi-channel GPR surveys [10]; the improvement of SNR and the penetration depth of phased arrays [11,12]; and the optimization of the location accuracy of three dimensional (3D) objects [13][14][15][16][17][18][19]. ...
... When ψ approaches 0, Equation (18) can be obtained as follows: ...
Traditional controlled-source audio-frequency magnetotellurics (CSAMT) radiates symmetric beams using a grounded symmetric dipole (GSD). Only a tiny fraction of radiant energy is taken advantage of during the far-field (Ff) observation due to the low directivity of the GSD. In order to enhance the signal-to-noise ratio (SNR) during the Ff observation, it is necessary to reduce the transceiving distance (TD) or increase the transmitting power (TP), but both methods will cause many problems. Further, when using the tensor method for observation, GSDs in two vertical directions will be employed to radiate energy, and then a series of problems will occur such as an asymmetry of the SNR in two vertical directions if the geological conditions under the two GSDs vary widely. An arithmetic phase difference (APd) weighting asymmetric beamforming method (ABFM) in CSAMT is proposed in this paper, which uses a GSD array instead of a single GSD, and a signal with APd is transmitted to control the wavefront for beam steering. A significant enhancement (about 3 dB) of the SNR will occur by collecting the radiant energy in the region of concern (RoC) using ABFM. The analysis and simulation results demonstrate that under the premise of the same TD and TP, the ABFM has obvious advantages in improving energy utilization in CSAMT. In other words, the APd-weighted ABFM can deal with a complex noise environment in the field better than the traditional method.
