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In this paper, we consider single-link mmWave transmission. We investigate the usual hybrid beamforming architecture under an additional constraint on the analog precoding stage. Namely, for practical reasons only partial interconnection between the antennas and the RF chains is allowed. We present a novel upper bound for spectral efficiency under this architecture constraint. We evaluate the tightness...
Direction of arrival (DOA) estimation is of great importance to signal processing, and, as a consequence, various arrays have recently been studied to get good DOA estimation performance. Particularly, spherical arrays have the advantage of three-dimensional orientation which benefits three-dimensional processing and analysis. Also, spherical symmetric structure of spherical arrays could promote the...
Matched-field processing (MFP) is an underwater acoustic signal processing method for passive source localization. It works by matching the measured field with the full-field solution for sound wave propagation in an oceanic waveguide. The popular Minimum Variance Distortionless Response (MV-DR) algorithm is known to be highly sensitive to environmental mismatch, which is one of the main obstacles...
Performance of matched-field source localization is highly dependent on the precision of the model to actual physical processes. Model mismatch, including sound propagation environmental mismatch, statistical mismatch, and system mismatch, causes severe performance degradation. Statistical mismatch occurs when an insufficient snapshot set is used to estimate the data covariance matrix. Diagonal loading...
In order to provide the passive and active array with replica vector for achieving transmitting and receiving focusing on proud and burried targets, the time reversal mirror-virtual source array-refracted spherical wave beamforming (TRM-VSA-RSBF) method is proposed. The original idea is from the work of S.C. Walker et.al. We develop their work in two aspects. First, we generalizes the method to the...
Synthetic aperture sonar (SAS) is an emerging technology for seafloor imaging, which has an appealing property of range- and frequency-independent spatial processing resolution. However, for a low-frequency SAS system operated in shallow water environments, there are often strong sea surface and bottom reflected multipath components that interfere with the desired echo signals. Previously a steered...
For a Multi-Beam Echo Sounder (MBES) operating in very shallow water environments or close to seafloor, near-field beamforming shall be used to estimate the direction and range of the backscattering sources along the bottom. The most common beamforming method is the so-called weight-delay-sum (WDS) beamformer. In this paper, we present an approximation method to calculate time delays between individual...
Matched field processing (MFP) is an important technique for source localization in shallow water waveguides. To obtain high resolution, some adaptive methods are frequently used, for example, the minimum variance distortionless response (MVDR) MFP. It is well-known that MVDR is quite sensitive to model mismatch, which can hardly be avoided in practical applications. In this paper a robust MVDR method,...
Beamforming as a basic approach of array signal processing has been widely used in many important applications such as radar, sonar, and communications. Typical algorithms include time-delay-based and FFT-based, and various implementation structures have been developed. For bandpass sampled signals, a true time-delay beamformer involves three processes: signal demodulation to obtain its complex envelop;...
Array-based bearing estimation is commonly used in many sonar/radar applications. Typical performance of a practical implementation displays a threshold behavior, that is, below certain signal-to-noise ratio (SNR) the estimation mean- square error increases dramatically. The error increase is known to be largely attributed to sidelobe ambiguities in signal field correlation along with estimation bias...
The Cramer-Rao lower bound (CRB) has been extensively used in parameter estimation performance analysis. It can be achieved by a maximum likelihood estimator (MLE) for sufficiently high SNR; however below certain SNR the MLE mean-square error departs significantly from the CRB, displaying a threshold behavior. This departure is partially attributed to the fact that an MLE with nonlinear parameter...
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