In the presence of steering vector model mismatches, a novel robust adaptive beamformer is proposed based on interference-plus-noise covariance matrix reconstruction. An interference region is first selected according to the coarsely estimated desired signal direction, and then the interference steering vectors are estimated with the robust Capon beamformer. Finally, the interference-plus-noise covariance matrix is reconstructed by integrating the Capon spatial spectrum over the interference region by using the estimated steering vectors.

A diode pumped tunable single-frequency Tm:YAG laser using the twisted-mode cavity is reported. The maximum single-frequency output power is 514 mW with a slope efficiency of 9.7%. The wavelength tuning range from 2011.587 nm to 2016.065 nm is achieved by tuning the obliquity of a 1-mm-thick etalon. The single frequency laser has a beam quality of M2 < 1.3 at the maximum single-frequency output power.

The beamformers by joint estimation of the steering vector (SV) and reconstruct the interference-plus-noise covariance (INC) matrix have been investigated. However, few of them concerned about the effectiveness of reconstruction. In this paper, a novel beamformer is proposed, which introduces the improve factor (IF) to evaluate the improvement scale of output signalto-interference-plus-noise ratio (SINR) with and without reconstruction. By exploiting the relationship between the IF and input signal-to-noise ratio (SNR), it can be made a trade off between the extent of the performance improved and computational load that reconstruction required. Therefore, the SV is estimated at first, and then the level of SNR determines whether the INC matrix is required to reconstruct. During the implementation, a spherical uncertainty set and the sparsity of interference direction are used. Simulation results indicate that the proposed beamformer has better perfor

No abstract