Narrowband line-array beamforming: practically achievableresolution limit of unbiased estimators

Based on an approximation to the Cramer-Rao lower bound, it is demonstrated that meaningful resolution with an unbiased narrowband estimator requires a source separation of at least about 1/10 of a Rayleigh beamwidth, even under ideal circumstances, with 1/4 beamwidth being a more practically achievable figure     

CRB approximations for a horizontal array observing a narrow-bandtarget with partial coherence

It is demonstrated that simple approximations are available for the Cramer-Rao lower bounds on estimates of range, bearing and frequency using a moving line array. The results are extended to include the effects of the partial coherence of the source     

Finite-time performance of a quadratically constrained MVDRbeamformer

The finite-time behavior of a quadratically constrained version of the minimum-variance, distortionless-response line-array beamformer is examined. An entity known as the weight ratio is defined and it is demonstrated that there are simple expressions that relate the weight ratio to the field scenario which explicitly take into account the finite-time misadjustment phenomenon. It is further demonstrated that holding the weight ratio to a value of about 0.5 produces an adaptive beamformer with a beneficial combination of robustness to nonideal situations (e.g., sensor misalignment, pointing errors, correlated interferers, misadjustment effects, etc.) while retaining the ability to adapt quickly in highly dynamic fields