Elimination of Pre-Steering Delays in Space-Time Broadband Beamforming Using Frequency Domain Constraints

One of the most popular methods in broadband beamforming is the Frost space-time processing. In this method, a pre-steering delay is followed by a tapped delay line (TDL) filter in each branch of the beamformer. Pre-steering delays are used to compensate for the effect of misalignment between the array geometry and the look direction. However, any error in implementing these delays drastically degrades the performance of the array. In this letter, a new set of constrains are introduced to substitute the pre-steering delays. These constraints are defined in frequency domain and adjust the beamformer weights such that the desired signal is passed without any distortion. Setting nulls at interference directions can also be incorporated in these constraints and can further improve the performance of the beamformer.