Design of two-dimensional FIR digital filters used for broadband digital beamforming by combination of spectral transformation and window method

We propose a method for designing two-dimensional (2D) complex coefficient digital filters for digital beamforming (DBF) antennas. In our method, the DBF network is regarded as a 2D digital filter designed by spectral transformations. The spectral transformations are approximated such that the beam pattern of the resulting broadband digital beamformer is nearly independent of frequency including sidelobe characteristics. We use a window method to approximate the transformations. This method is suitable for designing DBF networks used for our proposed beamspace adaptive array antenna for broadband signals.