Robust Transmit Nulling in Wideband Arrays

The ability to create nulls in the transmit pattern of a phased array antenna has many applications in communication and radar systems, including interference and clutter mitigation. This paper describes the implementation of transmit nulls in wideband arrays through the use of a filter bank inserted behind each array element. The filter bank decimates and partitions the transmit signal into independent subbands and utilizes a tapped delay line (TDL) in each subband to form frequency invariant spatial nulls in the array´s transmit pattern. New contributions developed in this paper include an algorithm for determining the TDL coefficients and a novel band partitioning scheme based on principal component filter banks (PCFBs), which is shown to be optimal for minimizing spectral errors if the TDL coefficients are quantized. Numerical techniques are presented for approximating ideal PCFBs using practical paraunitary filter banks (PUFBs) and perfect reconstruction filter banks (PRFBs).