Array architecture for wideband transmit nulling

The ability to create nulls in the transmit pattern of a phased array antenna has many applications for communication and radar systems, including interference and clutter mitigation. Most nulling techniques introduce small perturbations in amplitude and phase, or phase-only, at each element of the phased array. For ease of implementation, phase-only perturbations are usually desired and provide acceptable null depths. However, the phase shift at each array element will vary with the frequency of the transmitted signal. As a result, the depth and pointing accuracy of the transmit null will not be uniform over the bandwidth of the transmitted signal. A more robust transmit nulling approach is to insert a tapped delay line (TDL) behind each array element instead of a phase shift. As shown in this paper, the null depths achieved over wide signal bandwidths are far superior to conventional phase-only approaches.