Superselectivity in the azimuth and frequency dimensions

The possibility of extrapolation from a limited segment of a well-behaved waveform or wavefield is briefly discussed, in terms of elementary information theory, in order to establish its basic limitations and possible applications. Next, the paper briefly outlines the superdirective null forming technique for generating wideband superdirective antennas of moderate total directivity. It then develops the analogous concept of superselective frequency-notch generation. A number of possible embodiments of this technique are then described, and the frequency-domain and time-domain techniques are compared. Finally some suggestions are made for further work.