“…The properties of individual azimuthal modes were pursued by Tillman and colleagues Hilburn and Hickman, 1968;Tillman, 1968;Hilburn, 1969). The harmonic (Bessel) series analysis has been used for sidelobe control through excitation tapering, and for pattern synthesis (Fenby, 1965;James, 1965;Royer, 1966;Longstaff et al, 1967;Redlich, 1970;Lim and Davies, 1975). Beam cophasal excitation (see Section 11.2.1), in which all elements contribute to the main beam in phase, is almost always used.…”