Different　from　traditional　phased　array　(PA),　frequency　diverse　array　(FDA)　employs　an　additional　frequency　offset　to　its　array　element　so　that　the　transmitted　signal　is　angle-range-dependent.　Therefore,　FDA　can　be　utilized　to　realize　directional　modulation　(DM)　in　both　angle　and　range　dimensions.　However,　traditional　DM　is　mainly　realized　through　optimization　methods,　which　is　time-consuming.　This　article　proposes　an　analytical　method　to　address　this　problem.　For　a　transmitter　with　$M+1$　elements,　the　proposed　approach　adopts　a　chaotic　sequence　to　map　out　the　frequency　offsets　and　the　weights　of　the　first　$M$　elements.　Then,　the　weight　of　the　last　element　can　be　determined　in　an　analytical　way.　Numerical　simulations　are　implemented　to　validate　the　proposed　approach.　©　1967-2012　IEEE.