Abstract

This paper is concerned with the existence of almost periodic solutions of neutral functional differential equations of the form ddtDxt=Lxt+f(t), where D, L are bounded linear operators from C:=C([−r,0],Cn)to Cn , f is an almost (quasi) periodic function. We prove that if the set of imaginary solutions of the characteristic equations is bounded and the equation has a bounded, uniformly continuous solution, then it has an almost (quasi) periodic solution with the same set of Fourier exponents as f.