Periodic Solutions in a Simple Delay Differential Equation

Simple form scalar differential equation with delay and nonlinear negative periodic feedback is considered. The existence of several types of slowly oscillating periodic solutions is shown with the same and double periods of the feedback coefficient. The periodic solutions are built explicitly in the case of piecewise constant nonlinearities involved. The periodic dynamics are shown to persist under small perturbations of the equation which make it smooth. The theoretical results are verified by extensive numerical simulations.