Improved transmission design algorithms by utilizing variable-strength projections

The iterative Fourier transform algorithm (IFTA) is accepted as a powerful tool for the design of transmission functions under consideration of various kinds of design freedom. In this algorithm, projection operations are utilized for incorporating the existing design freedom. By introducing a variable projection-strength parameter, the projection operators can be relaxed or tensed up. We investigate the dependency of the convergence rate of the design algorithm from the projection strength parameter for various design problems at various states of iteration. From insights about this relation we derive strategies for modifying the projection strength during iteration, in order to increase the performance of the algorithm. We demonstrate that the convergence rate can be drastically increased for the design of phase-only transmissions and show that stagnations, occurring when using the IFTA for the design of quantized transmissions, can be overcome in many cases.