Crest-Factor Minimization Using Nonlinear Cheby shev Approximation Methods

Low crest-factor of excitation and response signals is desirable in transfer function measurements, since this allows the maximization of the signal-to-noise ratios (SNR’s) for given allowable amplitude ranges of the signals. The paper presents a new crest-factor minimization algorithm for periodic signals with prescribed power spectrum. The algorithm is based on approximation of the nondifferentiable Chebyshev (minimax) norm by Z,,-norms with increasing values of p , and the calculations are accelerated by using FFT’s. Several signals related by linear systems can also be compressed simultaneously. The resulting crest-factors are significantly better than those provided by earlier methods. Moreover, it is shown that the peak value of a signal can be further decreased by allowing some extra energy at additional frequencies. Keywords-Crest-factor, multisine, optimal excitation.