  In this paper, an iterative method is proposed for nonlinear frequency
modulation (NLFM) waveform design based on a constrained optimization problem
using Lagrangian method. To date, NLFM waveform design methods have been
performed based on the stationary phase concept which we have already used it
in a previous work. The proposed method has been implemented for six windows of
Raised-Cosine, Taylor, Chebyshev, Gaussian, Poisson, and Kaiser. The results
reveals that the peak sidelobe level of autocorrelation function reduces about
an average of 5 dB in our proposed method compared with the stationary phase
method, and an optimum peak sidelobe level is achieved. The minimum error of
the proposed method decreases in each iteration which is demonstrated using
mathematical relations and simulation. The trend decrement of minimum error
guarantees convergence of the proposed method.
