REFERENCES

m, N 128, and f 2.75 GHz. Also, a much higher accu-racy is obtained in our algorithm. V. CONCLUSION We have presented a fast algorithm for the evaluation of the Fourier transform of piecewise smooth functions. By using a double-interpolation procedure, the algorithm can be applied to both uniformly and nonuniformly sampled data. Hence, this algorithm can also perform a nonuniform fast Fourier transform for unequally spaced data. The complexity of the Ž.. Ž 2.algorithm is O Np N log N plus O Np for precalcu-lation. The numerical results show that the sampling density in our new CGFFT method reduces to five points per wave-length, and the contrast of the medium parameters can be much higher