Small Angular Scale Simulations of the Microwave Sky

We describe and compare two types of microwave sky simulations that are good for small angular scales. The rst type uses expansions in spherical harmonics, and the second one is based on plane waves and the fast Fourier transform. The angular power spectrum is extracted from maps corresponding to both types of simulations, and the resulting spectra are appropriately compared. In this way, the features and usefulness of Fourier simulations are pointed out. For l 100, all the simulations lead to similar accuracies ; however, the CPU cost of Fourier simulations is D10 times smaller than that for spherical harmonic simulations. For l 100, the simulations based on spherical harmonics seem to be preferable.