  We develop a new method for deconvolving the smearing effect of the survey
window in the analysis of the galaxy multipole power spectra from a redshift
survey. This method is based on the deconvolution theorem, and is compatible
with the use of the fast Fourier transform. It is possible to measure the
multipole power spectra deconvolved from the window effect efficiently.
Applying this method to the luminous red galaxy sample of the Sloan Digital Sky
Survey data release 7 as well as mock catalogues, we demonstrate how the method
works properly. Using this deconvolution technique, the amplitude of the
multipole power spectrum is corrected. Besides, the covariance matrices of the
deconvolved power spectra get quite close to the diagonal form. This is also
advantageous in the study of the BAO signature.
