A discrete resampling technique to correct for Doppler effect in continuous gravitational wave search

The detection of continuous gravitational waves has to deal with the Doppler effect induced by the Earth motion with respect to the source. This frequency shift must be taken into account to recover the signal energy as a monochromatic peak with a high signal-to-noise ratio. The correction to be applied to the antenna output depends on the source sky direction, on the source spin and also on the spin-down rate. Since they are, in general, unknown parameters a large computational effort is necessary to correct for any possible value. A correction technique independent of the source frequency is discussed here. The method consists to anticipate or delay the antenna clock by removing or doubling one of its digital signal sample, in order to mantain the clock of the moving observer well locked to the rest one. The method, which requires just a little computational effort, appears to be very effective for "semi-targeted" searches, where the source direction is known but the emission frequency is not.