A digital radio receiver comprises: a first section arranged to receive an analog radio signal and to generate therefrom digital intermediate frequency I and Q channel samples, a second section arranged to convert said I and Q channel samples to a lower, baseband frequency, said second section comprising: a first coordinate rotation digital computer module arranged to perform a complex rotation of the I channel samples; a second coordinate rotation digital computer module arranged to perform a complex rotation of the Q channel samples; a phase accumulator arranged to provide an output signal representing a complex rotation to be applied to each of the I and Q channel samples, wherein the second section is arranged such that the phase accumulator output signal is modified by a phase offset signal prior to being supplied to one of the first and second coordinate rotation digital computers.