A programmable digital down-converter (DDC) for SDR receivers is presented. It can be used in various wireless communication systems, including LTE-Advanced. The DDC converts a digitized complex signal centered at an intermediate frequency (IF) to a baseband complex signal centered at zero frequency. In addition to down conversion, it also decimates the sigma-delta ADC’s output signal from a high sampling rate to a lower one, easing the following signal processing by lowering down the operation speed and improving SNR of the signal.