Patent ID: 7127227
Filing Date: 2006-10-24
Classification: H03D

Abstract:
1. A digital down-converter comprising: first and second local oscillators for outputting a sine wave and a cosine wave, the first and second local oscillators being direct digital synthesizers wherein a phase operation word length of the direct digital synthesizer corresponding to the first local oscillator is identical to an input word length of a sine/cosine wave table for converting phase data to sine and cosine waves; a first mixer for receiving, as a first IF (Intermediate Frequency) input signal, a digital signal obtained by sampling a received signal with an RF (Radio Frequency) signal or a separate IF signal, and converting the first IF input signal to a second IF signal using the first local oscillator; a digital filter for suppressing an outband signal of the second IF signal provided from the first mixer; and a second mixer for converting an output of the digital filter to a detection process frequency using the second local oscillator; wherein an available frequency step of the first local oscillator is larger than an available frequency step of the second local oscillator.