Patent ID: 7139329

Claim:
A receiver comprising: first and second local oscillators; a phase locked loop operating on an output of the first local oscillator; a first mixer for receiving one of an RF (Radio Frequency) signal and an IF (Intermediate Frequency) signal, and converting the received signal to a second IF signal according to an output signal of the phase locked loop; an analog-to-digital converter for converting an output signal of the first mixer to a digital signal; a second mixer for converting the digital signal to a detection process frequency according to an output of the second local oscillator; and a filter for bandpass filtering, interposed between one of (i) the first mixer and the analog-to-digital converter and (ii) the analog-to-digital converter and the second mixer; wherein an oscillation frequency step of the first local oscillator is larger than an oscillation frequency step of the second local oscillator, wherein the first and second local oscillators are each comprised of a direct digital synthesizer (DDS) outputting a sine wave and a cosine wave, and 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/cosine waves.