Radio frequency signal reception using frequency shifting by discrete-time sub-sampling down-conversion

A radio receiver comprising:

• a receiving means for receiving an RF signal containing an RF channel of carrier frequency f.sub.c within a channel allocation band having bandwidth B;
• a filtering means for filtering the RF signal to a bandwidth W to yield a band-limited signal, the band-limited signal containing the channel allocation band;
• a discrete-time sampling means for sampling the band-limited signal at a sampling frequency f.sub.s to yield an image signal containing an image channel of frequency f.sub.i, where f.sub.i <f.sub.s <f.sub.c ;
• a discrete-time down-converting means for down-converting and down-sampling the image signal using sub-sampling to yield a non-zero-frequency, low-frequency signal containing a down-converted channel of frequency f.sub.k, where 0<f.sub.k <f.sub.i ;
• a discrete-time channel-select filtering means for removing adjacent-channel interference from the low-frequency signal to isolate the down-converted channel;
• and
• a demodulation means for demodulating the down-converted channel to yield a baseband signal.

A method for filtering and frequency translating an RF signal containing an RF channel of carrier frequency f.sub.c to yield a non-zero-frequency, low-frequency signal, the low frequency signal containing a down-converted channel of frequency f.sub.k >0, the method comprising:

• (a) filtering the RF signal to yield a band-limited signal of bandwidth W, the band-limited signal containing a channel allocation band of bandwidth B, where the channel allocation band contains the RF channel;
• (b) discrete-time sampling the band-limited signal at a sampling frequency f.sub.s to yield an image signal that contains an image channel of frequency f.sub.i, where f.sub.i <f.sub.s <f.sub.c ;
• (c) discrete-time filtering the image signal to remove adjacent-channel interference and unwanted aliasing interference and thereby further isolate the image channel from within the image signal to produce a discrete-time filtered image signal;
• (d) discrete-time sub-sampling the discrete-time filtered image signal to simultaneously shift in frequency and reduce the sample rate of the discrete-time filtered image signal;
• (e) repeating steps (c) and (d) in order to down-convert the image signal to yield the low-frequency signal containing the down-converted channel of frequency f.sub.k >0.