Digital FM demodulator with a reduced sampling rate
AssigneeMotorola, Inc.
InventorJames D. Solomon
Life of this patent
Estimating the term…
Abstract
A method of recovering a frequency modulated signal wherein the frequency modulated information signal is sampled at a rate less than the Nyquist sampling rate, following which the under sampled signal can be demodulated to extract the original information signal.
Claims10
A method of recovering an information signal that has been frequency modulated at a peak frequency deviation f.sub.p on a radio frequency carrier and contained substantially within an allotted communication channel to provide a frequency modulated signal, said allotted communication channel having a predetermined bandwidth of approximately plus/minus f.sub.MAX, said method comprising the steps of:
- A) sampling said frequency modulated signal at a sample rate f.sub.S, wherein said sample rate f.sub.S is:
- i) less than 2f.sub.MAX ;
- but
- ii) greater than 2f.sub.D ;
- to provide a resultant sampled signal that includes aliased information;
- B) demodulating said resultant sampled signal to recover said information signal without degradation that is attributable to the sample rate f.sub.S.
A device for recovering an information signal that has been frequency modulated at a peak frequency deviation f.sub.D on a radio frequency carrier and contained substantially within an allotted communication channel to provide a modulated signal, said allotted communication channel having a predetermined bandwidth of approximately plus/minus f.sub.MAX, said device comprising:
- A) sampling means for sampling said frequency modulated signal at a sample rate f.sub.S, wherein said sampling rate f.sub.S is;
- i) less than 2f.sub.MAX ;
- but
- ii) greater than 2f.sub.D ;
- to provide a resultant sampled signal that includes aliased information;
- B) demodulating means for demodulating said resultant samples signal to recover said information signal without degradation that is attributable to the sample rate f.sub.S.
A radio for use with an information signal that has been frequency modulated at a peak frequency deviation f.sub.D on a radio frequency carrier and contained substantially within an allotted communication channel to provide a modulated signal, said allotted communication channel having a predetermined bandwidth of approximately plus/minus f.sub.MAX, said radio comprising:
- A) receiving means for receiving said modulated signal;
- B) sampling means for sampling said modulated signal at a sample rate f.sub.S,
- wherein said sample rate f.sub.S is;
- i) less than 2f.sub.MAX ;
- but
- ii) greater than 2f.sub.D ;
- to provide a resultant sampled signal that includes aliased information;
- C) demodulating means or demodulating said resultant sampled signal to recover said information signal without degradation that is attributable to the sample rate f.sub.S.
Dependencies are inferred from the claim text.