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US 4,893,341 AGranted
Digital receiver operating at sub-nyquist sampling rate
AssigneeAT&E Corporation
InventorMark R. Gehring
Life of this patent
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Abstract
A digital receiver samples data from an amplitude modulated subcarrier at a rate less than twice the subcarrier's maximum frequency by sampling at known phase points. Sampling at known phase points is achieved by generating a sampling clock from a signal phase locked to and transmitted with the modulated data subcarrier.
Claims4
A receiver for receiving an amplitude modulated subcarrier, said subcarrier being transmitted as part of an RF composite signal that includes a pilot signal, the receiver including:
- a front end for converting the RF composite signal to a baseband composite signal;
- a frequency source for producing a sampling clock signal;
- means for phase locking said frequency source to the pilot signal in the baseband composite signal;
- sampling means for sampling said composite signal at a rate determined by the sampling clock signal;
- analog to digital conversion means for converting the samples produced by the sampling means into digital form;
- digital filter means for digitally filtering said digitized samples to attenuate the non-subcarrier components thereof;
- wherein said sampling clock signal has a frequency less than twice the maximum frequency of the modulated subcarrier.
4 more elements
A method of receiving data that is modulated on a subcarrier of a composite signal, the method comprising the steps:
- deriving from said composite signal a reference frequency having a known relationship with the subcarrier frequency;
- sampling the composite signal periodically at certain phase conditions of the reference frequency;
- digitizing the sampled composite signal to yield digital data;
- and
- filtering said digital data to attenuate the non-subcarrier components of the digitized composite signal;
- wherein said sampling occurs at a frequency twice the subcarrier frequency.
3 more elements
Dependencies are inferred from the claim text.