US 4,885,756 A · Method of demodulating digitally modulated signals, and apparatus implementing such a method

Abstract

A signal may be demodulated without using any analog components by using a digital processor. A digitizer delivers the amplitude of the signal to be demodulated at a sampling rate. The signal is acquired from the digitizer and stored in a common memory. The amplitude samples are converted to phase samples. Symbol rate phase hypotheses are generated for splitting the time signal into slices. The carrier phase for one symbol is then calculated for each symbol rate phase hypothesis so that the carrier phase can be estimated over a plurality of (S) symbols. The symbol phase is compared to the carrier phase so that the demodulated signal may be extracted and so that the quality of the demodulation may be estimated.

Claims13

Dependent claims

A digital method of demodulating digitally modulated signals, said method comprising the steps of:

acquiring digitized samples of said signals;
calculating phase samples from said digitized samples and storing said phase samples;
generating a plurality of symbol rate phase hypotheses on the basis of said stored phase samples;
calculating a carrier phase from said phase samples for each of said plurality of hypotheses, selecting one of said calculated carrier phases and its corresponding symbol rate phase hypothesis to obtain a selected carrier phase and symbol rate phase over a predetermined number of symbols;
and
demodulating said digitally modulated signals by comparing the selected carrier phase to the phase of said digitally modulated signal during a symbol under consideration.

3 more elements

A device for demodulating digitally modulated signals, said device comprising:

a stable reference clock;
a digitizer receiving said digitally modulated signals as an input and for digitizing said signals in accordance with said stable reference clock;
and
a digital processor receiving the digitized signal output from said digitizer and for sampling said digitized signals, calculating phase samples from the digitized samples and storing said phase samples, generating a plurality of symbol rate phase hypotheses from the stored phase samples, calculating from said phase samples and for each of said plurality of hypotheses a carrier phase and symbol rate phase over a predetermined number of symbols, selecting a carrier phase and symbol rate phase from amongst the calculated carrier and symbol rate phases, and demodulating said digitally modulated signals by comparing the selected phase of said carrier to the phase of said digitally modulated signal during a symbol under consideration.

1 more element

Dependencies are inferred from the claim text.

Method of demodulating digitally modulated signals, and apparatus implementing such a method

Life of this patent

Method of demodulating digitally modulated signals, and apparatus implementing such a method

Life of this patent

Abstract

Claims13