Demodulator for Manchester-coded FM signals
AssigneeEricsson GE Mobile Communications Inc.
InventorPaul W. Dent
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Abstract
Binary signals that are transmitted by Manchester coding and frequency modulation are demodulated based on the behavior of the phase or complex vector value of the received signal. The polarities of the information bits may be determined by measuring the phase excursions in the middles of the Manchester symbols. A phase reference is established from a plurality of candidate phase references as a basis for comparison of the mid-symbol phase. The phase can be measured at the start-points and end-points of the symbols and averaged, or measured a plurality of times during each symbol period to generate a reference phase.
Claims45
A method for demodulating coded information bits, wherein the information bits have been converted to Manchester-coded symbols that modulate a carrier signal's frequency and the modulated carrier signal has a phase that depends on the symbols comprising the steps of:
- sampling the modulated carrier signal's phase a plurality of times during each symbol;
- and
- determining the information bits represented by the symbols from phase samples obtained near the centers of the symbols.
A method for demodulating coded information bits, wherein the information bits have been converted to Manchester-coded symbols that modulate a carrier signal's frequency and the modulated carrier signal has a complex vector value that depends on the symbols, comprising the steps of:
- sampling the modulated carrier signal's complex vector value a plurality of times during each symbol;
- and
- determining the information bits represented by the symbols from complex vector value samples obtained near the centers of the symbols.
A demodulator for recovering information bits that have been converted to Manchester-coded symbols that modulate a signal's frequency comprising:
- means for generating a first phase signal from the signal, the first phase signal comprising successive phase values, a plurality of phase values being generated during each symbol;
- means for dividing the first phase signal into a plurality of second phase signals, each second phase signal comprising respective ones of the phase values generated during successive symbols;
- means for averaging each of the second phase signals and for generating a plurality of candidate phase reference signals;
- means for comparing each of the candidate phase reference signals and selected ones of the second phase signals and for generating a plurality of estimated demodulated signals;
- and
- means for selecting one of the estimated demodulated signals and providing the selected one to an output of the demodulator as a demodulated information bit signal.
A demodulator for recovering information bits that have been converted to Manchester-coded symbols that modulate a signal's frequency comprising:
- means for generating a first signal from the signal, the first signal comprising successive complex vector values, a plurality of complex vector values being generated during each symbol;
- means for dividing the first signal into a plurality of second signals, each second signal comprising respective ones of the complex vector values generated during successive symbols;
- means for averaging each of the second signals and for generating a plurality of candidate reference signals;
- means for generating products of complex conjugates of each of the candidate reference signals and selected ones of the second signals and for generating a plurality of estimated demodulated signals;
- and
- means for selecting one of the estimated demodulated signals and providing the selected one to an output of the demodulator as a demodulated information bit signal.
Dependencies are inferred from the claim text.