Method and device for receiving a signal the phase or frequency of which is modulated by a sequence of two-state symbols
A method allowing a receiver device of a wireless communication system to receive a useful signal emitted by an emitter device. The useful signal corresponding to a signal, the phase or frequency of which is modulated by a sequence of two-state symbols corresponding to a sequence of binary data. A temporal envelope of the useful signal is detected and compared to a preset threshold value. Transitions between consecutive useful-signal symbols are detected, on the basis of the result of the comparison. A sequence of binary data is extracted from the useful signal depending on the detected transitions.
1. A method for receiving, by a receiver device of a wireless communication system, of a useful signal transmitted by a transmitter device, the method comprising steps of:
detecting a time-domain envelope of the useful signal, the useful signal corresponding to a signal that is phase-modulated or frequency-modulated by a sequence of two-state symbols corresponding to a binary data sequence;
comparing the detected time-domain envelope with a predetermined threshold value;
detecting transitions between consecutive symbols of the useful signal, a transition between two consecutive symbols, respective states of which are different, being detected when the detected time-domain envelope is less than the predetermined threshold value, and a transition between two consecutive symbols, the respective states of which are identical, being detected when the detected time-domain envelope is greater than the predetermined threshold value; and
extracting the binary data sequence from the useful signal as a function of detected transitions between different states and as a function of detected transitions between identical states.
2. The reception method as claimed in claim 1 , wherein the symbols of a sequence are transmitted at a symbol period; and the reception method further comprises steps of determining decision instants separated by the symbol period; and detecting the transitions between consecutive symbols of the useful signal as a function of the decision instants.
3. The reception method as claimed in claim 2 , wherein the decision instants are determined as a function of at least one instant of detection of a transition between different states.
4. The reception method as claimed in claim 2 , wherein the decision instants correspond to instants for which the detected time-domain envelope is greater than the predetermined threshold value; wherein the transition between different states is detected when the detected time-domain envelope becomes less than the predetermined threshold value between two consecutive decision instants; and wherein the transition between identical states is detected when the detected time-domain envelope remains greater than the predetermined threshold value between two consecutive decision instants.
5. The reception method as claimed in claim 1 , wherein the useful signal is an ultra-narrowband signal.
6. The reception method as claimed in claim 1 , wherein the useful signal is a BPSK or DBPSK signal.
7. The reception method as claimed in claim 1 , wherein the useful signal is a GFSK or DGFSK signal.
8. The reception method as claimed in claim 1 , wherein the time-domain envelope of the useful signal is detected and compared to the predetermined threshold value by the receiver device to receive amplitude-modulated signals.
9. The reception method as claimed in claim 1 , wherein the time-domain envelope of the useful signal is detected directly at an output of a low-noise amplifier of the receiver device.
10. A receiver device of a wireless communication system to receive a useful signal transmitted by a transmitter device, the receiver device comprising a processing circuit configured to:
detect a time-domain envelope of the useful signal, the useful signal corresponding to a signal that is phase-modulated or frequency-modulated by a sequence of two-state symbols corresponding to a binary data sequence;
compare the detected time-domain envelope with a predetermined threshold value;
detect transitions between consecutive symbols of the useful signal, a transition between two consecutive symbols, respective states of which are different, is detected when the detected time-domain envelope is less than the predetermined threshold value, and a transition between two consecutive symbols, the respective states of which are identical, is detected when the detected time-domain envelope is greater than the predetermined threshold value; and
extract the binary data sequence from the useful signal as a function of detected transitions between different states and as a function of detected transitions between identical states.
11. The receiver device as claimed in claim 10 , wherein the processing circuit is configured to carry out time-envelope detection of the useful signal directly at an output of a low-noise amplifier of the receiver device.
12. The receiver device as claimed in claim 10 , wherein the processing circuit comprises a processor and a memory.
13. The receiver device as claimed in claim 10 , wherein the processing circuit comprises a programmable logic circuit.