Method and device for calculating zero-crossing reference sequences for signal detection of angle-modulated signals based on zero crossings of the received signal
View Patent ↗A method for calculating zero-crossing reference sequences ({t i }) for the data detection of a sequence of zero crossings ({{circumflex over (t)} i }) of a received signal is disclosed. The data detection is determined in a receiver, wherein the received signal is based on a data symbol sequence ({d k }) angle-modulated at a transmitter and transmitted to the receiver. The zero-crossing reference sequences ({t i }) are calculated in accordance with an equation specifying an output of a finite state machine that describes, at least approximately, the signal generation in the transmitter.
1. A method for calculating zero-crossing reference sequences ({t i }) for the data detection of a sequence of zero crossings ({{circumflex over (t)} i }), determined in a receiver, of a received signal that is based on a data symbol sequence ({d k }) angle-modulated at a transmitter and transmitted to the receiver, wherein the relationship between the data symbol sequence ({dk}) and the zero crossings of the signal generated at the transmitter is non-linear, comprising:
calculating the zero-crossing reference sequences ({t i }) according to a linear equation specifying an output of a finite state machine, wherein the linear equation results from a linearization of the non-linear relationship between the data symbol sequence and the zero crossings of the signal generated at the transmitter; and
performing a demodulation by determining a transmitted data sequence ({{circumflex over (d)} k }) by comparing the calculated zero-crossing reference sequences ({t i }) with a detected sequence of zero crossings ({{circumflex over (t)} i }) at the receiver,
wherein determining the transmitted data symbol sequence ({d k }) is performed in accordance with the Viterbi algorithm by processing a trellis diagram that describes a state diagram of the finite state machine, for each time increment, wherein transition metric values between a precursor state and a target state in the trellis diagram are calculated by comparing the state-dependent zero-crossing reference sequences with the sequence of zero crossings detected for the time increment considered.
2. A method of demodulating a received angle-modulated signal, comprising:
detecting a sequence of zero-crossings ({{circumflex over (t)} i }) based on the received angle-modulated signal;
generating a plurality of zero-crossing reference sequences ({t i }) in accordance with a predetermined algorithm that is a function of a transmitter performing the angle-modulation of the received signal or a similar transmitter; and
determining one or more data symbols associated with the received signal by comparing the detected sequence of zero-crossings ({{circumflex over (t)} i }) with the plurality of zero-crossing reference sequences({t i }), wherein determining the one or more data symbols comprises:
correlating the detected sequence of zero-crossings ({{circumflex over (t)} i }) with the plurality of zero-crossing reference sequences({t i });
selecting one of the zero-crossing reference sequences having a correlation associated with a predetermined criteria; and
determining the one or more data symbols based on the selected zero-crossing reference sequence.
3. The method of claim 2 , wherein correlating comprises calculating a Euclidean distance between the detected sequence of zero-crossings and each of the zero-crossing reference sequences.
4. The method of claim 3 , wherein selecting one of the zero-crossing reference sequences comprises selecting the reference sequence having the smallest Euclidean distance from the detected sequence of zero-crossings.