Patent ID: 9551786
Date: 2017-01-24
CPC Classifications: G01S

Claim:
1. A system comprising at least a transmitting device, and a receiving device, each device comprising a time reference and being arranged for transmitting and receiving radio signals that include a plurality of chirps, wherein each chirp is limited in time between an initial instant, at which the signal has an initial instantaneous frequency and a final instant at which the signal has a final instantaneous frequency, said initial and final instants and said initial and final frequencies being determined by the time reference, said devices having a ranging mode, in which a ranging request is transmitted from the transmitting device to the receiving device, and wherein the receiving device is arranged for receiving the ranging request and for determining the time and frequency shifts of the time reference of the receiving device with respect to the time reference of the transmitting, based on the time and frequency of chirps contained in the ranging request, wherein the ranging request comprises a series of identical chirps, and the receiving device is arranged for performing a dechirp operation, in which each received chirp is multiplied by a locally-generated conjugate chirp, and a FFT is executed on the result, whereupon the peak of the FFT is an indication of the time shift between the received chirps and the locally generated ones, and the receiving device is arranged for performing an adjusted dechirp, in which a different locally-generated chirp is used at each received chirp in order to adjust for the timing and frequency shifts of the time reference.