| 摘要 |
A communications system including a modulator for generating a chirp signal aimed at spreading the frequency spectrum of an information signal over a specified spectral bandwidth of a communications channel is described. The chirp signal has an initial and a final instantaneous frequency. The system is characterized in that it is arranged so that the chirp signal is controlled by an in-phase control signal and a quadrature-phase control signal to have, in a complex plane, a constant amplitude and an instantaneous phase. The modulator is adapted so that the instantaneous frequency is defined by the speed at which the instantaneous phase is changed in the complex plane by the in-phase and quadrature-phase control signals; the instantaneous frequency is linearly changed between the initial instantaneous frequency and the final instantaneous frequency over the whole duration of the chirp signal; the initial and final instantaneous phases of the chirp signal are identical.
The communications system also described an adapted demodulator capable of working even in presence of a significant frequency and/or timing offset between the transmitting and receiving clocking systems. |
