A novel ranging method by code and multiple carriers of FHSS systems

This paper gives a novel idea for two-way range estimation in FHSS (Frequency- Hopping Spread Spectrum) systems. The coarse measurements are obtained by the correlation computations of the PN (Pseudo-Random Noise) code. The fine measurements are obtained by the phase difference computations of a pair of carrier signals. In order to eliminate the integer ambiguities occurred in phase measurements, the frequency difference of these two selected carriers is set to the reciprocal value of the code correlation step time interval. The accuracy can be improved further if several pairs of carriers are weight -averaged according to their SNR (Signal to Noise Ratio). In our simulation, the ranging error of 1500 meters distance measurement is 0.7 meter under the condition of 6dB SNR (Signal Noise Ratio).