Relationship between chirp-rate resolution of LFM signals and phase difference in FRFT domain

Phase difference between signals effects deeply on signal resolution. In fractional Fourier transform (FRFT) domain, the relationship between phase difference and chirp-rate resolution of two linear frequency modulation (LFM) signals at high oversampling rate is investigated. By establishing a resolution model of chirp rate, the curves of upper bound and lower bound of phase difference is calculated when two LFM signals are distinguished. Only when phase difference is located at between the upper bound and the lower bound, can the two LFM signals be distinguished. Simulation results show the deviation of resolution is so small that theoretical values of resolution are consistent basically with actual values.