Code acquisition with diversity combining for FFH/MFSK spread spectrum systems

Pseudonoise code acquisition based on hard-decision and clipped diversity combining is investigated for fast frequency-hopped MFSK systems under the effects of white Gaussian noise, band multitone jamming and multipath fading. Multipath fading may affect the signal or jamming channel or both. An analytical method is developed to evaluate the mean acquisition time and the operating characteristics of the acquisition system for various jamming and channel conditions. Numerical results show that the time diversity offered by a fast hopper can provide a significant performance improvement and may be indispensable in some cases to obtain a satisfactory performance; the clipped diversity combining outperforms the hard-decision diversity combining, and under some jamming and channel conditions the performance difference of these two methods can be significant; and multipath fading on the signal path degrades the acquisition performance. 1-4 dB degradation is observed, whereas fading on the jamming path reduces the effectiveness of a jamming signal. Computer simulations are also conducted to substantiate the analytical results