Keystone Transform-Based Parameter Search for Wide-Band Hybrid DS/FH Systems

High dynamics for wide-band hybrid direct sequence/frequency hopping (DS/FH) systems may cause Doppler frequency dispersion (DFD). Existing parameter-search schemes use a serial mode to avoid high signal-to-noise ratio (SNR) loss caused by DFD, however, these schemes have large computation loads. To mitigate this problem, we propose a keystone transform-based method to eliminate DFD. The proposed scheme reduces the computational cost by parallel search without performance degradation. First, referring to the differential-coherent integration algorithm, the proposed scheme cancels out the pseudo-noise code in the received signal. Then, the keystone transform is utilized on each hop to eliminate the DFD and focus the signal energy on a certain frequency. Finally, using a fast Fourier transform, the dynamics parameter can be searched in parallel. The detection performance and computational cost of the proposed scheme are analyzed and compared with those of existing search schemes. The result confirms that, for the same detection performance, the proposed scheme significantly reduces computational cost.