  Ultra-high-resolution target sensing has emerged as a key enabler for various
cutting-edge applications, which can be realized by utilizing the millimeter
wave/terahertz frequencies. However, the extremely high operating frequency
inevitably leads to significant Doppler shift effects, especially for
high-mobility applications, causing the degradation of sensing performance with
high false alarm rate. To this end, this paper proposes a parameter design
methodology of the well-known constant amplitude zero auto correlation (CAZAC)
sequences, which aims at enhancing their resilience to Doppler shifts.
Specifically, we suppress the sidelobes incurred by Doppler shifts for the
peak-to-sidelobe ratio (PSLR) improvement within the range of interest (RoI) of
the radar range profile. The Zadoff-Chu (ZC) sequence, as a representative
member in the CAZAC family, is firstly considered. The impacts of its root
index on range sidelobes are investigated based on number theory. For an
arbitrary-length ZC sequence, a feasible range of the root index is derived to
satisfy the requirement of PSLR within the scope of RoI. Furthermore, these
design guidelines are extended to a general form of CAZAC sequences, where a
low-complexity heuristic algorithm is developed for PSLR improvement.
Simulation results demonstrate that under severe Doppler shifts, our proposed
methodology could enhance the sensing performance by lowering the false alarm
rate while maintaining the same detection rate, compared with its classical
counterpart.
