Short-Range Imaging System With a Nonuniform SFCW Approach

Stepped-frequency continuous-wave (SFCW) radar systems with real-time capability can utilize only a moderate number of frequency points to achieve a high sweep rate. Thus, range ambiguities of clutter become crucial because of a possible obscuration of the target response. An optimized nonuniform SFCW concept is introduced to reduce the maximum ambiguity level. This nonuniform frequency sweep is applied to an active multistatic imaging system for personnel screening. The sweep design improves the system's robustness against clutter due to reflections from surrounding objects outside the ambiguity-free imaging area of the system. This paper extends the prior work with an analytical approach to estimate the maximum ambiguity level, which is important for the design of an appropriate frequency sweep. Based on the analytical work, an optimum sweep design is proposed and verified with simulation and experimental results. Measurements are conducted with bi- and multistatic radar setups.