Multistatic short range imaging with a nonuniform SFCW concept

The concept of a stepped frequency continuous wave (SFCW) radar is well known for short range radar applications. By using homo- or heterodyne receivers with a fixed intermediate frequency (IF), IF filters with a small bandwidth can be applied. This offers signals with high signal to noise ratio (SNR) and high phase accuracy. In general the measurement frequencies are equally distributed within the desired frequency band. This leads to an unambiguous range zA which is inverse proportional to the frequency step width Δf. Thus a target with distance z > zA appears at the position z̃ = z mod zA. This is critical for active imaging systems working indoors since the clutter response from the surroundings (e.g. walls) could be mapped into the desired target response. This paper presents a SFCW concept with non equidistant frequency steps. This results in a spatial smearing of the range ambiguities and a decrease of the maximum ambiguity level.