Radar Distance Measurement With Viterbi Algorithm to Resolve Phase Ambiguity

In this article, a precise phase-based radar distance measurement system using a Viterbi decoder to resolve phase ambiguity is presented. Relying on the frequency-modulated continuous-wave radar principle, the introduced method evaluates both the frequency and the phase of the intermediate frequency signal, thus achieving absolute distance measurement with high accuracy. To avoid ambiguity in the distance estimates by half the wavelength of the radio frequency signal, which commonly arises due to 2π ambiguity in the measurement of the phase, the proposed Viterbi-based method estimates the most likely sequence of distances between the radar front end and the target. To verify the system concept, measurements using a commercial 77 GHz radar module were carried out, whereby the contour of a predefined surface containing steps in the height profile had to be determined. The experimental results confirm that the Viterbi-based approach is suitable to resolve phase ambiguity since accurate and repeatable distance estimates were obtained.