UWB Microwave Frequency-Stepped Continuous Wave Sensor for Dual Virtual-Gate Detection of Metallic Objects

This work presents a sensor system based on frequency-stepped continuous wave (SFCW) signals for the detection of metallic objects within dual virtual gates of tunable width. These gates are formed by an electric wall generated through system symmetry and differential-mode signaling. The performance of this variable electric wall was evaluated in three scenarios with different gate widths. In all cases, a coefficient of determination greater than 0.9922 was obtained when compared to a physical barrier formed by a metallic body, thereby confirming the equivalence of their behavior. Additionally, the work includes a step-by-step methodology for metal object detection, which is experimentally validated with the system operating in ultra-wideband (UWB) with signals from 2.5 to 4.5 GHz. From repeated measurements and an ANOVA analysis, a p-value of 0.9988 was obtained, which exceeds the 0.05 significance level, demonstrating the repeatability of the experiments in different conditions. Furthermore, the displacement resolution, average sensitivity, and precision were also evaluated, yielding results of 10 mm, 29.90 cm/ns, and 4.97×10⁻⁴ ns, respectively.