Improved Ground Target Detecting System Based on Both Miniaturized FMCW Radar and Radiometer

The frequency-modulated continuous-wave (FMCW) radar is generally applied in ground target detecting devices mounted on small shells or projectiles because of its compact size. However, the FMCW radar often produces false alarms when detecting ground targets surrounded by heavy clutter. To overcome this problem, this paper proposes a ground target detection system based on both the miniaturized FMCW radar and the total power radiometer (TPR), consisting of the common millimeter-wave (MMW) front ends and an antenna. However, its intermediate frequency (IF) parts are separated using different frequency bands to miniaturize the entire system. The minimum detectable temperature (MDT) increases and the sensitivity is thus degraded because the TPR for the hybrid sensor inevitably includes an undesirable transmitter section owing to the widespread usage of the front ends with the radar. The proposed system employs optimization of the physical path delay and duplexing the IF band for the TPR and FMCW radar to improve the sensitivity of the TPR in the proposed hybrid sensors and reduce the system noise. The system includes a matching circuit and a voltage doubler to improve the sensitivity of the detector. Therefore, the MDT of TPR in the proposed hybrid system can be reduced to 47.5 K from 734.6 K in the initial design. The drop test demonstrates that the proposed hybrid sensor can reduce false alarms when compared to using either the FMCW radar or only the TPR.