Design of a Hybrid Radar Sensor to Monitor the Behavior of a Projectile in a Circular Tube

This study proposes a hybrid radar sensor that can monitor the behavior of projectiles in near real-time in a soft recovery system (SRS) to verify the high-impact characteristics of key components in smart ammunitions. The sensor comprises a frequency-modulated continuous wave (FMCW) radar mode to check whether the soft recovery of the projectile is normal after being launched and a CW Doppler radar mode to estimate the projectile velocity, distance traveled, and deceleration characteristics during the test. As the proposed sensor is installed inside a 155.8 mm circular tube, 1.4 GHz is chosen as the operating frequency to ensure that the sensor only operates in the dominant mode. Moreover, the radar equations in free space are modified to consider radar operation inside the tube and ensure accurate calculations. A hybrid radar sensor is installed and operated inside an SRS test device. The position of the projectile after the test is determined from the positions of the peaks of the receiving signals in the FMCW mode. The projectile velocity, traveling distance, and decay velocity are accurately predicted using the CW Doppler mode.