Extraction of micro-Doppler data from vehicle targets at x-band frequencies

The authors are utilizing an X-band radar to recover the natural resonance frequencies of a tractor trailer truck (18 wheeler) moving at highway speed. The aspect at which the truck is observed will be from the front and the radar will be raised above the roadway. The natural resonant frequency of the tractor and trailer can be as low as 1 Hz, and as high as 5 Hz depending on the gross weight of the cargo and how the cargo is arranged within the trailer. The condition of the truck's shock absorbers and other suspension stiffening members may also determine the natural resonance frequency of the tractor and trailer. The technical challenge is recovering the 1 to 3 Hz resonance induced signal that is imposed on the normal Doppler shifted signal of the truck when it is moving at 70 Miles Per Hour (MPH) using an X-band homodyne radar. This paper discusses: 1) the research goals; 2) the instrumentation being used for a test target; 3) tests that have been conducted using controlled test targets; and 4) signal processing methods that are being used to extract the micro-Doppler signal components.