  We introduce a radar system capable of tracking a $5$mm spherical target
continuously in three dimensions. The $10$GHz (X-band) radar system has a
transmission power of $1$W and operates in the near field of the horn antennae.
By comparing the phase shift of the electromagnetic wave traveling through the
free space with an IQ-Mixer, we obtain the relative movement of the target with
respect to the antennae. From the azimuth and inclination angles of the
receiving antennae obtained in the calibration, we reconstruct the target
trajectory in a three-dimensional Cartesian system. Finally, we test the
tracking algorithm with target moving in circular as well as in pendulum
motions, and discuss the capability of the radar system.
