A Micro Ground-Based Interferometric Radar System for Deformation Monitoring

  Objectives  Ground-based multiple-input multiple-output(MIMO) radar can avoid using large antennas or long linear guide rail. Compared with real aperture radar and synthetic aperture radar, MIMO radar has more advantages under the limitation of volume and weight. It is more suitable for use in narrow spaces like tunnels. In order to be used in these scenes, a micro ground-based interferometric radar based on MIMO technology is presented and discussed.

  Methods  Millimeter wave frequency band is used to achieve the miniaturization. MIMO technology can be used to construct large-scale virtual aperture antenna to improve angular resolution. The high range resolution is provided by the wideband frequency modulated continuous wave (FMCW) technology. Fast Fourier transform and beamforming algorithms are used to replace the traditional back projection algorithms as imaging algorithms, which can achieve better real time performance. Differential interferometry can obtain the high-precision deformation of the target in the direction of line of sight.

  Results  The prototype radar is a 77 GHz FMCW radar based on two transmitter antennas and four receiver antennas, can offer up to 4 GHz sweep bandwidth. Corner reflector is moving along a guide rail under control of stepper motor to simulate the small deformation of the monitoring target. The displacement curve of the corner reflector that varied with time is measured by the radar and compared with its actual displacement curve.

  Conclusions  The experimental results show that the radar system can get the image of short-range targets, obtain better displacement accuracy than sub-millimeter and have strong anti-interference ability.