Microwave internal imaging with 1/100 wavelength accuracy
Our objective is to establish a foundation for innovative internal radar sensors by extending our originally proposed "super-resolution imaging principle of the RPM method"
to internal imaging to realize super-resolution internal dielectric imaging, and to achieve imaging "resolution" and "accuracy" that surpass the conventional performance.
Figure 1 shows the results of applying the synthetic aperture (SA) and RPM methods to scattering data generated by a sophisticated electromagnetic field analysis
for detecting cracks in concrete.
The results of the SA method show that the location and shape of cracks cannot be accurately determined due to phase uncertainties and false images caused by coherent processing.
On the other hand, the RPM method accurately reconstructs the 3D shape of the spiral cavity.
This accuracy is about 1/100th of the wavelength of the electromagnetic waves used, which is significantly greater than the accuracy of conventional radar imagery.
Figure 2 shows the results of the interior of a concrete test specimen with four cavities actually inside, estimated by UWB radar in the 1-3 GHz band.
The figure shows that both methods were able to identify the location of cracks in the concrete with a diameter of about 30 cm.
However, it is clear that the SA method cannot accurately identify the size and shape of the cavities.
On the other hand, the three-dimensional shape estimation using the RPM method can estimate the size of four cavities with a diameter of about 1 cm with good accuracy.
Future Prospects
We are conducting research to extend the advantages of high-resolution and high-precision interior imaging estimation by the RPM method to the estimation of interior dielectric constants. Since internal properties (cavities, rebar, liquefaction) can be discriminated by their dielectric constants, we expect to significantly improve the accuracy of such discrimination when used in conjunction with tomographic processing.
Shuto Takahashi and Shouhei Kidera,
" Acceleration of Range Points Migration Based Microwave Imaging for Non-destructive Testing ",
IEEE Antennas and Wireless Propagation Letters, Vol. 17, No.4, pp. 702-705, Apr., 2018. Toshiki Manaka, Shouhei Kidera and Tetsuo Kirimoto,
" Experimental Study on Embedded Object Imaging Method with Range Point Suppression of CreepingWave for UWB Radars ",
IEICE Trans. Electron Vol.E99-C,No.1,pp.138-142, Jan. 2016
Ryunosuke Souma, Shouhei Kidera and Tetsuo Kirimoto,
"Fast and Accurate Permittivity Estimation Algorithm for UWB Internal Imaging Radar",
Asia-Pacific International Conference on Synthetic Aperture Radar (APSAR) 2011, Seoul, Korea, 26-30th, Sep., 2011. Ken Akune, Shouhei Kidera and Tetsuo Kirimoto,
"Fast and Accurate Imaging Algorithm for Targets Buried in Dielectric Medium for UWB Radars",
The XXX General Assembly and Scientific Symposium of the International Union of Radio Science (URSI), Istanbul, Turkey, 13-20 Aug, 2011.
Future Prospects
We are conducting research to extend the advantages of high-resolution and high-precision interior imaging estimation by the RPM method to the estimation of interior dielectric constants. Since internal properties (cavities, rebar, liquefaction) can be discriminated by their dielectric constants, we expect to significantly improve the accuracy of such discrimination when used in conjunction with tomographic processing.
Figure 1: Example of 3D interior imaging using the extended RPM method (numerical simulation)
Figure 2: Example of 3D internal imaging using the extended RPM method (actual experiment)
References
" Acceleration of Range Points Migration Based Microwave Imaging for Non-destructive Testing ",
IEEE Antennas and Wireless Propagation Letters, Vol. 17, No.4, pp. 702-705, Apr., 2018.
" Experimental Study on Embedded Object Imaging Method with Range Point Suppression of CreepingWave for UWB Radars ",
IEICE Trans. Electron Vol.E99-C,No.1,pp.138-142, Jan. 2016
"Fast and Accurate Permittivity Estimation Algorithm for UWB Internal Imaging Radar",
Asia-Pacific International Conference on Synthetic Aperture Radar (APSAR) 2011, Seoul, Korea, 26-30th, Sep., 2011.
"Fast and Accurate Imaging Algorithm for Targets Buried in Dielectric Medium for UWB Radars",
The XXX General Assembly and Scientific Symposium of the International Union of Radio Science (URSI), Istanbul, Turkey, 13-20 Aug, 2011.
