d_R.npy -- a sample data file with microwave holography data (SAR principle)
methods -- a class this methods to preprocess radar data and reconstruct a radar image. The most important method is def focus(self, d) -- it's the backpropagation in Fourier frequency domain from the scanning plane to the object's plane.
For detailed information on radar image reconstruction see the classic work:
Sheen D.M., McMakin D.L., Hall T.E., “Three-dimensional millimeterwave imaging for concealed weapon detection,” IEEE Trans. Microwave Theory Tech., vol. 49, no. 9, pp. 1581–1592, Sep. 2001.
or its recent non-destructive testing application in our paper:
M. Chizh, A. Zhuravlev, V. Razevig and S. Ivashov, "Broadband Microwave Imaging for Foam Insulation Diagnostics," 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), Toyama, 2018, pp. 1887-1894. DOI: 10.23919/PIERS.2018.8598093