Time-domain microwave target imaging

The basic principle of time-domain imaging (i.e. the synthesis of the scattered electromagnetic field distribution over an object plane) is outlined. We have shown that from a set of responses obtained from different viewing directions, the two-dimensional field distribution can be synthesised using a technique similar to the computerised tomographic reconstruction. The limitations of the theory together with the practical difficulties in experimental realisation, are discussed. We have reconstructed the images of two flat metallic plates: one elliptical, one bow-tie shaped. Close resemblance between the objects the reconstructed images is observed for target sizes comparable to the source pulse width, this has given us confidence in the theory for imaging larger targets. The use of time-domain imaging as a broadband scattering measurement technique is also demonstrated. Results are given for a `one-dimensional¿¿ metallic strip, 36 cm in width. The simple experimental arrangements the remarkable accuracy of the magnitude phase responses obtained over a broadband of frequencies warrants a further investigation in this area.