On the Calibration of a Multistatic Scatter- Ing Matrix Measured by a Fixed Circular Ar- Ray of Antennas

Abstract—The calibration of the multistatic scattering matrix plays an important part in the construction of a quantitative microwave imaging system. For scattering measurement applications, the calibration must be performed on the amplitude and on the phase of the fields of interest. When the antennas are not completely identical, as for example with a multiplexed antennas array, a specific calibration procedure must be constructed. In the present work, we explain how a complex calibration matrix can be defined which takes advantage of the geometrical organization of the antennas. Indeed, for arrays of antennas positioned on a circle, the inherent symmetries of the configuration can be fully exploited by means of an adequate reorganization of the multistatic scattering matrix. In addition, the reorganization permits to detect antenna pairs which are not properly functioning and to estimate the signal-to-noise ratio. Experimental results obtained within a cylindrical cavity enclosed by a metallic casing are provided to assess the performance of the proposed calibration procedure.This calibration protocol, which is described here in detail, has already been applied to provide quantitative images of dielectric targets [1, 2].