Use of Field-Perturbing Elements to Increase Nonredundant Data for Microwave Imaging Systems

Field-perturbing elements (FPEs) are introduced for microwave imaging. These elements affect the imaging performance by increasing the amount of nonredundant data. Although this technique can be implemented in nonmetallic chambers, it is especially effective inside metallic enclosures where small perturbations can change the interrogating fields significantly. Results of simulations and a numerical investigation based on synthetic data are presented. The method is validated using an experimental system comprised of 24 coresident radially oriented monopoles that collect the normal component of the electric field on the inside surface of the enclosure. The measured data are used as input to a finite-element contrast source inversion algorithm. To investigate the effectiveness of the approach, a second experimental example is presented where a simplistic breast phantom with a tumor inclusion is imaged inside a smaller cylindrical chamber with 18 radially oriented monopoles and a single FPE. Because FPEs are easy to manufacture and are low costs, they can reduce the cost of an imaging system significantly by reducing the number of required RF ports, as well as reducing the system complexity and modeling error.