Estimation of the discrete spectrum of relaxation frequencies using multiple measurements

The EMI response of a target can be accurately modeled by a sum of relaxations. However, it is difficult to obtain the model parameters from measurements when the number of relaxations is unknown. We have previously proposed estimation methods for the model parameters from single measurements. In this paper, we exploit the invariance property of the relaxation frequencies and propose to obtain more accurate estimates using multiple measurements that are often available. This is accomplished by casting the modeling problem into a jointly-sparse vector recovery problem. The proposed method is shown to deliver robust estimation using synthetic, laboratory data, and field data.