Frequency-Diverse Near-Field Sensing Using Multiple Coupled-Resonator Probes

A scalable multiple-probe near-field sensing technique using coupled resonators is presented. The technique captures perturbation information about metal scatterers near each probe and exactly distinguishes the contribution of each probe to the variations of the scattering parameters. The multiple-probe structure can be utilized to save scanning time compared with single-probe designs. A systematic extraction approach based on a coupling matrix theory and a vector fitting algorithm is employed. A design principle that provides stable structures utilizing the concept of condition number is also presented so that better calculation stability can be achieved under noisy conditions. The proposed technique is illustrated by an inline three-probe implementation with three numerical examples and two experimental validations, in which both single and multiple metal scatterers are used. The agreement between the predicted results and the extraction results validates the proposed technique.