US Patent 11181661 Identifying antenna system parameter changes

Systems, methods, and devices for evaluation of an earth formation intersected by a borehole using a logging tool. Methods include performing EM logging in a borehole intersecting an earth formation using a measurement signal from an antenna system in the borehole, the measurement signal dependent upon a parameter of interest of the formation and at least one antenna system parameter of the antenna system, comprising feeding a calibration signal into a signal path of the antenna system to generate a resultant signal; estimating at least one value of the at least one antenna system parameter by using the resultant signal; and performing further logging operations in dependence upon the at least one value of the at least one antenna system parameter. The calibration signal comprises at least two calibration subsignals with a first calibration subsignal having a first frequency and a second calibration subsignal having a second frequency.