Δ f L ≅ f L – f r MathType@MTEF@5@5@+=feaagCart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeqabiGaciGacaqadmaadaqaaqaaaOqaaiabfs5aejaadAgadaWgaaWcbaGaaeitaaqabaGccqGHfjcqcaWGMbWaaSbaaSqaaiaabYeaaeqaaOGaai4eGiaadAgadaWgaaWcbaGaaeOCaaqabaaaaa@3E88@
where
fr is the resonance frequency
fL is the load resonance frequency