The authors made an error in the phase term of Eq. (13). The correct phase is expressed as an integral.1,2 Thus, the corrected expression of Eq. (13) is
(13)
with ktest(x) defined with coefficients k and ε of a first order Taylor expansion following Eq. (10) as
(14)
Thus, in a first order Taylor expansion, it implies that Eq. (13) also expresses as
You do not currently have access to this content.