### The signal frequency axis

The rest signal frequency must be kept fixed. Indeed, the user is trying to characterize a line at the rest signal frequency. But the rest frequency axis changed

|  |  |  | (57)
|  |  |  | (58)

This equality must be true whatever . This implies that the reference channel and the frequency resolution must be recomputed with
(59)
and
(60)
The last equation just indicates that the channel spacing, which were measured in the measurement frame, did not changed. Indeed, this is the source frame (and not the measurement frame) which is changed through this transformation. The equation for the computation of the rest frequency resolution from measurement frequency resolution is the usual one (Eq. ).