### Image frequency axis

The image frequency axis must also be kept fixed. This implies

|  |  |  | (48)
|  |  |  | (49)

We thus yield for the new tuned signal and image frequency the following relations

|  |  |  | (50)
|  |  |  | (51)

Adding them gives
(52)
This relation can be used to computes the new image frequency. It can be interpreted as the LO tuning frequency is kept fixed under the transformation. But the side band separation changed.