Abstract: To minimize abrupt changes in modulated signal amplitude when switching between modulation types in a multi-modulation system, a “smoothing” circuit is used. When the modulation type is changed in a multi-slot modulation, the last symbol of the previous slot is overwritten and modulation is controlled by a smoothing circuit during the time of the final symbol of the previous slot to effect the trajectory smoothing. The IQ-plane is divided into two (or more) zones, each with an associated safe point. After the next-to-last symbol is modulated, modulation is made to jump to the safe point associated with the zone and modulation continues to a starting point. From the starting point, the next slot can be modulated using the new modulation type.