An integrated circuit device has a modulator module that provides a modulation signal comprising one frequency keyed on and off, or alternating between two or more different frequencies or phases that are selected based upon a modulator signal. The one or more frequencies or phases may be selected from a plurality of frequency sources. Switching the one frequency on or off, or between the at least two different frequencies or phases may be synchronized with one or both of the two or more different frequencies or phases so that “glitches” or spurs are not introduced into the modulation signal. The integrated circuit device may also comprise a processor, memory, digital logic and input-output. Frequency sources may be internal to the digital device or external. The modulator signal may comprise serial data generated from the digital logic and/or processor of the digital device.