Gerund; refers to the act or process of modulation, usually uncountable.
Definitions
The act or process of modulating; an instance of varying or adjusting something, especially a signal. Modulating the carrier wave improves transmission quality.
modulategerund / present participle Used attributively, e.g. "modulating control voltage".
Definitions
That modulates; involving or causing modulation. A modulating control voltage shapes the filter's response.