A system, method and system are disclosed for using a variable frequency clock generator to synchronize an average data rate over intervals of time in a variable clock domain to make it equal to a fixed data rate in a fixed clock domain while reducing electromagnetic interference, among other things. In various embodiments, setting the data rates equal to each other minimizes storage used to transition data signals between clock domains. In one embodiment, a variable frequency clock generator includes a phase modulator configured to form a variable frequency clock. Also, the variable clock generator is configured to maintain an average frequency over specific periods of time for the range of discrete frequencies. The phase-offset controller sets an average clock having substantially no offset between a fixed data rate in the fixed clock domain and an average data rate in the variable clock domain.