Described are apparatus and methods for fractional synchronization using direct digital frequency synthesis (DDFS). A DDFS device includes a memory with N address spaces, a write port circuit configured to sequentially write a digital desired pattern into the N address spaces, a read port circuit configured to readout the digital desired pattern from the N address spaces using continuous sequential automatic addressing from 0 to N−1 at a memory operating frequency clock, where the memory operating frequency clock is based on a sampling frequency clock used for high-speed data processing, and an analog signal processing circuit configured to process a readout digital desired pattern into an analog representation; and output a synthesized frequency clock from the analog representation to a digital core, where the synthesized frequency clock is fractionally synchronized with the sampling frequency clock.