Patent attributes
An FPGA having a programmable frequency output is provided that achieves a (theoretical) M-times reduction in output jitter from a conventional direct digital synthesis (DDS) circuit, by running M accumulator circuits in parallel and combining the outputs in a time-staggered way. I Initially the frequency number N added into the accumulators is varied slightly for each accumulator by multiplying by a number, such as X/16 where X varies from 1 to 16 for each of 16 accumulator circuits. The accumulator circuits are further reconfigured so that the output of a register from a first accumulator provides feedback to the adder input in all of the accumulator circuits. The number of overflowing accumulator registers in a clock cycle will then indicate granularity spatially. To translate spatial granularity to time, a programmable delay circuit is connected to the output of each accumulator register.
