Digital frequency synthesizer based on two coprime moduli DDS

A new concept for direct digital synthesizer (DDS) design is presented in this brief. The originality of the method consists on the use of a traditional modulus [2.sup.L] DDS and a novel modulus ([2.sup.L] - 1) DDS whose outputs are digitally mixed by means of a complex multiplier. This way, the number of different frequencies achievable equals [2.sup.L]([2.sup.L] - 1) using two independent L-bits wide accumulators. No phase truncation is required resulting in extremely low spurs, while the size of the memories for the trigonometric look-up tables is only [2.sup.L] positions. The design has been implemented in a field-programmable gate array to demonstrate its performance and logic requirements. Index Terms--Algorithms, field-programmable gate array (FPGA), frequency synthesizers, receivers.