A wide-tuning-range and reduced-fractional-spurs synthesizer combining Σ-Δ fractional-N and integer Flying-Adder techniques

A frequency synthesizer architecture with a wide tuning range and reduced fractional spurs is presented. The proposed topology includes a Sigma-Delta fractional-N synthesizer and an integer flying-adder architecture. Compared to the conventional Sigma-Delta fractional-N frequency synthesizer, this approach has much wider tuning range. Compared to the fractional flying-adder frequency synthesizer, the proposed approach can achieve the same frequency resolution with reduced fractional spurs and alleviates the constraints on the adder design in the flying-adder architecture.